Unfamiliar Individuals Research Articles

Influence of body size and familiarity on mating and reproductive parameters in the zig-zag ladybird beetle, Menochilus sexmaculatus (Coleoptera: Coccinellidae)

Body size often indicates an individual’s quality and so mate selection is typically for larger individuals, including in ladybirds (Coccinellidae). Many organisms including ladybirds are also are known to refuse mating attempts with familiar individuals, but whether at the expense of mating with larger individuals is not clear. We assessed the cumulative effect of body size and familiarity on mating and reproductive behaviour in the zig-zag ladybird beetle (Menochilus sexmaculatus (Fabricius, 1781) = Cheilomenes sexmaculata (Fabricius, 1781)). For this study, individuals were separated into small- and large-bodied individuals and allowed to mate in all possible combinations. Furthermore, following the first mating, an immediate second mating was provided to the males, with either a familiar (same as in the first mating) or an unfamiliar (new female with the same mating status) female. Mating and reproductive parameters were recorded. The mating duration was longer with familiar partners than unfamiliar individuals. Mating duration was shorter for the second mating, suggesting that mating and ejaculate transfer are costly, to assure higher reproductive success. In this ladybird beetle, familiarity modified mating duration, whereas fecundity and egg viability were influenced by body size.

Effect of face-related task on rapid individual face discrimination

Human adults can typically visually discriminate the faces of unfamiliar individuals accurately, rapidly, and automatically, i.e. even without the explicit intention to do so. Recent studies have used fast periodic visual stimulation (FPVS) coupled with electroencephalography (EEG) to measure this process with objectivity and high sensitivity during simple non-face related tasks (Liu-Shuang et al., 2014). Here we consider to what extent fast individual face discrimination measured in the human brain with this approach is modulated by a direct face-related task. We recorded 128-channel EEG while participants viewed 70s sequences of a random female face identity (A) repeating at 6 Hz. Female faces of different identities (B, C…), interleaved regularly every 7th image (AAAAAABAAAAAAC…) led to significant periodic responses at 0.857 Hz (i.e., 6 Hz/7) and its harmonics, thereby indexing individual face discrimination. Participants performed two tasks: (1) an orthogonal Fixation task, monitoring random colour changes of the central fixation cross, and (2) a Face task, detecting male faces randomly replacing a female face. While the implicit Fixation task elicited robust individual face discrimination responses peaking over the (right) occipito-temporal region, the Face task led to significantly greater overall response amplitude (∼100% increase). However, this attentional boost strongly reduced response specificity by disproportionately recruiting prefrontal and central parietal regions, thereby blurring the occipito-temporal topography typical of specialized high-level face processing. The individual face discrimination response over face-selective occipito-temporal cortex was modulated by the face-sex task starting from 180 ms onset, followed by activations over prefrontal and central parietal region from 200 ms to 450 ms, respectively. Overall, these findings show that even a robust automatic individual face discrimination response can be further enhanced when explicitly searching for face-related information, albeit with a decrease in response specificity.

Social experiences shape behavioral individuality and within-individual stability

AbstractIndividual repeatability characterizes many behaviors. Repeatable behavior may result from repeated social interactions among familiar group members, owing to adaptive social niche specialization. In the context of aggression, in species like field crickets, social niche specialization should also occur when individuals repeatedly interact with unfamiliar individuals. This would require the outcome of social interactions to have carry-over effects on fighting ability and aggressiveness in subsequent interactions, leading to long-term among-individual differentiation. To test this hypothesis, we randomly assigned freshly emerged adult males of the southern field cricket Gryllus bimaculatus to either a solitary or social treatment. In social treatment, males interacted with a same-sex partner but experienced a new partner every 3 days. After 3 weeks of treatment, we repeatedly subjected treated males to dyadic interactions to measure aggression. During this time, we also continuously measured the 3-daily rate of carbohydrate and protein consumption. Individual differentiation was considerably higher among males reared in the social versus solitary environment for aggressiveness but not for nutrient intake. Simultaneously, social experience led to lower within-individual stability (i.e., increased within-individual variance) in carbohydrate intake. Past social experiences, thus, shaped both behavioral individuality and stability. While previous research has emphasized behavioral individuality resulting from repeated interactions among familiar individuals, our study implies that behavioral individuality, in the context of aggression, may generally result from social interactions, whether with familiar or unfamiliar individuals. Our findings thus imply that social interactions may have a stronger effect on individual differentiation than previously appreciated.

