title: Peeling plaids apart: context counteracts cross-orientation contrast masking.
abstract: BACKGROUND
  Contrast discrimination for an image is usually harder if another image is superimposed on top. We asked whether such contrast masking may be enhanced or relieved depending on cues promoting integration of both images as a single pattern, versus segmentation into two independent components.
  
  
  RESULTS
  Contrast discrimination thresholds for a foveal test grating were sharply elevated in the presence of a perfectly overlapping orthogonally-oriented mask grating. However thresholds returned to the unmasked baseline when a surround grating was added, having the same orientation and phase of either the test or mask grating. Both such masking and 'unmasking' effects were much stronger for moving than static stimuli.
  
  
  CONCLUSIONS
  Our results suggest that common-fate motion reinforces the perception of a single coherent plaid pattern, while the surround helps to identify each component independently, thus peeling the plaid apart again. These results challenge current models of early vision, suggesting that higher-level surface organization influences contrast encoding, determining whether the contrast of a grating may be recovered independently from that of its mask.
authors: Department of Psychology, City University, London, United Kingdom. elliot.freeman@city.ac.uk
authors: Elliot
authors: E
authors: Freeman
authors: Preeti
authors: P
authors: Verghese
mesh_terms: D015350:Contrast Sensitivity / Q000502:physiology*; D006801:Humans; D010470:Perceptual Masking / Q000502:physiology*; D010775:Photic Stimulation; D012684:Sensory Thresholds / Q000502:physiology