What is second-order vision for? Discriminating illumination versus material changes

Andrew Schofield, Paul B. Rock, Peng Sun, Xiaoyue Jiang, Mark A. Georgeson

Research output: Contribution to journalArticlepeer-review


The human visual system is sensitive to second-order modulations of the local contrast (CM) or amplitude (AM) of a carrier signal. Second-order cues are detected independently of first-order luminance signals; however, it is not clear why vision should benet from second-order sensitivity. Analysis of the first-and second-order contents of natural images suggests that these cues tend to occur together, but their phase relationship varies. We have shown that in-phase combinations of LM and AM are perceived as a shaded corrugated surface whereas the anti-phase combination can be seen as corrugated when presented alone or as a flat material change when presented in a plaid containing the in-phase cue. We now extend these findings using new stimulus types and a novel haptic matching task. We also introduce a computational model based on initially separate first-and second-order channels that are combined within orientation and subsequently across orientation to produce a shading signal. Contrast gain control allows the LM + AM cue to suppress responses to the LM-AM when presented in a plaid. Thus, the model sees LM -AM as flat in these circumstances. We conclude that second-order vision plays a key role in disambiguating the origin of luminance changes within an image. © ARVO.

Original languageEnglish
Article number2
JournalJournal of Vision
Issue number9
Publication statusPublished - 16 Jul 2010

Bibliographical note

Creative Commons Attribution Non-Commercial No Derivatives License


  • 3D surface and shape perception
  • computational modeling
  • shading
  • spatial vision


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