Often, when someone dashes a smile your way, you reciprocally dash one back, regardless of whether that person is categorised as a stranger or a friend to you – a social reflex you might say, or something of a contagion i.e. when one-person smiles, that communique is irrevocably passed on. You would have thought, as many neuroscientists once built a theory around, that such a social reflex hinged upon our awareness of such a process; from perceiving the sender of the smile, from receiving the visual cues from the persons facial arches and contusions that indicate a smile. Neuroscientists believed we had to have visual awareness to receive and reciprocate the intention of emotion behind a gesture, such as a smile.
You can imagine the surprise, then, when Alan Pegna, director of the Laboratory of Experimental Neuropsychology at Geneva University Hospital in Switzerland, greeted a long-time cortically blind patient – accrued through damage to the primary visual areas of the brain — with a smile and, with a snap, received one back. When Pegna enquired about this episode to the patient, he replied with confusion, insisting he neither perceived or reciprocally send a smile back. The patient was unaware of taking part in any such socially contagious behaviour.
When the brains primary visual areas (occipital lobes of the brain) are destroyed, as is the case with Pegna’s patient, cortical blindness usually ensues: although a cortically blind person can still receive a visual stimulus that activates the optic receptors within the eye, they are no longer able to consciously perceive, or verbally report on any such stimulus.
Research originating a few decades ago found that patients with damage to the visual cortex, resulting in cortical blindness, were still able to reliably navigate around objects and react to motion; a phenomenon that came to be known as ‘blindsight.’ This means visual information, although unable to be processed by the complex visual cortex, can nonetheless be transferred to less complex and more evolutionary ancient modules of the brain, such as the superior colliculus. In turn, it’s thought that these areas navigate motor activity in response to visual stimuli, allowing a blindsight patient, for instance, to successfully move around objects. In summary, visual information can affect behaviour without any need for conscious recognition or directive.
Pegna’s patient, conversely, did something a little subtler than react to motion or navigate around a static object, this particular patient was able to unconsciously detect and reciprocate the intricacies of a smile.
Pegna, intrigued by this serendipitous experience and as all scientists worth their salt do, took his patient to the lab. In order to gauge a baseline of visual performance, Pegna asked his patient to guess whether a shape, presented via a computer screen, was either a square or a circle. 200 trials later, and as to be expected from a person impaired by cortical blindness, performance was no different to a chance level performance (only 45 per cent correct answers.) This was only the control trial — developed here to ensure the participant really is cortically blind and was not merely responding to lines or edges, but to emotional stimuli — what followed was the experimental trial: the patient was shown a randomised series of pictures portraying angry or happy faces, and was asked to guess which one of the two emotions were depicted; 59 per cent of the patient’s answers were correct. That’s to say, a person with no conscious experience of any visual stimuli, was guessing the emotion depicted upon human faces correctly, above chance level. “Guessing” is now the wrong word, Penga’s patient was, instead, intuiting what emotions were depicted on a human face.
The complexities maintained by a six-layer visual cortex are not integral for “seeing” emotion, but the amygdala apparently is. When Pegna’s patient was subject to an Fmri brain scan (a method of tracking activity, in response to a stimulus, within the brain), where faces depicting angry, happy and fearful emotions were shown, the amygdala region lit up enough to attract the mosquitos. This suggests our evolutionarily ancient amygdala (a resident in the mammalian general limbic system), even without ourselves knowing or being conscious of it, maintains a capacity to register and respond to emotionally salient facial expressions.
Evolution, using its prolific tools of natural and sexual selection, has thus seen fit to install a module within the brain that can unconsciously detect a compatriot’s facially expressed emotions. Considering our tribal heritage, it would have been wise, in order to gain allies to hunt and gather with, to intuitively know what another person maybe feeling. This would allow a certain degree of emotional empathy and an uncanny ability to gauge if what you’re saying is hitting the right emotional chord of conversation. Additionally, this speciality allows us to instantaneously pick-up on a fearful stimulus just by looking at a friend’s face: we don’t need to actually see the predator, we just need to see our allies’ face…guess who gets away first?
We, Home Sapiens, are the perceivers of emotion, whether we consciously concede as such or not.