Of the importance to reconsider individual variability in infant studies: Family traits do impact turn-taking perception in 6-month-olds.

Turn-taking is a universal pattern of human conversations characterized by a fast exchange of turns between speakers and an avoidance of overlaps. Language is embedded in this conversational skill acquired well before it during infancy, through everyday interactions with caregivers. The earliness of this skill and its link with language allows us to test whether social environment shapes early language development. We therefore study turn-taking perception of 6-month-old infants by measuring their gazes during video presentation of three different conversational situations where the turn is explicitly given, normally taken or taken with an overlap. We studied 51 infants to cover several family and infant characteristics: infants' sex, presence of siblings, and family socioeconomic status (SES). We found that infants looked more at the second speaker when she overlapped the first speaker than in the other situations, but not all infants were equally sensitive. Indeed, infants from high-SES families reacted differently to the three situations, while infants from the two lower SES categories did not. Also, only singletons reacted differently by looking more at the second speaker after the overlapping and turn-giving situations, and not after the turn-taking situation. Our results emphasize the importance of early social experiences on language development.

Social factors drive vocal exchanges in red-capped mangabeys (Cercocebus torquatus).

Of all the calls made by non-human primates, the function of short-distance contact calls has largely remained to be determined. These calls are the most frequent in the repertoire and are most often exchanged between individuals in a non-random way. To our knowledge, no study has ever examined how vocal exchanges are structured in red-capped mangabeys (Cercocebus torquatus), a semi-terrestrial monkey living in the African forest with a complex semi-tolerant/semi-despotic social system. Our goal was to assess the organization of contact call exchanges in this species and their relationship with individual and social factors such as age, affinity, and hierarchy. Therefore, we observed several captive groups of red-capped mangabeys and collected data on vocal behavior, as well as grooming, agonistic behavior, and spatial proximity. We defined a vocal exchange in this species as a series of contact calls made by two or more individuals within a maximum inter-caller interval of 2 s. At the individual level, the higher the individual's hierarchical rank, the less they initiated exchanges. Furthermore, the most socially integrated individuals had a longer average response time than the less integrated ones. At the dyadic level, preferred exchange partners were individuals often observed near one other or individuals most distant in age. Also, the further apart two individuals were in the dominance hierarchy, the shorter the response time. Our results support both the social bonding hypothesis and a modulating key role of the dominance hierarchy on the social use of contact calls, which is in line with the social style of this species.

The vocal repertoire of preterm infants: Characteristics and possible applications.

We investigated infants' capacities to express themselves orally at very early developmental stages. Most reports focus on crying when in pain or hungry. We evaluated young preterm infants' spontaneous vocal production in non-painful contexts. We identified a vocal repertoire composed of nine types of vocalisations. High-pitched sounds were associated with relaxed postures, implying a positive valence, whereas long low-pitched vocalisations, associated more with grimaces and muscle tensions, appeared to have a more negative valence. Infants' vocalisations were useful indicators of their internal state in two situations (when exposed to clothing constraints and environmental noises).

A novel, short and easy-to-perform method to evaluate newborns' social olfactory preferences.

Humans' early olfactory perception has been studied mainly within the framework of mother-offspring interactions and only a few studies have focused on newborns' abilities to discriminate body odors per se. The aim of this study was to develop a method to evaluate olfactory social preferences of infants at term-equivalent age. Twenty dyads of infants (10 born preterm and 10 born at term) at term-equivalent age and their mothers were included. We analyzed the behavioral reactions of infants to their mother's upper-chest odor (that bears social, non-food related information). The two impregnated gauzes and a control gauze were presented to the infants for 10 s each, in a random order. We compared two durations of gauze impregnation: 30 min and 12 h. This study reveals that mothers' upper chest emits sufficient olfactory information to induce reactions in infants born full-term or born preterm and that a short impregnation is preferable to evaluate their perception of body odors, notably for those born preterm.

Higher tactile sensitivity in preterm infants at term-equivalent age: A pilot study.