Affiliation, Aggression, and Selectivity of Peer Relationships in Meadow and Prairie Voles.

Relationships between adult peers are central to the structure of social groups. In some species, selective preferences for specific peers provide a foundation for consistent group composition. These preferences may be shaped by affiliation toward familiar individuals, and/or by aversion to unfamiliar individuals. We compared peer interactions in two vole species that form selective preferences for familiar same-sex individuals but differ in mating system. Prairie voles (Microtus ochrogaster) form pair bonds with mates and may reside in family groups. Meadow voles (Microtus pennsylvanicus) are promiscuous breeders that form communal winter groups in the wild, and exhibit greater social behavior in short day (SD) lengths in the laboratory. We characterized affiliative, anxiety-like, and aggressive interactions with familiar and novel same-sex conspecifics in meadow and prairie voles housed in summer- or winter-like photoperiods. Species differences in affective behaviors were pronounced, with prairie voles exhibiting more aggressive behavior and less anxiety-like behavior relative to meadow voles. Meadow voles housed in short (vs. long) day lengths were more affiliative and more interactive with strangers; prosocial behavior was also facilitated by a history of social housing. Prairie voles exhibited partner preferences regardless of sex or day length, indicating that selective peer preferences are the norm in prairie voles. Prairie vole females formed preferences for new same-sex social partners following re-pairing; males were often aggressive upon re-pairing. These data suggest that preferences for familiar peers in prairie voles are maintained in part by aggression toward unfamiliar individuals, as in mate partnerships. In contrast, social tolerance is an important feature of meadow vole peer affiliation, demonstrated by low aggression toward unfamiliar conspecifics, and consistent with field data on winter tolerance.

Seeing myself through my heart: Cortical processing of a single heartbeat speeds up self-face recognition

Recent research has highlighted the contribution of interoceptive signals to different aspects of bodily self-consciousness (BSC) by means of the cardio-visual stimulation - i.e. perceiving a pulsing stimulus in synchrony with one’s own heart. Here, for the first time, we investigate the effects of individual heartbeats on a critical feature of BSC, namely the recognition of one’s own face. Across two studies, we explored the cardiac-timing effects on a classic self-face recognition task. In Study 1, participants saw morphed faces that contained different percentages of the self-face and that of another unfamiliar individual. Study 2 used a similar design, albeit participants saw morphed faces of the self-face and that of a familiar other to provide a better control of self-familiarity. Results from both studies consistently revealed that the cortical processing of cardiac afferent signals conveyed by the firing of arterial baroreceptors affects the speed, but not the accuracy, of self-face recognition, when a single picture is presented during cardiac systole, as compared to diastole. This effect is stronger and more stable for stimuli with more self-cues than other-cues and for ‘ambiguous’ stimuli – i.e. at the individual point of subjective equality. Results from Study 2 also revealed that cardiac effects on the speed of self-face recognition cannot be explained simply on the basis of the imbalanced familiarity between the self’s and other’s faces used. The present findings highlight the interoceptive contributions to self-recognition and may be expand our understanding of pathological disturbances of self-experience.

