Summation of perceptual cues in natural visual scenes

M. To, P. George Lovell, T. Troscianko, D.J. Tolhurst

Research output: Contribution to journalArticlepeer-review

24 Citations (Scopus)


Natural visual scenes are rich in information, and any neural system analysing them must piece together the many messages from large arrays of diverse feature detectors. It is known how threshold detection of compound visual stimuli (sinusoidal gratings) is determined by their components' thresholds. We investigate whether similar combination rules apply to the perception of the complex and suprathreshold visual elements in naturalistic visual images. Observers gave magnitude estimations (ratings) of the perceived differences between pairs of images made from photographs of natural scenes. Images in some pairs differed along one stimulus dimension such as object colour, location, size or blur. But, for other image pairs, there were composite differences along two dimensions (e.g. both colour and object-location might change). We examined whether the ratings for such composite pairs could be predicted from the two ratings for the respective pairs in which only one stimulus dimension had changed. We found a pooling relationship similar to that proposed for simple stimuli: Minkowski summation with exponent 2.84 yielded the best predictive power (r=0.96), an exponent similar to that generally reported for compound grating detection. This suggests that theories based on detecting simple stimuli can encompass visual processing of complex, suprathreshold stimuli.
Original languageEnglish
Pages (from-to)2299-2308
Number of pages10
JournalProceedings of the Royal Society B: Biological Sciences
Issue number1649
Publication statusPublished - 22 Oct 2008
Externally publishedYes


  • Natural scenes
  • Vision
  • Perception
  • Minkowski summation
  • Cue summation


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