Samuel P Caro
email: samuel.caro@cefe.cnrs.fr

Ségolène Delaitre

Bruno Buatois

Francesco Bonadonna

Jessica L Graham

The influence of plant odours on sexual readiness in an insectivorous songbird

Keywords: olfaction, herbivore induced plant volatiles, seasonal timing, reproduction, gonadal cycles, birds

Many organisms rely on environmental cues to predict and anticipate the annual optimal timing of reproduction. In insectivorous birds, preparation for breeding often coincides with the time vegetation starts to develop in spring. Whether there is a direct relationship between the two, and through which mechanisms this link could come about, has rarely been investigated.

Plants release Herbivore-Induced Plant Volatiles (HIPVs) when they are attacked by insects, and recent studies have shown that birds can detect and orient to those odours when searching for food. If those volatiles also stimulate sexual reproductive development and timing of reproduction remains to be discovered. We tested this hypothesis by monitoring gonadal growth in pairs of blue tits (Cyanistes caerueus) exposed to air from caterpillar infested oak trees or from a control, in spring. We found that while males and females grew their gonads over time, gonads grew at the same rate in both odor treatments. More exploratory (i.e. a proxy of personality) females did however have larger ovarian follicle sizes when exposed to the HIPVs than to the control air, which is consistent with earlier results showing that fast explorers have larger gonads in spring and are more sensitive to HIPVs. If HIPVs constitute powerful attractants in foraging birds, their influence on gonadal development prior to breeding appears to be relatively subtle and only enhance reproductive readiness in some individuals. These results are nevertheless important as they set olfaction as a new player in seasonal timing of reproduction in birds.

Introduction

Photoperiod (i.e., day length) is the predominant cue used by temperate breeding organisms to determine the appropriate time of year to undergo the physiological and behavioral changes to prepare for seasonal breeding [START_REF] Dawson | Photoperiodic control of the annual cycle in birds and comparison with mammals[END_REF]. However, photoperiod does not vary annually, which means that it is of no use for predicting year-to-year variation in environmental conditions. This is what supplementary, or non-photic cues do (reviewed by Chmura et al., 2019). Temperature has received vast attention as a supplementary cue (Caro et al., 2013a) since rapidly occurring changes to the environment are shifting timing of life history traits across a broad array of taxa [START_REF] Parmesan | Ecological and Evolutionary Responses to Recent Climate Change[END_REF]. However, results from studies manipulating temperature and observing effects on timing of breeding have been mixed. If a causal relationship between ambient temperature and timing of reproduction has been shown in some songbirds [START_REF] Meijer | Temperature and timing of egglaying of European starlings[END_REF][START_REF] Visser | Temperature has a causal effect on avian timing of reproduction[END_REF], the amplitude of this effect has proven variable and, in all cases, smaller than expected, particularly on the physiological mechanisms of reproduction (Caro et al., 2013b;[START_REF] Dawson | The effect of temperature on photoperiodically regulated gonadal maturation, regression and moult in starlings -potential consequences of climate change[END_REF][START_REF] Perfito | Seasonal gonadal recrudescence in song sparrows: Response to temperature cues[END_REF]Schaper et al., 2011a;[START_REF] Verhagen | Temperature has a causal and plastic effect on timing of breeding in a small songbird[END_REF][START_REF] Visser | Temperature has a causal effect on avian timing of reproduction[END_REF]2011;[START_REF] Watts | Effects of temperature on the timing of breeding and molt transitions in house finches[END_REF]. This suggests that temperature is not the only player regulating annual variation in seasonal timing of reproduction in temperate-zone species and it calls for investigations on other non-photic signals.

Vegetation development, and more specifically timing of bud burst in trees, has also received attention as a possible reproductive cue, particularly in insectivorous birds. Relying on bud development to decide when to start breeding could be a good proxy for predicting the optimal timing for breeding in several bird species because buds and young leaf shoots constitute the exclusive food of the caterpillars that these birds provide to their chicks [START_REF] Du Merle | Stades phénologiques et infestation par Tortrix viridana L. (Lep., Tortricidae) des bourgeons du chêne pubescent et du chêne vert[END_REF][START_REF] Naef-Daenzer | The foraging performance of great and blue tits (Parus major and P. caeruleus) in relation to caterpillar development, and its consequences for nestling growth and fledging weight[END_REF][START_REF] Van Asch | Evolutionary response of the egg hatching date of a herbivorous insect under climate change[END_REF]. Many studies have indeed found significant correlations between tree phenology and laying date in wild populations of insectivorous birds [START_REF] Bison | Best environmental predictors of breeding phenology differ with elevation in a common woodland bird species[END_REF][START_REF] Bourgault | Spring vegetation phenology is a robust predictor of breeding date across broad landscapes: a multi-site approach using the Corsican blue tit (Cyanistes caeruleus)[END_REF][START_REF] Hinks | Scale-dependent phenological synchrony between songbirds and their caterpillar food source[END_REF][START_REF] Hinks | Scale-dependent phenological synchrony between songbirds and their caterpillar food source[END_REF][START_REF] Nilsson | Leafing phenology and timing of egg laying in great tits Parus major and blue tits P. caeruleus[END_REF][START_REF] Shutt | The environmental predictors of spatiotemporal variation in the breeding phenology of a passerine bird[END_REF][START_REF] Slagsvold | Annual and geographical variation in time of breeding of great tit Parus major and pied flycatcher Ficedula hypoleuca in relation to environmental phenology and spring temperature[END_REF]. However, bud burst is tightly linked with temperature and only a handful of studies have experimentally tested the effect of vegetation cues independently from temperature cues on bird reproduction [START_REF] Schaper | Spring phenology does not affect timing of reproduction in the great tit (Parus major)[END_REF][START_REF] Visser | No evidence for tree phenology as a cue for the timing of reproduction in tits Parus spp[END_REF][START_REF] Voigt | Green matters! Growing vegetation stimulates breeding under short-day conditions in wild canaries (Serinus canaria)[END_REF]2011). To complicate things further, the effect of plants on seasonal timing could occur through various sensory channels, which include visual, gustatory, tactile and olfactory pathways [START_REF] Ettinger | Consumption of green wheat enhances photostimulated ovarian growth in white-crowned sparrows[END_REF][START_REF] Voigt | Multisensory non-photoperiodic cue advances the onset of seasonal breeding in island canaries (Serinus canaria)[END_REF].

