Reaction time to motion onset of luminance and chromatic gratings is determined by perceived speed

David C. Burr, Adriana Fiorentini, Concetta Morrone

Research output: Contribution to journalArticlepeer-review

Abstract

We measured reaction times for detecting motion onset for sinusoidal gratings whose contrast was modulated in either luminance or chromaticity, for various drift rates and contrasts. In general, reaction times to chromatic gratings were slower than to luminance gratings of matched cone contrast, but the difference in response depended critically on both contrast and speed. At high image speeds there was virtually no difference, whereas at low speeds, the difference was pronounced, especially at low contrasts. At high image speeds there was little dependence of reaction times on contrast (for either luminance or colour), whereas at low speeds the dependence was greater, particularly for chromatic stimuli. This pattern of results is reminiscent of those found for apparent speed of drifting luminance and chromatic gratings. We verified the effects of contrast on perceived speed, and went on to show that the effects of contrast on reaction times are totally predictable by the perceived speed of the stimuli, as if it were perceived rather than physical speed that determined reaction times. Our results support the idea of separate systems for fast and slow motion (with separate channels for luminance and colour at slower speeds), and further suggest that apparent speed and reaction times may be determined at a similar stage of motion analysis.

Original languageEnglish
Pages (from-to)3681-3690
Number of pages10
JournalVision Research
Volume38
Issue number23
DOIs
Publication statusPublished - Dec 1998

Keywords

  • Apparent speed
  • Equiluminance
  • Motion
  • Reaction times

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems

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