Anthony Favier
email: anthony.favier@laas.fr

Shashank Shekhar
email: sshekhar@laas.fr

Rachid Alami
email: rachid.alami@laas.fr

Robust Planning for Human-Robot Joint Tasks with Explicit Reasoning on Human Mental State

We consider the human-aware task planning problem where a human-robot team is given a shared task with a known objective to achieve. Recent approaches tackle it by modeling it as a team of independent, rational agents, where the robot plans for both agents' (shared) tasks. However, the robot knows that humans cannot be administered like artificial agents, so it emulates and predicts the human's decisions, actions, and reactions. Based on earlier approaches, we describe a novel approach to solve such problems, which models and uses execution-time observability conventions. Abstractly, this modeling is based on situation assessment, which helps our approach capture the evolution of individual agents' beliefs and anticipate belief divergences that arise in practice. It decides if and when belief alignment is needed and achieves it with communication. These changes improve the solver's performance: (a) communication is effectively used, and (b) robust for more realistic and challenging problems.

Introduction

Consider a scenario where you (the human agent) want to prepare, together with a robot, some pasta in your kitchen. This joint task comprises several components and activities, e.g., pasta is kept either in the kitchen or the living room, covering a pot, turning a furnace on, the salt container, adding salt to the pasta, etc. Sometimes, some components and activities might be accessible only to you (the robot) from your (its) current position, while some are accessible to both. Like this subclass of joint task, its multiple instantiations exist across many real-world domains, e.g., homes, offices, hospitals, etc.

Naturally, while achieving such tasks, you would want a pleasant and flexible collaboration. This involves behaviors like not being bothered too much by the robot or being able to delegate tasks to it, even if it delays the overall process. Here, we consider the human agent cooperative and rational but cannot be administered like a robot (a controllable agent). So, if the human agent has several ways to achieve a goal or accomplish a task, the robot cannot instruct them explicitly which one to choose. However, it can still act to influence their choices, thus eliciting future actions.

Presented at the AI-HRI Symposium at AAAI Fall Symposium Series (FSS) 2022

The above example outlines an important point about human-robot collaboration. The robot should not only plan for agents' joint actions but also predict and emulate human decisions, actions, and reactions, to achieve a joint goal seamlessly. It must put itself in the shoes of the human in order to better predict their decisions based on an accurate estimation of their beliefs; this would open the possibility for the robot to "create" circumstances that promote actions to be performed by humans and relevant to achieving the joint task or to prevent them from making errors based on false, outdated or inaccurate beliefs.

Human-aware planning has been a topic of interest, and a framework proposed and upgraded over the years is called HATP (Human-Aware Task Planner) [START_REF] Alami | Toward Human-Aware Robot Task Planning[END_REF][START_REF] Alili | A task planner for an autonomous social robot[END_REF][START_REF] Lallement | HATP: An HTN planner for robotics[END_REF][START_REF] Lallement | HATP: hierarchical agent-based task planner[END_REF]. Precisely, the HATP framework extends the existing Hierarchical Task Network (HTN) framework [START_REF] Ghallab | Automated planning -theory and practice[END_REF], extending its representation and semantics to make it more suitable for robotics and, more specifically, human-robot collaboration. The agents become the first class entities while "social rules" are added to classify planned behaviors for the robot as (un)acceptable.

A more elaborate planning architecture, inspired by HATP although extends HTNs differently, has been recently proposed [START_REF] Buisan | A Human-Aware Task Planner Explicitly Reasoning About Human and Robot Decision, Action and Reaction[END_REF][START_REF] Buisan | HATP/EHDA: A Robot Task Planner Anticipating and Eliciting Human Decisions and Actions[END_REF]. It introduced the first planning framework of this type, discussing the abilities and framework's broad spectrum. It is called HATP/EHDA, which extends HATP by emulating human decisions and actions. The new planning scheme raises several interesting, non-trivial questions to be investigated, and their principled will improve the proposed HAT-P/EHDA framework toward task-level autonomy for humanrobot interaction or human-robot collaboration.

HATP/EHDA comprises a dual-HTN structure that can be seen as a joint hierarchical task specification model. We assume such specifications are given by a domain modeler. The joint model describes agents' capabilities, initial beliefs, shared tasks, world dynamics, understanding of common ground, etc. Moreover, the modeler implicitly captures hypothetical variables to represent the human mood, intentions, etc., that are non-trivial to manage explicitly but "affect" the human behavior.

HATP allows only one search thread for a shared plan, re-sulting in two coordinated plan streams for the robot and human team. However, HATP/EHDA proposed a two-threaded search process, generating a policy tree comprising both agents' actions. The human agent is uncontrollable, so it is not trivial to determine their exact "next" feasible action for the overall joint task. It captures the impact of their mental state, mood, intention, etc. Also, it is important to note that both the robot's and human's HTNs are within the robot. At each stage, it must plan their joint actions following the specifications while predicting, managing, and emulating human's decisions, goals, beliefs, etc. However, the current implementation of the HATP/EHDA framework makes some simplistic assumptions. E.g., an action performed by an agent would also impact the beliefs of other agents, i.e., considering that other agents are always aware of the action execution and share the same perspective as the actor. In reality, a robot's action can influence human's beliefs differently under different scenarios. For example, adding salt to the pasta or switching on the furnace (in the kitchen) would impact the human's belief state differently depending on whether the human is also in the kitchen or not at the time of action execution.

We introduce a novel paradigm for implementing suitable conventions understood during plan execution in this context. This paradigm helps upgrade the HATP/EHDA's planning system. A high-level idea to formalize it is inspired by existing situation assessment reasoners which perform spatial reasoning and perspective taking [START_REF] Flavell | Perspectives on perspective taking[END_REF][START_REF] Trafton | Enabling effective human-robot interaction using perspective-taking in robots[END_REF][START_REF] Johnson | Perceptual perspective taking and action recognition[END_REF][START_REF] Sisbot | Situation assessment for human-robot interactive object manipulation[END_REF][START_REF] Warnier | When the robot puts itself in your shoes. Managing and exploiting human and robot beliefs[END_REF][START_REF] Lemaignan | Artificial Cognition for Social Human-Robot Interaction: An Implementation[END_REF]. The upgraded planning system handles divergences in human-robot individual beliefs (computed using our proposed model) and plans with explicitly modeled communication actions such that it tackles belief divergences via communication, if and when needed.

Effective use of a communication modality is essential to achieve the motivation behind their development, say, a seamless collaboration. However, in reality, communication incurs some costs. Moreover, in human-robot interaction (HRI), communicating too much or too little can disturb the overall task achievement process. Hence, deciding "how" to communicate is crucial, but it is equally crucial to decide, "if", "when", and "what" to communicate. Assume that a speech modality is available while the decisional aspect of communication is handled by the new solver with an enhanced reasoning system on the human mental state.

Related Work

Several attempts to model human activities are made such that these models are used to design a system, which integrates into another paradigm dealing with human tasks to improve the latter's performance.

A common way to represent human activity and interaction with a computer at an abstraction level is by using task models. The hierarchical structure of activities was first exploited by [START_REF] Annett | Task analysis and training design[END_REF], and they said a task could be seen at several abstraction levels until some criterion is satisfied. Each can, thus, refine into more concrete subtasks detailing the procedure followed by the hu-man to achieve the higher-level task. Task modeling evolved to introduce system interactions, produced and needed information, potential errors, and a variety of operators specifying how tasks interact with each other during their execution. Task models' usage is common in user-centered and user interface designing processes. Most advanced notations include CONCURTASKTREES [START_REF] Paternò | ConcurTaskTrees: an engineered notation for task models. The handbook of task analysis for humancomputer interaction[END_REF]) and HAMSTERS [START_REF] Martinie | Analysing and demonstrating tool-supported customizable task notations[END_REF]. Such models are used for designing or evaluating interactive systems, provide a task understanding, and inspire this work since they share a highlevel architecture with HTNs.

Previous approaches are based on decomposing tasks hierarchically to human-aware task planning and assume a fully controllable and cooperative human agent willing to participate in achieving a joint-goal [START_REF] Alami | Toward Human-Aware Robot Task Planning[END_REF]Alili et al. 2009;[START_REF] Lallement | HATP: An HTN planner for robotics[END_REF][START_REF] De Silva | The HATP hierarchical planner: Formalisation and an initial study of its usability and practicality[END_REF][START_REF] Lallement | HATP: hierarchical agent-based task planner[END_REF]. Moreover, the agents are assumed to have established a shared goal before planning. Later, the generated plan gets shared with the human before the execution [START_REF] Milliez | Using human knowledge awareness to adapt collaborative plan generation, explanation and monitoring[END_REF]. We note that HATP does not represent humans as regular agents with separate decision processes, which may lead to diverging plans without robot communication.

Other approaches are distantly related to what we do, consider an external human model (e.g., Agent Markov Models (AMMs) (Unhelkar, Li, andShah 2020a, 2019)), which predicts human activities, and hence the robot plans accordingly [START_REF] Hoffman | Effects of anticipatory action on human-robot teamwork efficiency, fluency, and perception of team[END_REF]Unhelkar, Li, andShah 2020a, 2019). Such systems can determine actions that influence human future actions. While some systems interact with humans even when they are non-collaborating (Buckingham, Chita-Tegmark, and Scheutz 2020).

In human psychology, especially in human-human interaction or collaboration, spatial reasoning and perspectivetaking are crucial [START_REF] Flavell | Perspectives on perspective taking[END_REF][START_REF] Tversky | Why do speakers mix perspectives? Spatial cognition and computation[END_REF]. Through them, a person can mimic the mind of another person to understand their point of view. Indeed, Theory of Mind (ToM) refers to the ability to ascribe distinct mental states to other people and update them by reasoning about their perceptions and goals [START_REF] Premack | Does the chimpanzee have a theory of mind?[END_REF][START_REF] Baron-Cohen | Does the autistic child have a "theory of mind[END_REF].

