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Updated: May 27, 2026

Psychophysiological Assessment of the Effectiveness of Emotion Regulation Strategies in Childhood
Published on: February 11, 2017
The nursing hypothesis: an evolutionary account of emotional modulation of the postauricular reflex
Gabriella M Johnson1, Fernando Valle-Inclán, David C Geary
1Department of Psychological Sciences, University of Missouri-Columbia, Columbia, Missouri 65211, USA.
Abstract:
The postauricular reflex (PAR) is anomalous because it seems to be potentiated during positive emotions and inhibited during negative states, unlike eyeblink and other components of the startle reflex. Two evolutionary explanations based on simian facial emotion expressions were tested. Reflexes were elicited while 47 young adult volunteers made lip pursing or grimacing poses and viewed neutral, intimidating, or appetitive photos. The PAR was enhanced during appetitive slides, but only as subjects carried out the lip-pursing maneuver. These results support the nursing hypothesis, which assumes that infant mammals instinctively retract their pinnae while nursing in order to comfortably position the head. Appetitive emotions prime the ear-retraction musculature, even in higher primates whose postauricular muscles are vestigial.
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