Plants have been shown to defend against herbivores by releasing volatile alarm signals (Herbivore-Induced Plant Volatiles: HIPV) that attract predators. This ability to attract predators has been well studied in insects [START_REF] Turlings | Effects of plant metabolites on the behavior and development of parasitic wasps[END_REF], where alarm signals emitted by plants in response to caterpillar grazing attract parasitoid wasps [START_REF] Van Poecke | Herbivore-induced volatile production by Arabidopsis thaliana leads to attraction of the parasitoid Cotesia rubecula: chemical, behavioral, and gene-expression analysis[END_REF], but also in seabirds that use degradation products of phytoplankton to identify fishrich zones [START_REF] Dell'ariccia | Olfactory foraging in temperate waters: sensitivity to dimethylsulphide of shearwaters in the Atlantic Ocean and Mediterranean Sea[END_REF][START_REF] Savoca | Evidence that dimethyl sulfide facilitates a tritrophic mutualism between marine primary producers and top predators[END_REF]. It was shown plants are capable of reducing the number of herbivores by greater than 90% through release of such volatiles [START_REF] Kessler | Defensive Function of Herbivore-Induced Plant Volatile Emissions in Nature[END_REF]. Recent evidence also reveals that songbirds are capable of detecting caterpillar infestation of apple trees completely by smell [START_REF] Amo | Birds exploit herbivore-induced plant volatiles to locate herbivorous prey[END_REF]. However, there is very little knowledge concerning the effects of plant volatile emissions in contexts other than foraging. Carnivorous arthropods will invest more in reproduction when presented with olfactory cues from infested plants while undergoing a food shortage [START_REF] Rondoni | Behavioural and physiological responses to prey-related cues reflect higher competitiveness of invasive vs. native ladybirds[END_REF].

We have also recently shown that birds with higher levels of testosterone, the main reproductive hormone in males, were more attracted to areas diffusing HIPVs characteristics of a caterpillar infestation [START_REF] Graham | Olfactory detection of trace amounts of plant volatiles is correlated with testosterone in a passerine bird[END_REF], and that more eggs and fledglings were produced in forest zones diffusing artificial HIPVs (Delaitre et al., unpublished results).

Whether and how these volatile emissions from infested plants directly influence the physiological mechanisms underlying reproduction is however still unknown.

The goal of this study was to determine if insectivorous songbirds use HIPVs emitted by tree buds in response to initial caterpillar infestation in the spring as a cue to prepare for breeding. We exposed breeding pairs of blue tits (Cyanistes caerueus) in captivity to the odors of caterpillar infested trees or a control odor, over two consecutive years using a complex experimental setting in which we controlled the air birds breathed. While photoperiodic and temperature cues were identical to all breeding pairs, we only exposed birds to the tree odors so any potential visual, gustatory or tactile cues provided by vegetation would not be present [START_REF] Amo | Birds exploit herbivore-induced plant volatiles to locate herbivorous prey[END_REF]. We monitored breeding pairs for gonadal development and hypothesized that pairs exposed to odors from caterpillar infested trees would develop their gonads more quickly than pairs in the control group.

Gonadal development might not only differ between the experimental and the control groups, but also among birds exposed to the odor treatment. Exploring variance among individuals is central to understand ecological and evolutionary processes, and it has long been neglected by endocrinologists [START_REF] Williams | Individual variation in endocrine systems: moving beyond the 'tyranny of the Golden Mean[END_REF]. One way individuals differ reliably is in their temperament or personality, which in songbirds is often measured through exploratory behaviors [START_REF] Réale | Integrating animal temperament within ecology and evolution[END_REF]. Several of these behaviors have indeed been shown to be repeatable, heritable, and to covary with one another, like exploration of new environments, new objects and aggression [START_REF] Dingemanse | Repeatability and heritability of exploratory behaviour in great tits from the wild[END_REF]. Interestingly these temperaments also covary with physiological traits and environmental perception [START_REF] Van Oers | Correlated response to selection of testosterone levels and immunocompetence in lines selected for avian personality[END_REF]. In great tits for example, ovarian follicle volumes differ between selection lines for personality, with fast exploring females having larger ovarian follicles [START_REF] Caro | Personality and gonadal development as sources of individual variation in response to GnRH challenge in female great tits[END_REF]. We also recently showed that more exploratory male blue tits are more attracted to HIPVs than less exploratory males (Delaitre et al., unpubl. results). Exploration behavior thus seems to be linked to both HIPV sensitivity and reproductive mechanisms in tits, and therefore constitutes a potential source of variation in how individuals integrate and respond to HIPV signals.

Methods

Ethical note

Blue tits were trapped and maintained under licenses 2018-s-11 issued by the Direction Régionale de l'Environnement, de l'Aménagement et du Logement Languedoc-Rousillon; and 15-XIX-116 issued by the Direction Départementale de la Protection des Populations de l'Hérault. These experiments were carried out under license D34-172-11 from the Direction Départementale de la Protection des Populations de l'Hérault, and approved by the animal experimentation ethical committee of the French Ministry of Higher Education and Research (APAFIS#8608-2017012011062214 v4).

Animal Housing

The experiment took place over two years at the CNRS in Montpellier, France (43 o 37'56"N, 3 o 52'E). Twenty-four hand raised blue tits (born in 2015 in our long-term studied population of La Rouvière, near Montpellier; [START_REF] Caro | Mutual mate preferences and assortative mating in relation to a carotenoid-based color trait in blue tits[END_REF] were housed in 12 terrariums (120 x 50 x 50 cm, one opposite-sex pair per terrarium) on 20 February 2019 and 21 February 2020 to allow approximately one month to adjust to new housing before starting the experiment (n = 48 birds total). We randomly assigned 12 male-female pairs each year to either a HIPV exposure treatment (n = 6 per year) or control (n = 6 per year). Within each terrarium, a wire mesh was used to separate males and females (see figure 1), because males are usually ready to reproduce before females [START_REF] Caro | Simultaneous pituitary-gonadal recrudescence in two Corsican populations of male blue tits with asynchronous breeding dates[END_REF]2009) and can therefore become overly aggressive toward females in confined environments [START_REF] Caro | Non-photoperiodic factors and timing of breeding in blue tits: Impact of environmental and social influences in semi-natural conditions[END_REF]. If physical contacts were prevented, males and females could still interact visually and acoustically, which has been shown to be sufficient for birds to develop their gonads and often for laying eggs [START_REF] Kroodsma | Reproductive development in a female songbird: differential stimulation by quality of male song[END_REF]. Every individual had access to a nest box (not shown on figure 1) that was built around the wire mesh, with one entrance hole on each side, in a way that males and females could also see each other inside the nest box. Ad libitum food and water were replaced three times per week.

Terrariums were housed indoors to remove any potential visual cues provided by vegetation. We housed the birds in three different rooms with four breeding pairs per room.