High test-retest reliability of a neural index of rapid automatic discrimination of unfamiliar individual faces

ABSTRACTAn important aspect of human individual face recognition is the ability to discriminate unfamiliar individual. Since many general processes contribute to explicit behavioural performance in individual face discrimination tasks, isolating a measure of unfamiliar individual face discrimination ability in humans is challenging. In recent years, a fast periodic visual stimulation approach (FPVS) has provided objective (frequency-locked) implicit electrophysiological indices of individual face discrimination that are highly sensitive at the individual level within a few minutes of testing. Here we evaluate the test-retest reliability of this response across scalp electroencephalographic (EEG) recording sessions separated by more than two months, in the same 30 individuals. We found no test-retest difference overall across sessions in terms of amplitude and spatial distribution of the EEG individual face discrimination response. Moreover, with only 4 stimulation sequences corresponding to 4 min of recordings per session, the individual face discrimination response was highly reliable in terms of amplitude, spatial distribution, and shape. Together with previous observations, these results strengthen the diagnostic value of FPVS-EEG as an objective and rapid flag for specific difficulties at individual face recognition in the human population.

Eating with Familiar Friends Decreases the Electrical Taste Threshold

Communal eating reportedly induces changes in food-related behaviors such as increased consumption and alleviation of indefinite complaints. Here, we examined the influence of intimacy with co-eaters on the palatability of the food and the physiological taste thresholds. The study was a single-blind crossover trial with 16 healthy women aged 18 - 19 years (two close friends × 8) as participants. We examined the effect of four preset conditions with regard to taste (condition 1 = tasting alone; condition 2 = tasting with a friend; condition 3 = tasting with three unfamiliar individuals; condition 4 = tasting with a friend and two unfamiliar individuals). Electrical taste thresholds were measured pre-and post-eating. The subjective evaluation of taste did not show any significant difference between the four conditions (p > 0.05). However, the electrical taste threshold significantly decreased when eating with close friends (p < 0.05). As a factor associated with the meal environment, co-eating with family or friends appears to influence tastiness; however, in the present study, it showed no effect on the perception of taste. Nevertheless, eating with friends significantly decreased the electrical taste threshold and enhanced the perception of taste. Decrease in the electrical taste threshold was observed only when eating with a close friend; it was not observed when eating with other people and showed no association with the total number of individuals co-eating.

Better the devil you know? How familiarity and kinship affect prey responses to disturbance cues

Prey can greatly improve their odds of surviving predator encounters by eavesdropping on conspecific risk cues, but the reliability of these cues depends on both previous accuracy as well as the cue's relevance. During a predator chase, aquatic prey release chemical disturbance cues that may vary in their reliability depending on the individuals receiving them. Thus, prey may rely differentially on disturbance cues from familiar individuals (due to previous experience) or from kin (due to their relatedness). We examined the responses of wood frog (Lithobates sylvaticus) tadpoles to disturbance cues from familiar versus unfamiliar conspecifics and kin versus non-kin. In accordance with our prediction, tadpoles responded differently to disturbance cues from familiar versus unfamiliar conspecifics. Tadpoles receiving disturbance cues from unfamiliar individuals displayed a fright response, whereas tadpoles ignored disturbance cues from familiar individuals. Tadpoles may have habituated to familiar cues since they were unaccompanied by a true threat, hence rendering these cues functionally unreliable. Tadpoles responded similarly to disturbance cues from related and unrelated individuals suggesting they were similarly reliable and this mirrors the matching reliability of prey responses to damage-released alarm cues from kin and non-kin. Our findings shed light on a seldom-studied chemical communication system in aquatic prey.

Does the grey mouse lemur use agonistic vocalisations to recognise kin?

