Carole Adam
email: adam@irit.fr

Benoit Gaudou
email: gaudou@irit.fr

Andreas Herzig
email: herzig@irit.fr

Dominique Longin
email: longin@irit.fr

OCC's emotions: a formalization in a BDI logic

Nowadays, more and more artificial agents integrate emotional abilities, for different purposes: expressivity, adaptability, believability... Designers mainly use Ortony et al.'s typology of emotions, that provides a formalization of twenty-two emotions based on psychological theories. But most of them restrain their agents to a few emotions among these twenty-two ones, and are more or less faithful to their definition. In this paper we propose to extend standard BDI (belief, desire, intention) logics to account for more emotions while trying to respect their definitions as exactly as possible.

Introduction

Recently, the agent community gets very interested in emotional artificial agents with enhanced abilities including expressivity, adaptability and believability. To cope with the increasing complexity of such agents, designers need rigorous formal models offering properties like genericity and verifiability.

Current computer models of emotions are mainly semi-formal or only manage a limited number of emotions, and are thus often specific to the context of use. However, Meyer [START_REF] Meyer | Reasoning about emotional agents[END_REF] proposes a very formal model of four emotions, but as he states himself [1, p.11], his goal was not to "capture the informal psychological descriptions exactly (or as exact as possible)" but rather to describe what "makes sense for artificial agents". In this paper we provide a logical formalization of twenty emotions while staying as close as possible to one of the most cited psychological approaches, viz. that of Ortony, Clore, and Collins (OCC) [START_REF] Ortony | The cognitive structure of emotions[END_REF]. Compared to the previous version of this work, we manage twelve more emotions, and we have modified the existing ones to be more faithful to OCC. These emotions are formalized inside a BDI modal logic (Belief, Desire, Intention), that has numerous advantages: widespread thus broadly studied, established results of verifiability and genericity, strong explicative power of the agent's behavior... Our architecture grounds on previous work [START_REF] Herzig | C&L intention revisited[END_REF]. We here omit the notions of choice and intention (that turned out to be avoidable), and add a probabilistic belief operator, as well as a refined notion of desire with its symmetric notion of "undesire", and deontic operators.

There exist several kinds of models of emotions. Discrete models (e.g. [START_REF] Darwin | The expression of emotions in man and animals[END_REF][START_REF] Ekman | An argument for basic emotions[END_REF]) are mainly descriptive. Dimensional models (e.g. [START_REF] Russell | How shall an emotion be called[END_REF]) are practical when aiming at describing the dynamics and expression of emotions (e.g. [START_REF] Becker | Simulating the emotion dynamics of a multimodal conversational agent[END_REF]) but not explicative of the triggering of emotions. Finally, cognitive models (e.g. [START_REF] Ortony | The cognitive structure of emotions[END_REF][START_REF] Lazarus | Emotion and Adaptation[END_REF][START_REF] Frijda | The emotions[END_REF]) assume that emotions are triggered by the cognitive evaluation of stimuli following some judgement criteria or appraisal variables. They are more normative than other models, and thus we can find them as a basis in many intelligent agent architectures. Some rare researchers prefer the complex theories from Lazarus (e.g. [START_REF] Gratch | A domain-independent framework for modeling emotion[END_REF]) or Frijda (e.g. [START_REF] Staller | Introducing emotions into the computational study of social norms: a first evaluation[END_REF]), but most of them (e.g. [START_REF] Jaques | Applying affective tactics for a better learning[END_REF]), including this paper, ground on the model of Ortony, Clore, and Collins (OCC).

The OCC typology has three branches, each of which corresponds to the appraisal of a different type of stimulus with respect to a particular appraisal variable, and related to particular mental attitudes. For example, the stimulus event "it is raining" is appraised as being undesirable w.r.t. the agent's goal of taking coffee on a terrace. These branches are then differentiated into several groups of emotion types with similar eliciting conditions.

Section 2 introduces our logical framework allowing to express the necessary intensity variables. Sections 3 and 4 detail the event-based and agent-based branches of the typology.

Logical framework

Our formal framework is based on the modal logic of belief, choice, time, and action of Herzig and Longin [START_REF] Herzig | C&L intention revisited[END_REF] which is a refinement of Cohen and Levesque's works [START_REF] Cohen | Intention is choice with commitment[END_REF]. We need neither choice nor intention (build from belief and choice), thus we do not use them. We extend this logic with modal probability operators defined by Herzig [START_REF] Herzig | Modal probability, belief, and actions[END_REF], as well as obligation and desirability operators.

Semantics. Let AGT be the set of agents, ACT the set of actions, ATM = {p, q...} the set of atomic formulas. The set of complex formulas will be noted FORM = {ϕ, ψ...}. A possible-worlds semantics is used, and a model M is a triple W, V, R where W is a set of possible worlds, V is a truth assignment which associates each world w with the set Vw of atomic propositions true in w, and R is a tuple of structures made up of:

-A : ACT → (W → 2 W ) which associates each action α ∈ ACT and possible world w ∈ W with the set Aα(w) of possible worlds resulting from the execution of action α in w; -B : AGT → (W → 2 W ) which associates each agent i ∈ AGT and possible world w ∈ W with the set Bi(w) of possible worlds compatible with the beliefs of agent i in w. All these accessibility relations are serial; -P : AGT → (W → 2 2 W ) which associates each agent i ∈ AGT and possible world w ∈ W with a set of sets of possible worlds Pi(w). Intuitively for U ∈ Pi(w), U contains more elements than its complement Bi \ U ; -G : W → 2 W which associates each possible world w ∈ W with the set G(w) of possible worlds in the future of w. This relation is a linear order (reflexive, transitive and antisymmetric). G ⊇ Aα for every α;

-

L : AGT → (W → 2 W ) (resp. L : AGT → (W → 2 W
)) which associates each agent i ∈ AGT and possible world w ∈ W with the set Li(w) (resp. Di(w)) of possible worlds compatible with what the agent i likes (resp. dislikes) in the world w. All these accessibility relations are serial. Moreover, for the sake of simplicity, we make the simplistic hypothesis that what is liked persists: if wGw then Li(w) = Li(w ). Similarly for what is disliked; -I : AGT → (W → 2 W ) which associates each agent i ∈ AGT and possible world w ∈ W with the set Ii(w) of ideal worlds for the agent i. In these ideal worlds all the (social, legal, moral...) obligations, norms, standards... of agent i hold. All these relations are serial. 1We associate modal operators to these mappings: After α ϕ reads "ϕ is true after every execution of action α", Before α ϕ reads "ϕ is true before every execution of action α", Bel i ϕ reads "agent i believes that ϕ", Probi ϕ reads "for i ϕ is more probable than ¬ϕ", Gϕ reads "henceforth ϕ is true", H ϕ reads "ϕ has always been true in the past", Idl i ϕ reads "ideally it is the case for i that ϕ" and Desi ϕ (resp. Undesi ϕ) reads "ϕ is desirable (resp. undesirable) for i".

The truth conditions are standard for almost all of our operators: w ϕ iff w ϕ for every w ∈ R (w) where R ∈ A ∪ B ∪ {G} ∪ I and ∈ {After α : α ∈ ACT } ∪ {Bel i : i ∈ AGT } ∪ {G} ∪ {Idl i : i ∈ AGT } respectively. For the converse operators we have: w ϕ iff w ϕ for every w such that w ∈ R (w ) where R ∈ A ∪ {G} and ∈ {Before α : α ∈ ACT } ∪ {H } respectively. Furthermore, w Probi ϕ iff there is U ∈ Pi(w) such that for every w ∈ U, w ϕ.

Intuitively, ϕ is desirable for agent i if i likes ϕ and does not dislike ϕ, viz. ϕ is true in every world i likes and is false in at least one world i dislikes:

w Des i ϕ iff for every w ∈ Li(w), w ϕ and there is a world w ∈ Di(w) such that w ϕ. In a similar way: w Undes i ϕ iff for every w ∈ Di(w), w ϕ and there is a world w ∈ Li(w) : w ϕ. It follows from these constraints that ϕ cannot be simultaneously desirable and undesirable, and that there are ϕ that are neither desirable nor undesirable (e.g. tautologies and inconsistencies).

We have the following introspection constraints: if w ∈ Bi(w ) then Bi(w) = Bi(w ), Pi(w) = Pi(w ), Li(w) = Li(w ) and Di(w) = Di(w ), insuring that agents are aware of their beliefs, probabilities, desires, and "undesires". We also require that U ⊆ Bi(w) for every U ∈ Pi(w), ensuring that belief implies probability.

Dynamic operators. After α and Before α are defined in the standard tense logic K t , viz. logic K with conversion axioms (see [START_REF] Burgess | Basic tense logic[END_REF] for more details). For every α and ϕ, as G ⊇ Aα, we have that Gϕ → After α ϕ. As we suppose that time is linear, Happens α ϕ def = ¬After α ¬ϕ reads "α is about to happen, after which ϕ" and Doneα ϕ def = ¬Before α ¬ϕ reads "α has just been done, and ϕ was true before". In the following, the notation i:α reads "agent i is the author of action α".

Belief operators. Bel i operators are defined in the standard KD45 logic that we do not develop here (see [START_REF] Hintikka | Knowledge and Belief: An Introduction to the Logic of the Two Notions[END_REF][START_REF] Chellas | Modal Logic: an introduction[END_REF] for more details).

Temporal operators. The logic of G and H is linear temporal logic with conversion axioms (see [START_REF] Burgess | Basic tense logic[END_REF] for more details). F ϕ def = ¬G¬ϕ reads "ϕ is true or will be true at some future instant". P ϕ def = ¬H ¬ϕ reads "ϕ is or was true".

Probability operators. The probability operators correspond to a notion of weak belief. It is based on the notion of subjective probability measure. The logic of Prob is much weaker than the one of belief, in particular it is non-normal: the necessitation rule and the axiom K of belief operators do not have any counterpart in terms of Prob .

Belief and probability. They are related by the validity of:

Bel i ϕ → Probi ϕ (BPR)
We define an abbreviation Expect i ϕ, reading "i believes that ϕ is probably true, but envisages the possibility that it could be false".