Ideas from psychology got employed in many humanrobot contexts. In robotics, ToM often focuses on perspective taking and belief management such that a robot reasons out what humans can perceive [START_REF] Berlin | Perspective taking: An organizing principle for learning in human-robot interaction[END_REF][START_REF] Milliez | A framework for endowing an interactive robot with reasoning capabilities about perspective-taking and belief management[END_REF]) and builds representations of the environment from their perspective, which sometimes helps solve ambiguous tasks, predict human behavior, etc. [START_REF] Johnson | Perceptual perspective taking and action recognition[END_REF] propose a method based on visual perspective taking for a robot recognizing an action executed by another robot. While [START_REF] Milliez | A framework for endowing an interactive robot with reasoning capabilities about perspective-taking and belief management[END_REF] propose visual and spatial perspective taking to find out the referent indicated by the human. In [START_REF] Sisbot | Situation assessment for human-robot interactive object manipulation[END_REF], based on spatial reasoning and perspective taking, a reasoner generates online (symbolic) relations between agents and objects co-present in the environment. Such relations are stored in databases, allowing access to the complete framework, and used for planning, acting, or both.

The framework proposed in [START_REF] Devin | An implemented theory of mind to improve human-robot shared plans execution[END_REF] al-lows the robot to estimate the mental state of the human, which contains not only the human's belief but their actions, goals, and plans. It supports the robot's capabilities to do spatial reasoning w.r.t. the human and track their activities.

In particular, it shows how to manage the execution of shared plans in a collaborative object manipulation context and how a robot can adapt to human decisions and actions while communicating when needed. This work is motivated by the main ideas of ToM [START_REF] Devin | An implemented theory of mind to improve human-robot shared plans execution[END_REF] and situation assessment based on spatial reasoning and observability while abstractly employing them during planning.

Communication is a key to successful human-robot collaboration, used to align an agent's belief, clarify its decision or action, fix errors, etc. [START_REF] Tellex | Asking for Help Using Inverse Semantics[END_REF][START_REF] Sebastiani | Dealing with on-line human-robot negotiations in hierarchical agent-based task planner[END_REF]. We already discussed the ToM-enabled framework by [START_REF] Devin | An implemented theory of mind to improve human-robot shared plans execution[END_REF]. The framework handles execution time subtleties such that it decides at the execution time if communication is needed and then the content that should be transmitted. They achieve it by monitoring the divergence between the robot knowledge and the estimated human knowledge. If a belief divergence is detected that can endanger the plan, then verbal communication takes place. Recent work deals with an explicit usage of communication actions in planning [START_REF] Buisan | Human Aware Task Planning Using Verbal Communication Feasibility and Costs[END_REF][START_REF] Nikolaidis | Planning with verbal communication for human-robot collaboration[END_REF][START_REF] Roncone | Transparent role assignment and task allocation in human robot collaboration[END_REF][START_REF] Sanelli | Short-term human-robot interaction through conditional planning and execution[END_REF]Unhelkar, Li, and Shah 2020b). E.g., in [START_REF] Roncone | Transparent role assignment and task allocation in human robot collaboration[END_REF]Unhelkar, Li, and Shah 2020b), the authors represent and plan with explicit communication actions, considering them as regular POMDP actions, such that execution policies generated contain communication actions.

However, this work estimates the evolution of the agents' beliefs and decides "if" and "when" belief alignment is necessary for planning. And, it is achieved via explicit communication actions, answering "what" to communicate. Our solver does not use these actions (for the deliberation process) like (non-) primitive tasks but to minimally align an agent's belief with the ground reality so that the belief divergence does not impact the overall task achievement. At each stage, if needed, a sequence of communication actions is computed by a modified Breadth-First Search planning subroutine and appended to the sender's plan. We provide clarification on this when we formalize our contributions.

Relevant Background Hierarchical Task Networks

Generalized basic terminologies and definitions related to HTNs are presented, e.g., task network, problem, and solution definitions [START_REF] Ghallab | Automated planning -theory and practice[END_REF].

A task network is a 2-tuple w = (U, C), where u ∈ U is a task node, while t u is the task associated to this node. C is the set of constraints -including orderings between task nodes, binding constraints, etc. If ∀u ∈ U , t u is a primitive task, the task network is primitive; otherwise, non-primitive. Definition 1. (HTN Planning Problem.) The HTN planning problem is a 3-tuple P = (s 0 , w 0 , D) where s 0 is the initial belief state (the ground truth), w 0 is the initial task network, and D is the HTN planning domain which consists of a set of tasks and methods.

A domain is a 2-tuple D = (O, M ) where O is the set of operators and M is the set of methods. An operator o ∈ O is a primitive task described as o = (name(o), pre(o), eff(o)), i.e., its name, precondition, and effect, respectively.

A task consists of a task symbol and a list of parameters. It is called a primitive task if its task symbol is an operator name and its parameters match, otherwise, it is a nonprimitive task. A primitive task is assumed to be directly executable, while to execute a non-primitive task, we need to decompose it into sub-tasks using methods.

A method (m

∈ M ) is a 4-tuple m = (name(m), task(m), subtasks(m), constr(m))
which are method name, a non-primitive task, a set of sub-tasks, and a set of constraints, respectively. m is relevant for a task t, if for a parameter substitution σ, σ(t) = task(m). There could be different methods relevant for a single task t, decomposing it differently, depending on the context.

(subtasks(m), constr(m)) is a task network in m.
Suppose m is an instantiated method, and task(m

) = t u then m decomposes u into subtasks(m ′ ), produc- ing a new task network, δ(w, u, m) = ((U -{u}) ∪ subtasks(m ′ ), C ′ ∪ constr(m ′ )).
Here, every precedence, before, after, and between constraints between tasks are carefully maintained after each decomposition.

Definition 2. (Solution Plan.) A sequence of primitive ac- tions π = (o 1 , o 2 , o 3 ..., o k
) is a solution plan for the HTN planning problem P = (s 0 , w 0 , D) iff there exists a primitive decomposition w p (of the initial task network w 0 ), and π is an instance of it.

The HATP/EHDA Framework

The framework comprises a dual-HTN based joint-task specification model. For ease of exposition, consider a team of a single human and a single robot. Two categories: the robot model, HTN r , represents the task specifications for the controllable agent, while HTN h , represents the model for the human, who is an uncontrollable one but the planner has its model representation and relevant interpretations to predict and emulate their decisions, actions, and reactions.

We restrict the framework's description to what is relevant but briefly discuss its ability to capture a broad class of scenarios. It supports the robot to act in the presence of a human agent even when they do not share a task to achieve in the beginning. Or, it can also support the robot planning for both agents by asking the human to help it occasionally, can manage the creation of shared tasks, handle human reactions modeled explicitly via triggers, etc. More details on triggers in [START_REF] Ingrand | PRS: A high level supervision and control language for autonomous mobile robots[END_REF][START_REF] Alami | An Architecture for Autonomy[END_REF].

A brief working description of the HATP/EHDA framework is as follows. The structure manipulated by it is "agent" [START_REF] Buisan | Planning For Both Robot and Human: Anticipating and Accompanying Human Decisions[END_REF][START_REF] Buisan | HATP/EHDA: A Robot Task Planner Anticipating and Eliciting Human Decisions and Actions[END_REF]. Two such structures are used, one for the human and one for the robot, each includes a model of the corresponding agent. Each model (structure) has its own belief state, action model, task network, plan, and triggers. We are interested in solving the HATP/EHDA problem, P hr , in which agents start with a joint task, i.e., a shared initial task network, w 0 , to decompose. The existing planner uses agents' action models and beliefs to decompose the given task network into its legal primitive components. Decomposition updates the current network by inserting new (non-) primitive tasks, additional constraints, etc., such that the single-agent process is generalized for the two-agent scenario. While doing so, it also updates the belief state of each agent and models their reaction by executing the triggers.

A simplifying assumption is that agents act alternatively, while only one is allowed to act at a time. Hence, the framework may face problems dealing with real concurrent actions [START_REF] Crosby | A Single-Agent Approach to Multiagent Planning[END_REF], especially when they are interacting [START_REF] Shekhar | Representing and planning with interacting actions and privacy[END_REF]. As a result, the framework is sound and complete only for the problem specifications in which action concurrency is handled carefully. Later, one can find a sound parallelization of the agent's plans (by respecting the flexibility proposed for the human agent) in the post-processing phase, e.g., by managing the causal links and synchronizing agents' action orderings. Note that it is not trivial to formally handle interacting actions in the current HATP/EHDA framework, and out of the scope of this work, and it is a part of our future work.

First, the framework builds the whole search space considering all possible, feasible decompositions [START_REF] Buisan | HATP/EHDA: A Robot Task Planner Anticipating and Eliciting Human Decisions and Actions[END_REF]. The framework uses specific actions during the search. IDLE is inserted into the agent's plan when its task network is empty or fully decomposed, and WAIT, when none of its actions is applicable. Then, it can adapt offthe-shelf graph search algorithms, e.g., the well-known algorithms like A * and AO * , and consider social cost, plan legibility, acceptability [START_REF] Alili | A task planner for an autonomous social robot[END_REF], etc., to search for a joint solution plan for the agents.

