Assumed Lighting Direction in the Interpretation of Cast Shadows

Tomomi Koizumi, Hiroyuki Ito, Shoji Sunaga, Masaki Ogawa, Erika Tomimatsu

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


Assumed lighting direction in cast-shadow interpretation was investigated. Experiment 1 used an ambiguous object–shadow-matching task to measure bias in shadow-matching direction. The shadow-matching bias was largest when the lighting direction was on average 38.3° left from above (a median of 25.1°). Experiment 2 tested the effect of body posture (head orientation) on cast-shadow interpretation using stimuli aligned in a head-centrically vertical or horizontal orientation. The below-shadow (light-from-above) bias in the head-centric frame was robust across the sitting upright, reclining-on-the-left-side, reclining-on-the-right-side, and supine conditions. A right-shadow (light-from-left) bias in the head-centric frame was found for the sitting upright and reclining-on-the-right-side conditions. In the reclining-on-the-left-side condition, shadow biases to the gravitational below direction and head-centric right direction may have cancelled each other out. These results are consistent with findings from previous shape-from-shading studies, suggesting that the same light-source assumption is applied to shading and shadow interpretations.

Original languageEnglish
Issue number4
Publication statusPublished - Jul 1 2018

All Science Journal Classification (ASJC) codes

  • Experimental and Cognitive Psychology
  • Ophthalmology
  • Sensory Systems
  • Artificial Intelligence


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