Handbook of Experimental Phenomenology by Albertazzi Liliana;

Author:Albertazzi, Liliana;
Language: eng
Format: epub
Publisher: John Wiley & Sons, Incorporated
Published: 2013-05-27T16:00:00+00:00

Stimulus orientation and viewing angle

Recent studies have manipulated orientation of the visual display in order to investigate how an otherwise unchanged stimulus (i.e., all stimulus properties remain physically the same apart from display orientation) can affect synchrony perception. This idea of display orientation was inspired by the visual orientation shifts often occurring in our daily interaction, where shifts in the orientation of a speaker’s head during conversation do not hinter our ability to understand the audiovisual message sent by the speaker. Vatakis and Spence (2007a, 2008) first explored this idea by utilizing dynamic complex speech and nonspeech (e.g., musical and animal call stimuli) stimuli presented in a normal-oriented or inverted orientation (Vatakis & Spence, 2008). The results of these experiments revealed that the inversion of a dynamic visual-speech stream did not have a significant effect on the sensitivity of participants’ TOJs concerning the auditory- and visual-speech and nonspeech stimuli (i.e., the JNDs were unchanged). The perception of synchrony was, however, affected in terms of a significant shift of the PSS being observed when the speech stimuli were inverted. Specifically, inversion of the speech stimulus resulted in the visual stream having to lead the auditory stream by a greater interval in order for the PSS to be reached. Similar TOJ results for nonspeech stimuli were also obtained by Petrini, Holt, and Pollick (2010) when using point-light musical stimuli and novice participants; however, the contrary was true when participants completed SJs. Inversion effects for nonspeech stimuli were also obtained for video clips of different objects being dropped in terms of JND changes (Vatakis & Spence, 2011). Specifically, inverting the visual display of the falling object led to a significant difference in participants’ ability to judge the temporal order of the auditory/visual components of the desynchronized video clips. That is, participants were more sensitive to audiovisual asynchrony when viewing normally oriented video clips of the falling object as compared to viewing the same clips inverted. Further research is required in order to establish whether or not display of the visual stimulus affects synchrony perception and in what way (i.e., PSS or JND shift).

In terms of viewing angle and synchrony perception, Steinmetz (1996) conducted a study using video segments of television news reports that were presented at three different viewing angles (head, shoulder, and body view) under various degrees of asynchrony. At the end of each video, the participants had to complete a questionnaire regarding the quality of the video presented and which of the two modality-streams they had perceived as leading or lagging. Steinmetz reported that the participants exhibited a lower sensitivity to the desynchronization of speech events occurring far away (i.e., body view) than for events occurring proximal to the observer (i.e., consisting of a view of the head and shoulders). Overall, the breakdown of the perception of synchrony for the news report videos was found to occur at intervals exceeding ±80 ms auditory or visual lag. Steinmetz performed a number of control studies utilizing other complex stimuli under different viewing angles. Specifically, he presented the participants with various views of an object-action video (i.

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