Toshikazu Hasegawa

Direct gaze captures visuospatial attention

This study investigated whether the direct gaze of others influences attentional disengagement from faces in an experimental situation. Participants were required to fixate on a centrally presented face with varying gaze directions and to detect the appearance of a peripheral target as quickly as possible. Results revealed that target detection was delayed when the preceding face was directly gazing at the subject (direct gaze), as compared with an averted gaze (averted gaze) or with closed eyes (closed eyes). This effect disappeared when a temporal gap was inserted between the offset of the centrally presented face and the onset of a peripheral target, suggesting that attentional disengagement contributed to the delayed response in the direct gaze condition. The response delay to direct gaze was not found when the contrast polarity of eyes in the facial stimuli was reversed, reinforcing the importance of gaze perception in delayed disengagement from direct gaze.

Rise and fall of political complexity in island South-East Asia and the Pacific

There is disagreement about whether human political evolution has proceeded through a sequence of incremental increases in complexity, or whether larger, non-sequential increases have occurred. The extent to which societies have decreased in complexity is also unclear. These debates have continued largely in the absence of rigorous, quantitative tests. We evaluated six competing models of political evolution in Austronesian-speaking societies using phylogenetic methods. Here we show that in the best-fitting model political complexity rises and falls in a sequence of small steps. This is closely followed by another model in which increases are sequential but decreases can be either sequential or in bigger drops. The results indicate that large, non-sequential jumps in political complexity have not occurred during the evolutionary history of these societies. This suggests that, despite the numerous contingent pathways of human history, there are regularities in cultural evolution that can be detected using computational phylogenetic methods.

Deviant gaze processing in children with autism: an ERP study

This study investigated event-related potentials (ERP) during an oddball task in which detection of specific eye direction was required of children with and without autism. The detection of a change in eye direction elicited occipito-temporal negativity, which had two major differences between children with and without autism. First, while this occipito-temporal negativity predominated in the right hemisphere of typically developed children, it was distributed equally bilaterally in children with autism. Second, the amplitude of this negativity was more pronounced in typically developed children in response to the detection of direct gaze as compared to averted gaze, but was not sensitive to direct/averted gaze direction in children with autism, which converges with behavioral reports. The results concur with previous literature, suggesting the importance of the right hemisphere, especially the superior temporal sulcus, in gaze processing. Results indicate that deviant neural substrates might be involved in gaze processing in individuals with autism.

Absence of contagious yawning in children with autism spectrum disorder.

This study is the first to report the disturbance of contagious yawning in individuals with autism spectrum disorder (ASD). Twenty-four children with ASD as well as 25 age-matched typically developing (TD) children observed video clips of either yawning or control mouth movements. Yawning video clips elicited more yawns in TD children than in children with ASD, but the frequency of yawns did not differ between groups when they observed control video clips. Moreover, TD children yawned more during or after the yawn video clips than the control video clips, but the type of video clips did not affect the amount of yawning in children with ASD. Current results suggest that contagious yawning is impaired in ASD, which may relate to their impairment in empathy. It supports the claim that contagious yawning is based on the capacity for empathy.

Does perceived direct gaze boost detection in adults and children with and without autism? The stare-in-the-crowd effect revisited

This study extended that of von Grünau and Anston (1995) and explored whether perceived direct gaze is easily detected by individuals with and without autism, utilizing a visual-search paradigm. Participants detected target faces with either direct gaze or averted gaze. Laterally averted faces were used to eliminate the involvement of lower perceptual characteristics such as symmetry, which were inherent with the “straight gaze” used by von Grünau and Anston. Both typically developed adults and children detected targets with direct gaze more quickly than those with averted gaze, but face inversion distorted this asymmetrical performance, suggesting the contribution of configurative facial processing. In contrast, children with autism were not affected by the gaze direction presented by realistic facial stimuli. They were, however, faster to detect straight gaze defined solely by local features, which suggests that their impairment might be specific to the detection of direct gaze presented within a facial context.

Eye contact does not facilitate detection in children with autism

Eye contact is crucial in achieving social communication. Deviant patterns of eye contact behavior are found in individuals with autism, who suffer from severe social and communicative deficits. This study used a visual oddball paradigm to investigate whether children with high functioning autism have difficulty in detecting mutual gaze under experimental conditions. The results revealed that children with autism were no better at detecting direct gaze than at detecting averted gaze, which is unlike normal children. This suggests that whereas typically developing children have the ability to detect direct gaze, children with autism do not. This might result in altered eye-contact behavior, which hampers subsequent development of social and communicative skills.

