Associative Learning Research Articles

Behavioral screening reveals a conserved residue in Y-Box RNA-binding protein required for associative learning and memory in C. elegans.

RNA-binding proteins (RBPs) regulate translation and plasticity which are required for memory. RBP dysfunction has been linked to a range of neurological disorders where cognitive impairments are a key symptom. However, of the 2,000 RBPs in the human genome, many are uncharacterized with regards to neurological phenotypes. To address this, we used the model organism C. elegans to assess the role of 20 conserved RBPs in memory. We identified eight previously uncharacterized memory regulators, three of which are in the C. elegans Y-Box (CEY) RBP family. Of these, we determined that cey-1 is the closest ortholog to the mammalian Y-Box (YBX) RBPs. We found that CEY-1 is both necessary in the nervous system for memory ability and sufficient to promote memory. Leveraging human datasets, we found both copy number variation losses and single nucleotide variants in YBX1 and YBX3 in individuals with neurological symptoms. We identified one predicted deleterious YBX3 variant of unknown significance, p.Asn127Tyr, in two individuals with neurological symptoms. Introducing this variant into endogenous cey-1 locus caused memory deficits in the worm. We further generated two humanized worm lines expressing human YBX3 or YBX1 at the cey-1 locus to test evolutionary conservation of YBXs in memory and the potential functional significance of the p.Asn127Tyr variant. Both YBX1/3 can functionally replace cey-1, and introduction of p.Asn127Tyr into the humanized YBX3 locus caused memory deficits. Our study highlights the worm as a model to reveal memory regulators and identifies YBX dysfunction as a potential new source of rare neurological disease.

Does a Polyherbal Medicine Enhance Cognition in Healthy Older Adults? An Exploratory Open-Label Study.

Objective: This 12-week open-label study evaluated a multi-herbal tablet containing Reynoutria japonica, Vitis vinifera, Silybum marianum, Ginkgo biloba, and Panax ginseng, for potential improvement of cognitive function in 25 healthy older adults (50-75 years). Methods: The primary outcome, cognition, was assessed using the Cambridge Neuropsychological Test Automated Battery. Results: Significant improvement in working memory was observed. Errors in the Paired Associate Learning (PAL) task and spatial working memory reduced by -7.9 (95%CI: -12.3, -3.5) and -3.3 (95%CI: -6.3, -0.3) respectively, while PAL memory score increased by 2.0 (95%CI: 0.9, 3.1). Conclusion: These preliminary results suggest memory improvement, but further rigorous testing is needed.

Early disruption of entorhinal dopamine in a knock-in model of Alzheimer's disease.

The entorhinal cortex (EC) is a critical brain area for memory formation, while also the region exhibiting the earliest histological and functional alterations in Alzheimer's disease (AD). The EC thus has been long hypothesized as one of the originating brain areas of AD pathophysiology, although circuit mechanisms causing its selective vulnerability remain poorly understood. We found that dopamine neurons projecting their axons to the lateral EC (LEC), critical for memory formation in healthy brains, become dysfunctional and cause memory impairments in early AD brains. In amyloid precursor protein knock-in mice with associative memory impairment, LEC dopamine activity and associative memory encoding of LEC layer 2/3 neurons were disrupted in parallel from the early pathological stage. Optogenetic reactivation of LEC dopamine fibers, as well as L- DOPA treatment, rescued associative learning behavior. These results suggest that dysfunction of LEC-projecting dopamine neurons underlies memory impairment in AD from early stages, pointing to a need for clinical investigation of LEC dopamine in AD patients.

Spontaneous Color Preferences and Associative Learning in Protaetia brevitarsis (Coleoptera: Scarabaeidae).