Frequent kin-biased coalitionary behaviour is a hallmark of mammalian social complexity. Furthermore, selection to understand complex social dynamics is believed to underlie the co-evolution of social complexity and large brains. Vocalisations have been shown to be an important mechanism with which large-brained mammals living in complex social groups recognise and recruit kin for coalitionary support during agonistic conflicts. We test whether kin recognition via agonistic calls occurs in a small-brained solitary foraging primate living in a dispersed social network, the grey mouse lemur (Microcebus murinus, Miller JF, 1777). As mouse lemurs are frequent models for ancestral solitary foraging mammals, this study examines whether kin recognition via agonistic calls could be the foundation from which more complex, kin-based coalitionary behaviour evolved. We test whether female wild mouse lemurs in Ankarafantsika National Park, Madagascar, react differently to agonistic calls from kin and nonkin and to calls from familiar and unfamiliar individuals during playback experiments. Subjects showed no significant differences in reactions to the different stimuli; thus they did not react differently based upon kinship or familiarity. Results suggest that this solitary foraging species does not use agonistic calls to recognise kin and monitor agonistic interactions involving kin, unlike several species of Old World monkeys and hyenas. Thus, kin recognition via agonistic calls may have evolved independently in these lineages in parallel with greater social complexity and frequent coalitionary behaviour.

Male-inflicted wounds have opposite effects on hair cortisol for captive male and female rhesus macaques (Macaca mulatta) following new group formation.

Sexual dimorphism in body size, aggression, and dispersal patterns may affect the degree to which males and females perceive aggression from either sex as stressful. Whereas male macaques typically disperse to new groups at maturity, thus encountering many unfamiliar individuals of both sexes, females are philopatric, usually only encountering unfamiliar males who transfer into their natal groups. In rare circumstances, however, group fusions can expose both males and females to many novel individuals, which often increases aggression. Here, we use a captive new group formation of rhesus macaques (Macaca mulatta) as a model of social instability during fusions and examine differences in male and female chronic stress responses to male-pattern and female-pattern trauma (i.e., trauma inflicted by males or by females, respectively). We found that male- but not female-pattern traumas predicted hair cortisol concentrations during the first 9months after new group formation, but in opposite ways for males and females. A greater number of male-pattern traumas was linked to elevated hair cortisol concentrations in females but slightly lower hair cortisol concentrations in males. We suggest that the apparent importance of male-pattern trauma, but not female-pattern-trauma, in predicting higher hair cortisol concentrations in females can be attributed to the more acutely intense but less persistent nature of male aggression toward females.

Separate brain areas for processing human and dog faces as revealed by awake fMRI in dogs (Canis familiaris)

Functional magnetic resonance imaging (fMRI) has emerged as a viable method to study the neural processing underlying cognition in awake dogs. Working dogs were presented with pictures of dog and human faces. The human faces varied in familiarity (familiar trainers and unfamiliar individuals) and emotional valence (negative, neutral, and positive). Dog faces were familiar (kennel mates) or unfamiliar. The findings revealed adjacent but separate brain areas in the left temporal cortex for processing human and dog faces in the dog brain. The human face area (HFA) and dog face area (DFA) were both parametrically modulated by valence indicating emotion was not the basis for the separation. The HFA and DFA were not influenced by familiarity. Using resting state fMRI data, functional connectivity networks (connectivity fingerprints) were compared and matched across dogs and humans. These network analyses found that the HFA mapped onto the human fusiform area and the DFA mapped onto the human superior temporal gyrus, both core areas in the human face processing system. The findings provide insight into the evolution of face processing.

Does attachment security to a human handler influence the behavior of dogs who engage in animal assisted activities?

