Startle is modulated by approach/avoidance rather than valence stimuli.
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1
University of Wollongong, Australia
Aims: There are currently mixed findings in the literature as to whether affective stimuli modulate startle EMG magnitude, with methodological limitations a possible explanation for the lack of consistency (specifically, failure to use gender specific norms for affective stimuli and failure to match arousal levels across valence). The present study determined whether valence stimuli modulate the startle response after accounting for methodological issues.
Method: EMG activity was recorded from the orbicularis oculi muscle from 26 participants (13 male) who passively viewed 300 affective stimuli (600ms duration, 800-1200ms ISI) selected from the International Affective Picture System (IAPS). Startle probes (50ms, near-instantaneous rise/fall times, 95-dB) were administered pseudo-randomly 3500-4500ms, equally across 5 conditions (20 probes for each of low and high arousal pleasant, low and high arousal unpleasant and low arousal neutral). Stimuli were selected based on IAPS norms separately for gender, and comparisons were made between 1/ matched arousal and valence groupings, 2/ gender combined versus gender specific ratings, and 3/ norm versus individual ratings.
Results: Affect did not modulate startle EMG magnitude for low-arousal images, whereas unpleasant stimuli (relative to pleasant) potentiated startle to high-arousal images. Gender-combined ratings of valance and arousal levels differed, as did gender specific norms and individual ratings.
Conclusions: Given that 1/ arousal independently affected startle, 2/ gender-combined IAPS norms are not applicable for either genders, and that 3/ IAPS norms differ from individual ratings, suggests that 1/ literature failing to match arousal has been importantly confounded, 2/ studies with gender-combined norms are not appropriate, and 3/ IAPS norms result in a weaker experimental manipulation. Accounting for these limitations, the study has shown that valence does affect startle magnitude, but only for high arousing images. This is consistent with the view that startle magnitude is related to appetitive/defensive behaviours, rather than valence per se.
Keywords:
startle magnitude,
Valence,
Arousal,
Appetitive Behavior,
defensive behavior
Conference:
Australasian Society for Psychophysiology, Inc, Coffs Harbour, Australia, 26 Nov - 28 Nov, 2014.
Presentation Type:
Oral Presentation
Topic:
Psychophysiology
Citation:
Boyall
S,
Camfield
D and
Croft
RJ
(2014). Startle is modulated by approach/avoidance rather than valence stimuli..
Conference Abstract:
Australasian Society for Psychophysiology, Inc.
doi: 10.3389/conf.fnhum.2014.216.00040
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Received:
21 Oct 2014;
Published Online:
05 Dec 2014.
*
Correspondence:
Miss. Sarah Boyall, University of Wollongong, Wollongong, Australia, seb937@uowmail.edu.au