Color vision, which varies among species, plays an important role in foraging, mating, and habitat selection among insects. Protaetia brevitarsis (Coleoptera: Scarabaeidae, Lewis) is an omnivorous beetle that damages both crops and fruit. Here, to understand the effect of vision and olfaction in host selection, experiments were conducted on the spectral wavelength preference, color preference, and associative learning ability of adult P. brevitarsis using LED lights and grapes. In our experiments, adults showed the strongest spontaneous preference toward the red spectrum, particularly 730 nm. Non-preferred lights were used to train adults with a food reward (grapes). Green-trained adults had an increasing tendency to prefer green light, and blue-trained adults had a clear preference for blue light. Furthermore, adults significantly preferred red grapes in the absence of olfactory cues, but their selectivity for grapes differed in the presence of olfactory cues, indicating that vision was not the only factor in foraging decisions, but that olfactory cues also influenced their decision making. The results lay the groundwork for revealing their host localization mechanism and provide promising avenues for biological control in the field.

Reward and punishment contingency shifting reveals distinct roles for VTA dopamine and GABA neurons in behavioral flexibility.

In dynamic environments where stimuli predicting rewarding or aversive outcomes unexpectedly change, it is critical to flexibly update behavior while preserving recollection of previous associations. Dopamine and GABA neurons in the ventral tegmental area (VTA) are implicated in reward and punishment learning, yet little is known about how each population adapts when the predicted outcome valence changes. We measured VTA dopamine and GABA population activity while male and female rats learned to associate three discrete auditory cues to three distinct outcomes: reward, punishment, or no outcome within the same session. After learning, the reward and punishment cue-outcome contingencies were reversed, and subsequently re-reversed. As expected, the dopamine population rapidly adapted to learning and contingency reversals by increasing the response to appetitive stimuli and decreasing the response to aversive stimuli. In contrast, the GABA population increased activity to all sensory events regardless of valence, including the neutral cue. Reversing learned contingencies selectively influenced GABA responses to the reward-predictive cue, prolonging increased activity within and across sessions. The observed valence-specific dissociations in the directionality and temporal progression of VTA dopamine and GABA calcium activity indicates that these populations are independently recruited and serve distinct roles during appetitive and aversive associative learning and contingency reversal.

Like a Punch in the Gut: A Novel Perspective On Annual Recurrences of Ulcerative Colitis.

Ulcerative colitis (UC), a chronic inflammatory bowel disease, causes stomach pain, diarrhea, and rectal bleeding. The exact cause is unknown, but it is thought to involve genetic, environmental, and psychological factors. Some people experience annual flare-ups without obvious reason. This article adopts a theory-driven approach to consider how and why past traumatic events may contribute to annual flare-ups. We applied learning theory, which explains the development of re-experiencing phenomena in post-traumatic stress disorder (PTSD), to better understand the occurrence of annual flares in patients living with UC. Two possibilities emerged in which associative learning may contribute to annual UC flares. First, flare-ups could be a physical response to sensory cues in the present that overlap with trauma experienced at the first onset of UC. Annual episodes may strengthen the UC flare as a learned physiological response to trauma reminders. Second, flare-ups may result from elevated stress due to trauma re-experiencing at anniversaries. Sensory features of the initial UC trauma may be associated with strong reactions, which generalize to similar stimuli, triggering re-experiencing symptoms and increasing psychological stress. Elevated stress raises glucocorticoid levels, promoting UC-specific inflammation. Stimulus discrimination from cognitive therapy for PTSD may help to over-ride the associations that have formed between sensory features of past trauma, linked reactions, and similar cues in the present. Research is needed to understand how traumatic events influence the onset and recurrence of ulcerative colitis, as well as the potential benefits of stimulus discrimination for reducing the frequency of annual flares.

Contextual modulation of human associative learning following novelty-facilitated extinction, counterconditioning, and conventional extinction.

