Double dissociation between first- and second-order processing

Vision Res. 2007 Apr;47(9):1129-41. doi: 10.1016/j.visres.2007.01.010. Epub 2007 Mar 23.


To study the difference of sensitivity to luminance- (LM) and contrast-modulated (CM) stimuli, we compared LM and CM detection thresholds in LM- and CM-noise conditions. The results showed a double dissociation (no or little inter-attribute interaction) between the processing of these stimuli, which implies that both stimuli must be processed, at least at some point, by separate mechanisms and that both stimuli are not merged after a rectification process. A second experiment showed that the internal equivalent noise limiting the CM sensitivity was greater than the one limiting the carrier sensitivity, which suggests that the internal noise occurring before the rectification process is not limiting the CM sensitivity. These results support the hypothesis that a suboptimal rectification process partially explains the difference of LM and CM sensitivity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Contrast Sensitivity / physiology*
  • Humans
  • Lighting
  • Models, Psychological
  • Pattern Recognition, Visual / physiology*
  • Photic Stimulation / methods
  • Psychophysics
  • Sensory Thresholds / physiology