Solvent-Induced Negative Energetic Elasticity in a Lattice Polymer Chain.

The negative internal energetic contribution to the elastic modulus (negative energetic elasticity) has been recently observed in polymer gels. This finding challenges the conventional notion that the elastic moduli of rubberlike materials are determined mainly by entropic elasticity. However, the microscopic origin of negative energetic elasticity has not yet been clarified. Here, we consider the n-step interacting self-avoiding walk on a cubic lattice as a model of a single polymer chain (a subchain of a network in a polymer gel) in a solvent. We theoretically demonstrate the emergence of negative energetic elasticity based on an exact enumeration up to n=20 and analytic expressions for arbitrary n in special cases. Furthermore, we demonstrate that the negative energetic elasticity of this model originates from the attractive polymer-solvent interaction, which locally stiffens the chain and conversely softens the stiffness of the entire chain. This model qualitatively reproduces the temperature dependence of negative energetic elasticity observed in the polymer-gel experiments, indicating that the analysis of a single chain can explain the properties of negative energetic elasticity in polymer gels.

Preschool children aged 4 to 5 years show discomfort with trypophobic images.

The fear or disgust of clustered patterns, such as honeycomb or lotus seed pods, is known as trypophobia. A previous developmental study reported that 4-year-old children prefer neutral images over clustered images. However, whether those results indicated higher rating scores for trypophobic images has been controversial. In this study, we examined discomfort with trypophobic images in adults and children aged 4-9 years using an identical experimental procedure. A modified rating scale applicable for children was used that was based on the established Trypophobia Scale for adults. The participants were required to rate five trypophobic and five neutral images on four rating items (disgusting, fear, feel itchiness, and like) on a 4-point scale ranging from 1 (not at all) to 4 (very much). The participants in all age groups indicated higher rate scores for trypophobic images than for neutral images in terms of 'disgust', 'fear', and 'feeling itchiness', whereas they indicated higher scores for neutral images than for trypophobic images in terms of 'like'. These results suggest that children aged 4-5 years have responses comparable to the responses of adults with respect to trypophobic and neutral images; thus, trypophobia appears to emerge at least by the age of 4-5 years.

Influence of Heat Exposure on Motor Control Performance and Learning as Well as Physiological Responses to Visuomotor Accuracy Tracking Task.

This study aimed to determine whether heat exposure attenuates motor control performance and learning, and blunts cardiovascular and thermoregulatory responses to visuomotor accuracy tracking (VAT) tasks. Twenty-nine healthy young adults (22 males) were divided into two groups performing VAT tasks (5 trials × 10 blocks) in thermoneutral (NEUT: 25 °C, 45% RH, n = 14) and hot (HOT: 35 °C, 45% RH, n = 15) environments (acquisition phase). One block of the VAT task was repeated at 1, 2, and 4 h after the acquisition phase (retention phase). Heat exposure elevated skin temperature to ~3 °C with a marginally increased core body temperature. VAT performance (error distance of curve tracking) was more attenuated overall in HOT than in NEUT in the acquisition phase without improvement in magnitude alteration. Heat exposure did not affect VAT performance in the retention phase. The mean arterial blood pressure and heart rate, but not for sweating and cutaneous vascular responses to VAT acquisition trials, were more attenuated in HOT than in NEUT without any retention phase alternations. We conclude that skin temperature elevation exacerbates motor control performance and blunts cardiovascular response during the motor skill acquisition period. However, these alternations are not sustainable thereafter.

Developmental Changes in the Magnitude of Representational Momentum Among Nursery School Children: A Longitudinal Study.