A joint solution plan generated, prior to the preprocessing stage, is defined as follows (extending Definition 2 for the HATP/EHDA case). Definition 3. (Joint Solution Plan.) It is a solution for P hr , represented as a tree or a graph, i.e., G = (V, E). Each vertex (v ∈ V ) represents the ground truth starting from the root node (i.e., s r 0 ). Each edge (e ∈ E) represents a primitive action performed either by the robot (o r ) or the human (o h ). G is branched on possible human choices (o h 1 , o h 2 , ..., o h m ). The requirement from this solution tree is that for each branch, from the root to a leaf node, the sequence of primitive actions, say,

π = (o r 1 , o h 2 , o r 3 , ..., o h k-1 , o r k
) is a solution plan for P hr . Here, each o h i represents a choice (often out of several choices) the human could make during execution.

Situation Assessment

In human psychology, especially in human-human interaction, spatial reasoning and perspective-taking are crucial. In practice, we often build relations between entities in the environment and estimate the knowledge and capabilities of agents around us to have a seamless collaboration with them.

This work abstractly employs the main ideas of situation assessment based on spatial reasoning and observability during planning. The goal is to predict the situation assessment of a collaborative human agent to have a better estimate of their knowledge and next possible actions, and thus, produce better plans.

Execution-Time Observability Conventions

We formally model run-time observability conventions, understood during plan execution, and use them for task planning in human-robot collaboration.

At a high-level, the formalization below is based on the standard state-variable representation (we refer the reader to [START_REF] Ghallab | Automated planning -theory and practice[END_REF]) such that we abuse the standard notations slightly, sometimes to maintain the flow of the discussion.

A General Understanding of Common Ground

To describe an environment a set of constant symbols is used. Constants are often classified as different groups (gr), e.g., places, pots, agents, etc. Each constant can be represented as an object symbol, e.g., robot1, human2, pasta-pkt1, etc. An object variable belonging to a group can be instantiated using any constant symbol of that group.

Suppose S is the complete state-space and s ∈ S represents a single state (or a belief state in the current context). Definition 4. (State Variable Function.) It is represented as: f svs : (?g 1 (gr 1 ), ?g 2 (gr 2 ), ..., ?g k (gr k ), S) → ?g k+1 (gr k+1 ).

Here, svs is state-variable symbol (or the attribute name), while each term with "?" (a question mark symbol), can be instantiated with a constant symbol from its respective group (mentioned inside "()") appears right besides the term. For example, to model agents' location we use f AgtAt : (?a(Agents), S) →?r(Rooms), representing, for each given legal state (s i ∈ S), the room where each agent is located. Each such possible instantiation of defined state variable functions represents s i partially, and is also called a characteristic attribute of s i .

If a variable is of the form f svsi : (?g1(gr 1 ), S) → ?g 2 (gr 2 ) such that gr 1 contains only one element, then, for a given state s ∈ S, we simplify this expression to, f s svsi →?g 2 (gr 2 ). Suppose s ∈ S is the real state with the ground truth. As per our assumptions, the belief state of the robot w.r.t. the real-world is always the real world state, i.e., B s φr = s, and the human belief w.r.t. s is B s φ h -that is estimated when the robot takes the human's perspective. Each state variable function instantiation w.r.t. a belief state, B s φr (B s φ h ), represents the truth value of that state attribute (grounded statevariable function) with the perspective of φ r (φ h ). While both these perspectives are managed by the robot. Definition 5. (Belief Divergence.) Suppose that f svsi : (g (1)l , g (2)m , ..., g (k)n , s) → g (k+1)p , for a legal state s and g (i) is the i th group while g (i)j is its j th element, represents a possible grounding for a state-variable function. Belief divergence is caused if there exists an instantiation such that f svsi : (g (1)l , g (2)m , ..., g (k)n , B φr ) = g (k+1)p ̸ = f svsi : (g (1)l , g (2)m , ..., g (k)n , B φ h ).

Uncertainty in agents' knowledge is not captured explicitly, implying that they are convinced about their beliefs.

Place-Based Observability

We now define place-based observability criteria inspired by some standard execution time observability conventions that are relevant for the human-robot context. Definition 6. (Places.) Represented as Places, it captures a group of constant symbols such that each member individually captures a pre-specified area in an environment declared by the domain modeler.

Agents are always situated in a place or moving between two places. Two agents situated in a same place p ∈ Places, at a given time instance, are said to be co-present.

Definition 7. (Place Specific State Attribute Function.) A grounded attribute of a given state is explicitly associated with some place or, in a generalized way, it can be expressed as, f loc : (f svsi (?g 1 (gr 1 ), ..., ?g k (gr k ), S)) → P laces Here, loc is a location specific symbol for place specific attribute, while the function captures the associated place w.r.t. a state attribute, f svsi (...).

Defining it this way captures and maintains the explicit places linked with "only" the state attributes of our interests. These explicit mappings suggest that an attribute is effective (or observable) in its dedicate place. Such mappings can change when an action changes the place of effectiveness of a state attribute, e.g., holding a cup and moving to an adjacent room. Such updates are currently manually handled.

Definition 8. (State Variable Observability Function.)

The state variable observability function maps each grounded state attribute to either OBS or INF; or a more general and formal way to express it is, f obs :

svsi (?g 1 (gr 1 ), ..., ?g k (gr k ), S)) → {INF, OBS}.

Here, obs represents an observability symbol to capture state-variable observability such that a state-variable function, for a legal state s ∈ S, is classified as either observable (OBS) or inferrable (INF). Here, we further generalize it, assuming that an attribute is either observable or inferrable, and hence, relaxing the individual state based restrictions, that means, the above expression can be further simplified to, f obs : (f svsi (?g 1 (gr 1 ), ..., ?g k (gr k ))) → {INF, OBS}.

When a state-variable function (f svsi (...)) belongs to the class OBS, it indicates that an agent can assess/observe the correct knowledge of its exact status in a given state s l , if the agent fulfills certain requirements w.r.t. the state s l . But when a state-variable function (f svsj (...)) belongs to the class INF, unlike the previous case, it means that an agent cannot observe it directly. However, under certain scenarios, the agent can definitely predict or infer its exact status in s l .

To better understand observability classes, consider the following scenario with a cup of coffee and some sugar on the table (Figure 1). Initially, the cup is far from the man, with no sugar. When he is not attentive, the robot adds some sugar to the cup and pushes it toward him. Once he is attentive again, he would notice that the cup is closer as its position is observable to him. But, without seeing the robot adding sugar, he cannot assess if there is sugar in the cup. Hence, we say the SugarInCup attribute is inferrable, and the human agent would know if they observed the robot act.

Belief Updating

An agent's belief can get updated in four ways as follows.

When Acting If the agent executes an action, its belief is updated based on its effects. The state attributes appearing in the action's effect get updated with the new values, while the remaining attributes keep their same old values.

When Being an Observant (Action Observability.) An action executed by an agent is observed by another agent copresent throughout the action execution. Therefore, we state that if an agent observes an action getting executed, the agent will infer the inferrable effects of the action. Consequently, the agent immediately updates its belief state while each inferrable attribute affected by the action receives a new value.

However, when the human executes an action not observed by the robot, we keep it simple and consider that humans make only deterministic moves. The robot does not need to be co-present to get the effects of human actions. And, its belief state is always updated with both their inferrable and observable effects. More complex cases are part of our future work where the robot's beliefs can diverge, too.

Via Situation Assessment

The agent assesses the situation from its current location via spatial reasoning and its reference frame, i.e., the observability model. Consequently, it updates its existing belief with the relevant ground truth.

(Based on Definition 7) We can always associate specific state attributes to places. For example, suppose that being in the state s 1 , the robot switches on the furnace placed in kitchen, and this generates a new state s 2 . Also, assume that f TurnOn is OBS (Definition 8). Then, the place specific attribute function, f loc : (...), w.r.t. the states s 1 and s 2 can be expressed as, f loc (f s1 TurnOn ) and f loc (f s2 TurnOn ), respectively, and both map to kitchen ∈ P laces.

Consider the following scenario: The search progresses from s 2 , along s 1 , s 2 , ..., such that the next action applicable in it is, the agent (φ h ) moving to the kitchen. This generates a new state s 3 , and hence f loc (f AgtAt (φ h , s 3 )) maps to kitchen, but so does f loc (f s3 TurnOn ). In such cases, φ h assesses the status of the furnace, i.e., the exact value of f s3

TurnOn in s 3 , which is ON, and hence the human agent updates their belief.

Note that the robot is always aware of the ground reality hence, technically, the idea is effective only for the human agent. Here, the robot takes the human's perspective and performs spatial reasoning as per the human's frame of reference or their current location in the environment. The human's belief is updated w.r.t. what they can see as ground truth (mimicked by the robot). This enables φ h to learn an observable attribute's value achieved earlier by the robot.

The agent updates its belief with relevant ground truth learned via situation assessment, performed "immediately" (i.e., takes 0 seconds) at each stage, before the execution of the next action. Technically, the robot performs situation assessment for the human and itself.

When Being Communicated The agent's belief is updated by learning the ground truth when another agent communicates an attribute-value pair. Communication occurs via a distinct set of actions, modeled as a predefined communication protocol for a pair of sender-receiver agents.

Planning With Communication Actions

For an agent to decide if, when, and what to communicate to another agent, it first needs to establish a common protocol with that agent even before planning. In this work, we establish such communication protocols between each sender-receiver agents pair, where we use speech modality, and model explicit communication actions between two agents. However, we note that these actions are different from agents' (non-) primitive actions, and they are used only in special circumstances during planning and execution.

Modeling Communication Actions

Next, we propose a generic communication action schema (ca) in this context. Suppose there exists a state-variable function, f svs : (?g 1 (gr 1 ), ?g 2 (gr 2 ), ..., ?g k (gr k ), S) → ?g k+1 (gr k+1 ), such that for the current world state s ∈ S, f svs (g (1)l , g (2)m , ..., g (k)n , s) maps to q.