Expect i ϕ def = Probi ϕ ∧ ¬Bel i ϕ (DefExpect )
Desirable/Undesirable operators. They represent preference in a wide sense. We here consider that an agent finds ϕ desirable, undesirable or ϕ leaves him indifferent. Due to the truth condition for Des i , the following principles are valid:

if ϕ ↔ ψ then Desi ϕ ↔ Desi ψ (REDes ) Desi ϕ → ¬Desi ¬ϕ (DDes ) ¬Desi ( Des i ) ¬Desi ⊥ (⊥Des i ) Desi ϕ → GDesi ϕ (PersDes i ) ¬Desi ϕ → G¬Desi ϕ (Pers¬Des i ) Desi ϕ → ¬Undesi ϕ (RDU)
(PersDes i ) and (Pers¬Des i ) illustrate that what is desirable is atemporal. We also have corresponding principles for Undes i . Note that desires are neither closed under implication nor under conjunction: I might desire to marry Ann and to marry Beth without desiring to be a bigamist. Finally, (RDU) expresses that something cannot be desirable and undesirable at the same time.

Obligation operator. The notion of obligation considered here is very wide: it embraces all the rules agents ideally have to respect. They can be explicit (like laws) or more or less implicit (like social or moral obligations). They are a kind of social preferences, imposed by a group to which the agent pertains, and thus differ from the agent's personal desires. The logic of Idl is the standard deontic logic KD (thus an agent's "obligations" must be consistent).

We will now formalize Ortony et al.'s emotions: we cite OCC's informal definition, give a formal definition, and illustrate it by OCC's examples.

Event-based emotions

The event-based branch of the OCC typology contains emotion types whose eliciting conditions depend on the evaluation of an event, with respect to the agent's goals. Desirability is a central intensity variable accounting for the impact that an event has on an agent's goals, i.e. how it helps or impedes their achievement. We formalize it through our Des and Undes operators.

Well-being emotions

The emotion types in this group have eliciting conditions focused on the desirability for the self of an event. An agent feels joy (resp. distress) when he is pleased (resp. displeased) about a desirable (resp. undesirable) event.

Joy i ϕ def = Bel i ϕ ∧ Desi ϕ Distressiϕ def = Bel i ϕ ∧ Undesi ϕ
For example in [2, p. 88] 2 , when a man i hears that he inherits of a small amount of money from a remote and unknown relative k (Bel i (earn-money ∧ k-died)), he feels joy because he focuses on the desirable event (Desi earn-money). Though, this man does not feel distress about his relative's death, because this is not undesirable for him (¬Undesi k-died). On the contrary, a man j (p. 89) who runs out of gas on the freeway (Belj out-of-gas) feels distress because this is undesirable for him (Undesj out-of-gas).

Prospect-based emotions

The emotion types in this group have eliciting conditions focused on the desirability for self of an anticipated (uncertain) event, that is actively prospected. They use a local intensity variable, likelihood, accounting for the expected probability of the event to occur. We formalize this variable with the operator Expect .

An agent feels hope (resp. fear) if he is "pleased (resp. displeased) about the prospect of a desirable (resp. undesirable) event" 3 .

Hope i ϕ def = Expect i ϕ ∧ Desi ϕ Fear iϕ def = Expect i ϕ ∧ Undesi ϕ
The agent feels fear-confirmed (resp. satisfaction) if he is "displeased (resp. pleased) about the confirmation of the prospect of an undesirable (resp. desirable) event".

FearConfirmed i ϕ def = Bel i P Expect i ϕ ∧ Undesi ϕ ∧ Bel i ϕ Satisfaction i ϕ def = Bel i P Expect i ϕ ∧ Desi ϕ ∧ Bel i ϕ
The agent feels relief (resp. disappointment) if he is "pleased (resp. displeased) about the disconfirmation of the prospect of an undesirable (resp. desirable) event".

Relief i ϕ def = Bel i P Expect i ¬ϕ ∧ Undesi ¬ϕ ∧ Bel i ϕ Disappointment i ϕ def = Bel i P Expect i ¬ϕ ∧ Desi ¬ϕ ∧ Bel i ϕ
For example a woman w who applies for a job (p. 111) might feel fear if she expects not to be offered the job (Expect w ¬get-job), or feel hope if she expects that she will be offered it (Expect w get-job). Then, if she hoped to get the job and finally gets it, she feels satisfaction; and if she does not get it, she feels disappointment. An employee e (p. 113) who expects to be fired (Expect e f ) will feel fear if it is undesirable for him (Undese f ), but not if he already envisaged to quit this job (¬Undese f ). In the first case he will feel relief when he is not fired (Bele ¬f ), and fear-confirmed when he is.

Theorem. We can prove some links between emotions: Satisfaction i ϕ → Joy i ϕ and FearConfirmed i ϕ → Distressiϕ. This is in agreement with Ortony et al.'s definitions. Though, we can notice that the disconfirmation-centered emotions (relief and disappointment) do not imply the corresponding well-being emotions (joy and sadness). This seems rather intuitive, since they typically do not characterize a desirable or undesirable situation, but the return to an indifferent situation that was expected to change and that finally did not.

Fortunes-of-others emotions

The emotion types in this group have eliciting conditions focused on the presumed desirability for another agent. They use three local intensity variables: desirability for other, deservingness, and liking. Desirability for other is the assessment of how much the event is desirable for the other one: for example we write Bel i Desj ϕ for "agent i believes that ϕ is desirable for agent j". Deservingness represents how much agent i believes that agent j deserved what occurred to him. It often depends on liking, i.e. i's attitude towards j. Below, to simplify, we assimilate "i believes that j deserves A" and "i desires that j believes A". We thus only consider liking, through non-logical global axioms. For example, when John likes Mary this means that if John believes that Mary desires to be rich, then John desires that Mary is rich, or rather: gets to know that she is rich (Bel john Desmary rich → Des john Bel mary rich).

There are two good-will (or empathetic) emotions: an agent feels happy for (resp. sorry for) another agent if he is pleased (resp. displeased) about an event presumed to be desirable (resp. undesirable) for this agent.

HappyFor i,j ϕ def = Bel i ϕ ∧ Bel i F Bel j ϕ ∧ Bel i Desj ϕ ∧ Desi Bel j ϕ SorryFor i,j ϕ def = Bel i ϕ ∧ Bel i F Bel j ϕ ∧ Bel i Undesj ϕ ∧ Undesi Bel j ϕ
There are two ill-will emotions: an agent feels resentment (resp. gloating) towards another agent if he is displeased (resp. pleased) about an event presumed to be desirable (resp. undesirable) for this agent.

Resentment i,j ϕ def = Bel i ϕ ∧ Bel i F Bel j ϕ ∧ Bel i Desj ϕ ∧ Undesi Bel j ϕ Gloating i,j ϕ def = Bel i ϕ ∧ Bel i F Bel j ϕ ∧ Bel i Undesj ϕ ∧ Desi Bel j ϕ
For example (p. 95) Fred feels happy for Mary when she wins a thousand dollars, because he has an interest in the happiness and well-being of his friends (global axiom: Bel f Desm w → Des f Bel m w). A man i (p. 95) can feel sorry for the victims v of a natural disaster (Bel i Bel v disaster ∧ Bel i Undesv disaster) without even knowing them, because he has an interest that people do not suffer undeservedly (Undesi Bel v disaster). An employee e (p. 99) can feel resentment towards a colleague c who receives a large pay raise (Bel e pr, Bel e Desc pr) because he thinks this colleague is incompetent and thus does not deserve this raise (Undese Bel c pr). Finally, Nixon's political opponents (p. 104) might have felt gloating about his departure from office (Bel o Bel nixon d, Bel o Undesnixon d) because they thought it was deserved (Deso Bel nixon d).

Agent-based emotions

The agent-based branch of the OCC typology contains emotion types whose eliciting conditions depend on the judgement of the praiseworthiness of an action, with respect to standards. An action is praiseworthy (resp. blameworthy) when it upholds (resp. violates) standards. We represent standards through the deontic operator Idl .

Attribution emotions

The emotion types in this group have eliciting conditions focused on the approving of an agent's action. They use two local intensity variables: strength of unit 4 and expectation deviation. Expectation deviation accounts for the degree to which the performed action differs from what is usually expected from the agent, according to his social role or category 5 . We express this with the formula ¬Probi Happens j:α , reading "i does not believe that it is likely that j performs successfully action α". Then Done i:α ¬Probi Happens i:α expresses that surprisingly for himself, i succeeded in executing α. In the sequel, Emotion i(i:α) abbreviates EmotioniDonei:α where Emotion is the name of an emotion.

Self-agent emotions: an agent feels pride (resp. shame) if he is approving (resp. disapproving) of his own praiseworthy (resp. blameworthy) action. For example, a woman m feels pride (p. 137) of having saved the life of a drowning child (Belm Donem:α , where α is the action to save the child) because she thinks that her action is praiseworthy, i.e. its successful execution was not expected (before α, it held that ¬Probm Happens m:α ) but ideally she had to perform it (Belm Idl m Happens m:α ). A rich elegant lady l (p. 142) would feel shame if caught while stealing clothes in an exclusive boutique (Bel l Done l:β , where β is the action to steal), because this violates a standard (Idl l ¬Happens l:β ) and this was not expected of herself (¬Prob l Happens l:β ). A physicist p's colleagues c (p. 145) feel admiration towards him for his Nobel-prize-winning work (Belc Donep:γ , where γ is the action to make some Nobel-prize-winning findings) because this is praiseworthy, i.e. ideal (Bel c Idl p Happens p:α ) but very unexpected (¬Probc Happens p:γ ). A man i may feel reproach towards a driver j (p. 145) who drives without a valid license (Bel i Done j:δ , where δ is the action to drive without a valid license), because it is forbidden (Bel i Idl j ¬Happens j:δ ), and it is not expected from a driver (¬Probi Happens j:δ ).

Theorem. We can prove that Admiration i,i(ϕ) ↔ Pridei(ϕ) and Reproach i,i (ϕ) ↔ Shamei(ϕ). This is rather intuitive, all the more Ortony et al. introduce the term self-reproach for shame.

