The roles of physical and physiological simultaneity in audiovisual multisensory facilitation

Lynnette M. Leone, Mark E. McCourt

Research output: Contribution to journalArticlepeer-review

28 Scopus citations


A series of experiments measured the audiovisual stimulus onset asynchrony (SOAAV), yielding facilitative multisensory integration. We evaluated (1) the range of SOAAV over which facilitation occurred when unisensory stimuli were weak; (2) whether the range of SOAAV producing facilitation supported the hypothesis that physiological simultaneity of unisensory activity governs multisensory facilitation; and (3) whether AV multisensory facilitation depended on relative stimulus intensity. We compared response-time distributions to unisensory auditory (A) and visual (V) stimuli with those to AV stimuli over a wide range (300 and 20 ms increments) of SOAAV, across four conditions of varying stimulus intensity. In condition 1, the intensity of unisensory stimuli was adjusted such that d' ≈ 2. In condition 2, V stimulus intensity was increased (d'>4), while A stimulus intensity was as in condition 1. In condition 3, A stimulus intensity was increased (d>4) while V stimulus intensity was as in condition 1. In condition 4, both A and V stimulus intensities were increased to clearly suprathreshold levels (d'>4). Across all conditions of stimulus intensity, significant multisensory facilitation occurred exclusively for simultaneously presented A and V stimuli. In addition, facilitation increased as stimulus intensity increased, in disagreement with inverse effectiveness. These results indicate that the requirements for facilitative multisensory integration include both physical and physiological simultaneity.

Original languageEnglish (US)
Pages (from-to)213-228
Number of pages16
Issue number4
StatePublished - 2013
Externally publishedYes


  • D'
  • Inverse effectiveness
  • Multisensory integration
  • Neural coactivation
  • Race model
  • Reaction time
  • Simultaneity

ASJC Scopus subject areas

  • Experimental and Cognitive Psychology
  • Ophthalmology
  • Sensory Systems
  • Artificial Intelligence


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