These findings are consistent with those of previous studies of spatial integration in nonhuman primates. The findings with nonsense figures demonstrated that semantic processing couldn't account for the species differences. We found that both chimpanzees and humans integrated spatio–temporal visual information but that the extent of the integration differed between species. In this study, we compared the spatio–temporal visual integration of chimpanzees and humans by exploring dynamic shape perception under a slit-viewing condition. In a sequential presentation task, we examined whether the chimpanzees' inferior performance was due to preferential processing of local features. These findings suggest that the humans were better able to integrate local visual information into a whole global image than were chimpanzees. A two-way ANOVA with species (2) × speed (2) revealed significant main effects of species and speed. The mean rates of correct responses were lower among chimpanzees than among humans ( Fig. To exclude this possibility, we examined nonsense figures, which were novel to both species. However, the line drawings of objects used in this experiment were so familiar to humans that the performance of chimpanzees may have been underestimated. A two-way analysis of variance (ANOVA) with species (2) × speed (2) revealed significant main effects of species and speed. The mean rates of correct responses were lower among chimpanzees than among humans under both speed conditions ( Fig. In the present study, participants were required to choose the same drawing among three alternatives. In this task, a line drawing of a daily object or nonsense figure is moved behind a narrow slit and this is followed by three line drawings presented on a monitor screen ( Figs. Chimpanzees and humans have engaged in a “slit-viewing task” to compare their abilities to integrate visual information into an entire image. In recent studies, it has been used as a paradigm for measuring the ability of spatio-temporal integration in humans 24, 25, 26. Under the slit-viewing condition, the observer can not only see a part of an object at a time, however, it is possible to report the whole shape of an object by integrating the fragmented visual information. Anorthoscopic perception occurs object is moving behind the slit 21, 22, 23. In the present study, we used a “slit-viewing (anorthoscopic-viewing) task”. As studies of human infants and children have reported 19, 20, it is difficult to identify whether such species differences are due to the allocation of visual attention or to the ability to integrate local features into a global image. However, these previous studies using hierarchical stimuli required both humans and animals to ignore local shape when they perceived the global configuration. In contrast, developmental studies in humans have suggested that 3- and 4-month-old infants are more sensitive to the global level of visual stimuli 16, 17, although individual variations have been found depending on the amount of time that infants tend to fixate on stimuli 18. Studies of primates closely related to humans have also reported large individual variations and different results depending on experimental procedures, such as stimulus size and distances between elements 14, 15. In support of local processing, birds perceive reversed visual illusions (Ebbinghaus-Titchener illusion 10 Zollner illusion 11) and do not complete partly occluded objects 12, 13. Studies using other types of stimuli have also found differences between humans and avian species in perceptual organisation 9. For example, in response to a hierarchical stimulus consisting of a larger figure comprised of arrangements of smaller component shapes, humans tend to prioritise global over local information 2, whereas non-human animals, such as birds and primates, tend to prioritise the local features of such stimuli (pigeons 3 monkeys 4, 5, 6 chimpanzees 5, 7, 8). Comparative cognitive studies have clarified that the processing of global configuration is a unique characteristic of human vision 1.
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