The walking sick : what predicts the detection of walking sick individuals?

• Methods: In two studies, raters watched video recordings and point-light displays (i.e. dots depicting the body joints) of walking individuals who were either experimentally sick (after injection with lipopolysaccharide at 2.0 ng/kg bw) or healthy (after a placebo injection). In study 1, 106 raters classified each walking individual as either sick or healthy. In study 2, 106 other raters graded health of the stimuli on a visual analogue scale. We assessed the predicting effect on sickness detection (study 1) and apparent health (study 2) of walking parameters (objective measures of stride length, width, time, as well as knee angle, arm angle, and head angle) and well-known sickness responses (Sickness Questionnaire score, pain intensity, body temperature, and interleukin-6 concentration).Results: In study 1, shorter steps was the only predictor of the detection of sick individuals from video recordings (β=0.712(0.257), p=0.02). In the point-light displays, slower, wider, stiffer and shorter steps, all predicted a better sickness detection (β=0.0003(0.0001)-0.415(0.126), p<0.05).In study 2, lipopolysaccharide-induced slower, shorter and stiffer steps (B=5.214(1.888)-6.385(2.083), p<0.01), as well as higher interleukin-6 concentrations (B=0.051(0.020), p=0.01), predicted worse health ratings of sick individuals in the video recordings. In the point-light displays, lipopolysaccharide-induced slower, shorter and stiffer steps, and more head tilting, predicted worse health ratings of sick individuals (B=4.185(1.892)-6.701(2.092), p<0.05).Conclusions: The results imply that specific changes in walking parameters may aid in sickness detection, possibly regulating approach-avoidance behaviors towards sick peers.

Ämnesord

SAMHÄLLSVETENSKAP  -- Psykologi (hsv//swe)

SOCIAL SCIENCES  -- Psychology (hsv//eng)

Nyckelord

experimentally sick

walking parameters

sickness detection

psykologi

Psychology

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