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Infants' perception of lightness changes related to cast shadows
Kazuki Sato1,2, So Kanazawa3, Masami K Yamaguchi1
1Department of Psychology, Chuo University, Hachioji, Tokyo, Japan.
Plos One
|March 16, 2017
Summary
Seven to eight-month-old infants assume shadows dim surfaces, enabling them to detect unnatural lightness changes. Younger infants did not show this ability, suggesting a developmental aspect to this visual perception.
Area of Science:
- Developmental Psychology
- Visual Perception
- Cognitive Science
Background:
- Humans implicitly assume cast shadows darken surfaces.
- Understanding how infants perceive lightness in shadows is crucial for developmental studies.
Purpose of the Study:
- To investigate if 5- to 8-month-old infants utilize the 'shadow assumption' to perceive surface lightness.
- To determine if infants can detect unnatural lightness changes caused by shadows.
Main Methods:
- Two experiments using computer-generated movies of a duck moving through cast shadows.
- Infants' looking times were measured to assess preferences for natural versus unnatural lightness changes.
- Experiment 1: Assessed detection of unnatural lightness changes in shadows. Experiment 2: Removed shadows to confirm reliance on the shadow assumption.
Main Results:
- Seven to 8-month-old infants preferred stimuli with unnatural lightness changes in shadows, indicating detection.
- Five to 6-month-old infants did not show a significant preference in Experiment 1.
- Neither age group showed a preference when shadows were absent in Experiment 2, confirming the role of the shadow assumption.
Conclusions:
- Seven to 8-month-old infants can detect unnatural lightness changes in shadows.
- This suggests infants use the 'shadow assumption' to perceive an object's surface lightness under shadowed conditions.
- The ability to use the shadow assumption develops between 6 and 8 months of age.
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