Nobuyuki Kawai

Numerical memory span in a chimpanzee.

A female chimpanzee called Ai has learned to use Arabic numerals to represent numbers. She can count from zero to nine items, which she demonstrates by touching the appropriate number on a touch-sensitive monitor, and she can order the numbers from zero to nine in sequence. Here we investigate Ais memory span by testing her skill in these numerical tasks, and find that she can remember the correct sequence of any five numbers selected from the range zero to nine.

An infant chimpanzee (Pan troglodytes) follows human gaze

Abstract. The ability of non-human primates to follow the gaze of other individuals has recently received much attention in comparative cognition. The aim of the present study was to investigate the emergence of this ability in a chimpanzee infant. The infant was trained to look at one of two objects, which an experimenter indicated by one of four different cue conditions: (1) tapping on the target object with a finger; (2) pointing to the target object with a finger; (3) gazing at the target object with head orientation; or (4) glancing at the target object without head orientation. The subject was given food rewards independently of its responses under the first three conditions, so that its responses to the objects were not influenced by the rewards. The glancing condition was tested occasionally, without any reinforcement. By the age of 13xa0months, the subject showed reliable following responses to the object that was indicated by the various cues, including glancing alone. Furthermore, additional tests clearly showed that the subjects performance was controlled by the social properties of the experimenter-given cues but not by the non-social, local-enhancing peripheral properties.

Cognition: Numerical memory span in a chimpanzee

A female chimpanzee called Ai has learned to use Arabic numerals to represent numbers. She can count from zero to nine items, which she demonstrates by touching the appropriate number on a touch-sensitive monitor, and she can order the numbers from zero to nine in sequence. Here we investigate Ais memory span by testing her skill in these numerical tasks, and find that she can remember the correct sequence of any five numbers selected from the range zero to nine.

Rapid detection of snakes by Japanese monkeys (Macaca fuscata): an evolutionarily predisposed visual system.

Humans appear extremely sensitive to biologically threatening stimuli, such as snakes. In visual search tasks, humans respond to pictures of snakes faster than pictures of flowers. The authors report that macaque monkeys (Macaca fuscata), reared in a laboratory and with no experience with snakes, respond, as do humans, to pictures of snakes among flowers faster than vice versa (Experiment 1). This was also the case when grayscale pictures were used (Experiment 2). These results provide the first evidence of enhanced visual detection of evolutionarily relevant threat stimuli in nonhuman primates.

Fetal habituation correlates with functional brain development

In this study, we divided 26 fetuses at 32-37 weeks of gestation into three groups using combined criteria of gestational age and behavioral indicators. We investigated fetal habituation to vibroacoustic stimulation (VAS). Fetuses showed habituation from at least 32 weeks of gestation. Furthermore, fetuses less developed from behavioral standpoint took significantly more trials to achieve habituation than developed fetuses even in the same gestational age. Taken together with these data, it was proved that there was a relationship between aspects of behavioral development and habituation.

Human young children as well as adults demonstrate 'superior' rapid snake detection when typical striking posture is displayed by the snake.

Humans as well as some nonhuman primates have an evolved predisposition to associate snakes with fear by detecting their presence as fear-relevant stimuli more rapidly than fear-irrelevant ones. In the present experiment, a total of 74 of 3- to 4-year-old children and adults were asked to find a single target black-and-white photo of a snake among an array of eight black-and-white photos of flowers as distracters. As target stimuli, we prepared two groups of snake photos, one in which a typical striking posture was displayed by a snake and the other in which a resting snake was shown. When reaction time to find the snake photo was compared between these two types of the stimuli, its mean value was found to be significantly smaller for the photos of snakes displaying striking posture than for the photos of resting snakes in both the adults and children. These findings suggest the possibility that the human perceptual bias for snakes per se could be differentiated according to the difference of the degree to which their presence acts as a fear-relevant stimulus.

The influence of color on snake detection in visual search in human children

It is well known that adult humans detect snakes as targets more quickly than flowers as the targets and that how rapidly they detect a snake picture does not differ whether the images are in color or gray-scale, whereas they find a flower picture more rapidly when the images are in color than when the images are gray-scale. In the present study, a total of 111 children were presented with 3-by-3 matrices of images of snakes and flowers in either color or gray-scale displays. Unlike the adults reported on previously, the present participants responded to the target faster when it was in color than when it was gray-scale, whether the target was a snake or a flower, regardless of their age. When detecting snakes, human children appear to selectively attend to their color, which would contribute to the detection being more rapidly at the expense of its precision.

Color classification by chimpanzees ( Pan troglodytes) in a matching-to-sample task

We investigated chimpanzees color classification using a matching-to-sample procedure. One of the two subjects had learned symbolic color names through long-term training, while the other had received less training and had a limited understanding of color names. The results showed similar distributions of classified colors in a color space, irrespective of the subjects differential color-naming experience. However, the chimpanzee with little color-naming experience showed less stable classifications. These results suggest common features of color classification in chimpanzees, as well as the influence of color experience and/or the learning of color names on the stability of classification of colors.

Elimination of the enhanced Simon effect for older adults in a three-choice situation: Ageing and the Simon effect in a go/no-go Simon task

In a Simon task, participants show better performance when the irrelevant stimulus location corresponds with the response location than when it does not, and this effect is typically greater for older adults than for younger adults. To study the effect of cognitive ageing in the Simon task, we compared young and old adults using two versions of the Simon task: (a) a standard visual Simon task, for which participants respond with left and right key-presses to the red and green colours of stimuli presented in left and right locations; (b) a go/no-go version of the Simon task, which was basically the same, except that the shape of the stimulus in one third of the trials indicates that no response is to be made. In both tasks, both age groups showed the Simon effect. The magnitude of the effect for the standard Simon task was greater for the older adults than for the younger adults. Nevertheless, the two groups showed an equivalent Simon effect in the go/no-go version of the Simon task. Reaction time distribution analyses revealed basically similar functions for both age groups: a decreasing pattern of the Simon effect in the standard task and an increasing pattern of the effect in the go/no-go version of the task. The results suggest that older adults find it more difficult to suppress an automatic activation of the corresponding response, though this automatic activation was reduced in situations where the response was frequently inhibited.

Avoidance learning in the crayfish (Procambarus clarkii) depends on the predatory imminence of the unconditioned stimulus: a behavior systems approach to learning in invertebrates.

Signaled avoidance learning in crayfish (Procambarus clarkii) was investigated when the crayfish were not confined, by indexing two types of locomotive movement to the escape compartment. Mild shocks, which induced tail flipping in the crayfish, and light illumination were used as unconditioned and conditioned stimuli, respectively. In Experiment 1, two groups of crayfish were trained in a one-way shuttle box. The crayfish in Group Forward were placed in the start compartment facing the escape compartment and they were able to escape/avoid shocks by walking forward, while the crayfish in Group Backward were placed in the compartment facing the opposite direction and they were able to escape by tail flipping. Avoidance learning was achieved only by walking, and not by tail flipping despite the fact that consistent tail flipping allowed the crayfish to avoid shocks. In Experiment 2, the experimental conditions were switched by using the ABA design. In this experiment, we confirmed that avoidance behavior was restricted to walking. These results are readily explained by the behavior systems approach.