Despite a growing body of research on perinatal sensory abilities, data on the extent of tactile sensitivity and more particularly passive touch (i.e. sensitivity to a stimulation imposed on the skin) are relatively limited, and the development and processing of tactile function are still thus little known. This question is particularly of high importance for infants with atypical early development such as those born prematurely who are exposed to many sensory (including tactile) stimulations (being in a hospital setting) during a critical period of brain development and those born at early term whose birth occurs at the precise time of cortical reorganization, in particular in the sensory areas. Some parents and health-care providers have for instance reported that children born prematurely exhibit atypical (e.g. higher) sensitivity to "benign" tactile stimuli. In the present study, we hypothesized that preterm and early-term infants may show altered tactile sensitivity. We compared the behavioral responses around term-equivalent age of infants born either pre-term, early-term or at term to the application of a light (0.008 grams) mechanical stimulus. We found that almost all preterm infants perceive this tactile stimulus, contrarily to the two other groups of infants. This extreme tactile sensitivity may be due to experiential, maturational or more likely both processes. We also compared the tactile sensitivity of these infants to that of adults. We found that adults were irresponsive to the light mechanical stimulus. This finding opens not only new insights in understanding development of tactile processing, but also new lines of thought about the particular sensory world of premature and early-term infants and hence about the potential impact of early care practices.

Cortical Pain Response of Newborn Infants to Venepuncture: A Randomized Controlled Trial Comparing Analgesic Effects of Sucrose Versus Breastfeeding.

OBJECTIVE: Sucrose administration and breastfeeding decrease behavioral expressions of pain in neonates. However, recent studies indicated that there is a persistent cortical response with sucrose. This study compared the efficacy of sucrose administration versus breastfeeding to decrease cortical responses to pain during venepuncture. PATIENTS AND METHODS: A randomized, prospective, controlled trial was conducted in a tertiary level maternity ward. Healthy, 3-day-old term neonates, undergoing venepuncture for neonatal screening, were randomly assigned to receive sucrose solution or be breastfed before venepuncture. Variations in the total hemoglobin concentration [HbT] in the contralateral somatosensory cortex were assessed with near infrared spectroscopy. The Neonatal Facial Coding System (NFCS) was used to assess reactions. RESULTS: There were 114 term neonates included, with 102 included for the primary outcome (breastfed group: 48; sucrose group: 54). Similar maximum increases in [HbT] were observed in both groups (mean±SD: sucrose group: 31.2±58.1 µmol/L; breastfed group: 38.9±61.4 µmol/L; P=0.70). Breastfed neonates presented more behavioral expressions that indicated pain compared with sucrose-administered neonates (46.8% vs. 26.8% of NFCS ≥1, P=0.04). The maximum increase in [HbT] was persistent, although newborn infants who did not express behavioral signs of pain had lower concentrations than neonates who did (mean±SD: 21.2±29.1 vs. 60.0±89.8 µmol/L, P<0.01). DISCUSSION: There was no difference in the cortical responses to pain during venepuncture in newborn infants who were administered sucrose versus those who were breastfed.

The human newborn's umwelt: Unexplored pathways and perspectives.

Historically, newborns, and especially premature newborns, were thought to "feel nothing." However, over the past decades, a growing body of evidence has shown that newborns are aware of their environment, but the extent and the onset of some sensory capacities remain largely unknown. The goal of this review is to update our current knowledge concerning newborns' perceptual world and how ready they are to cope with an entirely different sensory environment following birth. We aim to establish not only how and when each sensory ability arises during the pre-/postbirth period but also discuss how senses are studied. We conclude that although many studies converge to show that newborns are clearly sentient beings, much is still unknown. Further, we identify a series of internal and external factors that could explain discrepancies between studies, and we propose perspectives for future studies. Finally, through examples from animal studies, we illustrate the importance of this detailed knowledge to pursue the enhancement of newborns' daily living conditions. Indeed, this is a prerequisite for assessing the effects of the physical environment and routine procedures on newborns' welfare.

Subsocial Cockroaches Nauphoeta cinerea Mate Indiscriminately with Kin Despite High Costs of Inbreeding.