The agent φ i can communicate this attribute-value pair to φ j (via the action ca φi,φj (f svs (...), q)), if the following conditions (i.e., its preconditions) meet: (1) For φ i , f svs (g (1)l , g (2)m , ..., g (k)n , B s φi ) = q, and (2) for φ j , f svs (g (1)l , g (2)m , ..., g (k)n , B s φj ) = r s.t. r ̸ = q. Later, φ j 's belief is updated, i.e., f svs (g (1)l , g (2)m , ..., g (k)n , B s φj ) ← q.

Planning with Reasoning on Human Mental State

Now that we have defined and described all essential tools, we describe the new approach and explain how these tools are utilized by it. First, we note that we put an effort to make our main contributions to have a "generic" state-variable representation. Hence, we believe that they are not limited to only our intended architecture (HATP/EHDA) in this paper. We plan to substantiate this claim experimentally in future.

We only describe the main changes made to enhance the underlying solver. Suppose an agent applies an action: First, the belief states of all agents co-present with this agent get updated with the action's inferrable effect. Later, the situation assessment process is used for every other agent to assess the changes (captured via observable state attributes). As a result, their beliefs are updated by the observable effects if the required conditions are satisfied. We discussed these subroutines in detail in earlier sections.

Communication in Planning

The following essential changes in the existing algorithm support efficient planning with communication. (Recall the sender-receiver pair discussed earlier.) The approach identifies whether the receiver's belief divergence is relevant, and thus if the receiver's belief needs to be corrected. If so, all state attributes where the receiver agent's belief differs w.r.t. the ground truth are identified. Then, we decide which of these state attributes and their exact values must be transmitted by the sender (i.e., the robot), supporting the idea of communicating minimally and avoiding verbosity. Once we determine that, the receiver's (i.e., human's) belief gets updated accordingly, ensuring that the remaining false knowledge of the receiver's updated belief is not effective, which also means that the belief divergence is not relevant anymore.

• Relevant Belief Divergence. At a given stage, if the human agent, based on their own belief, can perform a set of actions that differs from the one the human could perform w.r.t. to the robot's belief (or the ground reality), then we say that such divergence in their belief is relevant. A divergence is also declared as relevant if an action has different effects w.r.t the other agent's belief. However, currently, our reasoning system is myopic: We do not evaluate in a principled way the impact of different actions that humans could execute (based on their wrong belief), or of different effects, with their overall positive and detrimental effects on achieving the joint task. At this stage, it simply "decides" to align the agent's beliefs using communication actions whenever the belief divergence is relevant. However, a smarter approach would probably be to analyze the history of plan trace(s) or agents' future actions to decide whether their beliefs should get aligned or not, or for that matter, how much to communicate, but it is currently out of the scope of this work. • Communicate Only The Required Facts. It "decides"

the key changes in the human's belief to be made such that the relevance of their updated belief (might still be diverging) is non-effective. The subroutine that decides needed communication to be made appears in the robot's executable policy; is described in the following steps: 1. Store each attribute and its value if the attribute's value differs in the human's belief from the robot's belief. 2. For each stored attribute-value pair, build a communication action ca φr,φ h (...) based on the schema described earlier. They are considered equally costly. 3. At a given planning stage, e.g., the ground truth s i , follow the Breadth-First Search ordering. The source is B si φ h , and each ca φr,φ h (...) changes and aligns exactly one attribute while its updated value satisfies the ground truth. Applying ca φr,φ h (...) generates a new belief state following state transition rules, i.e., B si,1 φ h = γ(B si φ h , ca φr,φ h (...)). It continues until the first (updated) belief is selected to expand s.t. its remaining divergence is ineffective. The actions used from the root until the current belief state are retrieved.

Once the above subroutine finishes, the retrieved action set CA = {ca i φr,φ h (...)} is utilized for belief alignment. Agents may begin with different beliefs. Situation assessment (SA) can update human belief state, but humans cannot know inferable facts. So, we redefine Definition 3 to make Figure 2: Shows the plans obtained in three scenarios: Each scenario presents two plans -on the left, obtained by the old solver, and on the right, obtained via the proposed solver. The latter depicts more realistic and appropriate belief updates focusing on two attributes. Case (A): the plans are the same, but the updates in the human belief are more realistic with our approach. Case (B): the human has no certainty on SaltInPot, while ours decides to communicate to remove the ambiguity. And, Case (C): the initial belief divergence induces an "invalid" plan, but our approach predicts that the human agent will assess the situation and update their belief with all the facts without being communicated. (Other minor details are outlined in the figure .) it sound w.r.t. our new planning approach. Assume at each step (t = 0, 1, 2, ...), humans perform SA, while the robot executes each communication action ca ∈ CA, such that the human's belief state updates immediately (takes 0 seconds). Later, following the updated beliefs, the human's or robot's regular primitive action is executed, and the effects only appear in the next step. Hence, the other two types of belief updates happen post the action execution. And, continues.

Empirical Evaluation

Before we describe the two domains used for the experiments and the results to compare the old and new approaches, we first make a high-level distinction between the existing and new approaches. In principle, the existing solver can handle agents' individual belief divergences, but "not during planning" unlike our approach. To achieve that, the existing solver can use a cumbersome technique that intervenes by updating the (collaborative) task networks of the joint task model/specifications while using triggers.

Cooking Pasta Domain Suppose a stove and salt are available in Kitchen (Places), and the pasta is either in Kitchen or Room -they are adjacent. The agents have different roles and can only operate in the two places. Robot adds salt to the pot and turns-on the stove. Human grabs the pasta and pours it into the pot. The human can add pasta, but only after salt gets added to the pot and the stove is ON.

Focus on the following two attributes: For a given state, s i ∈ S, f si SaltInPot ∈ {true, false} and f si stove ∈ {on, off} such that only f si SaltInPot is inferrable, all others belong to OBS. Preparing Box Domain A box filled with a fixed number of balls and with a sticker pasted on is considered prepared and needs to be sent. Both the agents can fill the box with balls from a bucket, while only the robot can paste a sticker, and only the human can send the box. The bucket can run out of balls, so when there is only one ball left, the human moves to another room to grab more balls and refill it. A sticker pasted on the box is observable, while the number of balls in the box is inferrable. Other attributes belong to OBS.

Experiments

Qualitative analysis in the first domain mentions subtleties the old solver overlooks and how ours is aware of them, updates belief, and effectively manages divergences. Then, quantitative studies compare the solvers in both domains.

Qualitative Analysis Consider the first domain. We discuss the plans obtained in three different scenarios as shown in Figure 2. Assume that both the agents are in Kitchen and the pasta is in Room. Scenario (A) captures the agents' plans 1: In each domain: for the old solver, the success rate (S), the ratio of failed plans due to a non-applicable action (NA), and the ratio of failed plans due to an inactivity deadlock case (IDL), while for our solver, the success rate (S) and the ratio of plans including a communication action (Com).

when the robot starts while Scenario (B) shows when the human starts. Let us change the scenario: Suppose, in hindsight, the pasta is moved to kitchen such that the robot knows it, while the human still has the old belief. For this, Scenario (C) captures the plans obtained when the human starts.

• Scenario (A): Although the solvers generate similar plans, they update the human's belief differently if and when the human and robot are co-present. E.g., turning on the stove ideally (realistically) does not affect the human's mental state, which is not the case for the old solver. It considers agents omniscient, so the human knows everything immediately once achieved. Our solver predicts it when the human returns to the kitchen and assesses that the stove is ON, and their belief gets updated. • Scenario (B): Human leaves the kitchen. Practically, they are unaware of the changes achieved in the environment by the robot's actions: turn-on & add-salt. The old solver generated a similar plan as in Sce. (A) where the human already knew that the stove was ON, and salt was added. However, an appropriate situation assessment and inference based on action observability together guarantee that, when returning to the kitchen, the human assesses that the stove is ON. Moreover, the robot predicts that the human cannot know the SaltInPot fact and that it is a relevant divergence that needs to be handled via communication. • Scenario (C): With the old solver, the human moves to Room to grab the pasta, but in reality, being an illegal action w.r.t. the robot's belief or the ground truth, it fails.

In our case, the human agent assesses the environment to update their belief state, knowing the pasta is in the kitchen. Hence, no communication is required.

Quantitative Studies

The HATP/EHDA framework's current solver and ours are tested and compared on two domains in Table 1. We consider (in box domain) three boxes to be prepared and sent. While in both, we generated 512 different initial states, including 448 (87.5%) with divergent initial agents' beliefs and 64 states where both agent beliefs are fully aligned initially. Overall, 2048 plans were generated. With the old approach, a planning failure occurs due to: (a) an action of a plan not applicable in another agent's belief state, including the ground truth; (b) if an inactivity deadlock occurs, which is assumed to be the case after a succession of at least four WAIT and (or) IDLE actions. A deadlock occurs when the human has a belief divergence and waits for a never-happening robot's action, e.g., waiting for add salt, but SaltInPot is already achieved. For the old solver, the success rate (S), the ratios of the number of failed plans due to a inapplicable action (NA) and an inactivity deadlock (IDL) appear in the table. For ours, the success rate (S) is shown and the ratio of successful plans including a communication action is presented under Com.

As the existing solver does not handle belief divergence in planning, the applicability of actions was never an issue w.r.t. another agent's belief. Therefore, if the IDL case occurs, it is understood that the task specification is erroneous w.r.t. the old problem specification.