Pairs were visually isolated from other pairs and the terrariums also strongly reduced the ability of the pairs in the same room to hear each other. One terrarium in each room received air flow from one of four outdoor enclosures, so that each room had two treatment and two control terrariums. A window allowed natural light into the room. We additionally supplemented artificial light starting 15 min post-sunrise, until 15 min pre-sunset, so that birds were exposed to the natural increase and decrease in light intensity from the relatively small window (55 x 42 cm) [START_REF] Fleissner | Perception of Natural Zeitgeber Signals[END_REF]. Extra light aimed at increasing and homogenizing light intensity in the room during the day. Sunrise and sunset times were determined using the United States Naval Observatory data base (www.usno.navy.mil/USNO).

Equipment design

To control the odor cues individuals received, two pumps (KNF Neuberger, Cat #N026.1.2AN.18) pushed 40 L/min of air through a respective charcoal filter to purify the air [START_REF] Doughty | Purification of air in enclosed spaces[END_REF] (figure 1). Flow from each pump was then split to push air into one control and one experimental enclosure. The four enclosures were constructed by stainless steel structure (250 x 80 x 80 cm) covered with thermowelded, chemically resistant Flonfilm 300 ETFE film (100 µm thick, PolyFlon Technology, LTD, Cat #ETFE1000/1550). Acrylic flow meters (Dakota Instruments Inc, Cat #6A0111BV-AB) kept the flow to ~19 L/min in each enclosure. Three smaller pumps (KNF Neuberger, Cat #N86KN.18) then each pulled air from one enclosure and pumped through an acrylic flow meter at 5 L/min (Dakota Instruments Inc, Cat #6A0107BV-AB) and into the terrarium (figure 1). An overflow of ~4 L/min in the enclosures ensured outward pressure of the system in case any leaks were present, so unfiltered air was less likely to enter the system. Air passively exited the terrariums through two exhaust tubes that led outside. Air could also be diverted through a center enclosure (made of glass in 2019, aluminum container in 2020) shared by all 12 terrariums (see 9 on figure 1). When trees needed to be watered or changed out, birds continued to receive filtered, uncontaminated air while the treatment and control enclosures were open. A third pump (not shown on figure 1) was used to flush contaminated air out of the enclosures for several hours before resuming airflow from the enclosures. Due to high humidity levels inside the terrariums in 2019, particularly later in the season, several changes were made to the system in 2020 (figure S1). First, the tubing leading from the small pumps to the terrariums was run through a cooling system to remove water. The condensed water vapor was collected in glass jars below the cooling system before the air entered the terrarium. These jars were emptied at least once per week. Second, the center enclosure described above was filled with silica gel. Two times per week at the time trees in the other enclosures were manipulated, air was diverted through this silica gel for approximately 24 hours to dry air in the terrariums [START_REF] Yu | An evaluation of silica gel for humidity control in display cases[END_REF]. In reality, there were 4 enclosures, each leading to 3 terrariums (12 in total). See figure S1 for a more detailed view.

Infestation of Trees

Green oak tortrix moths (Tortrix viridana) were collected from Corsica in June 2018 and 2019 and placed in large nets on oak branches to lay eggs. Branches were returned to Montpellier and kept outside at ambient temperature to synchronize hatching of eggs with oak bud burst. Green oak tortrix caterpillars are oak specialists and hatching needs to be closely timed with elongation and development of oak buds so caterpillars can perforate the bud and eat young developing leaves inside the bud [START_REF] Du Merle | Egg development and diapause: ecophysiological and genetic basis of phenological polymorphism and adaptation to varied hosts in the green oak tortrix, Tortrix viridana L.(Lepidoptera: Tortricidae)[END_REF][START_REF] Ivashov | The role of host plant phenology in the development of the oak leafroller moth, Tortrix viridana L. (Lepidoptera: Tortricidae)[END_REF]. Thus, we utilized downy oak trees (Quercus pubescens Willd.) of approximately 2.5 meters high, grown in pots. To spread out timing of bud burst over the season, we housed 20 trees on the south side of a building, 20 trees on the north side, and 40 trees at higher elevation to delay bud burst. We began to expose birds to HIPV air as soon as bud burst and caterpillar hatching occurred simultaneously.

When bud development began to reach an appropriate stage for caterpillar infestation, four trees were placed into each of the two treatment enclosures and infested with freshly hatched green oak tortrix caterpillars (approx. 20 caterpillars per tree, depending on caterpillar availability). Control enclosures contained four soil-filled pots identical to those the trees were planted in. All pots (including those with trees) were wrapped in ETFE film bags to reduce any odors emitted from the soil and pots from entering the terrariums. When buds on the tree began turning into mature leaves, they were replaced with newly infested trees (generally 1 -2x per week). We used freshly hatched caterpillars on new trees until ~29 April 2019, when nearly all caterpillar eggs had hatched. We then began to transfer caterpillars from trees being removed to trees being added. This likely kept the HIPV production at a very early season stage for most of the experiment. We stopped changing trees and let them progress in the enclosures after the third laparotomy (details below). However, in 2020, the French lockdown caused by the COVID-19 pandemic made it impossible to transport the high elevation trees to the campus. Thus, when we ran out of trees (21 April 2020), trees and caterpillars were left to continue development. HIPVs emitted by buds are to our knowledge similar to those emitted by developed leaves, only the emission rates seem lower in buds than in leaves (unpublished results).

Control enclosures were treated exactly as treatment enclosures. When treatment enclosures were opened to water the trees, control enclosures were also opened and water added to the soil-filled pots. Similarly, when two old trees were exchanged for new ones, two soil filled pots would be replaced with two new soil filled pots.

Even if this was beyond the scope of the present study, a small number of air samples reaching the terrariums were pulled into cartridges containing an adsorbent to collect volatile compounds. These compounds were subsequently separated over a Gas Chromatograph -Mass Spectrometer coupled system (GC-MS) using a semi-standard non-polar column. Mass spectrum and linear retention index comparison enabled us to identify the compounds present.

Those samples revealed that (E)-β-ocimene, (E)-4,8-dimethyl nona-1,3,7-triene (DMNT), methyl salicylate, (E)-caryophyllene, aromadendrene, α-humulene and (E.E)-α-Farnesene, all known HIPVs (Röse and Tumlinson, 2004, Graham et al. unpublished data), were found in the terrariums of the HIPV treatment group (figure 2).

Reproductive measures

Three laparotomies were conducted each year to measure gonadal growth in all birds. Initial laparotomies were conducted when photoperiod was 11 hours of light (11L:13D) to obtain a pre-breeding measure of the gonads and confirm the two treatment groups did not differ. Two subsequent laparotomies were performed at four-week intervals (photoperiods 12.5L:11.5D and 14L:10D). Individuals were unilaterally laparotomized under isoflurane anesthesia. Left testis length and width were recorded in males and diameter of the largest developing ovarian follicle was measured in females. Measures were collected using the scale engraved in the ocular of a binocular microscope (Optika SZM-4) to the nearest 0.1mm. Testis volume was calculated as: 𝑉 = $ % 𝜋𝛼 ( 𝛽 where α is half the testis width and β is half the testis length. Follicle volume was calculated as: 𝑉 = $ % 𝜋𝛼 % where α is half the follicle width [START_REF] Visser | Genetic variation in cue sensitivity involved in avian timing of reproduction[END_REF]. The observer was blind to the treatments. Throughout the experiment, birds were provided with moss to build nests and monitored for possible nest building and egg laying.

