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Infant and adult perceptions of possible and impossible body movements: an eye-tracking study
Tomoyo Morita1, Virginia Slaughter, Nobuko Katayama
1Department of Integrative Physiology, National Institute for Physiological Sciences, Okazaki, Aichi 444-8585, Japan. morita@nips.ac.jp
Insights
By 12 months, infants recognize biomechanical movement rules and apply them to robots. However, their emotional processing of impossible human movements is still developing, suggesting immature body movement perception.
Area of Science:
- Developmental Psychology
- Cognitive Neuroscience
- Robotics
Background:
- Infant perception of human body movement is crucial for social interaction.
- Understanding how infants process biomechanical constraints informs theories of sensorimotor development.
Purpose of the Study:
- To investigate infant perception of biomechanically possible versus impossible human arm movements.
- To determine if 12-month-old infants extend their understanding of biomechanics to humanoid robots.
- To examine developmental differences in emotional responses to observed body movements.
Main Methods:
- Recorded eye movements and pupil dilation in 9- and 12-month-old infants and adults (N=14 per group).
- Participants observed animations of possible and impossible human and humanoid robot arm movements.
- Analyzed visual attention (dwell time) and autonomic responses (pupil dilation).
Main Results:
- 12-month-olds and adults focused more on elbows during impossible movements, regardless of the actor (human or robot).
- Adults showed increased pupil dilation to impossible human movements, indicating an emotional response.
- Infants (9- and 12-month-olds) did not exhibit differential pupil dilation to impossible movements.
Conclusions:
- By 12 months, infants possess knowledge of biomechanical constraints and generalize this to robots.
- Infant processing of human body movement perception and emotional response appears immature at 12 months.
- Findings support the hypothesis that perception of others' movements is linked to an infant's sensorimotor experience.
Abstract:
This study investigated how infants perceive and interpret human body movement. We recorded the eye movements and pupil sizes of 9- and 12-month-old infants and of adults (N=14 per group) as they observed animation clips of biomechanically possible and impossible arm movements performed by a human and by a humanoid robot. Both 12-month-old infants and adults spent more time looking at the elbows during impossible compared with possible arm movements, irrespective of the appearance of the actor. These results suggest that by 12 months of age, infants recognize biomechanical constraints on how arms move, and they extend this knowledge to humanoid robots. Adults exhibited more pupil dilation in response to the human's impossible arm movements compared with the possible ones, but 9- and 12-month-old infants showed no differential pupil dilation to the same actions. This finding suggests that the processing of human body movements might still be immature in 12-month-olds, as they did not show an emotional response to biomechanically impossible body movements. We discuss these findings in relation to the hypothesis that perception of others' body movements relies upon the infant's own sensorimotor experience.