Composed emotions

These emotions occur when the agent focuses on both the consequences6 of the event and its agency. They are thus the result of a combination of well-being emotions and attribution emotions.

Gratification i (i:α, ϕ) def = Pridei(i:α) ∧ Bel i Before i:α ¬Bel i F ϕ ∧ Joy i ϕ Remorsei(i:α, ϕ) def = Shamei(i:α) ∧ Bel i Before i:α ¬Bel i F ϕ ∧ Distressiϕ Gratitudei,j(j:α, ϕ) def = Admirationi,j(j:α) ∧ Bel i Before j:α ¬Bel i F ϕ ∧ Joy i ϕ Anger i,j (j:α, ϕ) def = Reproach i,j (j:α) ∧ Bel i Before j:α ¬Bel i F ϕ ∧ Distressiϕ
For example, a woman i may feel gratitude (p. 148) towards the stranger j who saved her child from drowning (Bel i Donej:α , where α is the action to save her child). Indeed, she feels admiration towards j because of j's praiseworthy action (i.e. ideal: Bel i Idl j Happens j:α , but unlikely: ¬Probi Happens j:α , for example because it needs a lot of courage). Moreover the effect of j's action (Beli son-alive) is desirable for her (Desi son-alive), so she also feels joy about it (Joy i son-alive). Similarly, a woman w (p. 148) may feel anger towards her husband h who forgets to buy the groceries (Bel w Done h:β , where β is his action to come back without groceries), because the result of this action (Belw ¬g) is undesirable for her (Undesw ¬g), and the action was blameworthy (¬Probw Happens h:β ∧ Bel w Idl h Happens h:β ). The physicist p may feel gratification about winning the Nobel prize because his action γ was praiseworthy, and its result (Belp is-nobel would have been false if p had not performed γ) is desirable for him (Desp is-nobel). Finally, a spy may feel remorse (p. 148) about having betrayed his country (action ω) if he moreover caused undesirable damages (Shamespy(ω) ∧ Distressspydamages ∧ Bel spy Before spy:ω ¬Bel spy F damages.

It follows from our logic, in particular from the introspection axioms for all operators, that Emotioniϕ ↔ Bel i Emotioniϕ and ¬Emotioniϕ ↔ Bel i ¬Emotioniϕ are valid.

Conclusion

We have formalized twenty emotions from Ortony et al.'s theory (all but the object-based branch), thus providing a very complete set of emotions. Moreover we have shown the soundness of our framework by illustrating each definition by an example from their book. We have privileged richness, genericity, and fidelity to the definitions over tractability. An optimization would have needed important concessions. For example [START_REF] Parunak | A model of emotions for situated agents[END_REF] proposes a numerical model of emotions in combat games, efficient in big real-time multi-agent systems, but domain-dependant.

We would like to highlight here some shortcomings of our model. Mainly, our emotions are not quantitative (they have no intensity). This prevents us from fine-grained differentiations among emotions of the same type (for example: irritation, anger, rage). A second (and linked) shortcoming is that our emotions are persistent as long as their conditions stay true. Thereby some emotions (like Joy or Satisfaction ) can persist ad vitam eternam, which is not intuitive at all. Indeed it is psychologically grounded that after an emotion is triggered, its intensity decreases, and when it is under a threshold, the emotion disappears. Finally, we cannot manage emotional blending of several emotions that are simultaneously triggered; [START_REF] Gershenson | Modelling emotions with multidimensional logic[END_REF] proposes an original solution to this issue. On our part, we leave these problems for further work.

=

  Bel i Donei:α (¬Probi Happens i:α ∧ Bel i Idl i Happens i:α )Shamei(i:α) def = Bel i Donei:α (¬Probi Happens i:α ∧ Bel i Idl i ¬Happens i:α )Emotions involving another agent: an agent feels admiration (resp. reproach) towards another agent if he is approving (resp. disapproving) of this agent's praiseworthy (resp. blameworthy) action.Admirationi,j(j:α) def = Bel i Donej:α (¬Probi Happens j:α ∧ Bel i Idl j Happens j:α ) Reproach i,j (j:α) def = Bel i Donej:α (¬Probi Happens j:α ∧ Bel i Idl j ¬Happens j:α )

We disregard thus conflicts between different kinds of standards.

Note that the object of hope is not necessarily about the future: I might ignore whether my email has been delivered to the addressee, and hope it has.

Strength of unit intervenes in self-agent emotions to represent the degree to which the agent identifies himself with the author of the action, allowing him to feel pride or shame when he is not directly the actor. For example one can be proud of his son succeeding in a difficult examination, or of his rugby team winning the championship. In this paper we only focus on emotions felt by the agent about his own actions, thus we do not represent this variable.

In self-agent emotions the agent refers to the stereotyped representation he has of himself.

Here, we represent the effects of an action α with the formula Bel i Before i:α ¬Bel i F ϕ reading approximately "i believes that ϕ would not have been true if he had not performed α".


domain: shs sdv sdv.sa

text:
Exchanges among farmers' collectives in support of sustainable agriculture: from review to reconceptualization

Keywords: Sustainable agriculture, transition, collectives, farmers, support, exchanges, experience Highlights

Successful sustainable transitions require an understanding of the drivers and resources needed to support the required changes. While the importance of farmers' collectives in these transitions is underlined by various scientific studies and public policies, we lack an overview of how scholars are dealing with this topic. This paper has two main objectives: i) a review of the studies that explore the interplay between exchanges among collectives and the farmers' transition pathways to sustainable agriculture, and ii) a conceptual framework to analyze this interplay. Drawing on a review of 43 scientific articles, it highlights a variety of possible theoretical and methodological approaches and interpretations to inform our understanding. Based on the literature, we have distinguished four perspectives in this field: i) the way farmers rely on collectives during their transition process; ii) the collectives as complex organizations; iii) the collectives as loci for knowing; and iv) learning processes among collectives. We also show that these studies fail to provide insights on the interplay between the farmers' dynamics of transitioning towards sustainable agriculture and those of the collectives, and the way it contributes to supporting professional transition. To illuminate this interplay, we introduce a conceptual framework based on Deweyian pragmatism and developmental approaches that allows us to analyze the transition process as one of farmer empowerment. We focus on the farmers' experience, on the way they are affected by their working situations, and on how support for inquiry can help them rebuild meaning and continuity in their transitions. This work should contribute to informing the circulation of agroecological knowledge issues and enable stakeholders who support these processes to find the most appropriate levers for a diversity of farmers and farming systems.

Introduction

Sustainable agriculture seems to be an alternative model to the green revolution paradigm which limits have been long pointed out. Defining sustainable agriculture remains a challenge and is controversial. For the present paper, we define it according to the FAO contribution: "the management and conservation of the natural resource base, and the orientation of technological change in such a manner as to ensure the attainment of continued satisfaction of human needs for present and future generations. Sustainable agriculture conserves land, water, and plant and animal genetic resources, and is environmentally non-degrading, technically appropriate, economically viable and socially acceptable" [START_REF] Fao | Report of the FAO Council, 94th Session[END_REF]. Thus, sustainable agriculture can embed several agricultural approaches and practices (soil conservation, agroforestry, agroecology, mixed croplivestock systems, rotational grazing, organic farming, etc.). Nevertheless, sustainable agriculture does not establish by maintaining existing systems: the entire agri-food system has to be transformed [START_REF] Elzen | Stimulating transitions towards sustainable farming systems[END_REF].

Researchers have invested this issue referring to transition processes which they explore from multiple perspectives raising how complex this phenomenon is. Some scholars addressed transitions as social processes: they acknowledged the transformation of the knowledge production and flow within local networks [START_REF] Compagnone | La production et la circulation des connaissances en agriculture interrogées par l'agro-écologie[END_REF], or from addressing the regime configuration taking place within the wider sociotechnical systems [START_REF] Ingram | Framing niche-regime linkage as adaptation: An analysis of learning and innovation networks for sustainable agriculture across Europe[END_REF][START_REF] Bui | Sustainability transitions: Insights on processes of niche-regime interaction and regime reconfiguration in agri-food systems[END_REF], or the way such transition is related to a process of social movement building [START_REF] Anderson | Transformative agroecology learning in Europe: building consciousness, skills and collective capacity for food sovereignty[END_REF]. Researchers also addressed transition at farm level. They studied practice change and redesign of farming systems through farmers' trajectories [START_REF] Lamine | Analyse des formes de transition vers des agricultures plus écologiques: Les cas de l'Agriculture Biologique et de la Protection Intégrée[END_REF][START_REF] Chantre | Trajectories of French Field Crop Farmers Moving Toward Sustainable Farming Practices: Change, Learning, and Links with the Advisory Services[END_REF], and pointed the learning processes during such trajectories [START_REF] Chantre | Transitional pathways towards input reduction on French field crop farms[END_REF][START_REF] Brédart | When farmers learn through dialog with their practices: a proposal for a theory of action for agricultural trajectories[END_REF] and the transformation of the farmer's professional world [START_REF] Coquil | Professional transitions towards sustainable farming systems: The development of farmers' professional worlds[END_REF].

These last studies invite us to reconsider the support provided to farmers in order to achieve a transition process at the on-farm level. As highlighted by [START_REF] Coquil | Questioning the work of farmers, advisors, teachers and researchers in agro-ecological transition[END_REF], facilitating farmers' transition towards a more sustainable agriculture requires a transformation of the agricultural community, e.g., the farmers but also the AKIS (Agriculture Knowledge Innovation System) players [START_REF] Klerkx | Evolution of systems approaches to agricultural innovation: concepts, analysis and interventions[END_REF]. AKIS players have to reconsider their organization and service provision in order to deal with site-specific processes and to better contribute to the farmer's experience development, both being key in the transition process at farmers' level.

In order to contribute to this issue, we choose to focus on the link between the way exchanges take place in farmers' collectives and the transition process farmers experienced in their move towards a more sustainable agriculture.

