Researchers at Dartmouth College have made an important breakthrough in the field of facial recognition. Professors Bradley Duchaine and Vincent Walsh, of the department of psychological and brain sciences at Dartmouth College, recently considered whether the facilitation of sensorimotor mechanisms promotes facial expression recognition. Their research addressed this question by considering individuals with a neurological condition known as mirror-touch synesthesia.
For mirror-touch synesthetes, the sensation of touch can be felt simply by observing it among other people. For example, if an individual sees someone being touched on the cheek, then he will feel his cheek being touched.
Previous studies have suggested that the visual face-processing mechanisms of the brain are inextricably linked with those of facial expression. They argue that in order to understand the facial expressions of others, our brains actually simulate the emotional response that we connect with those expressions. These accounts have indicated that exposure to emotion triggers a response in one’s own facial muscles, and that the perception of emotion and the generation of an emotional response stimulate many of the same premotor and somatosensory regions of the brain.
If this is truly the case, then mirror-touch synesthesia could be thought of as heightened sensorimotor simulation; this would make synesthetes ideal subjects in trying to understand the role of sensorimotor simulation mechanisms in social cognition. To explore this possibility, Professors Duchaine and Walsh compared mirror-touch synesthetes with non-synesthetes in the areas of facial expression recognition, identity recognition, and identity perception.
The participants in this study included eight individuals with mirror-touch synesthesia and a control group of 20 non-synesthetes. To evaluate facial expression recognition, the subjects were given an adjective describing an emotional state, and then were very briefly-about half a second-shown three images, in which an actor depicted three different facial expressions. The subjects were then asked which of the images best represented the given adjective.
Afterwards, the participants were evaluated with the Cambridge face memory test (CFMT+). Asked to study six unfamiliar male faces from three different views, the participants were then tested on their ability to recognize these faces at different angles and with different expressions, along with distractors like facial hair.
The subjects were also assessed with the Cambridge face perception test. The participants were shown a specific face, alongside six variations of that same face. The six additional images are transformed digitally, so that there is a systematic variation between each one and the original. The subjects were given one minute to sort the faces by their similarity to the target face, and then evaluated based on their choices.
As predicted, the individuals with mirror-touch synesthesia outperformed the control group in their ability to recognize and categorize facial expressions. However, there was no significant difference between the two groups in recognizing facial identities. Although synesthetes were significantly better at categorizing expressions, they were no better at memorizing those expressions. Ultimately, the findings were consistent with the view that facial perception depends on the simulation of that perceived expression. The results indicate that the somatosensory mechanisms of the brain are integral in our ability to recognize the emotions of others. Indeed, they are an essential aspect of human empathy.