Representational momentum (RM) is a well-known phenomenon that occurs when a moving object vanishes suddenly and the memory of its final or vanishing position is displaced forward in the direction of its motion. Many studies have shown evidence of various perceptual and cognitive characteristics of RM in various daily aspects, sports, development, and aging. Here we examined the longitudinal developmental changes in the displacement magnitudes of RM among younger (5-year-old) and older (6-year-old) nursery school children for pointing and judging tasks. In our experiments, the children were asked to point at by their finger (pointing task) and judge the spatial location (judging task) of the vanishing point of a moving stimulus. Our results showed that the mean magnitudes of RM significantly decreased from 5- to 6-year-old children for the pointing and judging tasks, although the mean magnitude of RM was significantly greater in the 5-year-old children for the pointing task but not for the judging task. We further examined the developmental changes in RM for a wide range of ages based on data from the present study (5-year-old children) and our previous study (7- and 11-year-old children and 22-year-old adults). This ad hoc examination showed that the magnitude of RM was significantly greater in 5-year-old children than in adults for the pointing and judging tasks. Our findings suggest that the magnitude of RM was significantly greater in young children than in adults and significantly decreased in young children through adults for the pointing and judging tasks.

Developmental changes in gaze patterns in response to radial optic flow in toddlerhood and childhood.

A large field visual motion pattern (optic flow) with a radial pattern provides a compelling perception of self-motion; a radially expanding/contracting optic flow generates the perception of forward/backward locomotion. Moreover, the focus of a radial optic flow, particularly an expansive flow, is an important visual cue to perceive and control the heading direction during human locomotion. Previous research has shown that human gaze patterns have an "expansion bias": a tendency to be more attracted to the focus of expansive flow than to the focus of contractive flow. We investigated the development of the expansion bias in children (N = 240, 1-12 years) and adults (N = 20). Most children aged ≥ 5 years and adults showed a significant tendency to shift their gaze to the focus of an expansive flow, whereas the youngest group (1-year-old children) showed a significant but opposing tendency; their gaze was more attracted to the focus of contractive flow than to the focus of expansive flow. The relationship between the developmental change from the "contraction bias" in early toddlerhood to the expansion bias in the later developmental stages and possible factors (e.g., global visual motion processing abilities and locomotor experiences) are discussed.

Effects of Body Orientation Relative to Gravity on Vection in Children and Adults.

We investigated the effects of the interaction between the body and gravitational axes on vection (visually induced self-motion perception) in school-age children and adults. Experiment 1 was a pilot study of adults that was conducted to determine the appropriate experimental settings for the main experiment that included children and adults. The adult participants experienced vection in four different directions in the head-centered coordinate (forward, backward, upward, and downward) under two postural conditions: standing (in which the body and gravitational axes were consistent) and supine (in which the body orientation was orthogonally aligned to the gravitational axis). The adults reported more rapid and longer lasting vection when standing than when supine. In the main experiment (Experiment 2), we tested adults and school-age children under conditions similar to those of Experiment 1 and found that the reported vection was more rapid and longer lasting in children than in adults, whereas the reported vection tended to be more rapid and longer lasting under the standing condition than the supine condition for both age groups. Based on the similarities and differences between children and adults found in the present and previous vection studies, child-specific features of vection are discussed.

Effects of visual information presented by augmented reality on children's behavior.

The effects on children's behavior of visual information presented by augmented reality (AR) were investigated. A human-like AR character was presented standing in one of two physical pathways to children aged 5-7 years old and 8-10 years old before they completed a filler task. After the task, the children were required to walk through one of the two pathways to obtain a reward. Both the 5-7- and 8-10-year-olds chose the pathway that was not associated with the AR character more frequently than the pathway that was. Subsequently, adult participants tested in a similar manner showed no significant bias in pathway selection. Taken together, these results suggest that the presentation of an AR character within the present experimental setting affected the behavior of children aged from 5-10 years but not that of adults. The results are discussed in the context of developmental changes in sensitivity to insubstantial agents (e.g., imaginary companion), the reality of information displayed by AR technology, and differences in the methods of AR presentation (e.g., hand-held devices vs. head-mounted devices).

Differences in the Magnitude of Representational Momentum Between School-Aged Children and Adults as a Function of Experimental Task.