The expression of an association between a conditioned stimulus (CS) and an unconditioned stimulus (US) can be attenuated by presenting the CS by itself (i.e., extinction, Ext). Though effective, Ext is susceptible to recovery effects such as renewal, spontaneous recovery, and reinstatement. Dunsmoor et al. (2015, 2019) have proposed that pairing the CS with a neutral outcome (novelty-facilitated Ext [NFE]) could offer better protection against recovery effects than Ext. Though NFE has been compared to Ext, it has rarely been compared to counterconditioning (CC), a similar procedure except that the CS is paired with a US having a valence opposite to the US used in initial training. We report two aversive conditioning experiments using the rapid-trial streaming procedure with human participants that compare the efficacies and susceptibilities to ABA renewal of Ext, CC, and NFE. Associative learning was assessed through expectancy learning and evaluative conditioning. CC and NFE equally decreased anticipation of the US in the presence of the CS (i.e., expectancy learning). Depending on how the CS-US association was probed, they were either as or more effective at doing so than Ext. All three interference treatments were equally susceptible to context manipulations. Only CC clearly altered the valence of the CS (i.e., evaluative conditioning). Valence ratings after Ext, CC, and NFE, as well as a no-interference control condition, were all equally susceptible to context effects. Overall, the present study does not support the assertion that NFE is consistently more resistant to recovery effects than Ext. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Weighting of sensory cues reflect changing patterns of visual investment during ecological divergence in Heliconius butterflies.

Integrating information across sensory modalities enables animals to orchestrate a wide range of complex behaviours. The relative importance placed on one sensory modality over another reflects the reliability of cues in a particular environment and corresponding differences in neural investment. As populations diverge across environmental gradients, the reliability of sensory cues may shift, favouring divergence in neural investment and the weight given to different sensory modalities. During their divergence across closed-forest and forest-edge habitats, closely related butterflies Heliconius cydno and Heliconius melpomene evolved distinct brain morphologies, with the former investing more in vision. Quantitative genetic analyses suggest that selection drove these changes, but their behavioural consequences remain uncertain. We hypothesized that divergent neural investment may alter sensory weighting. We trained individuals in an associative learning experiment using multimodal colour and odour cues. When positively rewarded stimuli were presented in conflict, i.e. pairing positively trained colour with negatively trained odour and vice versa, H. cydno favoured visual cues more strongly than H. melpomene. Hence, differences in sensory weighting may evolve early during divergence and are predicted by patterns of neural investment. These findings, alongside other examples, imply that differences in sensory weighting stem from divergent investment as adaptations to local sensory environments.

Associative Learning in Subclinical Hypothyroidism at Different Ranges of Thyroid Stimulating Hormone: A Cambridge Neuropsychological Test Automated Battery (CANTAB) Study of Visual Paired Association Learning Task.

Associative learning deficits are constantly found in subclinical hypothyroidism (SCH). Despite achieving normal thyroid stimulating hormone (TSH) levels, a considerable number of patients undergoing levothyroxine (LT-4) treatment frequently complain about memory retrieval. The Paired Association Learning (PAL) task involves computerised testing on the CANTAB- Cambridge Neuropsychological Test Automated Battery, also considered a screening tool for Alzheimer's disease (AD). This study aimed to investigate the impact of different levels of TSH on visual associative learning in SCH and determine if these impairments were reversed with LT-4. A total of 134 participants were included in this cross-sectional study. Group 1: 35 healthy controls; patients with SCH (Group 2: 33 newly identified cases; Group 3: 32 patients on LT-4 with elevated TSH; Group 4: 34 euthyroid but on LT-4). A thyroid profile and a neuropsychological clinical assessment were done. The visual PAL task was performed on CANTAB. PAL was significantly impaired (p = <0.05) in all 3 patient groups as compared to Group 1. The PAL total errors (adjusted) scores were significantly higher in Groups 2 and 3, indicating that associative learning is definitely impaired in SCH, reaching levels previously seen in patients with AD. Our findings encourage screening for visual associative learning or memory retrieval in patients with SCH. The study present has established a more reasonable threshold of TSH 2.5mIU/L to encourage examination of associative learning and the initiation of LT-4 in SCH. Poor PAL task performance in patients with SCH may have significant implications in clinical settings for suspecting AD.