Exploration scores

We scored exploration by releasing each bird separately in a novel environment, which here consisted in an artificially lid room (3.5 x 2 m) equipped with five two-storey perches.

Once the bird entered the room, its movements were observed for two minutes. The total number of movements between the five perches was counted, as well as hops up, and down, and based on these measures, birds were given an exploration score on a continuous scale with higher scores indicating faster exploration, and lower scores indicating slower exploration [START_REF] Dingemanse | Repeatability and heritability of exploratory behaviour in great tits from the wild[END_REF][START_REF] Reparaz | Mate preference of female blue tits varies with experimental photoperiod[END_REF].

Statistical Analysis

All analyses were performed with R version 4.1.0. Linear mixed-effects models were completed using the lme4 and lmerTest packages [START_REF] Bates | Fitting linear mixed-effects models using lme4[END_REF] [START_REF] Kuznetsova | lmerTest Package: Tests in Linear Mixed Effects Models[END_REF]. We set α = 0.05.

We started by running some preliminary analyses on the possible influence of variables that were not of primary interest to our study. Using two mixed-effect models (one for each sex), we tested whether the tree enclosures (four in total), the rooms housing the terrariums (three in total), the spatial position of the terrariums within a room (up or down the shelves, near or far from the window providing sunlight), the year, and body mass of the birds had any influence on gonadal size. We only found a significant influence of body mass on gonadal size in females, none of the other variables had any significant effect on gonadal size (all p-values >0.1, data not shown). We therefore decided to keep body mass in subsequent analyses, and ignored the other variables.

Male and female gonad size was analyzed separately as volume is not comparable between the sexes. In 2019, 24 individuals were measured during the first (T0) and second (T1) time point. There were only 22 measures for the third time point (T2) as we could not locate the ovary in one control female and one treatment male died during the experiment.

Additionally, one female in 2019 laid an egg before the third laparotomy. Since the female was laying, we did not operate it and rather assigned the mean yolk diameter calculated from 23 unfertilized blue tit eggs collected from our aviaries (𝑥̅ = 8.24 ± 0.12 mm) as a proxy for its largest ovarian follicle diameter. In 2020, 24 individuals were measured at the first and second time points. Twenty-three individuals were measured at the third time point because one treatment male died during the experiment.

Gonadal volume was log transformed before analysis to account for exponential growth. Linear mixed effects models included treatment (factorial), time point (continuous), exploration score (continuous), body mass (continuous), treatment by exploration score interaction, and treatment by time point interaction, as fixed factors. Individual ID was included as a random intercept to account for repeated measures. Non-significant interactions were removed from the models. Since the HIPV treatment was only provided after T0, we also ran the analyses described above, restricting data to T1 and T2. Results were very similar to those obtained with all three time points (data not shown). Not enough individuals built nests (7 out of 24; 3 in the HIPV group, 4 in the control group) or laid eggs (6 out of 24; 3 in each group), thus no statistical analyses were performed on breeding data.

Results

Ovarian follicle size increased over the course of the experiment (p < 0.001, table 1, figure 3), but follicles grew at the same rate in HIPV and control treatments (interaction treatment x time: p = 0.505, table 1, figure 3). There was a significant interaction between odor treatment and exploration score, with fast exploring females having larger ovarian follicles when exposed to HIPVs than to the control odor treatment (interaction treatment x exploration score: p = 0.037, table 1, figure 4). Finally, heavier females had larger ovarian follicles (p < 0.001, table 1). Male testes also increased in volume over time (p < 0.001, table 1, figure 5). Like in females, male gonads grew at the same rate in HIPV and control treatments (interaction treatment x time: p = 0.236, table 1, figure 5). Body mass or exploration score did not influence testis volume (all p ≥ 0.1, see table 1).

Discussion

Our results suggest that HIPVs produced in response to caterpillar infestation do not exert a strong influence on pre-breeding sexual development in blue tits. While gonad volume increased over time in both males and females, there were no striking differences in size between the control and the treatment pairs. A significant response to the odor treatment was nevertheless visible in more exploratory females, which had larger ovarian follicles in the HIPV than in the control group.

Experiments manipulating non-photic cues related to the initiation of reproduction in strictly seasonal breeding birds rarely result in striking differences between groups, owing to the fact that those cues are fine-tuning cues that only modulate the powerful effect of photoperiod [START_REF] Wingfield | Natural regulation of reproductive cycles[END_REF]. The case study of the influence of temperature cues on reproduction in great tit, highlighted in introduction, is probably the best example (Schaper et al., 2011a;[START_REF] Visser | Temperature has a causal effect on avian timing of reproduction[END_REF]. Experimental evidence for an effect of temperature on great tit timing of reproduction in an ecologically relevant context requested nearly 10 years of experiments in captivity. Furthermore, temperature was never found to influence some of the main physiological mechanisms underlying egg-laying, which includes gonadal size, luteinizing hormone, and prolactin concentrations (reviewed in Caro et al., 2013b). Only patterns of gene expression related to seasonal timing were found to differ between temperature treatments [START_REF] Laine | Exploration of tissue-specific gene expression patterns underlying timing of breeding in contrasting temperature environments in a song bird[END_REF], suggesting that the substrate for temperatureinduced changed in reproductive physiology is there, but hard to detect. It is possible that the same complexity applies to environmental cues linking vegetation to timing of breeding, as suggested here by the absence of an effect of HIPVs on gonadal development, except for a subset of females (see below). Only a few previous studies have manipulated vegetation cues in captivity in tits (mainly through the addition of cut branches to the aviaries where the birds were), and they found no effect on timing of reproduction, or at least not in the predicted direction [START_REF] Schaper | Spring phenology does not affect timing of reproduction in the great tit (Parus major)[END_REF][START_REF] Visser | No evidence for tree phenology as a cue for the timing of reproduction in tits Parus spp[END_REF]. In both cases however there was evidence for a positive effect of the leafing branches on luteinizing hormone, a central reproductive hormone, which called for more investigation on the topic. Other studies on other bird and mammal species sometimes found stronger evidence. In meadow voles (Microtus montanus), adding sprouted wheatgrass, or one of its constituent (6-methoxybenzoazolinone: 6-MBOA), triggered reproduction and modulated sex-ratio [START_REF] Berger | Effect of 6methoxybenzoxazolinone on sex ratio and breeding performance in Microtus montanus[END_REF][START_REF] Negus | Experimental triggering of reproduction in a natural population of Microtus montanus[END_REF], while in white-crowned sparrows (Zonotrichia leucophrys), adding wheat sprout leaves to the diet accelerated ovarian development [START_REF] Ettinger | Consumption of green wheat enhances photostimulated ovarian growth in white-crowned sparrows[END_REF]. In canaries (Serinus canaria) the presence of vegetation in the aviaries advanced egg-laying by several weeks [START_REF] Voigt | Green matters! Growing vegetation stimulates breeding under short-day conditions in wild canaries (Serinus canaria)[END_REF][START_REF] Voigt | Multisensory non-photoperiodic cue advances the onset of seasonal breeding in island canaries (Serinus canaria)[END_REF]. While the number of experimental studies on the possible influence of vegetation development on bird reproduction is already very limited, the sensory pathways through which the plant stimuli were provided varied tremendously and mixed in various proportions tactile, gustatory, olfactory and visual signals. The drawback is that in several of those earlier studies, animals from the experimental groups could physically interact with the plants, while the control animals received none, which introduces environmental enrichment as a confounded factor. Disentangling pathways by carefully controlling sensory modes of perception of plants, like [START_REF] Voigt | Multisensory non-photoperiodic cue advances the onset of seasonal breeding in island canaries (Serinus canaria)[END_REF] did for example, will be key for clarifying whether and how vegetation cues potentially affect reproduction in vertebrates. In our case, the only possible sensory mode of perception of infested oak trees was olfaction, and we show that more exploratory females responded to these HIPVs. Future studies will need to determine whether combining olfactory with other carefully selected cues (either visual or gustatory cues from plants, or other environmental cues like photoperiod or temperature) could enhance the results obtained here.