Indeed, public policies and AKIS players propose new support schemes which emphasize the role of farmers' collectives (e.g., Economic and Environmental Interest Grouping in France) and "the paramount importance of experience sharing as a key factor for success" during transition to sustainable agriculture 1 . This has also been recently emphasized through stakeholders' mobilization for the establishment of a new Common Agricultural Policy (CAP) for 2020, which calls for more financial support for farmers' collectives and cooperative dynamics, for the "greening of agriculture" 2 . Recent studies have highlighted the fact that transitions towards more ecological based farming systems often take place through collectively constituted peer or multi-actor networks [START_REF] Proost | Creating space for change: farmers' learning groups in the Netherlands[END_REF][START_REF] Chantre | Apprentissages des agriculteurs vers la réduction d'intrants en grandes cultures : Cas de la Champagne Berrichonne dans les années 1985[END_REF][START_REF] Curry | Knowledge networks for sustainable agriculture in England[END_REF][START_REF] Lucas | Local inter-farm cooperation: A hidden potential for the agroecological transition in northern agricultures[END_REF].

Considering peer-to-peer exchanges may be a way of better valuing the various ways of doing and thinking about agriculture, and thus moving away from the duality between specific and generic knowledge [START_REF] Girard | The interplays between singularity and genericity of agroecological knowledge in a network of livestock farmers[END_REF] and moving towards what [START_REF] Coolsaet | Towards an agroecology of knowledges: Recognition, cognitive justice and farmers' autonomy in France[END_REF] calls an "agroecology of knowledge". Accordingly, [START_REF] Blesh | Transitions to agroecological farming systems in the Mississippi River Basin: toward an integrated socioecological analysis[END_REF] describe farmers' networks as spaces where farmers "generated site-specific knowledge, and [recognize that] in the process of sharing this knowledge they forged connections to the wider sustainable agriculture movement and established an alternative knowledge system." Such claims relate to previous studies which showed the social dimension of the construction of knowledge [START_REF] Darré | La production des normes au sein d'un réseau professionnel L'exemple d'un groupe d'éleveurs[END_REF]Roling and Jiggins, 1998, p. 295;[START_REF] Šūmane | Local and farmers' knowledge matters! How integrating informal and formal knowledge enhances sustainable and resilient agriculture[END_REF] and the role of collectives to develop shared values and a vision of sustainable agriculture norms [START_REF] Kilpatrick | Effective farmer groups for defining best practices for sustainable agriculture[END_REF].

Farmers' collectives are investigated through multiple approaches: from social network analysis [START_REF] Isaac | Transfer of knowledge on agroforestry management practices: the structure of farmer advice networks[END_REF][START_REF] Bodin | The role of social networks in natural resource governance: What relational patterns make a difference?[END_REF][START_REF] Spielman | Rural innovation systems and networks: findings from a study of Ethiopian smallholders[END_REF][START_REF] Isaac | Agricultural information exchange and organizational ties: the effect of network topology on managing agrodiversity[END_REF][START_REF] Wood | Agricultural Science in the Wild: A Social Network Analysis of Farmer Knowledge Exchange[END_REF][START_REF] Compagnone | Farmers' Professional Dialogue Networks and Dynamics of Change: The Case of ICP and No-Tillage Adoption in Burgundy (France)[END_REF] to a more comprehensive approach [START_REF] Goulet | Narratives of experience and production of knowledge within farmers' groups[END_REF][START_REF] Prost | Les échanges virtuels entre agriculteurs: un soutien à leurs transitions professionnelles? Raisons éducatives[END_REF]. Nevertheless, although policymakers and scholars point out the potential contribution of farmers' collectives in the farmers' transition towards sustainable agriculture, there is a lack of knowledge about the way the exchanges within farmers' collectives influence, in a way or another, the farmers in the flow of their work. Therefore, this article aims to address the question of the interplay between farmers' collective exchanges, and the process of farmers' sustainable agriculture transition, with a wish to explore more specifically how experience-based-exchanges contribute to such transition. To do so, we propose: i) a review of the literature, to set light on how scholars have studied the interplay between farmers' exchanges among collectives and their transition pathways, and ii) a conceptual framework to address this interplay based on the inquiry theory [START_REF] Dewey | Logique: la théorie de l'enquête[END_REF]. After presenting our research strategy (Section 2), we describe four perspectives identified through an inductive approach, about how scholars address our question (Section 3). We then discuss the limits of the way the interplay is addressed in the review and the relevance of considering farmers' transition as dynamics for the study of the interplay (Section 4.1) and propose a conceptual framework (Section 4.2) for analyzing the interplay between experience-based exchanges among farmers' collectives and farmer's transitions.

Research strategy

Our research strategy was twofold. First, we reviewed the literature to capture scholars' approaches to understanding the interplay between farmers' exchanges among collectives and farmers' transition process towards more sustainable agriculture. Second, we proposed a conceptual framework to fill the gaps that our review identified in the literature with regard to our research question.

For our review process, we followed a procedure that consists of: 1) building a search request in line with our research question; 2) selecting a bibliographic database; and 3) synthesizing the main findings regarding our research question through an inductive and qualitative analysis. The request was built through an iterative protocol to explore multiple possibilities and combinations, and to find a set of papers that matched our research question. Through this iterative process, we used some papers as indicators of the relevance of the term combination. The articles were selected from the Web of Science and CABI databases limited in the time span and by their availability. The combination of two databases allowed us to have a wide range of sources, as CABI enabled us to catch more papers from Southern countries. The request below was designed to explore six main themes: agriculture, sustainability, transition, exchanges and collectives, knowledge, and the "empirical" nature of knowledge. Each theme was then specified with words often associated with it (e.g. sustainability with ecology and innovation). The words were put in their root form (e. The first author proceeded to the selection of relevant papers over 227 references. The table below sums up the procedure used to obtain the final corpus. We thus eliminated articles that:

-did not focus on agricultural activities (climate change, food chains, forestry, policy, and economics) from a sustainability perspective as defined by the FAO, and on the aim of supporting on-farm transition (e.g. support the design of a decision-support system) -more theoretical papers and papers that lacked methodological transparency or clarity in the presentation of the results.

The analysis was based only on the request results; we did not look for other papers.

The first author performed a qualitative analysis of the selected papers with the grid presented and illustrated in Table 3 in the appendix. It describes the papers through indicators such as: the scope of the research, considerations about farmers' collectives and exchanges, the case study, the conceptual framework, the methodology, the main results and the "take-home message" of the paper. To organize this literature review, we looked at the papers from our own point of view, that is, the ways in which they contribute to understand the literature on farmers' transition process, their collectives and exchanges, and the potential links between these two topics. We thus identified four main perspectives discussed in the next section of this article. Each paper does not necessarily fall into a single category as the authors' investigation was not always directly related to our research question, and could therefore show findings in more than one category. But to simplify the reading, we assigned a paper to a category by considering the "take-home" message of the papers.

The second step was then to build a conceptual framework to address one of the gaps we point out in our literature review: the lack of knowledge to analyze experience-based sharing and to understand its potential contribution to on-farm transitions. We built on the educational literature based on the work of John [START_REF] Dewey | Logique: la théorie de l'enquête[END_REF] to develop this framework. This theory constitutes an important contribution to the conceptualization of "experience" and how experience transforms and evolves over time and action. We found it fruitful to consider the interplay between farmers' experience-based exchanges among collectives, and their experiences of transition processes towards sustainability.

Table 1. Selection procedure of papers for the review analysis 3 Four perspectives to address the interplay between farmers' collective dynamics and farmers' transition towards more sustainable agriculture Our literature review allowed us to identify four perspectives according to the ways the articles address the interplay between farmers' collective dynamics and farmers' transition towards more sustainable agriculture.

While in the first perspective, the possible interplay is identified through the analysis of the resources mobilized by farmers during their transition, in the second one the collective dynamics are at the core of the research and less attention is paid to its influence on individuals, and in the third and fourth ones, the attention is clearly on the way knowing and learning developed inside the collectives. In Table 2 below, we identify the various papers that contribute to these perspectives.

Step

The farmers rely on collectives during their transition

This first perspective aggregates studies which focus on the farmers' environment and the resources that farmers mobilize to learn about innovative practices or face challenges in relation to their transition towards more sustainable agriculture. The role of farmers' collectives is not directly observed or addressed: it is inferred through close examination of the social dimension of farmer's work and the place given by farmers to experience sharing and experimentation, etc. Some authors begin by studying farmers' practices or strategies when they set up sustainable farming [START_REF] Warner | Extending agroecology: grower participation in partnerships is key to social learning[END_REF][START_REF] Kroma | Organic farmer networks: Facilitating learning and innovation for sustainable agriculture[END_REF][START_REF] Ingram | Technical and social dimensions of farmer learning: an analysis of the emergence of reduced tillage systems in England[END_REF][START_REF] Ryschawy | Analysis of support networks used by farmers making the agroecological transition: an initial study in the Tarn -Aveyron region[END_REF][START_REF] Mawois | Transition to legume-based farming systems requires stable outlets, learning, and peer-networking[END_REF], before exploring a more social dimension of the farmer's work. For instance, [START_REF] Mawois | Transition to legume-based farming systems requires stable outlets, learning, and peer-networking[END_REF], through their study of the diversification strategies of farmers introducing legumes, have deduced from interviews that the farmers with the most robust and radical transitions were the ones involved in collectives for experience sharing and in building local references through experimentations. [START_REF] Kroma | Organic farmer networks: Facilitating learning and innovation for sustainable agriculture[END_REF] went a step further by questioning farmers' opinions about the collectives' benefits and by participating in some collectives' activities for complementing her analysis. She describes these collectives as inclusive and flexible places where farmers can validate their experiences and find mutual support, motivation, reflection, trust.

