The Role of Clock and Memory Processes in the Timing of Fear Cues by Humans in the Temporal Bisection Task

Recent research on the effects of fear on timing has focused on two accounts proposed by Scalar Expectancy Theory for why the durations of fear stimuli are overestimated in comparison to the durations of neutral stimuli. One possibility is that fear serves as an arouser that increases the speed of a hypothetical internal clock. The other possibility is that fear increases attention to time, which results in organisms' beginning to time fear-evoking stimuli sooner than they do neutral stimuli. In Experiment 1, we asked which of these two possibilities was the underlying mechanism of temporal overestimation of fear cues by presenting emotion-evoking pictures (fear-evoking vs. neutral) across multiple duration ranges in the temporal bisection task. Larger effects of fear were observed at the longest duration range in comparison to the shortest duration range, supporting the arousal hypothesis. Penney et al. 1998 and Penney et al., 2000 memory-mixing hypothesis proposes that overestimation is only possible in preparations that allow for recalled reference memories for stimulus durations to be mixed across conditions. Therefore, in Experiment 2, we manipulated whether or not fear and neutral cues were presented within the same session, a condition that may be necessary for memory mixing to occur. Fear cues were overestimated relative to neutral cues within the session in which fear and neutral cues were both presented, but no effect of emotion was observed between the two sessions in which fear and neutral cues were presented separately.