Representational momentum (RM) is the phenomenon that occurs when an object moves and then disappears, and the recalled final position of the object shifts in the direction of its motion. Some previous findings indicate that the magnitude of RM in early childhood is comparable to that in adulthood, whereas other findings suggest that the magnitude of RM is significantly greater in childhood than in adulthood. We examined whether the inconsistencies between previous studies could be explained by differences in the experimental tasks used in these studies. Futterweit and Beilin used a same-different judgment between the position where a moving stimulus disappeared and where a comparison stimulus reappeared (judging task), whereas Hubbard et al. used a task wherein a computer mouse cursor pointed to the position where the moving stimulus disappeared (pointing task). Three age groups (M = 7.4, 10.7, and 22.1 years, respectively) participated in both the judging and pointing tasks in the current study. A multivariate analysis of variance with the magnitudes of RM in each task as dependent variables revealed a significant main effect for age. A one-way analysis of variance performed for each of the judging and pointing tasks also indicated a significant main effect of age. However, post hoc multiple comparisons detected a significant age effect only for the pointing task. The inconsistency between the judging and pointing tasks was discussed related to the distinct effect size of the age difference in the magnitude of RM between the two tasks.

Development of Asymmetric Vection for Radial Expansion or Contraction Motion: Comparison Between School-Age Children and Adults.

Vection is illusory self-motion elicited by visual stimuli and is more easily induced by radial contraction than expansion flow in adults. The asymmetric feature of vection was reexamined with 18 younger (age: 6-8 years) and 19 older children (age: 9-11 years) and 20 adults. In each experimental trial, participants observed either radial expansion or contraction flow; the latency, cumulative duration, and saturation of vection were measured. The results indicated that the latency for contraction was significantly shorter than that for expansion in all age-groups. In addition, the latency and saturation were significantly shorter and greater, respectively, in the younger or older children compared with the adults, regardless of the flow pattern. These results indicate that the asymmetry in vection for expansion or contraction flow emerges by school age, and that school-age children experience significantly more rapid and stronger vection than adults.

Perception of the average size of multiple objects in chimpanzees (Pan troglodytes).

Humans can extract statistical information, such as the average size of a group of objects or the general emotion of faces in a crowd without paying attention to any individual object or face. To determine whether summary perception is unique to humans, we investigated the evolutional origins of this ability by assessing whether chimpanzees, which are closely related to humans, can also determine the average size of multiple visual objects. Five chimpanzees and 18 humans were able to choose the array in which the average size was larger, when presented with a pair of arrays, each containing 12 circles of different or the same sizes. Furthermore, both species were more accurate in judging the average size of arrays consisting of 12 circles of different or the same sizes than they were in judging the average size of arrays consisting of a single circle. Our findings could not be explained by the use of a strategy in which the chimpanzee detected the largest or smallest circle among those in the array. Our study provides the first evidence that chimpanzees can perceive the average size of multiple visual objects. This indicates that the ability to compute the statistical properties of a complex visual scene is not unique to humans, but is shared between both species.

Emergence of the ability to perceive dynamic events from still pictures in human infants.

The ability to understand a visual scene depicted in a still image is among the abilities shared by all human beings. The aim of the present study was to examine when human infants acquire the ability to perceive the dynamic events depicted in still images (implied motion perception). To this end, we tested whether 4- and 5-month-old infants shifted their gaze toward the direction cued by a dynamic running action depicted in a still figure of a person. Results indicated that the 5- but not the 4-month-olds showed a significant gaze shift toward the direction implied by the posture of the runner (Experiments 1, 2, and 3b). Moreover, the older infants showed no significant gaze shift toward the direction cued by control stimuli, which depicted a figure in a non-dynamic standing posture (Experiment 1), an inverted running figure (Experiment 2), and some of the body parts of a running figure (Experiment 3a). These results suggest that only the older infants responded in the direction of the implied running action of the still figure; thus, implied motion perception emerges around 5 months of age in human infants.

Infant-specific gaze patterns in response to radial optic flow.