Authors' perspective Description

References from the request results

1/ The farmers rely on collectives during their transition

Analysis of the social environment of farmers engaged in processes of transition towards sustainable agriculture. [START_REF] Kroma | Organic farmer networks: Facilitating learning and innovation for sustainable agriculture[END_REF][START_REF] Warner | Extending agroecology: grower participation in partnerships is key to social learning[END_REF][START_REF] Ingram | Technical and social dimensions of farmer learning: an analysis of the emergence of reduced tillage systems in England[END_REF][START_REF] Ryschawy | Analysis of support networks used by farmers making the agroecological transition: an initial study in the Tarn -Aveyron region[END_REF][START_REF] Hayden | The importance of social support and communities of practice: farmer perceptions of the challenges and opportunities of integrated crop-livestock systems on organically managed farms in the northern U[END_REF][START_REF] Mawois | Transition to legume-based farming systems requires stable outlets, learning, and peer-networking[END_REF][START_REF] Wypler | Lesbian and Queer Sustainable Farmer Networks in the Midwest[END_REF] 2/ The collectives as complex organizations Analysis of the collectives' characteristics as potentially supporting farmers' transition towards sustainable agriculture. [START_REF] Vaarst | Danish stable schools for experiential common learning in groups of organic dairy farmers[END_REF][START_REF] David | Learning to think for ourselves: knowledge improvement and social benefits among farmer field school participants in Cameroon[END_REF][START_REF] Matuschke | Evaluating the impact of social networks in rural innovation systems: An overview[END_REF][START_REF] David | The impact of farmer field schools on human and social capital: a case study from Ghana[END_REF][START_REF] Michael Rosset | The Campesino-to-Campesino agroecology movement of ANAP in Cuba: social process methodology in the construction of sustainable peasant agriculture and food sovereignty[END_REF][START_REF] Schneider | No-tillage farming: co-creation of innovation through network building[END_REF][START_REF] Lubell | Extension 3.0: managing agricultural knowledge systems in the network age[END_REF][START_REF] Mashavave | Interaction patterns determining improved information and knowledge sharing among smallholder farmers[END_REF][START_REF] Charatsari | Building social capital and promoting participatory development of agricultural innovations through Farmer Field Schools: the Greek experience[END_REF][START_REF] Diaz-José | Innovation diffusion in conservation agriculture: a network approach[END_REF][START_REF] Manson | Modeling the effect of social networks on adoption of multifunctional agriculture[END_REF][START_REF] Aguilar-Gallegos | Social network analysis for catalysing agricultural innovation: From direct ties to integration and radiality[END_REF] 3/ The collectives as loci for knowing

Analysis of farmer-to-farmer interaction or multiactor one to understand the knowing process of farmers when they transition towards sustainable agriculture [START_REF] Millar | Moving farmer knowledge beyond the farm gate: an Australian study of farmer knowledge in group learning[END_REF][START_REF] Ridley | The role of farming systems group approaches in achieving sustainability in Australian agriculture[END_REF][START_REF] Lubell | Local diffusion networks act as pathways to sustainable agriculture in the Sacramento River Valley[END_REF][START_REF] Faysse | Local farmers' organisations: a space for peer-to-peer learning? The case of milk collection cooperatives in Morocco[END_REF][START_REF] Ingram | Agronomist-farmer knowledge encounters: an analysis of knowledge exchange in the context of best management practices in England[END_REF][START_REF] Murphy | The contribution of facilitated group learning to supporting innovation amongst farmers[END_REF][START_REF] Benyishay | Communicating with farmers through social networks[END_REF][START_REF] Kalra | Self-help groups in Indian agriculture: a case study of farmer groups in Punjab, Northern India[END_REF][START_REF] Curry | The role of tacit knowledge in developing networks for sustainable agriculture[END_REF][START_REF] Bruce | The CROPROTECT project and wider opportunities to improve farm productivity through web-based knowledge exchange[END_REF][START_REF] Burbi | The role of internet and social media in the diffusion of knowledge and innovation among farmers[END_REF][START_REF] Girard | The interplays between singularity and genericity of agroecological knowledge in a network of livestock farmers[END_REF][START_REF] Phillips | An investigation of social media's roles in knowledge exchange by farmers[END_REF][START_REF] Lucas | Local inter-farm cooperation: A hidden potential for the agroecological transition in northern agricultures[END_REF] 4/ Leaning process among collectives

Analysis of how collectives contribute to learning processes of farmers and under which condition it does in the context of transition towards sustainable agriculture [START_REF] Quiroz | The self-directed learning process in a selected group of adult farmers in Michigan[END_REF][START_REF] Millar | Moving farmer knowledge beyond the farm gate: an Australian study of farmer knowledge in group learning[END_REF][START_REF] Collins | Experiences from using Action Learning Groups to develop Sustainable Farming Systems for Central Queensland[END_REF][START_REF] Nerbonne | Rooted in grass: challenging patterns of knowledge exchange as a means of fostering social change in a southeast Minnesota farm community[END_REF][START_REF] Schneider | Social learning processes in Swiss soil protection -the "From Farmer-To Farmer" project[END_REF][START_REF] Morgan | Social learning among organic farmers and the application of the communities of practice framework[END_REF][START_REF] Anil | Strengthening the performance of farming system groups: perspectives from a Communities of Practice framework application[END_REF][START_REF] Kraaijvanger | Considering change: Evaluating four years of participatory experimentation with farmers in Tigray (Ethiopia) highlighting both functional and human-social aspects[END_REF][START_REF] Phuong | Using a social learning configuration to increase Vietnamese smallholder farmers' adaptive capacity to respond to climate change[END_REF][START_REF] Restrepo | Evaluating knowledge integration and co-production in a 2-year collaborative learning process with smallholder dairy farmer groups[END_REF] Kroma also argues that organic farming, as a form of agriculture that triggers an active involvement of farmers in experimentation, steers farmers towards collectives because access to ecological knowledge is less facilitated by research and extension institutions. [START_REF] Ingram | Technical and social dimensions of farmer learning: an analysis of the emergence of reduced tillage systems in England[END_REF] describes the social dimension at stake for farmers practicing tillage reduction. She argues that some individuals value learning by discussing problems when some others are reluctant to share knowledge and to interact with peers because of a fear of criticism, unwillingness to share information with a possible competitor, or a purist approach to reduced tillage technics. [START_REF] Hayden | The importance of social support and communities of practice: farmer perceptions of the challenges and opportunities of integrated crop-livestock systems on organically managed farms in the northern U[END_REF] address the challenges and opportunities that farmers experience when integrating crops and livestock on an organic farm. They consider collectives as communities of practices (CoP) and find they are an opportunity for the mitigation of the dominant farming system with providing an alternative normative environment and aid for management planning. CoP is described as "critical when deciding to try an integrated system, and vital for ongoing success in such systems". However, they also note that farmers are embedded in complex learning systems [START_REF] Oreszczyn | The role of networks of practice and webs of influencers on farmers' engagement with and learning about agricultural innovations[END_REF]) that make it difficult for farmers' collectives alone to meet all the challenges inherent in the transition process, such as financing and insurance, long-term horizons for returns, and county and farm infrastructure. Wypler (2019) also qualifies the influence of support collectives in terms of the effect of its inner dynamics, such as gender domination (e.g., heteropatriarchal discourses that deter LGBT farmers from participating). These authors thus provide a first glimpse of the interplay studied from the point of view of farmers' experiencing transition as they recognize support on addressing problems, accessing to alternative knowledge and norms, and motivation. However, these studies do not deal with the form of the collectives nor how they become part of the farmer's activity over time.

The collectives as complex Organizations

The second perspective encompasses research studies that specifically analyze the collectives and their characteristics that could influence the interplay between farmers' collectives and their transition to more sustainable agriculture. While some (3.2.1) focus more on the structure of the ties within the collectives to infer the way practices and knowledge spread within and out the collectives, others (3.2.2) pay attention to the methodologies built for the collectives to support the learning processes and then infer the interplay with farmers' transition. None of these approaches pays much attention to the processes taking place at individual level to achieve a transition towards more sustainable agriculture.

A focus on collectives' structure

Some papers [START_REF] Matuschke | Evaluating the impact of social networks in rural innovation systems: An overview[END_REF][START_REF] Lubell | Extension 3.0: managing agricultural knowledge systems in the network age[END_REF][START_REF] Mashavave | Interaction patterns determining improved information and knowledge sharing among smallholder farmers[END_REF][START_REF] Diaz-José | Innovation diffusion in conservation agriculture: a network approach[END_REF][START_REF] Manson | Modeling the effect of social networks on adoption of multifunctional agriculture[END_REF][START_REF] Aguilar-Gallegos | Social network analysis for catalysing agricultural innovation: From direct ties to integration and radiality[END_REF] draw on an analysis of the collectives' structure to inform the diffusion and adoption of sustainable practices. Most highlight the collectives' structure by the types of relations and the centrality of some clusters within the collectives and within the social landscape to infer its effect on farmers' decision-making and on innovation dissemination. [START_REF] Manson | Modeling the effect of social networks on adoption of multifunctional agriculture[END_REF] found that the widespread adoption of rotational grazing practices reflects existing social and spatial considerations: the number of dairy households in the area, the initial mix of farmers, the sharing of strong ties between neighboring farmers, and the role of space in how collectives are formed. [START_REF] Schneider | No-tillage farming: co-creation of innovation through network building[END_REF] adopts an actor-network theory approach [START_REF] Callon | Don't throw the baby out with the bath school! A reply to Collins and Yearley[END_REF] to highlight the fact that the no-tillage concept is a result of a network built between human (farmers, experts, scientists, etc.) and non-human actors (herbicides, earthworms, etc.). In this study, the collectives include a wide range of actors with specific activities that influence the evolution of the no-tillage concept over time and space, and transform each of the actors themselves. Nevertheless, such approaches give little empirical evidence of how the exchanges within the collectives contribute to the farmers' transition process towards more sustainable agriculture.