Our solver always finds legal plans, and on average, approx. 62% of them use communication. Thus, the robot doesn't need to communicate systematically as assessing situations handles a major part of the divergences (87.5% of the scenarios have divergent beliefs initially). For the old solver, if no initial belief divergence exists, it always finds a legal plan, considering the agents omniscient. E.g., Fig. 2(A). However, sometimes, this causes problems in practice. Scenarios beginning with distinct beliefs induce actions often not applicable in another agent's belief state (or the ground truth), evident by the (average) 21.8% success rate.

Discussion

Formalizing run-time observability conventions is crucial for planning as ignoring them may lead to problems in practice. E.g., Fig. 2(B) showing human knowing SaltInPot, is ambiguous in reality. We describe a far more realistic way to estimate the evolution of human belief during planning, using the situation assessment discussed in Qualitative Analysis. Explicit reasoning on the human mental state detects and prevents ambiguous situations with communication while also prohibiting the robot from being too verbose, as shown in Quantitative Studies. Compared to the old process, this produces consistent and more robust plans overall.

However, our approach does not refute something believed by an agent through situation assessment without assessing its exact true value. E.g., for some s i ∈ S, if the human wrongly believes that the pasta is in Kitchen. The situation assessment does not help refute this, while the human is in Kitchen. The reason is that f si PastaNotInKitchen (...) is not modeled explicitly as an attribute. Such issues do not affect the solver's completeness as far as the situation assessment is concerned. Moreover, our solver handles them as a relevant divergence to be aligned. Thus, the human is just communicated with correct updates.

Summary

Building on earlier work, we presented a new method to model execution-time observability conventions appropriate for HRI and to use them to estimate the evolution of the human mental state. It is based abstractly on situation assessment and action observability criteria. A new planning approach is described, utilizing this better estimation of human mental state to plan for more robust and consistent humanrobot joint activities such that a relevant belief divergence is tackled by explicitly modeled communication actions.

Figure 1 :

 1 Figure1: Human is not attentive when Robot adds sugar to the cup before pushing it forward. Assessing the new situation after the two actions, Human can only "know" the cup's new position (observable), but not SugarInCup (inferrable).


Samuel Joubert

Jessica Tcherdukian

Roger Mieusset
email: roger.mieusset@orange.fr

Jeanne Perrin

Thermal male contraception: A study of users' motivation, experience, and satisfaction

Keywords: male thermal contraception, men acceptance of health care, men satisfaction, sexual satisfaction

Purpose:

The aim of this study is to evaluate the motivations, experience, and acceptability of thermal male contraception (TMC) in male partners of couples requesting the use of TMC as the only couple contraceptive.

Materials and methods:

To the 72 men of couples seeking male contraception and using TMC between 2011 and 2019, we suggested an anonymous online survey (93 questions) exploring population characteristics, contraceptive histories, motivations for choosing TMC, patient experience at the successive phases of use, relations with partner and environment, and satisfaction with this method.

Results: Sixty-seven men agreed to participate (93% response rate); 63 responses were complete and were analyzed (94% participation rate). The main motivations for choosing TMC were "not using hormones" (n = 59/63, 94%) and using a method regarded as "natural" (n = 49/63, 78%). Most of the men surveyed (68%) adopted the method in less than 2 weeks. During the contraception use phase (n = 59 men), they described significantly improved sexual satisfaction, compared to that experienced with their previous contraceptive methods, and they reported high confidence (100% rather/totally confident partner) and support (88% rather/totally supporting partner) from their partner.

Most men (n = 35/59, 59%) also reported improved self-esteem. The main negative point was discomfort, reported by 24% of the men. The overall satisfaction score of using this method was 3.78 ± 0.46/4, and 100% of the men reported that they would recommend the method to other men.

Discussion and conclusion: Men using TMC successfully assumed the responsibility for and performed a daily task to provide couple contraception. This positive evaluation, together with the already published contraceptive efficacy and reversibility of TMC, should encourage the development of this method.

INTRODUCTION

Unintended pregnancies account for 50% of pregnancies worldwide, despite the numerous contraceptive methods available to women. The only contraceptive methods currently available to men are vasectomy, condoms, and withdrawal, which are used by 2%, 21%, and 5% of couples, respectively. [START_REF] Who | Contraceptive use by method[END_REF] The development of male contraceptive methods has been ongoing with different approaches. Among them, hormonal treatments with testosterone alone or associated with progestin-induced spermatogenesis inhibition (azoospermia or oligozoospermia) with a valuable contraceptive efficacy in thousands of male partners of couples. [START_REF]World Health Organization Task Force on Methods for the Regulation of Male Fertility. Contraceptive efficacy of testosteroneinduced azoospermia and oligozoospermia in normal men[END_REF][START_REF] Turner | Contraceptive efficacy of a depot progestin and androgen combination in men[END_REF][START_REF] Gu | Multicenter contraceptive efficacy trial of injectable testosterone undecanoate in Chinese men[END_REF][START_REF] Büchter | Clinical trial of transdermal testosterone and oral levonorgestrel for male contraception[END_REF][START_REF] Kamischke | An effective hormonal male contraceptive using testosterone undecanoate with oral or injectable norethisterone preparations[END_REF][START_REF] Mahabadi | Combined transdermal testosterone gel and the progestin nestorone suppresses serum gonadotropins in men[END_REF][START_REF] Nieschlag | Hormonal male contraception in men with normal and subnormal semen parameters[END_REF][START_REF] Soufir | Spermatogenetic inhibition in men taking a combination of oral medroxyprogesterone acetate and percutaneous testosterone as a male contraceptive method[END_REF][START_REF] Ilani | A new combination of testosterone and nestorone transdermal gels for male hormonal contraception[END_REF][START_REF] Behre | Efficacy and safety of an injectable combination hormonal contraceptive for men[END_REF] Moreover, the collected data on semen analyses have led to a strict definition of the sperm contraceptive threshold [START_REF] Nieschlag | th Summit Meeting Group. 10th Summit Meeting consensus: recommendations for regulatory approval for hormonal male contraception[END_REF] : The suppression of sperm counts to below 1 million/ml results in fertility rates commensurate with female oral contraceptive pills. [START_REF] Nieschlag | th Summit Meeting Group. 10th Summit Meeting consensus: recommendations for regulatory approval for hormonal male contraception[END_REF] Another way to achieve this sperm contraceptive threshold is based on the thermal dependence of spermatogenesis, that is, thermal male contraception (TMC). [START_REF] Mieusset | Contraception thermique de l'homme[END_REF][START_REF] Soufir | Guide pratique d'une contraception masculine hormonale ou thermique[END_REF] In most mammals, optimal spermatogenesis temperature is obtained by thermoregulatory systems; in humans, thermal regulation achieves a testicular temperature 2 to 5 • C lower than body temperature. [START_REF] Setchell | The Parkes Lecture. Heat and the testis[END_REF] Increased testicular temperature induces apoptosis in the most heat-vulnerable germ cells (pachytene and diplotene spermatocytes, spermatids) and impacts sperm production, in line with relative hyperthermia and exposure time. [START_REF] Liu | Temperature control of spermatogenesis and prospect of male contraception[END_REF] TMC is based on the induction of a +2 • C increase in testicular temperature for 15 to 24 h daily [START_REF] Shafik | Testicular suspension as a method of male contraception: technique and results[END_REF][START_REF] Mieusset | Inhibiting effect of artificial cryptorchidism on spermatogenesis[END_REF][START_REF] Mieusset | Hyperthermia and human spermatogenesis: enhancement of the inhibitory effect obtained by "artificial cryptorchidism[END_REF] using a contraceptive underwear (CU) that maintains the two testes near the external orifice of the inguinal canal. [START_REF] Setchell | The Parkes Lecture. Heat and the testis[END_REF] With such a CU, the inhibiting effects on spermatogenesis, as well as the recovery of sperm parameters after stopping CU have been reported. [START_REF] Shafik | Testicular suspension as a method of male contraception: technique and results[END_REF][START_REF] Mieusset | Inhibiting effect of artificial cryptorchidism on spermatogenesis[END_REF][START_REF] Mieusset | Hyperthermia and human spermatogenesis: enhancement of the inhibitory effect obtained by "artificial cryptorchidism[END_REF] The contraceptive efficacy of a +2 • C increase in testicular temperature was studied in three different studies using three types of device for 15 to 24 h daily: A total of 51 couples used TMC as their only contraceptive method over a total of 536 cycles and no pregnancy occurred. [START_REF] Shafik | Testicular suspension as a method of male contraception: technique and results[END_REF][START_REF] Mieusset | The potential of mild testicular heating as a safe, effective and reversible contraceptive method for men[END_REF][START_REF] Shafik | Contraceptive efficacy of polyester-induced azoospermia in normal men[END_REF] Since the 2010s, couples or male partner of couples have consulted the andrologists of the Department of Reproductive Medicine requesting a male contraceptive method different from condoms or withdrawal as the only couple contraception. Some chose vasectomy, others wanted reversible contraception. As is the case within the practice of male infertility, and in other areas of medicine, treatments may be prescribed without perfect proof of their effectiveness having been rigorously demonstrated by trials. This is the case for several treatments used in male infertility (e.g., antiestrogens, antioxidants, anti-inflammatories) whose indication is based on publications reporting efficacy but with a low level of evidence.

The management of these contraceptive requests was made as a clinical application of a method published in the literature. There has never been a process of recruiting volunteer couples. Of course, as required in this type of care, all contraindications, risks, and follow-up modalities were provided to applicants prior to the implementation of treatment.

