Simultaneous shape repulsion and global assimilation in the perception of aspect ratio

Timothy D. Sweeny*, Marcia Grabowecky, Satoru Suzuki

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Although local interactions involving orientation and spatial frequency are well understood, less is known about spatial interactions involving higher level pattern features. We examined interactive coding of aspect ratio, a prevalent twodimensional feature. We measured perception of two simultaneously flashed ellipses by randomly post-cueing one of them and having observers indicate its aspect ratio. Aspect ratios interacted in two ways. One manifested as an aspect-ratiorepulsion effect. For example, when a slightly tall ellipse and a taller ellipse were simultaneously flashed, the less tall ellipse appeared flatter and the taller ellipse appeared even taller. This repulsive interaction was long range, occurring even when the ellipses were presented in different visual hemifields. The other interaction manifested as a global assimilation effect. An ellipse appeared taller when it was a part of a global vertical organization than when it was a part of a global horizontal organization. The repulsion and assimilation effects temporally dissociated as the former slightly strengthened, and the latter disappeared when the ellipse-to-mask stimulus onset asynchrony was increased from 40 to 140 ms. These results are consistent with the idea that shape perception emerges from rapid lateral and hierarchical neural interactions.

Original languageEnglish (US)
Pages (from-to)1-16
Number of pages16
JournalJournal of Vision
Issue number1
StatePublished - 2011


  • Aspect ratio
  • Assimilation
  • Hierarchical interactionp
  • Lateral interaction
  • Repulsion
  • Shape perception

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems

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