Abstract
When confronted with threatening stimuli, animals typically respond with freezing behavior characterized by reduced movement and heart rate deceleration. Freezing-like responses during threat anticipation have also been observed in humans and are associated with anxiety. Recent evidence yet suggests that freezing does not necessarily reflect helpless immobility but can also aid the preparation of a threat escape. To investigate which further behavioral responses human freezing encompasses, we presented 50 young adults (10 male) with aversive stimuli that could sometimes be avoided while measuring gaze, cardiovascular and electrodermal activity. In trials in which the threat could be escaped, participants displayed reduced heart rate, increased electrodermal activity and reduced visual exploration. Furthermore, heart rate deceleration and restricted visual exploration predicted the speed of flight responses. These results provide evidence for freezing behavior in measures of visual exploration and suggest that such responding is adaptive in preparing the subsequent escape of approaching threats.
Highlights
When confronted with threatening stimuli, animals typically respond with freezing behavior characterized by reduced movement and heart rate deceleration
We looked at three different metrics to evaluate the dynamics of visual exploration during threat anticipation
We observed fewer and longer fixations, which were closer to the center of the screen, in trials in which a threat escape was possible
Summary
When confronted with threatening stimuli, animals typically respond with freezing behavior characterized by reduced movement and heart rate deceleration. Heart rate deceleration and restricted visual exploration predicted the speed of flight responses These results provide evidence for freezing behavior in measures of visual exploration and suggest that such responding is adaptive in preparing the subsequent escape of approaching threats. Rodents and non-human primates commonly respond with freezing as a reaction to relatively remote threat or threat-related cues[1,2,3,4,5,6] This reduced mobility enhances chances of survival in life-endangering situations as immobile prey is less likely to be eaten than its moving peers[7,8]. The use of dot-probe paradigms revealed shorter reaction times to threat-related or painful stimuli e.g.23 and difficulties disengaging from them[24,25] This attentional bias towards threat has further been implicated in the maintenance of anxiety disorders (as reviewed in[26]). Age (years) Sex (male/female) Handedness (right/left/both) STAI ASI BDI participants were not able to escape the painful shock, the study design did not allow for inferences about attentional processes during flight and freezing as a means to flight preparation
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