More exploratory females grew their ovarian follicles more rapidly when exposed to HIPVs. This is not the first time that a link between a behavior related to personality and HIPVs is discovered. In a recent study testing whether blue tits can innately detect and orient to a blend of artificial HIPVs mimicking an infestation of oak buds by caterpillars, we found that the preference for the side of a Y-maze containing the HIPVs was driven by fast exploratory males (Delaitre et al., unpub. results). The results of both experiments suggest that fast explorers might be more sensitive to HIPVs. Through which mechanisms this link operates is still unclear at present, but we know that high sensitivity to HIPVs in male blue tits is associated with testosterone [START_REF] Graham | Olfactory detection of trace amounts of plant volatiles is correlated with testosterone in a passerine bird[END_REF]. We also know that testosterone is locally produced in the olfactory epithelium in rats [START_REF] Horie | Presence of sex steroid-metabolizing enzymes in the olfactory mucosa of rats[END_REF][START_REF] Lupo | Testosterone metabolism in the olfactory epithelium of intact and castrated male rats[END_REF], providing a possible mechanistic link between sex steroids and olfactory sensitivity for HIPVs. On the other hand, in female great tits we have recently shown relationships between exploration behavior, ovarian follicle sizes and plasma concentrations of 17ß-estradiol, the main sexual steroid in female. Females from a line artificially selected for fast exploration more rapidly increased 17ßestradiol after a GnRH challenge, and had larger ovarian follicles than females from the line selected for slow exploration [START_REF] Caro | Personality and gonadal development as sources of individual variation in response to GnRH challenge in female great tits[END_REF]. This interplay between sex steroid hormones, HIPV sensitivity and personality clearly needs further investigation, in particular to understand if the enhanced olfactory sensitivity of fast explorers is driven through the action of steroid hormones.

There may also be technical limitations that could explain why we did not find stronger differences between the treatment and controls. First, birds were housed in relatively small compartments and blue tits are known to necessitate large enclosures to reproduce [START_REF] Caro | Non-photoperiodic factors and timing of breeding in blue tits: Impact of environmental and social influences in semi-natural conditions[END_REF]. Not enough birds may have approached reproductive readiness to detect an effect of HIPVs given the small sample sizes. Some females however laid eggs (6 out of 24, see methods), but we will need to experiment in larger settings to test this properly. A second potential issue is that HIPVs might not have reached the terrariums in sufficient concentrations.

That early in the season, the HIPV production in response to caterpillar herbivory is very low (Graham et al. unpublished data). With overflow in the enclosures used to keep contaminated air from entering through any leaks in the system, we may have further lowered the concentration of HIPVs. Additionally, water condensation in the system due to high humidity levels can lead to adsorption on solid surfaces and oxidation of some VOCs, particularly polar compounds, before they reach the bird enclosures [START_REF] Niinemets | Estimations of isoprenoid emission capacity from enclosure studies: measurements, data processing, quality and standardized measurement protocols[END_REF]. Despite this however, we still detected several HIPVs compounds in the air arriving to the terrariums (figure 2), showing that air to which birds were exposed in the treatment group included oak bud HIPVs.

In conclusion, our results do not provide strong evidence that HIPVs released by developing tree buds in response to caterpillar herbivory, trigger gonadal recrudescence in captive blue tits. This might however not be surprising given that vegetation cues, in the same way as temperature or rainfall, are considered supplementary cues that refine the preponderant influence of photoperiod in temperate zones. Our finding that more exploratory females had slightly larger gonads when exposed to HIPVs should be considered as promising insight and it calls for more investigation on the possibility that olfaction could be a new player in seasonal timing of reproduction in birds

Figure 1 .

 1 Figure 1. Diagram of the experimental setup. Air was pumped (1) and pushed through a charcoal filter (2). Purified air was then split and flow regulated at 19L/min (3) before reaching one control (4) and one experimental (5) enclosure. Smaller pumps (6) pulled air from the enclosures at 5 L/min (7) and to the terrariums (8). Silica gel (9) was used to remove moisture from the air when flow was not through the enclosures. For simplicity, diagram represents only a fraction of the experimental setup.

Figure 2 .

 2 Figure 2. Concentrations of the compounds detected in the terrariums. Concentrations depicted here are the means of the 6 aquariums either exposed to air from caterpillar infested trees (HIPV group), or to control air. List of the compounds: (1) (E)-β-ocimene, (2) DMNT, (3) methyl salicylate, (4) (E)caryophyllene, (5) aromadendrene, (6) α-humulene, (7) (E.E)α-Farnesene.

Figure 3 .

 3 Figure 3. Ovarian follicle growth in blue tits. While there was a significant increase in follicle size over time (LMM, F=36.83, p<0.001), they grew at the same rate in both treatments (LMM, F=0.45, p=0.505). Points indicate mean ± SEM; n=24, 12 birds per treatment.

Figure 4 .

