Human freezing in response to affective films

Abstract

Human freezing has been objectively assessed using a passive picture viewing paradigm as an analog for threat. These results should be replicated for other stimuli in order to determine their stability and generalizability. Affective films are used frequently to elicit affective responses, but it is unknown whether they also elicit freezing-like defense responses. To test whether this is the case, 50 participants watched neutral, pleasant and unpleasant film fragments while standing on a stabilometric platform and wearing a polar band to assess heart rate. Freezing-like responses (indicated by overall reduced body sway and heart rate deceleration) were observed for the unpleasant film only. The unpleasant film also elicited early reduced body sway (1–2 s after stimulus onset). Heart rate and body sway were correlated during the unpleasant film only. The results suggest that ecologically valid stimuli like films are adequate stimuli in evoking defense responses. The results also underscore the importance of including time courses in human experimental research on defense reactions in order to delineate different stages in the defense response.

Keywords:

• freezing
• orienting
• tonic immobility
• body sway
• stabilometric platform
• anxiety

Acknowledgments

M. Hagenaars was supported by VENI Grant (#016.105.142) from the Netherlands Organization for Scientific Research (NWO). K. Roelofs was supported by VIDI Grant (#452-07-008) from the NWO.

Notes

1. The SP-length analyses were rerun while controlling for weight and height. This yielded similar results for all analyses. Also, there were no significant differences in heart rate (F(2, 98)= 1.07, p= .35) or SP length (F(2, 98)= .64, p= .53) during the inter-stimulus black screen periods.