Associative Learning and Active Inference.

Associative learning is a behavioral phenomenon in which individuals develop connections between stimuli or events based on their co-occurrence. Initially studied by Pavlov in his conditioning experiments, the fundamental principles of learning have been expanded on through the discovery of a wide range of learning phenomena. Computational models have been developed based on the concept of minimizing reward prediction errors. The Rescorla-Wagner model, in particular, is a well-known model that has greatly influenced the field of reinforcement learning. However, the simplicity of these models restricts their ability to fully explain the diverse range of behavioral phenomena associated with learning. In this study, we adopt the free energy principle, which suggests that living systems strive to minimize surprise or uncertainty under their internal models of the world. We consider the learning process as the minimization of free energy and investigate its relationship with the Rescorla-Wagner model, focusing on the informational aspects of learning, different types of surprise, and prediction errors based on beliefs and values. Furthermore, we explore how well-known behavioral phenomena such as blocking, overshadowing, and latent inhibition can be modeled within the active inference framework. We accomplish this by using the informational and novelty aspects of attention, which share similar ideas proposed by seemingly contradictory models such as Mackintosh and Pearce-Hall models. Thus, we demonstrate that the free energy principle, as a theoretical framework derived from first principles, can integrate the ideas and models of associative learning proposed based on empirical experiments and serve as a framework for a better understanding of the computational processes behind associative learning in the brain.

Personality may modulate learning and memory differences in two taxa of the African striped mouse genus Rhabdomys

AbstractDifferent environments place different cognitive demands on constituent taxa. Learning and memory involve cognitive processes with associated costs, and it is expected that different levels of learning will occur in taxa from different environments. Greater memory loads linked to increased environmental complexity require greater learning and memory capacities. We investigated the variation in learning and memory in sister taxa of striped mice (genus Rhabdomys). We studied two populations each of the mesic grassland‐occurring R. d. chakae and the mostly arid‐occurring R. pumilio. We conducted two sets of experiments. (1) In a novel object recognition (NOR) test, we assessed memory by recording the duration of exploration of similar and novel objects by test mice. (2) In an associative learning task, we assessed whether mice could associate specific scents with or without a food incentive or with different quantities of the food incentive in previous training phases. We measured the latency of mice to contact scents in a two‐sample choice in the test phase. In the NOR test, R. pumilio spent less time investigating similar objects in a training trial than R. d. chakae but increased absolute exploration of the novel object when presented with a novel and a familiar object in the retention trial, suggesting a sensitization to the novel object by R. pumilio. In the associative learning experiments, R. pumilio approached the stimuli faster than R. d. chakae, whereas mice from both taxa preferred scents associated with a seed versus no seed and scents associated with 5 seeds versus 1 seed. The data provide evidence of taxon‐level differences in learning and memory, likely related to environmentally modulated personality differences between the taxa.

Mitochondrial DNA copy number associated dementia risk by somatic mutations and frailty.

