Horse (Equus caballus) whinnies: a source of social information

Many animal species that rely mainly on calls to communicate produce individual acoustic structures, but we wondered whether individuals of species better known as visual communicants, with small vocal repertoires, would also exhibit individual distinctiveness in calls. Moreover, theoretical advances concerning the evolution of social intelligence are usually based on primate species data, but relatively little is known about the social cognitive capacities of non-primate mammals. However, some non-primate species demonstrate auditory recognition of social categories and possess mental representation of their social network. Horses (Equus caballus) form stable social networks and although they display a large range of visual signals, they also use long-distance whinny calls to maintain contact. Here, we investigated the potential existence of individual acoustic signatures in whinny calls and the ability of horses to discriminate by ear individuals varying in their degree of familiarity. Our analysis of the acoustic structure of whinnies of 30 adult domestic horses (ten stallions, ten geldings, ten mares) revealed that some of the frequency and temporal parameters carried reliable information about the caller’s sex, body size and identity. However, no correlations with age were found. Playback experiments evaluated the behavioural significance of this variability. Twelve horses heard either control white noise or whinnies emitted by group members, familiar neighbours or unfamiliar horses. While control sounds did not induce any particular response, horses discriminated the social category of the callers and reacted with a sound-specific behaviour (vigilance and attraction varied with familiarity). Our results support the existence of social knowledge in horses and suggest a process of vocal coding/decoding of information.     

Another Paradox In Naive Set-Theory

Reasonning in naive set theory (with unlimited comprehension), we derive a paradox (a formal contradiction) which can be seen as a variant of the Burali-Forti paradox. Presented by Robert Goldblatt     

Essai sur la logique de l'indeterminisme et la ramification de l'espace-temps

Sans résumé     

The role of social identity in the explanation of collective action: An intergroup perspective on the Yellow Vests movement

Social psychologists have developed influential theoretical models to understand intergroup conflicts, radicalism, and collective action. November 2018 saw the emergence of a new powerful movement in France named the Yellow Vests. Born on social media, the movement has sustained an unprecedented period of intense protests and violent clashes with the police, challenging the French government. As such, this movement offers an ideal context to examine the real-world relevance of current social-psychological theorizing. Using a social identity and self-categorization perspective, two correlational studies (three samples, N = 1,849) tested the role of self-categorization as a group member, or social identity, in accounting for individual participation in normative and nonnormative collective action. Using different operationalizations of identification, both studies confirm a powerful role of identification as a Yellow Vest and provided evidence that the effect of social media use on collective action is fully mediated by self-categorization as a Yellow Vest. An alternative model suggesting that social media use mediated the relation between social identity and collective action was not supported by the data.     

Holistic face processing can be independent of gaze behaviour: Evidence from the composite face illusion

People tend to perceive identical top halves (i.e. above the nose) of two face stimuli as being different when they are aligned with distinct bottom halves. This composite face illusion is generally considered as the most compelling evidence that facial features are integrated into a holistic representation. Here, we recorded eye‐movements during the composite face illusion in a delayed matching task of top halves of faces. Behavioural results showed a strong composite face effect, participants making more mistakes and taking longer time to match two identical top halves of faces when they were aligned (vs. misaligned) with different bottom halves. Importantly, fixation sites and eye‐movements were virtually identical when the top and bottom parts were aligned (composite illusion) or misaligned (no illusion), indicating that holistic face processing can be independent of gaze behaviour. These findings reinforce the view that holistic representations of individual faces can be extracted early on from information at a relatively coarse scale, independently of overt attention.     

Evidence for an emotion-cognition interaction in the statistical prediction of suicide attempts

Suicidal behavior is a prevalent problem among adolescents and young adults. Although most theoretical models of suicide suggest that this behavior results from the interaction of different risk factors, most prior studies have tested only bivariate associations between individual risk factors and suicidal behaviors. The current study was designed to address this limitation by testing the effect of an emotion–cognition interaction on suicide attempts among youth. Specifically, we hypothesized that the interaction of emotion reactivity and problem-solving skills would statistically predict the probability of a recent suicide attempt among 87 adolescents and young adults. Results revealed a significant interaction, such that emotion reactivity was strongly associated with the probability of a suicide attempt among those with poor problem-solving skills, moderately associated among those with average problem-solving skills, and not significantly associated among those with good problem-solving skills. The next generation of studies on suicidal behavior should continue to examine how risk factors interact to predict this dangerous outcome.     

Familiarity and emotional expression influence an early stage of face processing: an electrophysiological study

Recent data indicate that the familiarity and the emotional expression of faces occur at an early stage of information processing. The goal of the present study was to determine whether these two aspects interact at the structural encoding stage as reflected by the N170 component of event-related potentials in tasks requiring the subjects either to identify whether the faces were familiar or the nature of the emotional expression. The results indicate that the neural responses to level of familiarity and emotional expression were observable at this early processing stage but without interacting. In particular, faces of personal importance to the subjects differed from those of less personal importance. Because familiarity did not interact with emotional expression at behavioral and electrophysiologic levels, our results support the contention of parallel and independent processing of faces.     

Modulation of recognition and temporal order memory retrieval by dopamine D1 receptor in rats

The present study examines the effects of SKF 81297, a selective D1 agonist, on information retrieval in recognition and temporal order memory for objects, using three different tasks. Separate groups of rats were trained in each task and then given an intraperitoneal injection of saline or the D1 agonist (0.03, 0.3 mg/kg), before the memory testing trial in an object recognition, object location, and object temporal order memory tasks. We show that SKF 81297, at high dose (0.3 mg/kg), facilitates information retrieval after a long delay (4 h) in the three memory tasks whereas both high and low doses of D1 agonist impair recognition memory after a short delay (15 min). These results indicate a significant role of dopamine D1 receptors in recognition memory for both familiarity and place of objects in addition to object temporal order memory.