The focus of a radial optic flow is a valid visual cue used to perceive and control the heading direction of animals. Gaze patterns in response to the focus of radial optic flow were measured in human infants (N = 100, 4-18 months) and in adults (N = 20) using an eye-tracking technique. Overall, although the adults showed an advantage in detecting the focus of an expansion flow (representing forward locomotion) against that of a contraction flow (representing backward locomotion), infants younger than 1 year showed an advantage in detecting the focus of a contraction flow. Infants aged between 13 and 18 months showed no significant advantage in detecting the focus in either the expansion or in the contraction flow. The uniqueness of the gaze patterns in response to the focus of radial optic flow in infants shows that the visual information necessary to perceive heading direction potentially differs between younger and mature individuals.

The interplay of intrinsic disorder and macromolecular crowding on α-synuclein fibril formation.

α-synuclein (α-syn) is an intrinsically disordered protein which is considered to be one of the causes of Parkinson's disease. This protein forms amyloid fibrils when in a highly concentrated solution. The fibril formation of α-syn is induced not only by increases in α-syn concentration but also by macromolecular crowding. In order to investigate the coupled effect of the intrinsic disorder of α-syn and macromolecular crowding, we construct a lattice gas model of α-syn in contact with a crowding agent reservoir based on statistical mechanics. The main assumption is that α-syn can be expressed as coarse-grained particles with internal states coupled with effective volume; and disordered states are modeled by larger particles with larger internal entropy than other states. Thanks to the simplicity of the model, we can exactly calculate the number of conformations of crowding agents, and this enables us to prove that the original grand canonical ensemble with a crowding agent reservoir is mathematically equivalent to a canonical ensemble without crowding agents. In this expression, the effect of macromolecular crowding is absorbed in the internal entropy of disordered states; it is clearly shown that the crowding effect reduces the internal entropy. Based on Monte Carlo simulation, we provide scenarios of crowding-induced fibril formation. We also discuss the recent controversy over the existence of helically folded tetramers of α-syn, and suggest that macromolecular crowding is the key to resolving the controversy.

Eleven-month-old infants infer differences in the hardness of object surfaces from observation of penetration events.

Previous studies have shown different developmental trajectories for object recognition of solid and non-solid objects. However, there is no evidence as to whether infants have expectations regarding certain attributes of objects, such as surface hardness, in the absence of tactile information. In the present study, we examined infants' perception of the hardness of object surfaces from visually presented penetration events using the familiarization-novelty preference procedure. Experiment 1 showed that by 11 months old infants distinguished a relatively soft surface from a crusty surface based on changes in the velocity of a moving object as the moving object penetrated the surface of the target object. Experiment 2 ruled out the possibility that infants were merely sensitive to differences in the velocity changes in the stimuli.

The development of gaze behaviors in response to biological motion displays.

Although the relationship between biological motion perception as depicted by point-light displays and social cognition has been investigated in recent decades, the developmental course of the integration of social cognition and the perception of biological motion is not well understood. To better understand this development, we investigated the ability of 9- and 12-month-old infants to shift their gaze toward a point-light upright human figure using a paradigm similar to that used by Yoon and Johnson (2009). We found that 12-month-old, but not 9-month-old, infants were able to follow the direction of attention of the upright point-light figure (Experiments 1 and 2). However, both the younger and older infants were able to follow the attentional shift of others under the full-view condition (Experimental 3). These results suggest that the ability to process the higher-level information provided by biological motion patterns, such as the attentional direction of others, develops by 12 months, but not by 9 months, of age. The relationship between the development of social cognition and that of biological motion perception is discussed.

Early development of dynamic shape perception under slit-viewing conditions.

The developmental processes underpinning global shape and global motion perception in infancy have been relatively well described. However, the development of the ability to integrate both global motion and global shape information has remained unclear. In this study we employed a slit-viewing task to investigate the ability to integrate spatiotemporal information among infants ranging in age from 3 to 12 months. In experiment 1 each infant was familiarised with a moving object that was only partly visible through a slit. One of the two objects in the test trial was a novel object, and the other object had appeared previously in familiarisation trials. The findings suggested that infants aged 5 months and over looked longer at the novel drawings compared with the more familiar objects in the test trials. This implies that the infants recognised the whole shape of the object under the slit-viewing condition. In experiment 2 each infant was presented with partial images in a random order. In this case the infants were unable to distinguish the whole shape of the object. The findings suggest that infants did not rely on the local cues provided in experiment .

