Mechanisms of visual threat detection in specific phobia

Abstract

People with anxiety or stress-related disorders attend differently to threat-relevant compared with non-threat stimuli, yet the temporal mechanisms of differential allocation of attention are not well understood. We investigated two independent mechanisms of temporal processing of visual threat by comparing spider-phobic and non-fearful participants using a rapid serial visual presentation task. Consistent with prior literature, spider phobics, but not non-fearful controls, displayed threat-specific facilitated detection of spider stimuli relative to negative stimuli and neutral stimuli. Further, signal detection analyses revealed that facilitated threat detection in spider-phobic participants was driven by greater sensitivity to threat stimulus features and a trend towards a lower threshold for detecting spider stimuli. However, phobic participants did not display reliably slowed temporal disengagement from threat-relevant stimuli. These findings advance our understanding of threat feature processing that might contribute to the onset and maintenance of symptoms in specific phobia and disorders that involve visual threat information more generally.

Keywords:

• Attention
• Threat
• Anxiety
• Sensitivity
• Attentional blink

We wish to thank Brian J. Scholl for his input on this paper.

This work was supported by the National Institutes of Health under NIMHD [grant number MD007599].

We wish to thank Brian J. Scholl for his input on this paper.

This work was supported by the National Institutes of Health under NIMHD [grant number MD007599].

Notes

¹ The stimulus onset asynchronies (SOAs) used in the original AB studies (i.e., 90 ms SOA; Raymond, et al., 1992; Shapiro et al., 1994) were calibrated for the speed necessary to process single letter stimuli. Given the perceptual differences between our photo stimuli and the original letter stimuli, we piloted the facilitation and disengagement tasks to determine the optimal SOA for each. Initial piloting of the facilitation task at 100 ms SOA revealed ceiling effects in non-fearful pilot participants. We therefore decreased the SOA by 10 ms increments until pilot participants performed at an average of 65% correct T2 detection at the lags most likely to show the effect (i.e., early lags). For the disengagement task, 100 ms SOA was optimal; we attribute this difference to the perceptual similarity between the fruit T2 targets and the distractors in the disengagement task (i.e., the greater difficulty of the disengagement task).

² Per reviewer suggestion, we conducted exploratory ANOVAs separately at each of the early lags: there were no significant Animal x Group interactions. Also, given the possibility of habituation within a task block, we conducted exploratory ANOVAs for the first half of the trials within the disengagement block. At Lag 2 only there was a significant Animal × Group interaction (p = .045). T-tests of differences at Lag 2 showed only a greater difference for Neutral–Threat (frog–spider) in phobics compared with controls (p = .017). This is an interesting preliminary suggestion that phobics might disengage more slowly from threat relative to neutral on the first few encounters with threat stimuli, but there is no suggestion of threat specificity (Negative–Threat). However, this analysis was purely exploratory and runs the risk of Type I error.