Emotional hybrids and Functional Cerebral Asymmetries: The role of the left and right hemispheres in processing unseen emotional content

Functional cerebral asymmetries have been demonstrated for emotional face perception but a conflicting pattern of results emerges from the literature. Previous studies suggest discrepancies may be driven by the spatial frequency content of emotional stimuli and also participant’s awareness. The current study investigated this using emotional hybrid faces which are created by combining low spatial frequency content of an emotional face with high spatial frequency information of a neutral face. An affective priming paradigm was employed to investigate whether emotional content conveyed by low spatial frequencies was sufficient to affect identification of target emotional hybrids; when presented to each cerebral hemisphere using the divided visual half-field technique. In Experiment 1, participants viewed neutral or emotional primes followed by emotional targets on congruent trials or neutral targets on incongruent trials, presented in each visual half-field. Participants indicated whether the target face was emotional or neutral. Experiments 2 and 3 adopted an expression identification task, requiring participants to identify the emotion displayed. The results revealed fearful faces were identified more accurately by the left hemisphere in Experiment 1 and that emotional congruency of prime and target had a positive effect on performance. Experiments 2 and 3 however, showed a general advantage for the right hemisphere and an adverse effect of emotional congruency. It was concluded that contrast effects accounted for the adverse effects of congruency in the later experiments and differences between Experiments 1 and Experiments 2 and 3 were the result of increased task difficulty in the latter. The results also suggest a general RH dominance for emotion processing as the left hemisphere advantage for fear in Experiment 1 was concluded to result from a hemispheric advantage for processing changes in the white sclera of the eye region.