The modes of implementation and monitoring of TMC are as follows: Before the first appointment for male contraception, a written document [START_REF] Soufir | Guide pratique d'une contraception masculine hormonale ou thermique[END_REF] is sent by e-mail for information. After a discussion about the chosen method, a medical interrogation and a clinical andrological examination look for contraindications: history of mal descended testicle, torsion of the spermatic cord, orchitis, inguinal hernia repair, chronic scrotal or inguinal skin diseases (eczema, recurrent mycoses), presence of a clinical varicocoele as well as a scrotal or inguinal skin condition in progress and a testis absence or atrophy without known causes. Then the man learns how to set up the CU model adapted to his morphology (Annexure Figures 1 and2). A semen analysis is prescribed; as recommended, only men with normal semen parameters are accepted. [START_REF] Nieschlag | th Summit Meeting Group. 10th Summit Meeting consensus: recommendations for regulatory approval for hormonal male contraception[END_REF] They receive a free CU, manufactured according to the patent previously registered by the Paul Sabatier University and the Toulouse University Hospital, France.

The objectives of the CU testing phase are: (1) to progressively learn to wear the CU in the different activities of daily life until wearing the CU at least 15 h/day; (2) to make sure that the permanent position of the testicles when wearing the CU is the expected one; (3) to check the absence of any unpleasant or painful sensation (penile, scrotal, testicular); and (4) to finally prepare four additional free CU copies.

The spermatogenesis inhibiting phase is the time required to reduce sperm production to the contraceptive threshold (less than 1 M/ml sperm) as established. [START_REF] Nieschlag | th Summit Meeting Group. 10th Summit Meeting consensus: recommendations for regulatory approval for hormonal male contraception[END_REF] Around the third month of daily CU wear for 15 h/day, a semen analysis is performed: If the threshold is not reached, a second or third semen analysis (at 1-month intervals) is performed; if the contraceptive threshold is reached, TMC can be used as the only form of the couple's contraception.

During the phase of CU-use as the only couple contraception (the phase of contraceptive use), the man is requested to perform a semen analysis every 3 months to check that the sperm count remains below the contraceptive threshold. The prescribing physician follows up by e-mail during the successive phases, with the possibility of physical or phone consultation, on request.

Usual male contraceptive methods (withdrawal and condoms) are directly related to the sexual act and are not used outside of it.

In contrast, methods inducing spermatogenesis inhibition (hormonal, thermal) are based on daily or repeated actions outside the act of sexual intercourse; these methods are thus rather similar to female contraceptive pills. As no commercially available male hormonal or thermal contraceptive exists, little information regarding the acceptability of these approaches for men has been reported. Publications mainly concern male hormonal contraceptives [START_REF] Meriggiola | Acceptability of an injectable male contraceptive regimen of norethisterone enanthate and testosterone undecanoate for men[END_REF][START_REF] Amory | Acceptability of a combination testosterone gel and depomedroxyprogesterone acetate male contraceptive regimen[END_REF][START_REF] Roth | Acceptability of a transdermal gel-based male hormonal contraceptive in a randomized controlled trial[END_REF][START_REF] Nguyen | Acceptability of oral dimethandrolone undecanoate in a 28-day placebo-controlled trial of a hormonal male contraceptive prototype[END_REF] ; only one publication analysed the hypothetical acceptability of TMC. [START_REF] Amouroux | Are men ready to use thermal male contraception? Acceptability in two French populations: new fathers and new providers[END_REF] The purpose of the current study was to evaluate the experience, acceptability, and satisfaction of TMC in men using TMC as a unique couple contraceptive. F I G U R E 2 Self-assessment of the adherence to CU wearing and the monitoring of semen analyses. n = 59 men. CU, contraceptive underwear; Q, number of the question (Supplement). (a) never (n = 1; 2%). Source: Supplement Q59-62

MATERIALS AND METHODS

Ethics statement

The survey protocol was approved by the institutional review board (IRB) of Aix Marseille University (IRB No. 2020-09-10-005), France.

Written informed consent was obtained from each participant.

Survey population, consent, and questionnaire responses

In a population of men seeking TMC as the couple's only contraceptive method since June 2011 in Toulouse University Hospital, the survey population was selected as follows: An initial e-mail was sent to each of the 72 men who had started the CU testing phase between June 2011 This ad hoc questionnaire was designed on purpose. Before diffusion to participants, the questionnaire was tested to validate clarity and duration.

Statistical analyses

The questionnaire was generated using "Google Forms" software;

responses were saved automatically in the same software program and extracted via an Excel spreadsheet in Microsoft Office 2019 (Microsoft Corporation). Only complete questionnaires were analyzed.

The results of the questions concerning the quality of sexual life were compared over time (from the contraceptive method used before TMC ["N-1" method] to the two previous methods ["N-2" and "N- Pearson's χ 2 test was used to compare the data in Table 3. A difference was considered significant when p < 0.05.

RESULTS

Demographics and contraceptive history

The flowchart of the survey is presented in Figure 1. The response rate was 93% (67/72): Five men never respond to the first e-mail, neither to the three recall e-mails. The participation rate was 94% (63/67): Three men refused to participate (broken relationship; refuse to use the questionnaire online; no explanation given), and one did not complete the questionnaire online. Note: Values are presented as number (%). a N-1: contraceptive method men were using immediately before the use of TMC; N-2: contraceptive method used immediately before the N-1 method; N-3:

contraceptive method used immediately before the N-2 method. b Female pill, intrauterine device (IUD), subcutaneous implant, thermal curve, female condom, or cervical cap.

* N-3 versus N-1: p<0.05; ** N-3 versus N-1: p < 0.001. Source: Supplement Q10, Q11, Q14, Q15, Q17, Q18; Q, number of the question (Supplement) activities were professionals (38%) or craft and related trade workers (19%).

Table 2 presents the last three contraceptive methods used prior to TMC. The proportion of men using a male method of contraception was stable over time (38% to 43%), except for male condom use, which decreased significantly with time. The proportion of men using a female method increased significantly over time, particularly with the use of the intrauterine device (IUD). The reasons for discontinuing these methods were comparable regardless of the time of use.

Motivations, criteria, and modalities for choosing TMC

Among the men whose couple's contraception method immediately before TMC (N-1) was a female method (n = 36/63, 57%), the main reasons for switching to a male contraceptive method were the wish to share the role of providing contraception in a couple (n = 31/36, 86%), the willingness to take responsibility for contraception (n = 21, 58%), and the absence of expected harmful effects on desire and pleasure in the couple (n = 19, 53%; Supplement Question (SQ) 20.b). Among the men whose couple's contraception method immediately before TMC (N-1) was a male method (condom or withdrawal, n = 20/63, 32%) (SQ10), the main reasons for stopping were decreased sexual pleasure (n = 9/20, 45%) and fear of unwanted pregnancy (n = 9/20, 45%; SQ11).

Changing the couple's contraceptive regimen from a female form or a traditional male method to a new method was introduced slightly more often by the man (n = 29/63, 46%) than by the woman (n = 23, 37%).

When choosing TMC, 65% of the men did not consider other methods (SQ26). The main reasons for choosing TMC were the non-use of hormones (n = 59; 94%) and the perception of TMC as a "natural" method (n = 49; 78%; SQ27). The evolution of fears and perceptions at the different phases of TMC are presented in Table 3. At the time of choosing TMC, the majority (70%) of men had specific fears about the method, which decreased significantly at the spermatogenesis inhibiting phase (p < 0.01).

Experience at different stages

The ease of adoption of the CU was evaluated at 2.89 (+/-0.67; SQ37) on a scale of 1 (very difficult) to 4 (very easy); 68% of the men adopted the CU in less than 2 weeks (SQ38). During this CU testing phase, 43% of the men did not experience any difficulties (SQ41). Difficulties related to the CU are described in 7%), of a method too difficult to access (n = 1; 2% and n = 0); of a method taking too long to set up (n = 5; 8% and n = 3; 5%). b The CU was uncomfortable (n = 20; 33% and n = 14; 24%), painful (n = 14; 23% and n = 4; 7%), other (n = 6; 10% and n = 8; 14%), I had trouble putting on and/or taking off CU (n = 1; 2% and n = 0 respectively). **p < 0.01; *p < 0.05.

(n = 48, 80%) was the satisfaction of having adopted the method and/or CU (Table 3).

During the contraception use phase (n = 59), adherence to CU wearing and the monitoring of semen analyses was high (Figure 2).

Most of the men had never been afraid of facing contraceptive failure (n = 38/59; 64%). For the remainder, this fear may have led them to wear the CU more than 15 h per day (n = 12, 20%)

or at night (n = 8; 14%; SQ77). Finally, the quarterly frequency of follow-up semen analysis was acceptable to most (n = 48, 81%) men (SQ63). Source: Supplement Q39.

At the different phases of TMC, fears and negative and positive aspects evolved (Table 3). The transition from the choice of TMC to the spermatogenesis inhibiting phase resulted in a significant decrease in fears about the method (70% vs. 35%, p < 0.01), and there was a downward trend in all but two concerns: that of not being able to ensure the couple's contraception on a daily basis (57% vs. 55%, respectively) and concerns about a lack of efficiency (17% vs. 18%, respectively).

The transition from the spermatogenesis inhibiting phase to the contraception use phase of TMC resulted in a significant increase in satisfaction: The proportion of men expressing no negative aspect increased from 25% to 47% (p < 0.05). The most frequently expressed negative aspect of the contraception use phase was discomfort (n = 14, 24%, SQ58).

At the spermatogenesis inhibiting phase, the main positive aspects were the satisfaction of having adopted the method and/or the CU (n = 48, 80%), satisfaction with being able to wear the CU 15 h a day (n = 36, 60%), and the absence of any deleterious effects on sexuality (n = 36, 60%). These positive points were not significantly altered in the contraception use phase (SQ57).