Opportunistic and restrictive matings among wild chimpanzees in the Mahale Mountains, Tanzania

The mating patterns of free-ranging chimpanzees (Pan troglodytes) of the Mahale Mountains, Tanzania, were studied. Opportunistic mating (non-competitive and temporary mating) was frequently observed in a large-sized unit-group, among young, low-ranking males, and among young, newcomer, non-ovulating females. Restrictive mating (a continuous sexual relationship between a particular pair which includes possessiveness and consortship) was frequently observed in a small-sized unit-group, among middle- and old-aged, high-ranking males, and among old, resident, ovulating females. Relations between those characteristics, such as group size and composition, ages of the individuals of both sexes, female estrous stages, and life history, and the 2 mating patterns are discussed.

Demographic study of a large-sized unit-group of chimpanzees in the Mahale Mountains, Tanzania: a preliminary report

Long-term demographic observations on a large-sized unit-group of chimpanzees in the Mahale Mountains, Tanzania, are summarized. The unit-group, the M group, contains over 100 individuals, which makes it the largest unit-group ever reported. The age-sex composition, natality, mortality and transfers of the M group are analyzed. An attempt is made to illustrate an age-sex pyramid of the group by estimating the ages of all the individuals in the group. The results reveal that: (1) the mortality rate of the male infants within 1 year almost doubled that of female infant; (2) adult male to adult female ratio of the M group is considerably higher than any other unit-groups elsewhere; and (3) the M group contains a relatively large number of old animals over 40 years of age, suggesting that the longevity of wild chimpanzees might be greater than estimated so far.

Oxytocin promotes social bonding in dogs

Significance Although the positive impact of social bonds on individual’s fitness has recently been demonstrated, the mechanisms underlying the motivation to form long-term associations remain largely unknown. Current evidence shows that oxytocin modulates social behavior but evidence of its effects in bond maintenance remains scant, especially in nonreproductive contexts. We provide evidence that in the domestic dog oxytocin enhances social motivation to approach and affiliate with conspecifics and human partners, which constitutes the basis for the formation of any stable social bond. Furthermore, endogenous oxytocin levels increased after dogs engaged in affiliation with their dog partners, indicating a stimulation of the oxytocin system during social interactions. Our findings highlight the important role that oxytocin has in the expression of sociality in mammals. Recent evidence suggests that enduring social bonds have fitness benefits. However, very little is known about the neural circuitry and neurochemistry underlying the formation and maintenance of stable social bonds outside reproductive contexts. Oxytocin (OT), a neuropeptide synthetized by the hypothalamus in mammals, regulates many complex forms of social behavior and cognition in both human and nonhuman animals. Animal research, however, has concentrated on monogamous mammals, and it remains unknown whether OT also modulates social bonds in nonreproductive contexts. In this study we provide behavioral evidence that exogenous OT promotes positive social behaviors in the domestic dog toward not only conspecifics but also human partners. Specifically, when sprayed with OT, dogs showed higher social orientation and affiliation toward their owners and higher affiliation and approach behaviors toward dog partners than when sprayed with placebo. Additionally, the exchange of socio-positive behaviors with dog partners triggered the release of endogenous OT, highlighting the involvement of OT in the development of social relationships in the domestic dog. These data provide new insight into the mechanisms that facilitate the maintenance of close social bonds beyond immediate reproductive interest or genetic ties and complement a growing body of evidence that identifies OT as one of the neurochemical foundations of sociality in mammalian species.

Is anyone looking at me? Direct gaze detection in children with and without autism

Atypical processing of eye contact is one of the significant characteristics of individuals with autism, but the mechanism underlying atypical direct gaze processing is still unclear. This study used a visual search paradigm to examine whether the facial context would affect direct gaze detection in children with autism. Participants were asked to detect target gazes presented among distracters with different gaze directions. The target gazes were either direct gaze or averted gaze, which were either presented alone (Experiment 1) or within facial context (Experiment 2). As with the typically developing children, the children with autism, were faster and more efficient to detect direct gaze than averted gaze, whether or not the eyes were presented alone or within faces. In addition, face inversion distorted efficient direct gaze detection in typically developing children, but not in children with autism. These results suggest that children with autism use featural information to detect direct gaze, whereas typically developing children use configural information to detect direct gaze.