Implied motion perception from a still image in infancy.

Visual motion perception can arise from non-directional visual stimuli, such as still images (implied motion, cf. Kourtzi, Trends Cogn Sci 8:47-49, 2004). We tested 5- to 8-month-old infants' implied motion perception with two experiments using the forced-choice preferential looking method. Our results indicated that a still image of a person running toward either the left or right side significantly enhanced infants' visual preference for a visual target that consistently appeared on the same side as the running direction (the run condition in Experiment 1). Such enhanced visual preference disappeared in response to an image of the same person standing and facing the left/right side (the stand condition in Experiment 1), an image of the running figure covered with a set of opaque rectangles (the block condition in Experiment 2) (Gervais et al. in Atten Percept Psychophys 72:1437-1443, 2010), and an image of the inverted running figure (the inversion condition in Experiment 3). These results suggest that only the figure that implied dynamic body motion shifted the infants' visual preference to the same direction as the implied running action. These findings demonstrate that even infants as young as 5 to 8 months old are sensitive to the implied motion of static figures.

Stronger vection in junior high school children than in adults.

Previous studies have shown that even elementary school-aged children (7 and 11 years old) experience visually induced perception of illusory self-motion (vection) (Lepecq et al., 1995, Perception, 24, 435-449) and that children of a similar age (mean age = 9.2 years) experience more rapid and stronger vection than do adults (Shirai et al., 2012, Perception, 41, 1399-1402). These findings imply that although elementary school-aged children experience vection, this ability is subject to further development. To examine the subsequent development of vection, we compared junior high school students' (N = 11, mean age = 14.4 years) and adults' (N = 10, mean age = 22.2 years) experiences of vection. Junior high school students reported significantly stronger vection than did adults, suggesting that the perceptual experience of junior high school students differs from that of adults with regard to vection and that this ability undergoes gradual changes over a relatively long period of development.

Looking away before moving forward: changes in optic-flow perception precede locomotor development.

Voluntary locomotion is one of the most important motor actions performed by animals, including humans, and vision plays an important role in controlling such action. We conducted cross-sectional (Experiment 1) and longitudinal (Experiment 2) investigations and found that the perception of visual motion (optic flow), a critical cue for perceiving and controlling the direction of locomotion, drastically changes just before the emergence of locomotion in infancy. The results suggest that developmental change in particular visual perceptions precedes and potentially promotes the emergence of related motor actions in early development. Our findings offer a new perspective on the development of visuomotor coordination, which has long been thought to derive from the development of motor actions rather than from changes in visual perceptions.

Structural flexibility of intrinsically disordered proteins induces stepwise target recognition.

An intrinsically disordered protein (IDP) lacks a stable three-dimensional structure, while it folds into a specific structure when it binds to a target molecule. In some IDP-target complexes, not all target binding surfaces are exposed on the outside, and intermediate states are observed in their binding processes. We consider that stepwise target recognition via intermediate states is a characteristic of IDP binding to targets with "hidden" binding sites. To investigate IDP binding to hidden target binding sites, we constructed an IDP lattice model based on the HP model. In our model, the IDP is modeled as a chain and the target is modeled as a highly coarse-grained object. We introduced motion and internal interactions to the target to hide its binding sites. In the case of unhidden binding sites, a two-state transition between the free states and a bound state is observed, and we consider that this represents coupled folding and binding. Introducing hidden binding sites, we found an intermediate bound state in which the IDP forms various structures to temporarily stabilize the complex. The intermediate state provides a scaffold for the IDP to access the hidden binding site. We call this process multiform binding. We conclude that structural flexibility of IDPs enables them to access hidden binding sites and this is a functional advantage of IDPs.