Jun 18 2012

Facial Processing

When you see a person for the first time your eyes quickly scan their face and in less than a second your brain has gathered a tremendous amount of information about this person, processed that information, and come to many simultaneous conclusions. Think about all the different kinds of information we quickly and simultaneously process – the age and gender of the person, their race (or more generally, the genetic group with which they belong), their personality and mood, their attractiveness, the status of their health, and whether or not we have ever seen them before (do we know them).

Our brains perform this processing quickly, efficiently, and subconsciously, and so we tend to take it for granted. There are regions of the brain dedicated to processing sensory information about human faces. We are still teasing apart all the various aspects of this subconscious processing, which not surprisingly is very complex and involves multiple layers.

It also always fascinates me to find that there is a scientific community and robust research, complete with ongoing controversies, about the smallest area of knowledge – how we process facial information. Modern science has drilled down deeply on even narrow questions, which I feel is part of its strength.

It is not surprising that humans are so good at facial processing. We are social creatures who live in cooperative groups. The information gained from another’s face can be critical to survival. Since humans are essentially tribal it makes sense that we would specifically process facial information to recognize when someone belongs to our group vs another group – and not just some other group, but which other group. Are they a member of a tribe with which we are currently hostile or friendly? This is apparently the root of stereotyping. When we are not familiar with a specific individual we judge them based upon the only available information that we have, the group with which they appear to belong.

Research has found this to be generally true. Within fractions of a second we can recognize a familiar face, based on specific structural information. This is a complex processing task also (something at which humans are still better than computers). We need to be able to recognize individuals from different angles, in different lighting, in different contexts, while displaying different facial expressions, and perhaps even within a disguise. Think about famous actors playing different roles, even with extreme makeup on. I remember watching Pirates of the Caribbean (the second one) and recognizing actor Bill Nighy behind all the Davy Jones makeup. There was something about the way his mouth moved and the expression in his eyes that “clicked” in my brain, and then I could see Bill Nighy.

Further, we are able to determine when someone resembles a person that we know vs being that person. Even subtle differences are enough for us to determine that the person is a “lookalike” but not the person themselves.

When we determine that we know someone¬†that information¬†supersedes¬†the next stage of facial processing about gender, social category, etc. In other words – we now see the person as an individual rather than a generic member of a group or category. This also helps explain the “cross-race effect” – the fact that it is more difficult to recognize individual members of an unfamiliar race or group (yes, it is a real effect).

Facial recognition and information processing is a excellent example that can be used to investigate how the brain organizes and processes information in general. Questions actively being researched include the degree to which facial processing occurs in parallel vs in sequence. There does appear to be early and late stages of facial processing – a hierarchy of information. Some research, however, suggests that there are different modules processing facial information at the same time and the results of these parallel processes are mixed together. Our net response to a human face, therefore, may be pulled in multiple directions simultaneously.

Further, our response to a human face is not fixed, but is influenced by our current social situation. Psychologists are therefore able to manipulate such responses by priming and other methods. This generally reflects our neurological function – there are built in biases and processes, this is then affected by our memories (do we recognize an individual, past experiences with a group), and then further modified by our current mood and situation. This also makes sense as the brain is a tool for adapting to our environment and situation.

Further, there appear to be conscious and subconscious aspects to facial processing. There are some conclusions that we are immediately consciously aware of, like whether or not we recognize the individual and our estimate of the age and gender. However, we have other reactions that are subconscious, such as how trustworthy we feel the other person is. Research has shown that we estimate both trustworthiness and dominance quickly upon viewing a face. Researchers have teased apart some of the variables that contribute to this, for example features of maturity tend to equate with dominance. Related to this are studies that look at our judgment about whether or not someone is a criminal. Criminality judgments are at least partly explained by perception of high dominance and low trustworthiness.

This is a type of subconscious heuristic or emotion – our brains evolved to make social judgments quickly and subconsciously that are of some adaptive value, but not necessarily always accurate. We trade a decrease in accuracy for an increase in speed of decision-making. We see someone and immediately have a feeling about whether or not they are safe to approach, probably erring on the side of being cautious. Now, however, those same evolved reactions can affect judgments concerning a police lineup or a defendant in a trial – situations in which we want maximum accuracy.

Individuals also vary in terms of their ability to detect various aspects of the human face – such as ability to recognize individuals or to sense the emotional state of another person. This involves not only inherent ability but the amount of attentional resources that we allocate to the task. In one interesting study, for example, giving subjects the social hormone oxytocin increased their sensitivity to “hidden” or subtle emotional expressions.

The science of facial information processing and recognition is fascinating in itself, but I am also interested in what it tells us about brain organization and functioning generally. The same story emerges no matter what narrow aspect of brain function researchers are looking at. There appear to be multiple factors simultaneously at work, with conscious and subconscious elements, with a mixture of inherent and situationally malleable tendencies. Further, there are generic neurological factors, such as attention, that strongly influence the specific function.

Finally, the more we study aspects of brain function like facial processing the more apparent it becomes that our conscious experiences and choices are just the tip of a subconscious iceberg. We largely operate under the illusion that our thoughts and behaviors are the result of a conscious rational process, when in fact a large body of research, looking at human behavior and brain function from many perspectives, finds that our thoughts and behaviors are more determined by subconscious processing – our evolved tendencies modified by recent memory and our current situation.

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