Effects of predictability of shock timing and intensity on aversive responses

Abstract

An important characteristic of aversive stimuli that determines emotional responses is whether the stimuli are predictable. Human laboratory studies in this area have typically operationalized predictability as being able to predict the occurrence of aversive events, but animal studies suggest that being able to predict other characteristics of the stimuli may also play a role in aversive responding. To examine this, the present study examined two characteristics: the timing and intensity of aversive stimuli. Specifically, participants were randomly assigned to receive shocks that were either predictable or unpredictable in terms of when they would occur (timing) and/or their intensity. Indicators of aversive emotional responses were EMG startle responses and subjective anxiety ratings. Results revealed that aversive responding was elevated for unpredictable timing and intensity suggesting that the predictability of both characteristics play a role in aversive responding (though the effects for timing were stronger). In sum, the anxiogenic effects of unpredictability may generalize to situations beyond unpredictable timing.

Uncertainty and anticipation in anxiety: an integrated neurobiological and psychological perspective

“…Across species, physiological responding to threat is enhanced when there is uncertainty about its nature, probability, or timing 15,16,129–134 . Humans show larger startle responses for cues that can precede either low or high intensity shocks than for cues that always precede high intensity shocks 129 , for cues preceding shock on 20% or 60% of trials than for cues that predict shock with 100% certainty 130 , and under conditions of temporal unpredictability 131 . Furthermore, aversive events that are not fully predictable have a greater negative impact on mood, state anxiety, and physiological indices of reactivity than those that are fully predictable 132–134 .…”

Using the Threat Probability Task to Assess Anxiety and Fear During Uncertain and Certain Threat

“…The Threat Probability task described here manipulates uncertainty about IF a shock will occur while holding all other dimensions of uncertainty constant thus making clear what aspect of uncertainty is responsible for the effects the task presents. Tasks that use startle potentiation to cued threat are flexible and can also be modified by affective scientists to manipulate uncertainty about WHERE the shocks are going to occur 25 and HOW BAD they will be 7,26 . Of all of these tasks, the Threat Probability Task is one of the easiest to interpret due to its focus on one dimension of uncertainty and most straightforward to implement due to its inclusion of only two threat uncertainty variants (low probability and high probability shock).…”

Assessing fear and anxiety in humans using the threat of predictable and unpredictable aversive events (the NPU-threat test)

“…Several other laboratories have adapted the NPU-threat test with minor changes to the original procedure (i.e., counting down to the shock 25 ), or alternative manipulations of predictability (i.e., using only short-duration cues with 100, 60 or 20% shock probability 26 ; manipulation of the predictability of the shock intensity 27 ). Although these adaptations offer interesting additional information, they have not been validated in anxious subjects or with anxiolytics.…”