Human and nonhuman primates comprehend the actions of other individuals by detecting social cues, including others’ goal-directed motor actions and faces. However, little is known about how this information is integrated with action understanding. Here, we present the ontogenetic and evolutionary foundations of this capacity by comparing face-scanning patterns of chimpanzees and humans as they viewed goal-directed human actions within contexts that differ in whether or not the predicted goal is achieved. Human adults and children attend to the actor’s face during action sequences, and this tendency is particularly pronounced in adults when observing that the predicted goal is not achieved. Chimpanzees rarely attend to the actor’s face during the goal-directed action, regardless of whether the predicted action goal is achieved or not. These results suggest that in humans, but not chimpanzees, attention to actor’s faces conveying referential information toward the target object indicates the process of observers making inferences about the intentionality of an action. Furthermore, this remarkable predisposition to observe others’ actions by integrating the prediction of action goals and the actor’s intention is developmentally acquired.
We examined the transformation process of visuomotor memory representation in far space. We conducted two experiments in which participants were asked to memorize target locations and, after a short delay, to point to the memorized target after body rotation to particular angles. The results were that (1) after body rotation, participants pointed to the locations displaced toward the body position before, not after, rotation, and the magnitude of the displacement increased as the rotational angle of the body increased, and (2) that participants reproduced the memorized space for pointing as shrunken after body rotation, and the ratio of reproduction decreased as the rotational angle of the body increased, to approximately 90% and 45% of the original space after 10-deg and 140-deg body rotation, respectively. We concluded that the effect of body rotation on the body-centered spatial representation and the compensative contribution of the environment-centered spatial representation in transforming the spatial memory after body rotation is considerable.Key words: spatial memory, body-centered coordinate system, environment-centered coordinate system, pointing, body rotationIn order to produce precise movements in space using visual cues, we must be able to take into account the spatial relationships among objects in the environment and the position of our body. While visual space is recognized as a uniform entity, neuropsychological and neurophysiological studies have suggested that the external space of humans is encoded in different brain regions according to the spatial distance from the body. At least three regions of external space have been identified, including the pericutaneous space, which is the region immediately proximate to the surface of the body, the space within arm's length, and the space beyond arm's length (Brain, 1941;Previc, 1998).When we attempt to operate or access a visual object, information regarding the location of the target is important. This information can be represented in different coordinate systems, including body-centered coordinate systems, in which the observer's own body or parts of the body are referenced, and environment-centered coordinate systems, in which the localization information of the object is represented relative to other
SUMMARYUsing an immersive VR system (the "CAVE"), we investigated the sensitivity and threshold of depth order judgment in the central visual field by subjects placed in a visual environment that simulated optical flow, producing vection in a wide-area visual field (front, floor, and both sides) associated with forward movement inside an endless toroidal tunnel. Experiments showed that when an optical flow is produced in the wide-area visual field, the sensitivity and threshold of depth judgment exhibit a systematic change that depends on the direction of rotation. Possible explanations of this result are the use of an implicit reference plane by the subject, and change of body sensation in response to the peripheral visual field information.
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