 4 Figure 4. Effect of odour treatment and personality on ovarian follicle size in female blue tits. Fast explorers had larger ovarian follicles when exposed to air containing HIPVs than to control air (LMM, F=5.04, p=0.037). Lines depict model estimates and 95% CI, n=24, 12 birds per treatment.

Figure 5 .

 5 Figure 5. Testes growth in blue tits. While there was a significant increase in testes volume over time (LMM, F=165.31, p<0.001), they grew at the same rate in both treatments (LMM, F=1.45, p=0.236). Points indicate mean ± SEM; n=24, 12 birds per treatment.

Table 1 .

 1 Analysis of the variables that potentially influence the volume of the gonads of female (n=24) and male (n=24) blue tits. Eliminated interactions (in grey) are presented in the reverse order in which they were removed from the model. Intercept includes Treatment = control. Volumes are log-transformed.

	Variable	Estimate	S.E.	F	p-value
	Females
	(Intercept)	-0.26	0.12
	Treatment	-0.37	0.17	4.98	0.038*
	Time	0.41	0.07 36.83	<0.001***
	Exploration score	-0.01	0.04	3.68	0.070
	Body mass	0.23	0.05 18.73	<0.001***
	Treatment x Expl. score	0.10	0.05	5.04	0.037*
	Treatment x Time	-0.09	0.13	0.45	0.505
	Males
	(Intercept)	1.07	0.07
	Treatment	-0.08	0.08	0.88	0.362
	Time	0.46	0.04 165.31	<0.001***
	Exploration score	-5e-04	0.01	0.01	0.914
	Body mass	0.06	0.04	2.68	0.113
	Treatment x Time	0.09	0.07	1.45	0.236
	Treatment x Expl. score	0.01	0.01	0.35	0.562

Acknowledgments

The authors would like to thank D. Gomis and many other members of the Lunaret zoo in Montpellier, and many students at the CEFE, for hand-raising the birds used in this experiment. A. Hoste for DNA sexing and personality testing the birds; D. Degueldre for building the tree enclosures and terrariums; I. Vlandis for assistance with the experiment in 2019; M. Staudt for discussions about the design of the experiment; C. de Franceschi for collecting tortrix moths and pupae in Corsica; and two anonymous reviewers for their constructive comments on an earlier version of this manuscript. VOCs analysis were made using the technical facilities of the Platform of Chemical Analysis in Ecology (PACE -CEFE, Montpellier, France), with the support of LabEx CeMEB, an ANR "Investissements d'avenir" program (ANR-10-LABX-04-01).

Funding

This work was supported by a grant from the Agence Nationale de la Recherche (ANR-15-CE02-0005 to SPC) and a PRESTIGE Postdoctoral Research Fellowship (PRESTIGE-2018-2-0007 to JLG).


Olivier Dodier
email: olivier.dodier@unimes.fr

Mickaël Morlet-Rivelli

Fanny Verkampt

France Lags Behind in the Application of Memory Science in the Courtroom

Keywords: Memory science, expert witness, Justice system, Applied science, cognitive science

France has a strong psychoanalytical tradition in the application of psychology, and the legal field is no exception. In this article, we discuss the consequences of the limited use in court of knowledge about memory from cognitive sciences. As illustrations, we present published data showing the limited knowledge of French expert witnesses on memory, and a brief overview of two reports highlighting the failure of expert witnesses to mobilize reliable scientific knowledge in their reports and in the courtroom. Finally, we propose recommendations for improving practices.

Discussing contributions of cognitive science to the practices of psychologists and psychiatrists in the French legal area is not easy. Traditionally, legal psychological or psychiatric reports are produced by clinical practitioners, whose theoretical orientation is mostly psychoanalytic. [START_REF] Guivarch | Is the French criminal psychiatric assessment in crisis[END_REF] conducted a survey showing that 41% of psychiatry experts claimed a psychoanalytical background and about 18% a neuroscientific background, while no expert claimed a cognitive science background. Researchers have also stressed the dominance of psychoanalysis in the practices of French expert psychologists [START_REF] Combalbert | Forensic mental health assessment in France: Recommendations for quality improvement[END_REF][START_REF] Dodier | The need for memory experts in French courts[END_REF], resulting in very little use of memory science in expert reports, either in the investigation stage or in trial. Indeed, psychoanalysis has been very popular in France since the 1970s and the great influence of Jacques Lacan in the fields of psychiatry and psychology. At the time, therapeutic tools based on scientific evidence were strongly associated with a North American culture and psychoanalysis was deemed a shield against approaches considered to control minds [START_REF] Amouroux | Beyond indifference and aversion: The critical reception and belated acceptance of behavior therapy in France[END_REF]. This popularity has never diminished in France, to the point where it is widely taught in the psychology department of French universities, and many master's degree programs in psychology are dedicated to it. Despite this popularity, the scientific community widely criticized the psychoanalytic conceptions of memory functioning [START_REF] Crews | The verdict on Freud[END_REF][START_REF] Mcnally | True and false recovered memories: Toward a reconciliation of the debate[END_REF][START_REF] Otgaar | The return of the repressed: The persistent and problematic claims of longforgotten trauma[END_REF]Otgaar et al., in press), such as traumatic repression (i.e., memories of traumatic events are pushed outside the boundaries of consciousness and are stored in an area inaccessible in their pristine form, for the purpose of protecting psychological well-being) or the functioning and role of false memories (i.e., false memories, according to Freud, would be oedipal fantasies; Freud, 1917Freud, /1962)). Therefore, because psychoanalytic practice appears to be predominant in psychology education, it is not surprising that it is also prevalent in clinical psychology practice and expert reports. It is not surprising as well to observe, in expert reports, memory-related opinions that are not sufficiently grounded in updated science.

The aim of this article is to provide an overview of France's delay in the application of memory science in the legal field. For that, we will develop arguments showing both the delay in comparison with other countries and the lack of knowledge that French experts have on this issue. We will then present two expert reports on a complainant's and a suspect's memory.

Finally, we will propose recommendations to improve the application of memory knowledge from cognitive sciences in the French legal field.

There Is No Official Role for Memory Experts in the French Legal System

To appear on the official lists of French judicial experts, psychologists and psychiatrists must apply to the Public Prosecutor at the High Court. In the application form, they must inform about their legitimacy (e.g., education, training, professional experience in the legal field) to provide expert reports. Peers and magistrates then assess the applications on the basis of specific criteria (e.g., professional skills, experience). The French judicial system is inquisitorial. Therefore, the judges appoint experts to answer technical questions at the time of the investigation. This is different from the adversarial system where experts are generally appointed by the prosecution and defense parties to intervene at the time of trial. Standardized questions asked to French psychology and psychiatry experts cover a variety of topics, with a predominance of clinical and psychopathological issues 1 .

