Ulf Dimburg and colleagues at Uppsala University in Sweden unconsciously exposed to happy and angry facial expressions. Through use of the backward-masking technique, the subjects were prevented from consciously perceiving 30-ms exposures of happy, neutral, and angry target faces, which immediately were followed and masked by neutral faces. Consciously, subjects only recalled seeing neutral faces.
Despite the fact that exposure to happy and angry faces was unconscious, subjects reacted with distinct facial muscle reactions that corresponded to the happy and angry stimulus faces.
The results show that emotional reactions can be unconsciously evoked, and can produce behavioral responses in us of which we aren’t even aware.