Abstract
To survive, animals must be able to react appropriately (in temporal and behavioral terms) when facing a threat. One of the essential parameters considered by the defensive system is the distance of the threat, the “defensive distance.” In this study, we investigate the visual depth cues that could be considered as an alarm cue for the activation of the defensive system. For this purpose, we performed an active-escape pain task in a virtual three-dimensional environment. In two experiments, we manipulated the nature and consistency of different depth cues: vergence, linear perspective, and angular size. By measuring skin conductance responses, we characterized the situations that activated the defensive system. We show that the angular size of the predator was sufficient information to trigger responses from the defensive system, but we also demonstrate that vergence, which can delay the emotional response in inconsistent situations, is also a highly reliable cue for the activation of the defensive system.
Highlights
To survive in the wild, animals must be able to detect approaching danger and to react in a timely way. Blanchard and Blanchard (2008) described the defensive system as a group of adaptive responses to a threat stimulus or situation, which is not yet comprehensively understood, but which includes inter alia avoidance, flight, freezing, or defensive attack. Fanselow (1994) defined three modes of this defensive system based on a continuum of contact imminence with a predator: preencounter, postencounter, and circa-strike modes
These modifications in brain activity are accompanied by an increase in skin conductance (SC), which means that the event triggers an emotion, and could correspond to a switch to the circa-strike mode of the defensive system
To understand better the involvement of the angular size cue and to verify whether vergence was involved in the activation of the defensive system, we conducted experiment 2
Summary
To survive in the wild, animals must be able to detect approaching danger and to react in a timely way. Blanchard and Blanchard (2008) described the defensive system as a group of adaptive responses to a threat stimulus or situation, which is not yet comprehensively understood, but which includes inter alia avoidance, flight, freezing, or defensive attack. Fanselow (1994) defined three modes of this defensive system based on a continuum of contact imminence with a predator: preencounter, postencounter, and circa-strike modes. Mobbs’ studies have identified a shift from the ventromedial prefrontal cortex to the periaqueductal gray, and Low observed an increase in the late positive event-related potentials in the central parietal area. These modifications in brain activity are accompanied by an increase in skin conductance (SC), which means that the event triggers an emotion, and could correspond to a switch to the circa-strike mode of the defensive system. The task is a “Pacman”like game, and one can question the relevance, in terms of the involvement in the defensive system mechanisms, of a scene perceived from a third-person perspective We believe that this type of view does not make the situation ecologically valid. Low et al (2008) used a first-person view, presenting looming images, they still did not fulfill the conditions for ecologically valid situation in our opinion, because they worked with a 2-D display
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