A meta-analysis of the facilitation of arm flexion and extension movements as a function of stimulus valence

This article presents a meta-analysis of research on the affective compatibility effect: the relative facilitation of arm flexion and extension movements, in response to positive and negative stimuli, respectively. Across 68 effect sizes (computed on 3169 participants), a small, significant average compatibility effect emerged (ES = .118; 95% CI [.051, .185]). Importantly, analyses also revealed significant heterogeneity in the set of effect sizes. Moderator analyses were conducted to explain this observed heterogeneity with a view to testing between extant theoretical accounts of the compatibility effect. Affective compatibility effects were significantly larger (1) for face stimuli than for words or pictorial stimuli; (2) when the negative stimuli partly comprising the effect were anger-related; (3) for responses made using vertical button press; (4) when situated aspects of the processing task framed flexion as approach and extension as avoidance; and (5) when explicit response labels framed flexion as positive and extension as negative. Significant reverse compatibility effects emerged (1) when aspects of the processing context framed flexion as avoidance and extension as approach and (2) when explicit response labels framed flexion as negative and extension as positive. The results of the meta-analysis provide little support for the strong embodiment, specific muscle activation account of affective compatibility and are broadly consistent with distance regulation, and, in particular, evaluative coding accounts.