Pet and working dogs raised with humans are known to form attachments to their caregivers and other humans with whom they have a stable relationship. Attachment style varies across dog-human dyads, with securely attached dogs exhibiting the secure base effect, an ability to find comfort in the presence of an attachment figure in unusual situations, allowing for greater exploration. The secure base effect is also known to facilitate interactions with unfamiliar individuals. Dogs who engage in Animal Assisted Activities (AAA) are often asked to engage with unfamiliar people in unfamiliar environments, therefore it is possible that dogs with a secure attachment to their human handlers may be more prepared for success in this role. This study evaluated the behavior of 16 dogs who engage in AAA. Using a secure base test dogs were categorized as demonstrating secure (exhibiting the secure base effect with their owner/handler; n = 8) or insecure (not exhibiting the secure base effect; n = 8) attachment styles toward their handlers. Later the dyads participated in a mock animal assisted activity session to evaluate their working behavior. Our findings indicate that independent of attachment style, dogs who engage in AAA spent significantly more time in proximity to, and touching, the AAA participant than their handler (p < 0.001 for both proximity and touch). However, on average the AAA dogs spent significantly more time gazing at their handler than at the participant during the session (p = 0.03). Dogs with an insecure attachment style appear to have driven this effect as evidenced by a non-significant trend suggesting that they gazed longer at their handlers than at the participant (p = 0.07), whereas secure dogs did not display the same trend (p = 0.24). This could suggest that while their training mandates proximity and interaction with unfamiliar people, dogs who engage in AAA may be using gaze to maintain contact with their handlers, especially in the absence of a secure attachment where prolonged comfort seeking from the attachment figure would be expected.

What can we learn about human individual face recognition from experimental studies in monkeys?

Typical human adults recognize numerous individuals from their faces accurately, rapidly and automatically, reaching a level of expertise at individual face recognition that is important for the quality of their social interactions. A non-human species of primates, the rhesus monkey, has been used for decades as a model of human face processing, in particular for understanding the neural basis of individual face recognition. However, despite responding specifically to faces behaviourally and neurally, this species, as well as other Old World and New World monkeys, is remarkably poor at individuating faces of conspecifics. Following extensive conditioning, monkeys only achieve moderate performance at individual face matching tasks where image-based cues are available. Contrary to humans, monkeys do not show a systematic inversion effect in such tasks, or an advantage for matching face pictures of familiar versus unfamiliar individuals, indicating that they do not rely on qualitatively similar individual face recognition processes as humans. These observations concur with the characteristics of the rhesus monkey cortical face processing system, which lacks two critical aspects for human expertise at individual face recognition: a distinct ventral face-selective pathway and a right hemispheric specialization. While the rhesus monkey brain is undoubtedly an informative non-human model for studying the neural basis of social behaviour and visual cognition, it does not provide an adequate model of human individual face recognition. More generally, this review urges for caution when drawing direct inferences across species without sufficient homologies in behaviour and anatomico-functional landmarks.

Social neuroscience of disgust.

Disgust can be thought of as an affective system that has evolved to detect signs of pathogens, parasite and toxins as well as to stimulate behaviors that reduce the risk of their acquisition. Disgust incorporates social cognitive mechanisms to regulate exposure to and, or anticipate and avoid exposure to pathogens and toxins. Social cognition entails the acquisition of social information about others (ie, social recognition) and from others (ie, social learning). This involves recognizing and assessing other individuals and the pathogen/parasite/contamination/toxin threat they pose and deciding about when and how to interact with and, or avoid them. Social cognition provides a frame-work for examining the expression of disgust and the associated neurobiological mechanisms. Here, we briefly consider the relations between social cognition and pathogen/parasite/toxin avoidance behaviors. We briefly discuss aspects of: (1) the odor mediated social recognition of actual and potentially infected individuals and the impact of parasite/pathogen threat on disgust mate and social partner choice; (2) the roles of "out-groups" (strangers, unfamiliar individuals) and "in-groups" (familiar individuals) in the expression of disgust and pathogen avoidance behaviors; (3) individual and social learning of disgust and empathy for disgust; (4) toxin elicited disgust and anticipatory disgust; (5) the neurobiological mechanisms, and in particular the roles of the nonapeptide, oxytocin and estrogenic mechanism associated with social cognition and the expression of disgust. These findings on the social neuroscience of disgust have a direct bearing on our understanding of the roles of disgust in shaping human and nonhuman social behavior.

Transmission of food preference between unfamiliar house mice (Mus musculus domesticus) is dependent on social context.

