Measuring the postauricular reflex as an indicator of appetitive processing

The postauricular reflex is a muscular microreflex behind the ear that is elicited by brief and abrupt sounds. Although it is vestigial in humans, it has been shown to have a potentiated response to the eliciting sound during the presentation of stimuli usually considered as pleasant relative to neutral or unpleasant stimuli across different sensory modalities; this response being even more prominent for appetitive stimuli, such as food and erotic images. This reflex can thus serve as a psychophysiological indicator of appetitive processing and could be a valuable tool for food science. Here, we describe a protocol that can be used to measure and analyze the postauricular reflex in humans. Our goal is to provide information on the materials and methods needed to record the postauricular reflex and to illustrate the preprocessing steps and quantification strategies that can be implemented to score this reflex.