The Effect of Relative Positive Over Negative Mood on Affect-Modulated Eye-Blink Startle Response

Abstract: Startle reflex is an involuntary defensive withdrawal response to a suddenly-occurring stimulus and is influenced by subjective affective states. However, most studies have examined the effect of positive and negative affect independently rather than in relation to one another, which is important since positive and negative affect co-exist within an individual. Thus, the present study examined the effect of participants’ relative dominance of current subjective positive over negative mood on their startle response. Participants ( N = 59) indicated the extent to which they were feeling certain positive and negative emotions using Positive and Negative Affect Schedule (PANAS) immediately before their participation in the experiment. Then, the affect-startle task presented participants with pleasant, unpleasant, and neutral IAPS photographs with loud acoustic startle probe presented on some pictures and some of the inter-stimulus intervals (to index baseline startle). The median-split of the relative dominance of positive over negative mood score gave two groups of High and Low Dominance of Positive Mood (HDP & LDP, respectively). Repeated-measures ANCOVA revealed that individuals with LDP showed significantly delayed startle onset on neutral and unpleasant photographs than those with HDP. The groups did not differ on amplitude or latency to the peak of startle in the affective or baseline conditions or the baseline latency to startle onset. The findings indicate that individuals with lower positive, relative to negative, mood require more time to interpret neutral and unpleasant emotional content. Nevertheless, once the emotional content is interpreted, their relative mood does not affect the involuntary emotional reaction, that is, the startle response.