Rodents obtain information about a new food source through olfactory cues of conspecifics and consequently develop an attraction for this diet. Generally, physical contact between an observer and a demonstrator that has recently consumed a novel food item is required to allow the social transmission of food preference (STFP). However, in natural populations of house mice, social encounters between unfamiliar individuals usually turn into a fight. Thus, social intolerance between the individuals involved could prevent STFP. It has been shown that the feces of rodents can act as a social stimulus and promote STFP in mice, which could reduce the social constraints associated with an encounter. Here, we examined the acquisition of the STFP in female house mice of wild origin (Mus musculus domesticus) after a direct encounter with a familiar and unfamiliar female, and after the presentation of olfactory marks of an unfamiliar female. Unlike in encounters between familiar females, our results did not provide significant support for the existence of STFP after encounters between two unfamiliar females, independently of the occurrence or absence of offensive agonistic behavior. However, STFP through olfactory marks of an unfamiliar female was effective. We suggest that the social context might strongly impair direct STFP, not necessarily via the unfamiliarity of the information provider but rather via its physical presence. (PsycINFO Database Record

The role of social cognition in parasite and pathogen avoidance.

The acquisition and use of social information are integral to social behaviour and parasite/pathogen avoidance. This involves social cognition which encompasses mechanisms for acquiring, processing, retaining and acting on social information. Social cognition entails the acquisition of social information about others (i.e. social recognition) and from others (i.e. social learning). Social cognition involves assessing other individuals and their infection status and the pathogen and parasite threat they pose and deciding about when and how to interact with them. Social cognition provides a framework for examining pathogen and parasite avoidance behaviours and their associated neurobiological mechanisms. Here, we briefly consider the relationships between social cognition and olfactory-mediated pathogen and parasite avoidance behaviours. We briefly discuss aspects of (i) social recognition of actual and potentially infected individuals and the impact of parasite/pathogen threat on mate and social partner choice; (ii) the roles of 'out-groups' (strangers, unfamiliar individuals) and 'in-groups' (familiar individuals) in the expression of parasite/pathogen avoidance behaviours; (iii) individual and social learning, i.e. the utilization of the pathogen recognition and avoidance responses of others; and (iv) the neurobiological mechanisms, in particular the roles of the nonapeptide, oxytocin and steroid hormones (oestrogens) associated with social cognition and parasite/pathogen avoidance.This article is part of the Theo Murphy meeting issue 'Evolution of pathogen and parasite avoidance behaviours'.

Learning and Socializing Preferences in Hong Kong Chinese Children.

The impact of social group information on the learning and socializing preferences of Hong Kong Chinese children were examined. Specifically, the degree to which variability in racial out-group exposure affects children's use of race to make decisions about unfamiliar individuals (Chinese, White, Southeast Asian) was investigated. Participants (N=212; Mage =60.51months) chose functions for novel objects after informants demonstrated their use; indicated with which peer group member to socialize; and were measured on racial group recognition, preference, and identification. Overall, children preferred in-group members, though out-group exposure and the relative social status of out-groups mattered as well. At a young age, children's specific experiences with different races influence how they learn and befriend others across racial group lines.

Friend or Family? Social Recognition and Physiological Stress in the Self‐Fertilizing Mangrove Rivulus Fish (Kryptolebias marmoratus)