Although the role of memory expert does not exist in France, forensic psychologists and psychiatrists often have to give their opinion on memory issues [START_REF] Dodier | The need for memory experts in French courts[END_REF]. For example, the exploration of any factors that might influence complainant's testimony in sexual violence cases is almost systematically requested from the psychologists (or even psychiatrists, see Case 1). Similarly, in a high-profile case in France concerning the murder of a 5-year-old child whose body has never been found, psychologists and psychiatrists were sought as to why the two 1 Standard questions are available here: https://doi.org/10.5281/zenodo.7303985 defendants (the mother and stepfather) stated that they could not remember where they had buried the young girl's body2 . All questions relating to memory functioning are therefore asked to experts officially registered on lists of experts, who are mainly clinical practitioners [START_REF] Dodier | The need for memory experts in French courts[END_REF] unlike other countries practices where the role of memory experts exists, and this, regardless of whether the legal system is inquisitorial or adversarial (e.g., Italy: Otgaar et al., in press;New Zealand: Zajac et al., 2013;UK: Conway, 2013;US: Brainerd, 2013;The Netherlands: Otgaar et al., 2017).

A notable difference between the practice of forensic psychological assessment and that of memory expertise is that the former refers to the work of a clinician, whereas the latter refers more to the work of a cognitive psychologist or, to some extent, a cognitive neuropsychologist.

Therefore, providing an expert report on memory does not require meeting the complainant or the suspect, but rather exploring in depth the case file in order to highlight factors known to influence event-related memories. Memory experts are generally not asked to give an opinion on facts of the case, but instead to extract these factors from a case file-if present-, relate them to the scientific literature (e.g., [START_REF] Otgaar | A case concerning children's false memories of abuse: Recommendations regarding expert witness work[END_REF] and to educate judges and the court on this.

French Experts Know Too Little About Memory

In addition to the absence of the role of memory expert in France, it also appears that French experts have a low level of scientific knowledge about how memory works, as shown by [START_REF] Dodier | Connaissances et croyances des psychologues et psychiatres experts judiciaires concernant le fonctionnement de la mémoire[END_REF]. In their study, 120 French psychologist and psychiatrist experts completed a 14-item questionnaire on memory. Results showed that participants had a belowaverage score of correct answers (M = 6; SD = 0.18). For instance, about 30% of the experts were either uncertain or disagreed with the existence of the misinformation effect (see [START_REF] Loftus | Planting misinformation in the human mind: A 30-year investigation of the malleability of memory[END_REF]. One in five experts agreed with the possibility to accurately remember events that occurred before the age of two (see [START_REF] Howe | Unravelling the nature of early (autobiographical) memory[END_REF]. A main result was that French expert psychologists and psychiatrists had significantly fewer correct answers on average than their non-expert colleagues (M = 6.64; SD = 0.20), but also than the general public (M = 7.06; SD = 0.10)-potential jurors.

In a following study, the knowledge on memory of French vs. Norwegian psychologist and psychiatrist experts were compared on a 12-item questionnaire [START_REF] Dodier | Psychologists and psychiatrists in court: What do they know about eyewitness memory? A comparison of experts in inquisitorial and adversarial legal systems[END_REF]. On the whole questionnaire, the French sample had significantly less knowledge on average. Despite that the French sample was predominantly composed of clinical practitioners, they also performed less well on items related to clinical psychology (i.e., 7 out of 12 items).

All these results were discussed in the light of two arguments. Firstly, the strong influence of psychoanalysis in the education of French psychologists and psychiatrists may prevent them from having sound scientific knowledge. Secondly, the chances for French experts to be challenged during the investigation or trial is lower than experts in adversarial systems. In the latter systems, safeguards often ensure the scientific validity of arguments experts provided in their reports (e.g., in the U.S., the Daubert standards; see also Areh et al., 2021), which may result in the rejection of some reports. In France, such safeguards do not exist. Despite the importance left in the law to the adversarial process (e.g., Lawyers can request a counterexpertise at the time of the investigation), French judges and lawyers do not have the necessary training to assess the reliability of expert reports. In fine, it can reflect difficulties for cognitive science inputs on memory to be applied in the French legal field. In the next section, we illustrate this lack of knowledge by two cases in which French experts failed to rely on memory science.

Two Cases 3 of Failure to Use Memory Science by French Experts Case 1

In 2016, a psychiatrist provided an expert report concerning a 16-year-old girl, accusing her grandfather's brother of sexual abuse when she was 8 years old. This appeared to be a case of recovered memory: the complainant suddenly and spontaneously remembered the event when she heard the suspect's name, with the feeling that she had never been aware that any abuse had occurred until she remembered. The defense counsel commissioned the first author of this article (OD) to examine and provide, if relevant, a critical examination on the psychiatrist's report about possible memory-related issues that the expert would not have explored.

Firstly, focused on complainant's credibility, the expert did not comment on possible factors influencing her testimony and its credibility. While the scientific community has tested tools to assess the credibility of testimonies (e.g., CBCA, Steller & Köhnken, 1989; the reality monitoring approach, [START_REF] Johnson | Reality monitoring[END_REF]; the expert based his conclusions regarding the complainant on his personal judgement, stating that she was "sincere", ignoring any evidencebased tools to establish credibility.

Secondly, regarding the recovered memories of sexual abuse suffered by the complainant, the expert referred to "a more or less conscious and active self-protective mechanism of memory repression, which lasted for about years, before completely breaking down in autumn 2015." First, the notion of repressed memory is widely debated within-and criticized bymemory researchers (Mangiulli et al., 2022a;[START_REF] Otgaar | The return of the repressed: The persistent and problematic claims of longforgotten trauma[END_REF]. Then, at no point did the expert refer to the road accident the complainant had between the target event and the memory recovery, even though this accident caused her a head injury and a coma putting her life in 3 The first case report is based on the expert report made by the first author of the article (OD). The second case report was provided by an expert in psychology who knew the purpose of our article and gave their consent to do a critical analysis of it anonymously.

danger. Therefore, potential links between head injury and autobiographical memory loss (e.g., [START_REF] Levine | Episodic memory and the self in a case of isolated retrograde amnesia[END_REF][START_REF] Roberts | Retrograde autobiographical memory from PTA emergence to six-month follow-up in moderate to severe traumatic brain injury[END_REF], and between head injury and memory accuracy (e.g., [START_REF] Ries | Heightened false memory: A long-term sequel of severe closed head injury[END_REF], have not been explored in this case.

To summarize, this expert (i) did not explore the issue of memory reliability when it was relevant, (ii) did not use any assessment tool, (iii) raised a controversial hypothesis (i.e., repressed memory), and (iv) did not explore a major factor of memory impairment (i.e., brain injury).