Mitochondrial dysfunction is linked to physical impairment and dementia. Mitochondrial DNA copy number (mtDNAcn) from blood may predict cognitive decline and dementia risk, but the effect of somatic mutations or frailty is unknown. We estimated mtDNAcn using fastMitoCalc and microheteroplasmies using mitoCaller, from Whole Genome Sequencing (WGS) data. In 189,566 participants free of dementia at study entry (mean age = 56 ± 8), we examined the association between mtDNAcn and subsequent dementia diagnosis using Cox regression. Cognition was assessed in a subset on average 8.9years later. We examined the associations between mtDNAcn and cognitive measures using multivariable linear regression, adjusted for demographic factors, mtDNAcn-related parameters, and apolipoprotein E ε4 status. We further stratified by frailty and microheteroplasmies. Over an average follow-up of 13.2years, 3533 participants developed dementia. Each SD higher mtDNAcn (16) was associated with 4.2% lower all-cause dementia hazard (HR = 0.958, p = 0.030), 6% lower non-AD dementia hazard (HR = 0.933, p = 0.022), and not-AD dementia hazard. The associations between mtDNAcn and all-cause dementia and non-AD dementia were stronger among those who were pre-frail or frail or with higher microheteroplasmies. Higher mtDNAcn was associated with higher DSST scores (p = 0.036) and significant only among those with higher microheteroplasmies or frailty (p = 0.029 and 0.048, respectively). mtDNAcn was also associated with delta TMT and paired associate learning only in pre-frail/frail participants (p = 0.007 and 0.045, respectively). Higher WGS-based mtDNAcn in human blood is associated with lower dementia risk, specifically non-AD dementia, and specific cognitive function. The relationships appear stronger in high somatic mutations or frailty. Future studies are warranted to investigate biological underpinnings.

Non-associative potentiation of proximal excitatory inputs to layer 2/3 pyramidal cells in rat visual cortex

Long-term changes of synaptic transmission can be induced by Hebbian-type homosynaptic mechanisms which require activation of both pre- and postsynapse and mediate associative learning, as well as by heterosynaptic mechanisms which do not require activation of the presynapse and are non-associative. The rules for induction of homosynaptic plasticity depend on the distance of the synapse from the soma. Does induction of heterosynaptic plasticity also depend on synaptic location? Here, we investigated heterosynaptic changes in pharmacologically isolated glutamatergic inputs arriving at either the proximal or the distal segments of the apical dendrite of layer 2/3 pyramidal neurons in rat visual cortex. We show that bursts of action potentials evoked without presynaptic stimulation induced potentiation of proximal inputs while having little effect on distal inputs. Such gradient of plasticity could be related to the attenuation of backpropagating action potentials along the dendrites. Thus, the location of the synapse on the dendritic tree is a determinant not only for homosynaptic but also for heterosynaptic plasticity.

Contributions of associative and non-associative learning to the dynamics of defensive ethograms.

Defensive behavior changes based on threat intensity, proximity, and context of exposure, and learning about danger-predicting stimuli is critical for survival. However, most Pavlovian fear conditioning paradigms focus only on freezing behavior, obscuring the contributions of associative and non-associative mechanisms to dynamic defensive responses. To thoroughly investigate defensive ethograms, we subjected male and female adult C57BL/6J mice to a Pavlovian conditioning paradigm that paired footshock with a serial compound stimulus (SCS) consisting of distinct tone and white noise (WN) stimulus periods. To investigate how associative and non-associative mechanisms affect defensive responses, we compared this paired SCS-footshock group with four control groups that were conditioned with either pseudorandom unpaired presentations of SCS and footshock, shock only, or reversed SCS presentations with inverted tone--WN order, with paired or unpaired presentations. On day 2 of conditioning, the paired group exhibited robust freezing during the tone period with switching to explosive jumping and darting behaviors during the WN period. Comparatively, the unpaired and both reverse SCS groups expressed less tone-induced freezing and rarely showed jumping or darting during WN. Following the second day of conditioning, we observed how defensive behavior changed over two extinction sessions. During extinction, the tone-induced freezing decreased in the paired group and mice rapidly shifted from escape jumping during WN to a combination of freezing and darting. The unpaired, unpaired reverse, and shock-only groups displayed defensive tail rattling and darting during the SCS, with minimal freezing and jumping. Interestingly, the paired reverse group did not jump to WN, and tone-evoked freezing was resistant to extinction. These findings demonstrate that non-associative factors promote some defensive responsiveness, but associative factors are required for robust cue-induced freezing and high-intensity flight expression.

Does bumblebee preference of continuous over interrupted strings in string-pulling tasks indicate means-end comprehension?