3.2.2. A focus on methodologies which support collectives

Some studies focus on the methodology of learning and diffusion that supports the collectives and they build correlations to infer the extent to which the collectives participate in the adoption of some practices or concepts related to agroecology. [START_REF] David | Learning to think for ourselves: knowledge improvement and social benefits among farmer field school participants in Cameroon[END_REF][START_REF] Vaarst | Danish stable schools for experiential common learning in groups of organic dairy farmers[END_REF][START_REF] David | The impact of farmer field schools on human and social capital: a case study from Ghana[END_REF][START_REF] Charatsari | Building social capital and promoting participatory development of agricultural innovations through Farmer Field Schools: the Greek experience[END_REF] to understand the effects of the program methodology on the social capital, knowledge adoption, experimentation and group formation. Based on a survey among FFS and non-FSS farmers about practices and knowledge acquired, [START_REF] David | Learning to think for ourselves: knowledge improvement and social benefits among farmer field school participants in Cameroon[END_REF] finds positive results on the effectiveness of the Cameroonian FFS for facilitating discovery learning. She also highlights participants' failure to retain or diffuse concepts and principles (i.e., agroecosystem analysis). On the other hand, [START_REF] Charatsari | Building social capital and promoting participatory development of agricultural innovations through Farmer Field Schools: the Greek experience[END_REF] find that bonding social capital is the most important aspect affecting farmers' engagement in the learning process.

These papers contribute to highlight some organizational characteristics of the collectives and how it influences the interplay with the farmers' transition through the diffusion of sustainable practices and knowledge. Though, these studies lack empirical elements to describe how farmers' interactions do contribute to farmers' transition pathway.

The collectives as loci for knowing

The third perspective encompasses research studies that address the way some practices or concepts or knowledge are discussed among collectives [START_REF] Ridley | The role of farming systems group approaches in achieving sustainability in Australian agriculture[END_REF][START_REF] Lubell | Local diffusion networks act as pathways to sustainable agriculture in the Sacramento River Valley[END_REF][START_REF] Faysse | Local farmers' organisations: a space for peer-to-peer learning? The case of milk collection cooperatives in Morocco[END_REF][START_REF] Girard | The interplays between singularity and genericity of agroecological knowledge in a network of livestock farmers[END_REF][START_REF] Lucas | Local inter-farm cooperation: A hidden potential for the agroecological transition in northern agricultures[END_REF]. For instance, in their study of the Pâtur'Ajuste collectives, [START_REF] Girard | The interplays between singularity and genericity of agroecological knowledge in a network of livestock farmers[END_REF] analyze the situated interactions between farmers and the development agent during collectives meetings in the field. They ground their approach in Dewey's pragmatism theory and used the experience categories of [START_REF] Rogalski | L'expérience professionnelle : expériences sédimentées et expériences épisodiques[END_REF] to highlight how farmers' exchanges refer to their local knowledge to infer the appropriate grazing practices and how the agents use this knowledge to argue their expertise. Other scholars focus more specifically on some variables which can explain the differences they identify between the ways such processes take place within collectives [START_REF] Ingram | Agronomist-farmer knowledge encounters: an analysis of knowledge exchange in the context of best management practices in England[END_REF][START_REF] Murphy | The contribution of facilitated group learning to supporting innovation amongst farmers[END_REF][START_REF] Benyishay | Communicating with farmers through social networks[END_REF][START_REF] Kalra | Self-help groups in Indian agriculture: a case study of farmer groups in Punjab, Northern India[END_REF][START_REF] Curry | The role of tacit knowledge in developing networks for sustainable agriculture[END_REF]. [START_REF] Benyishay | Communicating with farmers through social networks[END_REF] studied the effect of the position of the spokesperson (e.g., farmer leader, farmer peer) and found that peer farmers who faced conditions most comparable to those of the target farmers are the most persuasive about practice adoption. [START_REF] Ingram | Agronomist-farmer knowledge encounters: an analysis of knowledge exchange in the context of best management practices in England[END_REF] found evidence that farmer-agronomist interaction can be effective for knowledge exchange and practice transformation when it is built on a willingness to learn from each other, on an understanding of the farmer's situation, and on an accommodation of each other's knowledge. These papers address the interplay studied from the multiple functions and conditions that influence interaction and cooperation among farmers alone or with other stakeholders. However, the studies do not account for the way these elements process the farmers' transition.

Learning processes among collectives

Others analyzed the way the collectives contribute to foster learning processes among collectives [START_REF] Quiroz | The self-directed learning process in a selected group of adult farmers in Michigan[END_REF][START_REF] Millar | Moving farmer knowledge beyond the farm gate: an Australian study of farmer knowledge in group learning[END_REF][START_REF] Collins | Experiences from using Action Learning Groups to develop Sustainable Farming Systems for Central Queensland[END_REF][START_REF] Nerbonne | Rooted in grass: challenging patterns of knowledge exchange as a means of fostering social change in a southeast Minnesota farm community[END_REF][START_REF] Schneider | Social learning processes in Swiss soil protection -the "From Farmer-To Farmer" project[END_REF][START_REF] Morgan | Social learning among organic farmers and the application of the communities of practice framework[END_REF][START_REF] Anil | Strengthening the performance of farming system groups: perspectives from a Communities of Practice framework application[END_REF][START_REF] Kraaijvanger | Considering change: Evaluating four years of participatory experimentation with farmers in Tigray (Ethiopia) highlighting both functional and human-social aspects[END_REF][START_REF] Phuong | Using a social learning configuration to increase Vietnamese smallholder farmers' adaptive capacity to respond to climate change[END_REF][START_REF] Restrepo | Evaluating knowledge integration and co-production in a 2-year collaborative learning process with smallholder dairy farmer groups[END_REF]. For instance, [START_REF] Restrepo | Evaluating knowledge integration and co-production in a 2-year collaborative learning process with smallholder dairy farmer groups[END_REF] evaluated a two-year collaborative learning process for finding sustainable pathways to reduce milk losses, with two dairy farmer groups in Kenya. They used the evaluation framework of Kilpatrick (1998) to highlight: farmers' reactions about the process; learning in theory and practice, the change of action on the basis of the new knowledge; and the benefits from these changes. Based on farmers' answers, they showed that farmers learned by: (1) implementing corrective actions based on known cause-effect relations (single-loop learning); (2) discovering new cause-effect relations and testing their effect (double-loop learning); and (3) further questioning and changing their aims (triple-loop learning). Other authors used the Community of Practice (CoP) framework [START_REF] Lave | Situated learning: Legitimate peripheral participation[END_REF] to study the role of collectives in the dissemination of knowledge and their effectiveness in social learning [START_REF] Anil | Strengthening the performance of farming system groups: perspectives from a Communities of Practice framework application[END_REF][START_REF] Morgan | Social learning among organic farmers and the application of the communities of practice framework[END_REF]. For instance, [START_REF] Morgan | Social learning among organic farmers and the application of the communities of practice framework[END_REF] developed an understanding of the emergence, evolution and role of the groups in terms of social learning by describing: the "mutual engagement" of members through interaction and norms negotiated around their activity; "joint enterprises" that bind farmers together through a sense of mutual accountability; and "shared repertoire" of practices adopted by the members involved in the community.

Through the description of these dimensions for three groups of farmers converting to organic, Morgan (2011)concluded that social learning is influenced by the working style of farmers, as the interactions and degree of collaboration are differentiated on the basis of the perceived identity of peers as for instance the understanding of the organic agriculture concept. These papers address the interplay studied from the learning process that takes place among farmers' collectives whether it is an experiment or social-based process.

However, they do not enlighten how the learning process among collectives contribute to on-farm activity and how the farmers manage their learning process when facing so diverse working environments.

To sum up, this review highlights four perspectives from which scholars addressed the possible interplays between farmers' transition and the participation to collectives' exchanges (Figure 1). These four perspectives mobilize a wide range of theoretical and methodological approaches, leading to a non-unified vision. The interplays highlighted vary widely, thus revealing the complexity of the relationships that can exist between the farmers' transition and the participation of farmers in collectives or in groups of stakeholders who, to a greater or lesser degree, share the challenge of transitioning towards sustainability at the farm level.

4 Towards an integrative framework to explore the interplay between farmers' exchanges and transition towards sustainable transition

From an analysis of the review to the conceptual framework

In Section 3, we show that the studies which discuss the interplays between farmers' collectives and the transition to sustainability are far from providing a unified vision of how collectives and exchanges contribute to facilitating farmers' development of sustainable practices and knowledge. We lack information about how farmers' transition towards sustainable agriculture as a dynamic process in which collectives contribute to farmers' activity, and not only as a process of adopting farming practices considered to be more sustainable.

As our review has highlighted, transitioning involves many technical, social and educational dimensions; it makes it difficult to grasp how collectives actually contribute to this dynamic. We argue that an investigation of transition dynamics would afford some insight into the compromises constantly facing farmers within their process of transition and adaptation. It would also improve our understanding of the collectives' contribution to learning, guiding and rethinking the farmers' activity and their relationship to their working situations. To illustrate this claim, we could seek to understand how the collectives can support farmers in improving their capacity for critical analysis and action when they are faced with a specific problem, as Kroma (2008) has suggested.

Adopting such a perspective means understanding how exchanges match farmers' challenges and working environment, and how they influence their transition process. Beyond the question of adopting or changing Learning processes among collectives e.g., shared repertories, experimenting, etc.

Farmers rely on collectives during their transition e.g., find mutual support, motivation, reflection, trust, etc.

Collectives as complex organizations: e.g., learning methodologies, structural ties, etc.

Collectives as loci for knowing: e.g., conditions for effective facilitation, site-specific exchanges, storytelling, etc.