Many animals have evolved strategies to reduce risks of inbreeding and its deleterious effects on the progeny. In social arthropods, such as the eusocial ants and bees, inbreeding avoidance is typically achieved by the dispersal of breeders from their native colony. However studies in presocial insects suggest that kin discrimination during mate choice may be a more common mechanism in socially simpler species with no reproductive division of labour. Here we examined this possibility in the subsocial cockroach Nauphoeta cinerea, a model species for research in sexual selection, where males establish dominance hierarchies to access females and control breeding territories. When given a binary choice between a sibling male and a non-sibling male that had the opportunity to establish a hierarchy prior to the tests, females mated preferentially with the dominant male, irrespective of kinship or body size. Despite the lack of kin discrimination during mate choice, inbred-mated females incurred significant fitness costs, producing 20% less offspring than outbred-mated females. We discuss how the social mating system of this territorial cockroach may naturally limit the probability of siblings to encounter and reproduce, without the need for evolving active inbreeding avoidance mechanisms, such as kin recognition.

Unexpected behavioural consequences of preterm newborns' clothing.

Restrictions of preterm newborns' movements could have consequences ranging from stress enhancement to impairment of their motor development. Therefore, ability to freely express motor activities appears crucial for their behavioural and physiological development. Our aim was to evaluate behavioural issues of two types of clothing used in NICU. We observed 18 healthy 34-37 post-conception week-old preterm newborns, during resting periods, when they were undisturbed by any interventions. Newborns wore either light clothing (bodysuit and a light wrapping) or heavy clothing (pyjamas, cardigan and sleep-sack). The percentages of time each subject spent in different postures were compared between clothing situations. Arm and hand postures differed in relation to clothing: babies bent their arms more and held their hands nearer their heads when in bodysuits than when in sleepwear. Consequently, babies in bodysuits spent more time touching their body or their environment whereas the others generally were touching nothing. Self-touch is an important way to comfort one's self. Heavy clothing may impair self-soothing behaviours of preterm newborn babies that already lack other forms of contact. Results suggest that more attention should be paid to apparently routine and marginal decisions such as choice of clothes.

Locomotor Inhibition in Adult Horses Faced to Stressors: A Single Postpartum Experience May be Enough!

Despite the number of postpartum handling that a newborn experiences, few studies focus on their long-term consequences. In rats, regular long separations from the mother, during the early life, led to modifications of the locomotor activity when the animal is confronted to a stressor. In horses, one component of the behavioral response to stressful situation is active locomotion. We wondered if the routine postpartum handling undergone by foals, would affect their level of reactivity or the way they express their stress, when older. One single prolonged bout of handling just after birth clearly affected later adult expression of stress reactivity. In social separation associated with novelty, handled, and unhandled horses produced an equal amount of whinnies, showing a similar vocal response to stress. However, both groups differed in their locomotor response to the situations. Early handled foals expressed less of the active forms of locomotion than the control group. Our findings highlight the need of further reflections on long-term effects of routine handlings procedures close to birth.

Differential outcomes of unilateral interferences at birth.

Behavioural modifications, including modifications of emotional reactivity, can occur following early experience such as handling (manual rubbing). Here, we investigated the effects of unilateral tactile stimulation at an early stage on emotional reactions later on. We handled newborn foals intensively on one side of their body. This early unilateral tactile experience had medium-term effects: the reactions of foals to a human approach, when they were 10 days old, differed according to the side stimulated at birth. Fewer right-handled foals accepted contact with humans, they delayed first contact longer and they evaded approaching humans sooner than did non-handled and left-handled foals. These results raise questions concerning the organization of neonatal care in animals and humans.

The co-activation of snapshot memories in wood ants.

Insects can guide themselves along a familiar route to a familiar place by retrieving and using visual snapshots that they have stored both along the route and at their destination and moving so that their current views match the target snapshots. To learn more about the matching process, we have investigated the interaction of snapshots by engineering a situation in which ants simultaneously retrieve two sets of memories. Ants were trained from a fixed start position to feed in one site, after which the feeder was switched to a new one. It could take up to 30 trials after the switch before the ants headed directly to the new food site. We suppose that during this transition phase ants retrieve memories appropriate for both sites. We compared the ants' behaviour for two different sized separations between feeder sites. When the sites are relatively close together, the initial headings of the ants' paths rotated gradually from aiming directly at the first food site to aiming at the second food site, suggesting that ants' paths are controlled by the weighted average of two simultaneously activated snapshot attractors. By contrast, when the food sites were further apart, initial headings switched abruptly between the two sites - ants either headed for food site 1 or for food site 2. We show that these differences in transition behaviour can be simulated by the co-activation of snapshot attractors of restricted spatial extent, such that features encoded in a snapshot are only recognised if they occur within a limited retinal distance of the stored position of the feature.

