Behavioral and electrophysiological measures of the body inversion effect

Previous behavioral and electrophysiological studies examining the body inversion effect, where inversion of a body stimulus reduces its recognition, suggested that information regarding human bodies is processed configurally. However, few studies to date have examined how the magnitude of the body inversion effect may be impacted by varying degrees of configural information present in a stimulus of interest. In the current study, upright and inverted body stimuli were presented across three body posture conditions, the whole body, piecemeal body (without head and trunk), and random body posture conditions, while response times, error rates, and event-related potentials were recorded. Behavioral measures and assessment of the N170 component, particularly at occipital-temporal site, revealed a robust difference between upright and inverted postures for both the whole body and piecemeal body posture conditions, which was not observed in the random body posture condition. The behavioral measure showed less errors and faster reaction times for upright compared with inverted orientation; however, the N170 component only showed typical effect of orientation (more negative and more delayed peak in waveform for the inverted compared with upright orientation) in the left hemisphere. The magnitude and direction of these differences were comparable for whole body and piecemeal postures. Overall, these results were consistent with the notion that it is the first-order information of body posture rather than the presence of the head (and trunk) that determines the body inversion effect.