Case 2

In 2015, a psychologist provided an expert report concerning a man born in 1970, who was suspected of having killed with a rifle his wife from whom he was separated. Her written evaluation explicitly mentions that the suspect reported amnesia of the crime for which he was accused: "She was angry because she had seen him hanging around the house: 'She thought I was watching her, I left the room angry and went back in, she had a rifle in her hands, so I took one too', the rest is impossible for him to recall, claiming amnesia." Surprisingly, despite the substantial literature on amnesia reported by suspects (e.g., dissociative amnesia, e.g., [START_REF] Porter | Memory for murder: A psychological perspective on dissociative amnesia in legal contexts[END_REF][START_REF] Taylor | Amnesia for criminal offences[END_REF]malingering amnesia, e.g., Christianson & Merckelbach, 2004;[START_REF] Mangiulli | The memory-undermining effect of simulated crime-related amnesia and its legal implications: A review[END_REF], the psychologist did not explore this issue. Nor did she address the issue of a probable deficit in encoding abilities, while she mentioned difficulties with short-term memory functions (i.e., "His long-term memory works, but short-term memory is weak"; note that there is no indication in the report that shortterm memory and long-term memory were formally tested). Conversely, although the suspect denied the charges, she seemed to be convinced of his guilt: "The question of [the suspect 's] rehabilitation: it can be done provided that he accepts to do psychotherapy on his behavior, and on his responsibility for his wife's death." Finally, results obtained through the Rorschach test led the psychologist to suggest that the suspect is "in denial of his involvement in this tragedy", due to a "risk of collapse of the Ego" (for a criticism of the Rorschach in judicial contexts, see Areh et al., 2021) In short, the expert psychologist (i) seemed to find the suspect's denials not credible, and this in the absence of data gathered through evidence-based practice. By contrast, while he claimed amnesia, (ii) she used the Rorschach test-a highly controversial tool-which allowed her to conclude that the suspect was in a "narcissistic" denial of the crime he was accused of.

At no point (iii) did she explore a potential encoding failure or amnesia, for which approaches are currently developed to better discriminate between a feigned amnesia and genuine one [START_REF] Zago | The detection of malingered amnesia: An approach involving multiple strategies in a mock crime[END_REF].

Recommendations

Research outcomes and specific cases presented in this article suggest that, when addressing litigants' memory issues, French psychologists and psychiatrists probably rely little on evidence from cognitive sciences. It is thus unlikely that current experts would be able to identify critical factors that might influence accuracy and specificity of testimonies (e.g., misleading questions, event's repetition, stress), or even features of ordinary memory functioning that might be perceived as indicators of non-credibility (e.g., forgetting, inconsistency between accounts; [START_REF] Voogt | The development of a conceptual model of perceived victim credibility in child sexual assault cases[END_REF]. The risk of miscarriages of justice may therefore increase in two directions: conviction of innocent people, or discharge of guilty people. While further work is needed to further clarify how French experts deal with memory issues (e.g., quantitative analyses of a large and representative sample of expertise reports), current evidence shows that memory knowledge are not properly applied in the French justice system. To overcome these difficulties, it is necessary to provide recommendations for experts and legal professionals.

In France, the practice of psychological or psychiatric expertise is not controlled by a framework external to the magistrate-expert dyad. This raises questions because the magistrates use the experts' skills to counterbalance their lack of knowledge on psychological and/or psychiatrics aspects of a case and, at the same time, are not qualified to assess the expert's skills or the scientific validity of their report. They therefore have no choice but to place blind trust in the experts' conclusions.

Regarding the questions posed to expert, we identified three limitations. Firstly, they are standardized and do not invite the magistrate to adapt them to the nature of the case (for example, sexual violence vs. murder). Secondly, they are too vague and allow experts to use a wide variety of clinical and criminological assessment methods, including non-scientifically validated approaches (e.g., psychoanalysis). Thirdly, they do not require experts to explain and justify their method.

Two options could be recommended. The first one would deal with the rewording of the questions to lead the expert to specifically question memory issues, when the witness testimonies are crucial (e.g., sexual abuse cases where physical evidence may be lacking; suspects claiming amnesia). The experts could then combine their knowledge and clinical experience with validated tools, with the obligation to explain the assessment methods and theoretical background used. The second option would be to initiate work on the admissibility of the methods and tools used by French expert psychologists and psychiatrists to move towards practices that have a sound theoretical basis and that have been the subject of peer-reviewed publications, that are valid, reliable, based on accessible data and results, and that meet ethical standards (see Areh et al. 2021). This might for example result in the development of a tool based on the same model as actuarial scales (e.g., recidivism likelihood assessment) which, based on a list of validated criteria (e.g., use of a validated method/approach, mentions of peerreviewed references), would enable the magistrate to assess the validity of the report concerning the experts' analyses of the functioning of memory and the reliability of testimonies. The use of such a tool should first be tested in laboratory settings and field studies, and then could be integrated into the training of magistrates.

Among information available on the expert lists, it would be important for French experts to clearly indicate their areas of expertise so that magistrates can choose the expert best able to respond reliably to memory-related issues. Given the limited knowledge of psychologists and psychiatrists in the field of memory, the implementation of such a recommendation should highlight the lack of memory experts. Therefore, we also recommend appointing teams of experts including a legal psychologist (performing the clinical and criminological part) and a memory-expert when the case requires it. Furthermore, as the work of memory experts is based on the case file, it would also make it possible for the magistrates to ask questions on memory phenomena experienced by other actors in criminal cases (e.g., non-victim eyewitnesses), which is currently non-existent in French legal proceedings. This recommendation is at the heart of the work of the Memory and Law Network, created in 2022 by the Memory Research Group of the French National Centre for Scientific Research. This multidisciplinary network, made up of academics specialized in memory science, aims to promote the application of cognitive sciences of memory in the different stages of investigation process, from the first interviews of witnesses, victims, and suspects to the testimony of expert psychologists and psychiatrists in court.

Implementing such recommendations is challenging as it suggests profound changes in proceedings and practices. In addition to the institutional issues they raise, the proposed changes could face resistance from various stakeholders. To overcome this difficulty, we might consider (1) building a working group, composed of memory researchers and professionals (e.g., magistrates, experts ; see [START_REF] Pezdek | Psychological myths about evidence in the legal system: How should researchers respond[END_REF], for the importance for researchers to collaborate with stakeholders in the field to make them adhere to evidence-based recommendations) of the need to improve practices, to develop a framework that responds to

For more information on this case, see https://www.lefigaro.fr/actualite-france/2016/11/22/01016-20161122ARTFIG00380-affaire-fiona-la-face-cachee-de-cecile-bourgeon.php (in French)

the difficulties observed in the field; and (2) undertaking in-depth education and popularization of the cognitive sciences of memory to maximize their acceptance.