Switching destinations: memory change in wood ants.

We have studied the changing use of spatial memories in wood ants by charting how the ants' paths transform when ants are first trained to feed at one site and must then switch to another site. Because ants, which are trained to approach a single feeding site from a single starting point, are attracted directly to that goal when started from unfamiliar positions, we describe the ants' paths in terms of the use of two stored snapshots. Each snapshot consists of retinotopic views of the ants' surroundings acquired at one of the two feeding sites. When a snapshot is activated, it draws an ant to the related site from a wide range of directions. Here, we focus on routes that occur before ants have learnt to go directly from the start to the second site. The initial direction of the ant's path is then mostly aimed either at the first site or between the two sites. On 62.2% of all recorded paths, this segment is followed by an abrupt turn, after which the ant often aims directly at the second feeding site. The details of this behaviour suggest that, after the turn, control of the path switches from the snapshot recorded at the first feeding site (or some combination of the two snapshots) to the snapshot recorded at the second feeding site. We discuss different ways in which control might be transferred from one snapshot to the other.

The binding and recall of snapshot memories in wood ants (Formica rufa L.).

Insects can locate spatial goals by means of 2-D retinotopic views of the surrounding landmarks, which they memorise from the vantage point of the goal. Wood ants acquire such snapshot memories while fixating conspicuous landmarks with frontal retina, and their snapshots extend horizontally at least 120 degrees into the periphery. Are spatially separate items within such an extended snapshot bound together so that a snapshot is recalled as a whole, or are its components recognised individually? We approached this question by training ants to find food midway between two upright black cylinders of different sizes and then examined where they searched when they were given two cylinders of the same size. If the ants know which cylinder replaces the small cylinder and which the large, they should search at a position where the two equal-sized cylinders subtend the same angles as do the training cylinders when viewed from the feeder. Ants conformed to this prediction under one condition, searching at a shorter distance from the substitute for the large cylinder than from the substitute for the small cylinder. But, under another condition, ants were unable to distinguish between the two equal-sized cylinders. Ants failed when white curtains completely surrounded the platform on which the cylinders were placed. They succeeded when one side of the platform had a patterned curtain. We suggest that ants take two snapshots at the feeding site, one when facing the small cylinder and one when facing the large cylinder, and that each snapshot includes the patterned curtain, if it is there. Ants will view the patterned curtain with the lateral retina of one eye when facing the small cylinder and with the lateral retina of the other eye when facing the large cylinder. Our data suggest that there may be associative links between these spatially separate components of the snapshot, which cause the memory of the small cylinder or the large cylinder to be recalled according to which eye sees the curtain. It seems that an extended snapshot not only enhances the accuracy of localisation but can also increase the reliability of snapshot recall, provided that the components of a snapshot are bound together.

Route learning by insects.

Ants and other insects often follow fixed routes from their nest to a foraging site. The shape of an ant's route is set, initially, by navigational strategies, such as path integration and the ant's innate responses to landmarks, which depend minimally on memory. With increasing experience, these early routes are stabilised through the learning of views of landmarks and of associated actions. The substitution of memory-based strategies makes an insect's route more robust and precise. The ability to select between different learnt routes might incur additional memory requirements to those needed for performing a route, and lead to the associative grouping of those memories that relate to a particular route.

Snapshot memories and landmark guidance in wood ants.

Insects are thought to pinpoint a place by using memorized "snapshots," i.e., two-dimensional retinotopic views of the surrounding landmarks recorded when at the place (reviewed in ). Insects then reach the place by moving until their current view matches their snapshot. To determine when snapshots are recalled, and how differences between view and snapshot are translated into appropriate movements, we analyzed the approaches of wood ants to a feeding site that was located in the center of an array of two or three cylinders. In ants, contrary to flying hymenopterans, body orientation and direction of travel are collinear, so that an ant approaching an object always looks at it with frontal visual field. On their way to a food site, ants fixated and approached a cylinder predominantly when its angular size was smaller than when viewed from the food site. This finding implies that ants store snapshots at this place while fixating landmarks with frontal retina, so simplifying the later alignment of snapshots with their current view. It also means that ants recall snapshots well in advance of reaching the place. Although snapshots are centered on a landmark, we show that they extend at least 120 degrees into the periphery.