The interplays between farmers' exchanges among collectives and the transition process agricultural practices, various studies have shown that transitions towards more sustainable farming systems actually lead to transformations of the farmers themselves: their worldview, their values, their work organization, and so on [START_REF] Lamine | Transition pathways towards a robust ecologization of agriculture and the need for system redesign. Cases from organic farming and IPM[END_REF][START_REF] Chantre | Comment évolue l'expérience des agriculteurs engagés dans l'écologisation de leurs pratiques[END_REF][START_REF] Barbier | Cours de vie d'agriculteurs allant vers l'économie en intrants : les plaisirs associés aux changements de pratiques[END_REF][START_REF] Coquil | Professional transitions towards sustainable farming systems: The development of farmers' professional worlds[END_REF][START_REF] Cristofari | Supporting transition toward conservation agriculture: A framework to analyze the learning processes of farmers[END_REF][START_REF] Dupré | Diverse dynamics in agroecological transitions on fruit tree farms[END_REF][START_REF] Chizallet | Supporting farmers' management of change towards agroecological practices by focusing on their work: A contribution of ergonomics[END_REF][START_REF] Toffolini | Agroecology as farmers' situated ways of acting : a conceptual framework[END_REF]. Although such studies were conducted for various purposes and through different approaches, they all point out that the transition process towards sustainability is much more complex than just filling knowledge gaps or adopting new recommended practices [START_REF] Coquil | Questioning the work of farmers, advisors, teachers and researchers in agro-ecological transition[END_REF]. They show that the farmers experiencing such transition have to reconsider the entire relationship built with their human and non-human environment. They highlight the constant tensions between past experiences, organization and work routines, and the new knowledge, experiences, ways of thinking and expectations. To highlight this, most of these authors proceed by a retrospective long-term analysis of the transition process [START_REF] Lamine | Analyse des formes de transition vers des agricultures plus écologiques: Les cas de l'Agriculture Biologique et de la Protection Intégrée[END_REF][START_REF] Chantre | Comment évolue l'expérience des agriculteurs engagés dans l'écologisation de leurs pratiques[END_REF][START_REF] Coquil | Professional transitions towards sustainable farming systems: The development of farmers' professional worlds[END_REF], based on farmers' narratives. Only a few undertake a longitudinal approach to transition in the making, as [START_REF] Chizallet | Supporting the Design Activity of Farmers in Transition to Agroecology: Towards an Understanding[END_REF] have done.

So how can we understand this interplay between the dynamics of exchanges within the farmers' collectives, and the transition in which a farmer is engaged? How can we capture the way in which such collectives support farmers in overcoming the discontinuities that have been pointed out by some authors [START_REF] Beghuin | Dynamique identitaire, trajectoire biographique et apprentissage dans le processus de conversion d'agriculteurs « conventionnels » vers l'agriculture bio[END_REF] during the transition towards sustainability? The concept of experience as developed by [START_REF] Dewey | Logique: la théorie de l'enquête[END_REF] is key to our proposal, as it enables us to capture the diverse dimensions of the farmers' professional socio-ecosystem, including the contribution of collectives to transforming farmers' experience of their working environment.

A conceptual framework to analyze the processual interplay between farmers' collectives and their professional transition

Defining professional transition

As highlighted in the review, studying the interplays between collectives and farmers' transition goes along with studying their knowing and learning processes, not only what they are learning, but how they do so and what triggers it. Our conceptual framework is a continuation of these approaches intended to show how learning and change can occur in the flow of a farmer's activities. As there is no unified definition of transition in the papers that we reviewed, We considered studies that consider sustainable transition as professional transformation [START_REF] Chantre | Transitional pathways towards input reduction on French field crop farms[END_REF][START_REF] Coquil | Professional transitions towards sustainable farming systems: The development of farmers' professional worlds[END_REF][START_REF] Chizallet | Supporting the Design Activity of Farmers in Transition to Agroecology: Towards an Understanding[END_REF]. Following Masdonati and Zittoun (2012), we suggest that such transitions are characterized by three interdependent processes:

-Identity remodelling induced by the change of position in a given social field, and by the dynamics of peer recognition or lack of recognition; -Acquisition of new social, professional, cognitive and technical skills to act on new work situations through engagement in learning or adjustment; -Construction of meaning in the individual's experience. This involves standing back from a lived experience and reframing it, as compared to previous experiences. The emotional experience of these transitions, as well as evaluations of situations of past experiences, can then be integrated, thus contributing to the reconstruction of continuity in the individual's pathway.

Although this type of description is usually used in psycho-sociology to describe phenomena such as professional conversion, we found it relevant to the changes that underlie transition towards more sustainable agriculture at an individual level. It allows us to explore such transitions by considering changes in the praxis, identity, cognitive, social and experiential dimensions of individuals. Our framework is thus designed to identify how exchanges among collectives support the three interdependent processes. It is nevertheless difficult not to get lost in the complexity of these processes due to their personal nature, which is why we mobilize pragmatist theory to partially overcome these pitfalls, as explained below.

Experience as a fruitful concept

We postulate that farmers' professional transitions are processes in which their experiences are reframed in order to transform not only their farming activities but also themselves. As Dewey (1887) described and Bourgeois (2013) later emphasized, experience includes interdependent dimensions (cognitive, affective, conative, and body) that together contribute to individual coherence and continuity in the flow of one's activity.

Although experience is far from being a simple concept to work with, given its polysemic nature [START_REF] Rogalski | L'expérience professionnelle : expériences sédimentées et expériences épisodiques[END_REF][START_REF] Beaujouan | Quelle place tient l'expérience des autres dans la formation d'un professionnel ? Apport et limite du récit professionnel[END_REF][START_REF] Osty | Devenir un professionnel : le rôle multiforme de l'expérience[END_REF][START_REF] Barbier | Le Travail de l'expérience[END_REF][START_REF] Maillot | La transition professionnelle, "expérience de soi" face au changement[END_REF], we think it is a fruitful direction for understanding how the links are woven between the farmers' activity and the multiple resources they act with. In particular, in the context of sustainable agriculture where some scholars are calling for a profound redesign of farming systems, considering farmers' experience seems an interesting way to understand how they manage discontinuity and continuity on their pathways. Yet the transformation of farmers' experience can go unseen [START_REF] Jullien | Les transformations silencieuses[END_REF], especially when the focus is only on long trajectories and critical events on their pathway. It is therefore necessary to look at the lived situations affecting the individuals in the flow of their activities, and not only the technical ones but more broadly also those which they consider as crucial for being effective and efficient in their lives, at least from a professional point of view. As experience transforms, individuals review their previous experiences from a new perspective, develop useful resources to act on and with the environment, and put their experience into words to create a common understanding with others (Thievenaz, 2019). Dewey argued that experience emerges from reflexively linking one's action with the consequences: "When an activity is continued into the undergoing of its consequences, when the change made by action is reflected upon into a change made into us, the flux is loaded with significance" [START_REF] Dewey | Democracy and education: An introduction to the philosophy of education[END_REF]cited in McDermott, 1973: 495)

The experiential environment transformation

To further understand the processes of experience reframing, the pragmatist perspective leads us to focus on farmers' work situations. These situations are considered not as contexts, but as "experiential environments" [START_REF] Dewey | Logique: la théorie de l'enquête[END_REF]. They are not only environments in which individuals live, but environments that offer the means through which and on which the individuals have to act and build compromises. In their environments, farmers must act on or with the agroecosystem and with many technical, material, economic and social dimensions. Moreover, the farmers as subjects are not neutral, they influence their environment through their way of acting, thinking, valuing, being affected, and so on, which make the "experiential environment" singular. We introduce this notion because we believe that we could improve our understanding farmers' transition by investigating not only the structures of their farming activities but also the significance of every relationship they built in working with their environment, whether it is conflictual, binding or facilitating. So how is the experiential environment transformed? Dewey argued that not every working situation encountered by individuals is equivalent in its ability to reframe their experience.

He pointed out that specific situations trigger the transformation of experiential environments: the indeterminate situations which arise from an individual's ability to be surprised, embarrassed, doubtful, and so on. In these situations, the individual experiences a tension caused by a rupture between the known means to deal with a situation and the actual consequences. To resolve this tension and go back to a balanced experiential environment, the individual has to be involved in building and experimenting new means of action. Dewey thus put forward a learning theory, the inquiry (1938), to describe how individuals shift from an indeterminate situation to a well-balanced experiential environment. The inquiry process helps not only to understand the links between action and its consequences, but also to understand them in a way that supports new means of action to restore the flow of their activity. The inquiry is an iterative process through which individuals identify and formulate what composes the problem in the situation, suggest possible solutions, use deductive reasoning to identify the most feasible and effective solution, and finally experiment with the solutions temporarily chosen. The inquiry process ultimately makes it possible to produce intelligibility in the situation and new means, which make it possible to re-establish continuity in action and consequently the continuity of the individual's experience and meaning. This process is not linear; it unfolds over time and through diverse work and personal situations. We therefore propose to rethink the learning of farmers in transition as a process of inquiry embedded in their experiential environment.

Inducing inquiry to support farmers' transition

Seeing how the experiential environment is transformed through inquiry leads us to an interesting path to understand the interplay we want to explore. In fact, we believe that the interplay is about collectives supporting the inquiry process of farmers transforming their experiential environment. To analyze this support, we draw on studies from the educational field, such as that of [START_REF] Fabre | Les inducteurs de problématisation[END_REF] about inducing problematization behaviors, [START_REF] Wood | The role of tutoring in problem solving[END_REF] and [START_REF] Vial | L'accompagnement professionnel. Méthode à l'usage des praticiens exerçant une fonction éducative[END_REF] about scaffolding as a support to problem-solving, and [START_REF] Mayen | Apprendre à travailler avec le vivant: développement durable et didactique professionnelle[END_REF][START_REF] Mayen | Apprendre à travailler avec le vivant: développement durable et didactique professionnelle[END_REF][START_REF] Mayen | S'écarter du travail pour mieux l'apprendre: Une réflexion pour l'ingénierie de formation en situation de travail et pour la conception d'organisations apprenantes[END_REF] about learning from working situations.

Supporting inquiry is about fostering some inducers of the inquiry by taking into account the experiential environment, whether by problematizing a situation experienced by a farmer or by introducing new inferences built on cognitive, affective, conative and body-part dimensions, to build new means. Figure 2 summarizes these theoretical propositions.

As Dewey argued in his judgment theory (1938), not all suggestions are to become ideas for the one experiencing indeterminacy: "The suggestion becomes an idea when we wonder whether it is functionally appropriate; if it can be a way to solve a given situation " (1938: 175). Thus, supporting the inquiry process cannot be disconnected from knowing the farmers' experiential environments to understand their point of view on the problems they face. This is why we think that "peer" collectives are a most relevant space [START_REF] Ruault | Le conseil de groupe dans le développement agricole et local: pour quoi faire et comment faire[END_REF] to address and support the inquiry. [START_REF] Darré | La production des normes au sein d'un réseau professionnel L'exemple d'un groupe d'éleveurs[END_REF] showed that "peers" are the ones who share professional norms and common concerns about their activities to develop concrete solutions. Guiding the AKIS players and multi-actor collectives towards the support of inquiry that arises from individuals and their own concerns can therefore be an interesting avenue to address sustainable agriculture challenges. As [START_REF] Ruault | Le conseil de groupe dans le développement agricole et local: pour quoi faire et comment faire[END_REF] put it, building "relevant collectives" suggests the need to "adapt the configuration of the group and the scale of work according to the nature and progress of the problems."

