Visual determinants of a cross-modal illusion by ProQuest

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Contrary to the predictions of established theory, Schutz and Lipscomb (2007) have shown that visual information can influence the perceived duration of concurrent sounds. In the present study, we deconstruct the visual component of their illusion, showing that (1) cross-modal influence depends on visible cues signaling an impact event (namely, a sudden change of direction concurrent with tone onset) and (2) the illusion is controlled primarily by the duration of post-impact motion. Other aspects of the post-impact motion-distance traveled, velocity, acceleration, and the rate of its change (i.e., its derivative, jerk)-play a minor role, if any. Together, these results demonstrate that visual event duration can influence the perception of auditory event duration, but only when stimulus cues are sufficient to give rise to the perception of a causal cross-modal relationship. This refined understanding of the illusion's visual aspects is helpful in comprehending why it contrasts so markedly with previous research on cross-modal integration, demonstrating that vision does not appreciably influence auditory judgments of event duration (Walker & Scott, 1981). [PUBLICATION ABSTRACT]

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									Attention, Perception, & Psychophysics
2009, 71 (7), 1618-1627
doi:10.3758/APP.71.7.1618




                     Visual determinants of a cross-modal illusion
                                                        James a. armontrout
                                              University of Virginia, Charlottesville, Virginia

                                                            michael schutz
                                            McMaster University, Hamilton, Ontario, Canada
                                                                    and

                                                            michael Kubovy
                                              University of Virginia, Charlottesville, Virginia

                Contrary to the predictions of established theory, Schutz and Lipscomb (2007) have shown that visual in-
             formation can influence the perceived duration of concurrent sounds. In the present study, we deconstruct the
             visual component of their illusion, showing that (1) cross-modal influence depends on visible cues signaling an
             impact event (namely, a sudden change of direction concurrent with tone onset) and (2) the illusion is controlled
             primarily by the duration of post-impact motion. Other aspects of the post-impact motion—distance traveled,
             velocity, acceleration, and the rate of its change (i.e., its derivative, jerk)—play a minor role, if any. Together,
             these results demonstrate that visual event duration can influence the perception of auditory event duration, but
             only when stimulus cues are sufficient to give rise to the perception of a causal cross-modal relationship. This
             refined understanding of the illusion’s visual aspects is helpful in comprehending why it contrasts so markedly
             with previous research on cross-modal integration, demonstrating that vision does not appreciably influence
             auditory judgments of event duration (Walker & Scott, 1981).



   Schutz and Lipscomb (2007) reported a naturally oc-                  either fails to affect the perceived rate of concurrent audi-
curring audio–visual illusion in which visual informa-                  tory flutter (Shipley, 1964) or affects it minimally (Welch,
tion changes the perceived duration of simultaneous au-                 DuttonHurt, & Warren, 1986).
ditory information. They demonstrated this by showing
participants videos of a percussionist striking a marimba               Understanding the Illusion
with either a long flowing gesture (labeled “long”) that                   We believe that the perception of a causal link between
covered a large arc or with a short choppy gesture (la-                 auditory and visual information is crucial to explaining
beled “short”) that rebounded off of the bar and quickly                why the illusion reported by Schutz and Lipscomb (2007)
stopped. Although the resultant sounds were acoustically                conflicts so strongly with previous work on sensory inte-
indistinguishable and participants were asked to ignore                 gration. However, before presenting evidence in support
visual information when judging tone duration, duration                 of this view, we will first discuss two alternative explana-
ratings were longer when presented with long rather than                tions that have been previously dismissed by Schutz and
short gestures.                                                         Kubovy (in press). We will close this section by explaining
   In light of evidence that vision does not influence audi-            our reasons for proposing that causality plays an impor-
tory judgments of tone duration (Walker & Scott, 1981),                 tant role and by discussing links between this illusion and
this illusion is unexpected. It is an exception to the rule             previous work on the unity assumption.
that, with respect to a given task, the modality offering                  Post-perceptual processing cannot explain the il-
less accurate information does not appreciably influence                lusion. As has been shown by Arieh and Marks (2008),
the modality offering more accurate information. For ex-                certain patterns of cross-modal interactions may be ex-
ample, the superior temporal precision of the auditory                  plained by decisional changes, rather than by sensory
system generally translates into auditory dominance for                 shifts. Therefore, it is possible that longer gestures could
temporal tasks such as the judgment of tone duration.                   have suggested longer durations, affecting ratings through
Likewise, estimates of flash timings are more affected by               a top-down process (i.e., a response bias), without any ac-
temporally offset tones than estimates of tone timings are              tual perceptual shift. To test this explanation, Schutz and
affected by temporally offset flashes (Fendrich & Corbal-               Kubovy (in press) designed a series of experiments ma-
lis, 2001); and auditory flutter rate affects the perception            nipulating the causal relationship between the auditory
of visual flicker rate, whereas the rate of visible flicker             and visual components of the stimuli.


                                                      M. Schutz, schutz@mcmaster.ca


© 2009 The Psychonomic Society, Inc.                                1618
                                                                                  Deconstructing an illusion           1619

   In their first experiment, Schutz and Kubovy (in press)      Leventhal, 1952). Likewise, due to its superior temporal
paired the impact gestures with two classes of sounds:          acuity, audition dominates temporal tasks, such as esti-
percussive and non-percussive (i.e., sustained). The non-       mating tone duration (Walker & Scott, 1981), temporal
percussive sounds consisted of single tones produced by         order (Fendrich & Corballis, 2001), and visual flicker/
the clarinet, French horn, or human voice (singing), as         auditory flutter rate (Shipley, 1964; Welch et al., 1986).
well as white noise. The percussive sounds consisted
								
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