Bumblebees (Bombus terrestris) have been shown to engage in string-pulling behavior to access rewards. The objective of this study was to elucidate whether bumblebees display means-end comprehension in a string-pulling task. We presented bumblebees with two options: one where a string was connected to an artificial flower containing a reward and the other presenting an interrupted string. Bumblebees displayed a consistent preference for pulling connected strings over interrupted ones after training with a stepwise pulling technique. When exposed to novel string colors, bees continued to exhibit a bias towards pulling the connected string. This suggests that bumblebees engage in featural generalization of the visual display of the string connected to the flower in this task. If the view of the string connected to the flower was restricted during the training phase, the proportion of bumblebees choosing the connected strings significantly decreased. Similarly, when the bumblebees were confronted with coiled connected strings during the testing phase, they failed to identify and reject the interrupted strings. This finding underscores the significance of visual consistency in enabling the bumblebees to perform the task successfully. Our results suggest that bumblebees' ability to distinguish between continuous strings and interrupted strings relies on a combination of image matching and associative learning, rather than means-end understanding. These insights contribute to a deeper understanding of the cognitive processes employed by bumblebees when tackling complex spatial tasks.

Does bumblebee preference of continuous over interrupted strings in string-pulling tasks indicate means-end comprehension?

Bumblebees (Bombus terrestris) have been shown to engage in string-pulling behavior to access rewards. The objective of this study was to elucidate whether bumblebees display means-end comprehension in a string-pulling task. We presented bumblebees with two options: one where a string was connected to an artificial flower containing a reward and the other presenting an interrupted string. Bumblebees displayed a consistent preference for pulling connected strings over interrupted ones after training with a stepwise pulling technique. When exposed to novel string colors, bees continued to exhibit a bias towards pulling the connected string. This suggests that bumblebees engage in featural generalization of the visual display of the string connected to the flower in this task. If the view of the string connected to the flower was restricted during the training phase, the proportion of bumblebees choosing the connected strings significantly decreased. Similarly, when the bumblebees were confronted with coiled connected strings during the testing phase, they failed to identify and reject the interrupted strings. This finding underscores the significance of visual consistency in enabling the bumblebees to perform the task successfully. Our results suggest that bumblebees’ ability to distinguish between continuous strings and interrupted strings relies on a combination of image matching and associative learning, rather than means-end understanding. These insights contribute to a deeper understanding of the cognitive processes employed by bumblebees when tackling complex spatial tasks.

Formation and retrieval of cell assemblies in a biologically realistic spiking neural network model of area CA3 in the mouse hippocampus

The hippocampal formation is critical for episodic memory, with area Cornu Ammonis 3 (CA3) a necessary substrate for auto-associative pattern completion. Recent theoretical and experimental evidence suggests that the formation and retrieval of cell assemblies enable these functions. Yet, how cell assemblies are formed and retrieved in a full-scale spiking neural network (SNN) of CA3 that incorporates the observed diversity of neurons and connections within this circuit is not well understood. Here, we demonstrate that a data-driven SNN model quantitatively reflecting the neuron type-specific population sizes, intrinsic electrophysiology, connectivity statistics, synaptic signaling, and long-term plasticity of the mouse CA3 is capable of robust auto-association and pattern completion via cell assemblies. Our results show that a broad range of assembly sizes could successfully and systematically retrieve patterns from heavily incomplete or corrupted cues after a limited number of presentations. Furthermore, performance was robust with respect to partial overlap of assemblies through shared cells, substantially enhancing memory capacity. These novel findings provide computational evidence that the specific biological properties of the CA3 circuit produce an effective neural substrate for associative learning in the mammalian brain.

