Cognitive bias in emotional facial expression

The human face is a very special stimulus. The face is associated with our identity, and it is a mean to communicate feelings and emotional states. Thus, it is assumed that the role played on the regulation of social contacts was important to the survival chances of our ancestors. For example, the ability to quickly identify threatening intentions on a first encounter with a stranger. An automatic, non-aware, processing of angry faces has been showed in a series of classical conditioning experiments, using skin conductance responses as a measure of conditioning. When an angry facial expression was associated with an aversive stimulus, the conditioned response was larger than if a happy face was used as the conditioned stimulus. This was obtained even when awareness of the conditioned faces was prevented by means of backward masking. In two visual search experiments, using schematic faces displaying different emotional expressions, a bias for a better detection of angry faces was obtained. Thus, an angry face among happy faces was detected faster and with fewer errors than a happy face among angry ones. These results are consistent with the general perception bias found in anxiety disorders, and with the studies showing priority on the processing of stimuli and situations potentially threatening to the individuals.