For the 59 men involved in the contraception-use phase, their partner's confidence and support for TMC were perceived as high;

links of trust and male image were perceived as mostly strengthened (Figure 3). Most of the men reported having better self-esteem (n = 35; 59%; SQ80) and feeling an improvement in their partner's image (53%, SQ73). The man's overall sexual satisfaction increased significantly between stage N-3 and the phase of contraceptive use (Figure 4).

Finally, among the 59 men involved in the contraception-use phase, the overall satisfaction level with TMC was rated at 3.78 (+/-0.46; scale of 1 "not at all satisfied" to 4 "very satisfied"; SQ79). All the men responded that they would recommend this method to other men (SQ81), mainly because of sharing the contraceptive burden (49%), the simplicity of the method (47%), and its perception as "natural" (not chemical; 46%; Table 5).

DISCUSSION

The current TMC user population differs from the general population. TMC users had a high level of education: 81% had a bachelor's degree or higher versus 21% in the French working population. [START_REF]Le niveau de diplôme des catégories sociales. Observatoire des inégalités[END_REF] They were often overqualified for the trade they exercised: Occupations corresponding to a level of education above the high school degree (International Standard Classification of Occupation 1, 2, and 3) [START_REF] Brousse | L'édition 2008 de la classification internationale type des professions[END_REF] represented only 53% of the men (Table 1).

Before choosing TMC, the men already had a higher rate of use of male contraception than men in the general population

Prior to the use of TMC, the men in the survey showed a greater use of male contraceptive methods than men in the general French population: 38% versus less than 20% (especially withdrawal, 16% vs. less than 5%) at the expense of the contraceptive pill (24% vs. 33%). [START_REF] Guen | Men's contraceptive practices in France: evidence of male involvement in family planning[END_REF] This overuse of male contraceptive methods, however, was comparable to that of a population of new fathers for whom "contraception before pregnancy was primarily ensured by the female partner via contraceptive pills (51%) and by the male partner via condoms (30.4%) and withdrawal (13.4%)." [START_REF] Amouroux | Are men ready to use thermal male contraception? Acceptability in two French populations: new fathers and new providers[END_REF] Moreover, in a study of Italian men testing a male contraceptive hormonal regimen, 29% were using condoms before the study started. [START_REF] Meriggiola | Acceptability of an injectable male contraceptive regimen of norethisterone enanthate and testosterone undecanoate for men[END_REF]

Motivations for choosing TMC

The main reasons for choosing the thermal method of contraception were the non-use of hormones (94%) and its perception as a "natural" method (78%). These reasons are consistent with the benefits of TMC as perceived by potential users: "natural (52%), no adverse effect (38%), non-hormonal (36%), reversible (36%)." [START_REF] Amouroux | Are men ready to use thermal male contraception? Acceptability in two French populations: new fathers and new providers[END_REF] We can distinguish two types of situations at the time of choosing TMC. On the one hand, 36 men (57%) were "using" female methods; the reasons for discontinuing were the desire to reduce hormonal intake and the side effects impacting health and sexuality. The desire to share the burden of contraception in the couple and the willingness to take responsibility for it are well-represented in these men (86% and 53%, respectively). On the other hand, 24 men (38%) used the usual methods of male contraception (condom and/or withdrawal), which affected sexual intercourse. The reasons for stopping were the decrease in sexual pleasure and the fear of pregnancy (38% each). In these two types of situations, the mental load of the man is either absent (female methods) or of limited duration (during sexual intercourse [withdrawal, condom]). "Simple," "easy to use," "practical" method 27 (46%) "Natural," "non-hormonal," "non-chemical" method 26 (44%)

"Efficiency" 25 (42%)

"No side effects" or "fewer side effects than other methods" 14 (24%)

Ecological, non-polluting 13 (22%) Economic accessibility ("free" or "low cost" method) 13 (22%)

"Comfortable" or "no discomfort," "little discomfort," "pleasant" 9 (15%) "Fertility control," "paternity," "contraception by the man himself"

(8%)

Note: The open-ended responses were written in free text and then analyzed and grouped by themes spontaneously present in each response. Source: Supplement Q82; Q, number of the question (Supplement).

to wear CU") have already been reported. [START_REF] Amouroux | Are men ready to use thermal male contraception? Acceptability in two French populations: new fathers and new providers[END_REF] Learning the time-limited but daily manipulation of the penis and scrotum, as well as the new testicular position, were unknown factors that may explain these fears.

Indeed, the frequency of this type of concern was significantly reduced after the testing phase (Table 3).

Other fears related to sexuality (14%), infertility (13%), virility (8%), and testicular cancer (8% as already reported by some ("damage to virility; delayed reversibility") in new fathers. [START_REF] Amouroux | Are men ready to use thermal male contraception? Acceptability in two French populations: new fathers and new providers[END_REF] Studies have already shown that men who were asked about the possible use of male hormonal contraception were afraid of side effects and health implications. In 115 men, 71% associated the "male pill" with side effects. [START_REF] Brooks | Men's views on male hormonal contraception-a survey of the views of attenders at a fitness centre in Bristol, UK[END_REF] In a study in which a male contraceptive pill was offered to 54 men, 53% of the respondents were concerned about possible biological side effects and 26% about adverse health effects. [START_REF] Walker | Attitudes to a male contraceptive pill in a group of contraceptive users in the UK[END_REF] In the present survey, these fears appeared to decrease over time but not significantly; this should be further investigated in future studies on larger numbers.

Contraceptive mental load

In addition, the proportion of men who expressed the fear of not being able to ensure the couple's contraception on a daily basis remained stable between the time of choosing TMC (57%) and the spermatogenesis inhibiting phase (55%). The achievement of the contraceptive threshold as verified by the semen analysis at the end of the inhibitory phase appears to have resolved this fear; indeed, 63% (37/59) answered positively to the following question: "I was happy to ensure the couple's contraception by a male method that is neither withdrawal nor the use of condoms" (SQ57). This answer clearly illustrates one of the aspects of the mental load associated with the man's daily management of the couple's contraception in real life. Other aspects are reflected by the proportion of men reporting either their satisfaction with having assumed the different technical aspects of the method (80%) or having managed to wear the CU for 15 h a day (58%; SQ57). Some men went so far as to wear the CU more than 15 h/day (20%) for fear of an unwanted pregnancy (SQ77).

Improvement of sexual satisfaction

Our survey found that the overall sexual satisfaction of TMC users increased significantly between the N-3 method of contraception (long before TMC) and the phase of contraception use of TMC. It seems difficult to compare our results with those of men using male hormonal contraception, which may involve excessive testosterone intake or require compensation for progestin-induced hypotestosteronaemia. [START_REF] Tcherdukian | Contraception masculine: quelles (r)évolutions ?[END_REF] On the other hand, we can compare our results regarding sexual pleasure with those existing for the main methods used at N-3 (male condom, pill, withdrawal, IUD). In the survey population, the proportion of men using male condoms decreased significantly between the N-3 and N-1 periods, with the main reason being a decrease in sexual pleasure. The role of decreased sexual pleasure in the non-use of male condoms has already been established in the literature. [START_REF] Randolph | Sexual pleasure and condom use[END_REF] Fewer data exist regarding withdrawal; however, among 300 Iranian women "using" withdrawal, 34% reported a decrease in sexual pleasure, and 42% reported a decrease in sexual pleasure in their partner. [START_REF] Rahnama | Withdrawal users' experiences of and attitudes to contraceptive methods: a study from Eastern district of Tehran, Iran[END_REF] In a population of 1101 women, female hormonal contraceptive methods have also been associated with decreased sexual pleasure. [START_REF] Smith | Hormonal contraception and female pain, orgasm and sexual pleasure[END_REF] Only the IUD has not been clearly associated with a decrease in sexual pleasure. [START_REF] Higgins | The sexual acceptability of contraception: reviewing the literature and building a new concept[END_REF]

Strengths and weaknesses of the study

Our survey has at least two strengths. First, a high participation rate (94%) suggests strong involvement and interest in male contraception in our population. Second, our survey reports for the first time the acceptability, experiences, fears, and satisfaction of a series of men who have used TMC as the only form of a couple's contraception. With regard to the developing methods of male contraception based on inhibition of spermatogenesis, little information regarding their acceptability by men has been reported. The literature focuses on male hormonal contraceptives. [START_REF] Meriggiola | Acceptability of an injectable male contraceptive regimen of norethisterone enanthate and testosterone undecanoate for men[END_REF][START_REF] Amory | Acceptability of a combination testosterone gel and depomedroxyprogesterone acetate male contraceptive regimen[END_REF][START_REF] Roth | Acceptability of a transdermal gel-based male hormonal contraceptive in a randomized controlled trial[END_REF][START_REF] Nguyen | Acceptability of oral dimethandrolone undecanoate in a 28-day placebo-controlled trial of a hormonal male contraceptive prototype[END_REF] For each of those studies, the initial assessment was based on the suppression of spermatogenesis:

They reported that 50% to 66% of men would be willing to use it if it was available. The conditions of those assessments, in which the female partner had to continue using another contraceptive method, were not like the actual "real-life" conditions of our survey, in which TMC was the couple's only contraception. The assessment of acceptability was therefore made in these studies [START_REF] Meriggiola | Acceptability of an injectable male contraceptive regimen of norethisterone enanthate and testosterone undecanoate for men[END_REF][START_REF] Amory | Acceptability of a combination testosterone gel and depomedroxyprogesterone acetate male contraceptive regimen[END_REF][START_REF] Roth | Acceptability of a transdermal gel-based male hormonal contraceptive in a randomized controlled trial[END_REF][START_REF] Nguyen | Acceptability of oral dimethandrolone undecanoate in a 28-day placebo-controlled trial of a hormonal male contraceptive prototype[END_REF] without taking into account the risk for pregnancy. Nevertheless, these studies have provided information on men's attitudes toward male contraception.