The ventral tegmental area dopamine to basolateral amygdala projection supports acquisition of cocaine self-administration

Dopamine signaling in the amygdala is known to play a role in associative learning and memory, including the process of learning to associate environmental cues with the reinforcing properties of drugs like cocaine. Evidence suggests that the ventral tegmental area (VTA) dopamine (DA) projection specifically to the basolateral amygdala (BLA) participates in establishing cocaine-cue associations that can promote later craving- and relapse-like responses to the cue alone. In order to further investigate the specific role of VTA-BLA projections in cocaine-reinforced learning, we used chemogenetics to manipulate VTA DA inputs to the BLA during cocaine self-administration, cue- and cocaine-primed reinstatement, and conditioned place preference. We found inhibiting DA input to the BLA during cocaine self-administration inhibited acquisition and weakened the ability of the previously cocaine-paired cue to elicit cocaine-seeking, while acutely inhibiting the pathway on the day of cue-induced reinstatement testing had no effect. Conversely, exciting the projection during self-administration boosted the salience of the cocaine-paired cue as indicated by enhanced responding during cue-induced reinstatement. Importantly, interfering with DA input to the BLA had no impact on the ability of cocaine to elicit a place preference or induce reinstatement in response to a priming cocaine injection. Overall, we show that manipulation of projections underlying DA signaling in the BLA may be useful for developing therapeutic interventions for substance use disorders.

Looming stimuli reliably drive innate defensive responses in male rats, but not learned defensive responses

Survival relies on an organism's intrinsic ability to instinctively react to stimuli such as food, water, and threats, ensuring the fundamental ability to feed, drink, and avoid danger even in the absence of prior experience. These natural, unconditioned stimuli can also facilitate associative learning, where pairing them consistently with neutral cues will elicit responses to these cues. Threat conditioning, a well-explored form of associative learning, commonly employs painful electric shocks, mimicking injury, as unconditioned stimuli. It remains elusive whether actual injury or pain is necessary for effective learning, or whether the threat of harm is sufficient. Approaching predators create looming shadows and sounds, triggering strong innate defensive responses like escape and freezing. This study investigates whether visual looming stimuli can induce learned freezing or learned escape responses to a conditioned stimulus in male rats. Surprisingly, pairing a neutral tone with a looming stimulus only weakly evokes learned defensive responses, in contrast to the strong responses observed when the looming stimulus is replaced by a shock. This dissociation sheds light on the boundaries for learned defensive responses thereby impacting our comprehension of learning processes and defensive strategies.

Deleterious effect of social instability on broiler chicken learning abilities and behaviour

Broiler chickens are reared in very large groups and are submitted to repeated encounters with unknown conspecifics. Our aim was to assess the consequences of these encounters on broiler chickens learning abilities, social behaviour and emotional reactivity. Groups of 5 male medium-growing broiler chickens (JA 957) were reared under stable or unstable social conditions (n=16 groups in each condition). Under the unstable conditions, the 5 birds of the groups changed every 3–4 days from 1 to 52 days of age. Broiler chickens were tested in an associative learning task (conditioned place preference) between 14 and 18 days of age. A highly palatable food (mealworms) was delivered in a particular environment with coloured stripes and preference for this environment was then tested. Social behaviours were analysed between 21 and 43 days of age. Emotional reactivity of the birds when faced with novelty (reactivity to unknown food, object and human) was assessed at the end of the rearing period (46–51 days of age). Only birds from the stable condition were able to associate the palatable food to the environment in which it was delivered (p = 0.02). Furthermore, these birds had a higher social proximity than those from the unstable condition (p < 0.01) and showed less aggressive interactions such as aggressive pecking (p = 0.06), threat (p < 0.01) or facing each other with wing flapping in front of another bird (p = 0.03). The social conditions tested had no significant effect on their emotional reactivity. Our results evidenced that chickens exposed to social instability have some learning abilities impaired compared to chickens maintained in stable social conditions. In addition, social instability increases aggressive interactions between conspecifics, while social stability favours bird proximity. In conclusion, being reared in unstable social conditions likely impairs bird adaptation to their rearing environment and increases deleterious consequences of aggressive interactions with conspecifics.