Strong bodily responses have repeatedly been shown in participants fearful of spiders and snakes when they see pictures of the feared animal. In this study, we investigate if these fear responses affect voice intensity, require awareness of the pictorial stimuli, and whether the responses run their course once initiated.
Animal fearful participants responded to arrowhead-shaped probes superimposed on animal pictures (snake, spider, or rabbit), presented either backwardly masked or with no masking. Their task was to say ‘up’ or ‘down’ as quickly as possible depending on the orientation of the arrowhead. Arrowhead probes were presented at two different stimulus onset asynchronies (SOA), 261 or 561 ms after picture onset. In addition to vocal responses, electrocardiogram, and skin conductance (SC) were recorded.
No fear-specific effects emerged to masked stimuli, thereby providing no support for the notion that fear responses can be triggered by stimuli presented outside awareness. For the unmasked pictures, voice intensity was stronger and SC response amplitude was larger to probes superimposed on the feared animal than other animals, at both SOAs. Heart rate changes were greater during exposure to feared animals when probed at 561 ms, but not at 261 ms, which indicates that a fear response can change its course after initiation.
ConclusionExposure to pictures of the feared animal increased voice intensity. No support was found for responses without awareness. Observed effects on heart rate may be due to change in parasympathetic activation during fear response.