Some methodological considerations

From a methodological point of view, this is a matter of building a framework to study, over time, both the exchanges in collectives and the experiential environment of farmers who are actively involved in transition.

Longitudinal follow-up of farmers' collectives engaged in transition towards more sustainable agriculture will make it possible to collect the content exchanged, that is, data on the exchange situation, and to analyze it through the lens of whatever induces and supports inquiry. At the same time, based on elicitation methodology [START_REF] Vermersch | L'entretien d'explication[END_REF], interviews with the farmers participating in the collectives will make it possible to examine their overall experiential environments at a given point in time, and to look at how the exchanges are or are not transforming them. To capture this transformation, it is also necessary to look at the way in which the farmers are affectedwhat disturbs, contradicts, pleases, or frightens themto highlight a potential process of inquiry. We can thus investigate the element of the experiential environment that is indeterminate.

Conclusion

In this article, we highlighted the interplay between exchanges among farmers' collectives and farmers' transition towards more sustainable agriculture, by first conducting a comprehensive literature review and then proposing a conceptual framework. Our analysis of the literature points to a variety of possible approaches and interpretations for understanding the contribution of collectives to farmers' transition to sustainable agriculture, as perceived from multiple angles. But our review also reveals that the way the collectives affect a farmer's transition process (his/her way of farming, thinking and being a farmer) remains a blind spot. We therefore propose a conceptual framework based on Dewey's pragmatism and the developmental approaches inspired by it. The framework suggests considering the transformation of farmers' experiential environment through peer collectives' support of their inquiry process. Such an approach could lend more substance to an exploration of "the power of collectives", so often put forward as a key factor in the dynamics of supporting transitions to sustainability.

Our work led us to consider farmers' transitions as professional transitions, in particular through the concept of the experiential environment. [START_REF] Brédart | When farmers learn through dialog with their practices: a proposal for a theory of action for agricultural trajectories[END_REF] seem to go in a similar direction, highlighting the fact that farmers learn through "dialog" with their practices, as they give meaning to events and link them to the course of action. This concept of dialog does not however explain the structural obstacles and opportunities in the transformation of farming systems [START_REF] Rodriguez | Barriers to adoption of sustainable agriculture practices: Change agent perspectives[END_REF]. It supports the idea that farmers construct a singular meaning of them, through a point of view on the situation. The concept of experiential environment makes it possible to investigate the farmers' perception of the problems to be addressed in their working situations. It thereby enables us to recognize that farmers' working situations are singular and that not all individuals have the same ability and means to address their problematic situations. It suggest that experiential learning among farmers' as addressed by [START_REF] Chantre | Apprentissages des agriculteurs vers la réduction d'intrants en grandes cultures : Cas de la Champagne Berrichonne dans les années 1985[END_REF] and [START_REF] Catalogna | Diversity of experimentation by farmers engaged in agroecology[END_REF] is to be addressed through critical thinking of the functional balance of new inferences in the situation. As [START_REF] Heinrich | Critical thinking assessment across four sustainabilityrelated experiential learning settings[END_REF] emphasized, to operationalize experiential learning we have to consider farmers' zone of proximal development [START_REF] Vygotsky | Interaction between learning and development[END_REF], to help them connect new knowledge and situations with their familiar work situations they already understand. This work is in line with previous studies that highlight the necessity to break away from the diffusion of innovation paradigm [START_REF] Cerf | Contrasting intermediation practices in various advisory service networks in the case of the French Ecophyto plan[END_REF] and to focus more on horizontal experience-based exchanges which can afford new perspectives for innovative training strategies for rural extensionists [START_REF] Landini | Towards a new paradigm for rural extensionists' in-service training[END_REF]. It argues for a renewed vision of farming transitions which transforms not only technical dimensions but also farmers themselves as subjects and workers, as [START_REF] Coquil | Professional transitions towards sustainable farming systems: The development of farmers' professional worlds[END_REF] have already highlighted. It also describes an iterative process of constant readjustment [START_REF] Brédart | When farmers learn through dialog with their practices: a proposal for a theory of action for agricultural trajectories[END_REF] of farmers' experiential environment, and emphasizes the transformation of farmers' work as an interesting entry to address farmers' transition. This opens up the question of the ability of advisory services to provide support based on the involvement of farmers in their own problematization of their experiential environment. Our work suggests that support is not only about sharing innovative practices among collectives, whether composed of peers or other stakeholders as in PEI-AGRI focus groups, and should rather consider inducing and facilitating inquiry among relevant collectives that share common concerns. In managing innovation processes [START_REF] Klerkx | Evolution of systems approaches to agricultural innovation: concepts, analysis and interventions[END_REF] one has to consider using experiments or generic knowledge when it can nourish the farmer's perception of the problem and its resolution. Developing skills that support farmers' inquiry process can be considered as an intermediation skill to help on-farm redesign [START_REF] Cerf | Contrasting intermediation practices in various advisory service networks in the case of the French Ecophyto plan[END_REF] to overcome cognitive and psycho-affective barriers. We also suggest that such skills could benefit from professional discussions among advisers on their own work situations [START_REF] Cerf | Acting as a Change Agent in Supporting Sustainable Agriculture: How to Cope with New Professional Situations[END_REF] to help them become more aware of how they think about their work and interact with farmers [START_REF] Cerf | Designing support to enhance co-operation between farmers and advisors in solving farmmanagement problems[END_REF][START_REF] Coquil | Questioning the work of farmers, advisors, teachers and researchers in agro-ecological transition[END_REF]. The role of AKIS players is crucial as it has to support inducing inquiry, through dialog, and provide farmers with relevant information, according to the problem to be solved.

Appendix

Table 3. Excerpt of the analysis framework of the reviewed papers.

  g. sustain) to capture all possible forms (e.g. sustaining, sustainable) Title= (farm* OR agro* OR agri*) AND Topics= (*ecolog* OR sustain* OR innov*) AND Topics= (transit* OR learn* OR pathway* OR trajector* OR road*) AND Title= (*group* OR network* OR exchang* OR dialog* OR cooperat* OR shar* OR social) AND Topics= (experi* or know* or practice*) AND Topics= (indigen* OR local* OR empiri* OR tradition* OR peer* OR peasant* OR farm* OR tacit)

  For instance, Rosset et al. (2011) study the Campesino a Campesino movement in Cuba, based on Freire horizontal communication. The collective is built on "farmer-promoters" who devise new solutions or revive traditional ones, and who use popular education methodology to share them with their peers who have the same problems. In Cuba, this movement is led by a local association that structures collectives including farmer-promoters, communication facilitators, collectives' coordinators, etc. Rosset et al. (2011) study the influence of these collectives from a quantitative point of view (i.e., the number of family farmers engaged in the process of agroecological farming) and describe the evolution of farming practices in Cuba since 1959. Other scholars studied Farmer Field School (FFS) cases

Furthermore,

  [START_REF] Lucas | Local inter-farm cooperation: A hidden potential for the agroecological transition in northern agricultures[END_REF] considered the arrangements that take place in inter-farm co-operation collectives to understand their contribution to sustainable transition processes. She analyses several French machinery co-ops (CUMA) through an analytical framework in which she identifies the multidimensional nature of the co-operation, its processual nature (e.g., technical dialogues, sharing arrangements, etc.) and its positive or negative effects. She specifies five ways in which local inter-farm co-operation helps farmers in the development of sustainable agriculture: the satisfaction of new material needs induced by diversification, the facilitation of self-provisioning, and the reorganization of work patterns, the management of uncertainty and risk, and the emergence of technical dialogues that encourage the coproduction of local knowledge. Some scholars also studied the contribution of digital collectives to the farmer-to-farmer communication or the farmer-to-extension services one[START_REF] Bruce | The CROPROTECT project and wider opportunities to improve farm productivity through web-based knowledge exchange[END_REF][START_REF] Burbi | The role of internet and social media in the diffusion of knowledge and innovation among farmers[END_REF][START_REF] Phillips | An investigation of social media's roles in knowledge exchange by farmers[END_REF].[START_REF] Phillips | An investigation of social media's roles in knowledge exchange by farmers[END_REF] analyzed the content of Facebook groups and interpreted the use of publishing and commenting as a supportive and positive contribution to the validation of knowledge, the on-farm decision-making, changes in farm management thinking, modes of operation, and strategic management. They argue that personal storytelling occurring in the conversations is a powerful and effective without necessarily having existing social relationships.

Figure 1 .

 1 Figure 1. Organizing the literature review to see the way authors address farmers' transition processes, exchanges in the collectives and the links between the two in relation to sustainable agriculture.

Figure 2 .

 2 Figure 2. The conceptual framework describing the processual interplay between farmers' experiential environment and the peer collectives support for the inquiry process

1: Broad paper search Step 2: Merge and eliminate duplications and thematically irrelevant articles by reading titles Step 3: Eliminate articles which do not correspond to the thematic focus, by reading abstracts Step 4: Eliminate articles after a first reading (or the ones not available) Web Of Science: 128 CABI: 220 227 88 6Table 2 .

 2 The papers which we attributed to one or more perspectives on the interplay between individuals' transition and farmers'

	collectives dynamics.

Footnotes

1 Minister of Agriculture, Agri-Food and Forestry (2014). First International Symposium on Agro-ecology at FAO: Food Security and Nutrition as Major Issues. Press release. 2 Supporting collectives and the next CAP, a proposed framework from three organizations participating in Another Common Agricultural Policy (CAP) platform: CIVAM, TRAME and CUMA.

Acknowledgement

We would like to thank the CASDAR project Agor@gro, AgroParisTech and the department ACT of INRAE for the financial support. We also thank the reviewers for their precious and helpful advice and Liz Carey Libbrecht for language editing the English version of this paper.