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An infant chimpanzee (Pan troglodytes) follows human gaze
Sanae Okamoto1, Masaki Tomonaga, Kiyoshi Ishii
1Department of Psychology, School of Letters, Nagoya University, Nagoya, Aichi 464-8601, Japan. sokamot@yahoo.co.jp
Insights
Young chimpanzees can follow gaze cues from 13 months old. This study shows infant chimpanzees understand social cues, not just object location, demonstrating early cognitive development in gaze following.
Area of Science:
- Comparative Cognition
- Primate Behavior
- Developmental Psychology
Background:
- Gaze following is crucial for social interaction and learning in primates.
- Understanding the developmental trajectory of gaze following in infant chimpanzees provides insights into early social cognition.
Purpose of the Study:
- To investigate the emergence of gaze-following ability in a chimpanzee infant.
- To determine if infant chimpanzees respond to various social cues, including subtle ones like glancing.
Main Methods:
- An infant chimpanzee was trained to follow experimenter cues (tapping, pointing, gazing, glancing) to target objects.
- Food rewards were provided for some cues, but not for the crucial glancing condition, to isolate cue understanding.
- Performance was analyzed to differentiate responses to social cues versus non-social, local-enhancing properties.
Main Results:
- By 13 months of age, the infant reliably followed gaze cues, including simple glancing without head orientation.
- The infant's responses were primarily driven by the social nature of the cues, not peripheral visual stimuli.
- This indicates an understanding of the experimenter's communicative intent.
Conclusions:
- Infant chimpanzees develop gaze-following abilities early in life.
- Chimpanzees, even at a young age, interpret cues based on their social context.
- This research contributes to understanding the evolutionary basis of social cognition and communication in primates.
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 13 months, 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 subject's performance was controlled by the "social" properties of the experimenter-given cues but not by the non-social, local-enhancing peripheral properties.