Social behavior has the capacity to influence how animals respond to environmental stress. Living in social groups may be beneficial to animals as it can reduce predation risk and provide foraging benefits. Advantages may be further enhanced if animals associate with related individuals (kin), with individuals of the same phenotype and/or with familiar conspecifics, regardless of relatedness. On the other hand, grouping may incur costs if there is competition for resources or increased aggression. Given the potential influence of sociality on physiological responses to stress, it is important to understand an animal's social behavior and if certain social interactions result in physiological stress. The mangrove rivulus is a tropical, self‐fertilizing fish that forms isogenic lineages, providing a model fish with a natural and extreme form of kin. Using distinct strains of rivulus originating from Belize and Honduras, we predicted that rivulus would use both relatedness and familiarity as cues to recognize conspecifics. We used a choice chamber and in two separate experiments, gave focal fish of each strain the choice between related or familiar stimulus fish. We took water samples to determine cortisol concentrations, as we predicted that association with non‐kin and/or unfamiliar fish would be stressful and result in increases is the stress hormone. We found no significant differences in the proportion of time either lineage spent with familiar or related conspecifics. We further analysed association time for aggressive behaviour as we predicted that rivulus would be less aggressive to both familiar and related conspecifics. Interestingly, we determined that the Belize lineage is not aggressive towards related or unrelated individuals whereas the Honduran lineage is aggressive to unrelated conspecifics only. Collectively, our data suggest that rivulus detect conspecifics using both familiarity and relatedness; kin discrimination is not universal and appears to have a genetic basis. My further analyses will determine whether or not association with non‐kin and/or unfamiliar individuals is physiologically stressful.Support or Funding InformationResearch supported by APS UGSRF and Mount Allison University. Cortisol analysis is in collaboration with Dr. Ryan Earley, University of Alabama. Research supervised by Dr. Suzie Currie.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

EGR-1 Expression in Catecholamine-synthesizing Neurons Reflects Auditory Learning and Correlates with Responses in Auditory Processing Areas

Distinguishing between familiar and unfamiliar individuals is an important task that shapes the expression of social behavior. As such, identifying the neural populations involved in processing and learning the sensory attributes of individuals is important for understanding mechanisms of behavior. Catecholamine-synthesizing neurons have been implicated in sensory processing, but relatively little is known about their contribution to auditory learning and processing across various vertebrate taxa. Here we investigated the extent to which immediate early gene expression in catecholaminergic circuitry reflects information about the familiarity of social signals and predicts immediate early gene expression in sensory processing areas in songbirds. We found that male zebra finches readily learned to differentiate between familiar and unfamiliar acoustic signals (‘songs’) and that playback of familiar songs led to fewer catecholaminergic neurons in the locus coeruleus (but not in the ventral tegmental area, substantia nigra, or periaqueductal gray) expressing the immediate early gene, EGR-1, than playback of unfamiliar songs. The pattern of EGR-1 expression in the locus coeruleus was similar to that observed in two auditory processing areas implicated in auditory learning and memory, namely the caudomedial nidopallium (NCM) and the caudal medial mesopallium (CMM), suggesting a contribution of catecholamines to sensory processing. Consistent with this, the pattern of catecholaminergic innervation onto auditory neurons co-varied with the degree to which song playback affected the relative intensity of EGR-1 expression. Together, our data support the contention that catecholamines like norepinephrine contribute to social recognition and the processing of social information.

Infants help singers of familiar songs

Infants are highly selective in their help to unfamiliar individuals. For example, they offer more help to partners who move synchronously with them rather than asynchronously and to partners who interact with them in a “nice” rather than “mean” manner. Infant-directed song and speech may also encourage infant helping by signaling caregiver quality. In the present study, we investigated the effect of infant-directed song and recitation on 14-month-old infants’ subsequent helpfulness and proximity-seeking in relation to unfamiliar performers. During a 2.5-minute exposure phase, infants sat on their caregiver’s lap opposite an experimenter who sang “The Ants Go Marching” (song condition), recited the lyrics (recitation condition), or remained silent while parents read them a book (baseline condition). After the exposure phase, infants participated in a series of helping tasks that necessitated the return of objects dropped “accidentally”. Infants in the song and recitation conditions helped more than those in the baseline condition, but their helping of singers was moderated by song familiarity. Specifically, the extent of help directed to singers correlated positively with song familiarity. Singing (and to some extent, recitation) also encouraged infants to seek proximity with the experimenter. The findings indicate that rhythmic song and recitation by an unfamiliar adult foster infant affiliative behavior, but familiar songs may have special social importance.