Our survey has limitations. First, the survey population may seem small (63 men). However, it is not different from that of the aforementioned studies [START_REF] Meriggiola | Acceptability of an injectable male contraceptive regimen of norethisterone enanthate and testosterone undecanoate for men[END_REF][START_REF] Amory | Acceptability of a combination testosterone gel and depomedroxyprogesterone acetate male contraceptive regimen[END_REF][START_REF] Roth | Acceptability of a transdermal gel-based male hormonal contraceptive in a randomized controlled trial[END_REF][START_REF] Nguyen | Acceptability of oral dimethandrolone undecanoate in a 28-day placebo-controlled trial of a hormonal male contraceptive prototype[END_REF] on male hormonal contraception, which included 20, 38, 79, and 57 men, respectively. Second, our survey population

20472927, 2022, 8 ,

 8 Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/andr.13264 by Aix-Marseille Université, Wiley Online Library on [20/12/2022]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License and September 2019, including an information leaflet about the online survey. Inclusion criteria were men who agreed to answer the survey: They received a message containing a participant number. Participants completed the online questionnaire anonymously using their participant numbers. Exclusion criteria were men who did not respond to the e-mail, refused to participate, or did not complete the questionnaire entirely. The 93-question questionnaire is composed of three parts (completely available in the Supplement): -(A) "You" (seven questions) describes the survey population; -(B) "Contraception and you," with three sections: (I) "before TMC" (12 questions), description of men's contraceptive history from the contraceptive method used before TMC ("N-1" method) to the two previous methods ("N-2" and "N-3"); (II) "when changing contraceptive method to start TMC " (six questions), exploring the reasons for this change; (III) "at the time of choosing TMC" (three questions), exploring the determinants of the choice of TMC among the other methods; -(C) "The experience" (65 questions) comprising eight chapters: (I) "accessibility"; (II) "CU testing phase and first semen analysis"; (III) "spermatogenesis inhibiting phase"; (IV) "contraception use phase"; (V) "you stopped TMC"; (VI) "you and your partner while using the TMC"; (VII) "you and your entourage"; and (VIII) "satisfaction and discontent." These were primarily multiple-choice questions (Q). Some questions used an increasing satisfaction scale from 1 to 4 (Q13, 16, 19, 32-34, 36, 37, 42, 45, 48, 49, 52, 59-61, 62.b, 69, 74, 75.b, 79, 89, 91, 93.b); one question (Q82) was open-ended. For question 82, the open-ended responses were written in free text and then analyzed according to the themes presented in each response.

  3"]) among men who had reached the phase of CU use as the only form of the couple's contraception (contraception use phase): "N-3" stage versus "contraception use phase," "N-3" stage versus "CU testing phase," and "CU testing phase" versus "contraception use phase." These comparisons were made for each satisfaction parameter (mean of 59 values) and for all five parameters (mean of 295 values) by a paired samples Wilcoxon signed-rank test. TA B L E 1 Description of the included population (n = 63) Variable Category N (%) Age (years) Mean +/-SD Median [min-max]

20472927, 2022, 8 ,

 8 Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/andr.13264 by Aix-Marseille Université, Wiley Online Library on [20/12/2022]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License TA B L E 5 Reasons for recommending this method Main topics covered in the free text responses (

20472927, 2022, 8 ,

 8 Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/andr.13264 by Aix-Marseille Université, Wiley Online Library on [20/12/2022]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License

Table 1

 1

reports the description of the population. The majority (81%) of the men had a bachelor's degree or more, and the main occupational 20472927, 2022, 8, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/andr.13264 by Aix-Marseille Université, Wiley Online Library on [20/12/2022]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License TA B L E 2 Contraceptive history of the 63 men before the use of thermal male contraception (TMC) N-

3 a N-2 N-1 Contraceptive methods Use Main reasons for termination Use Main reasons for termination Use Main reasons for termination

	Male methods	27 (43%)		25 (40%)		24 (38%)
	-Male condom	20 (32%)	Decreased sexual pleasure	22 (35%)	Decreased sexual pleasures	10 (16%)*	Decreased sexual pleasure
	-Withdrawal	5 (8%)	Fear or experience of	2 (3%)	Fear of unwanted pregnancy	10 (16%)	Fear of unwanted pregnancy
			unwanted pregnancy
	-Male condom	2 (3%)	Not applicable	1 (2%)	Not applicable	4 (6%)	Not applicable
	and withdrawal
	Female methods b	23 (37%)		33 (52%)		36 (57%)*
	-Female pill	19 (30%)	Desire to reduce hormone	13 (21%)	Desire to reduce hormone	15 (24%)	Desire to reduce hormone
			intake		intake		intake
	-IUD (with or	4 (6%)	Desire to reduce hormone	13 (21%)	Too painful application	16 (25%)**	Desire to reduce hormone
	without		intake, too painful		and/or removal		intake, side effects on
	hormones)		application and/or				health and sexuality
			removal
	-Male and female	2 (3%)		3 (5%)		2 (3%)
	methods
	-No contraception 11 (17%)		2 (3%)		1 (2%)

Table 4

 4

	When choosing	Spermatogenesis	Phase of
	TMC (n = 63;	inhibiting phase (n =	contraception use
	Q28)	60; Q43, Q46, Q47)	(n = 59; Q57, Q58)

: they were easily resolved (n = 20/36, 56%) and/or may have required modifications to the CU (n = 19/36, 53%; SQ41).

During the spermatogenesis inhibiting phase (n = 60), the main fear of the men (n = 33, 55%) was that they would not be able to provide contraception for the couple on a daily basis. The main positive point 20472927, 2022, 8, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/andr.13264 by Aix-Marseille Université, Wiley Online Library on [20/12/2022]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License TA B L E 3 Evolution of concerns, negative and positive aspects in the successive phases of TMC a Concerns of discomfort (n = 40; 63% and n = 15; 25%), of pain (n = 12; 19% and n = 8; 13%), of lack of hindsight with a new method (n = 8; 13% and n = 4;

you experience any difficulties with the contraceptive underwear?

  (Several answers possible, n = 63)

	Initial underwear poorly adapted	59 (94%)
	Of which:
	-Discomfort when wearing CU	35 (56%)
	-Pain when wearing CU	22 (35%)
	-Skin irritation	37 (59%)
	-The testicles descended spontaneously	34 (54%)
	Erections did not give way and/or were painful a	9 (14%)
	Difficulties during installation and/or removal of CU	4 (6%)
	No difficulties	3 (5%)
	Hypersudation	3 (5%)
	Other	3 (5%)
	Note: Values are presented as number (%);
	Abbreviations: CU, contraceptive underwear; Q, number of the question
	(Appendix).

TA B L E 4 Difficulties encountered with contraceptive underwear during the testing phase Did a Related to night-time wearing of CU (not suitable for this type of CU).

20472927, 2022, 8, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/andr.13264 by Aix-Marseille Université, Wiley Online Library on [20/12/2022]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License

Fears when starting TMC

At the time of choosing TMC, 86% of the men had fears about this method. Some of these fears decreased over time, while others remained stable. The most frequent fears (70% of men) were about the method itself: discomfort, pain, method that was too difficult to access and/or too long to set up, lack of hindsight into a new method. Some of these fears ("delayed effectiveness"; "uncomfortable"; "time required may not be representative of the population of men using male contraception as the unique couple contraceptive method. Indeed, TMC is less accessible and known by the general French population than condom and vasectomy. [START_REF] Amouroux | Are men ready to use thermal male contraception? Acceptability in two French populations: new fathers and new providers[END_REF] The low accessibility of TMC consultations could have selected men much more interested in male contraception than men in the general population, and our results should be interpreted with this view. Nevertheless, this population is suitable for the study of men's motivations for choosing TMC, which was one of our survey's purposes. Third, our survey lacked a similar questionnaire for the female partners.

Perspectives

A wider diffusion of the CU would be possible for Phase III testing, as soon as a public funding supports a multicentric trial in France, and as soon as other European teams are ready to participate. The results of our survey indicate opportunities for future studies of TMC users, in particular, studies of their female partners (especially the impact on their sexual satisfaction); and the real-life contraceptive efficiency of this method over the entire period of use of this historical cohort.

Finally, a qualitative study on the social attitudes of men toward the availability of a male hormonal contraceptive suggested that Phase IV studies are necessary to establish long-term side effects [START_REF] Dismore | Social constructions of the male contraception pill: when are we going to break the vicious circle?[END_REF] ; such a suggestion also seems valid for TMC.

CONCLUSION

This first survey of the experience and acceptability of TMC in men using this method as a couple's only form of contraception showed that the men were mainly motivated to use a non-hormonal method that is regarded as "natural." Then, they rapidly adopted the method (despite frequent initial fears), and during the phase of contraception use, they described significantly improved sexual satisfaction with the method and reported confidence and support from their partner. These men successfully assumed the mental load of a daily action to provide the couple's contraception, and this improved their self-esteem. The main negative point was discomfort, which was reported by 24% of the respondents. The satisfaction score for using this method was high, and 100% of men reported they would recommend the method to other men. This positive evaluation, together with the already published contraceptive efficacy and reversibility of TMC, should encourage the development of this method.

CONFLICT OF INTEREST

The authors declare that they have no conflict of interest.

AUTHOR CONTRIBUTIONS

Research conception and design: RM and JP. Questionnaire design: All

SUPPORTING INFORMATION

Additional supporting information can be found online in the Supporting Information section at the end of this article.