October 1st, 2014

Psychologist studies how culture affects visual pathways

The scientific research that makes a big splash on the front page of local media or gets top billing in a scientific journal tends to be information that has a direct application in the real world. How exercise helps children with ADHD or research on how to attain happiness are samples of topics that will draw attention on the newsstand or get page clicks up. But what these outlets don’t usually show are the many years of research that led to those “groundbreaking” studies.

For some researchers, those who do not expect their work ever to make the front pages, the joy is in the work itself. Their research may not have immediate repercussions in our lives, but it is still important to take a look at the men and women who person the esoteric research halls and write the lesser-seen papers that pave the path to notoriety for others.

New England Psychologist’s Catherine Robertson Souter spoke with one such researcher, Todd Kahan, Ph.D., professor of psychology at Bates College and a recipient of a James McKeen Cattell Fund Fellowship. Kahan is on sabbatical this year, thanks to the fellowship, looking to get a better understanding of how culture affects visual pathways. He spoke about his study, what he hopes to prove and how this basic scientific research could lay the groundwork for studies that we will read about in future scientific and popular press outlets.

Q:  Tell us about the research you will be doing during this year-long sabbatical.

A:  To describe it at a broad level, I am interested in whether cultural expectations will influence early stages of visual perception.

Vision is a multi-stage process that begins when light hits the back of the retina, stimulates cells there and continues in a cascade through several regions. Along this processing pathway, different visual features, like edges, color, or motion, are extracted and these disparate features are eventually combined back together to form an object representation.

We have known about that visual processing pathway for a long time and it has also been known that culture and a person’s life experiences will exert an influence at some point in that processing stream. But it is not clear where in the processing stage that occurs.

That is the question I am hoping to address using visual illusions.

Q: Can you describe these illusions?

A:  The first I am using is something called object substitution masking. If you flash a target object and you put four tiny dots surrounding it in a notional square, people are great at identifying it. But if the dots persist on the computer screen for longer than the shape, the person can’t see the object.

This illusion tells us that the visual processing pathway is not simply feed forward. There is also what we call re-entrant pathways that come from higher level brain regions and they check for new incoming information. If the dots stay on the screen, when these re-entrant pathways check back all that is left there are the dots. So the dots supplant the triangle in your mind’s eye.

It is a later-acting illusion.

Q: And the other two illusions?

A: Object trimming is this finding that if I present you with a target, a digital clock 8, for example, and if I put two little dots aligned vertically and they flank the upper right edge of the target, the dots will trim off the nearby side. So, rather than seeing an 8, people will say they saw a 6.

The final one is object binding: if I present two dots next to a blank side of an object, people will sometimes bind the illusory edge with the target.

Based on our research findings, we believe that these are happening relatively early in the visual processing pathway, at the edge assembly stage.

(For examples of the illusions, visit: http://abacus.bates.edu/~tkahan/ot_demo.htm)

Q:  How will you be using these illusions?

A:  I am looking at whether cultural expectations will influence each of these. It would make sense that cultural expectations might influence object substitution masking since that illusion presumably occurs fairly late in the visual processing stream. What is less clear is whether cultural expectations will inform object trimming and object binding, which are pretty early in visual processing.

I am going to be collecting data at Bates College in Maine and then also at University of Queensland in Brisbane, Australia. Looking at object substitution masking, I might look at whether U.S. participants will get masking if they see a 5 that was preceded by a picture of Lincoln as depicted on the American $5 bill relative to if it was preceded by Queen Elizabeth as displayed on the Australian $5 bill. Will the cultural expectation of seeing a 5 make the number less susceptible to this type of masking? I am expecting that likely will happen because object substitution masking is fairly late in the game.

The question is what will happen with object trimming and binding? Will U.S. participants get more trimming if a 9 were trimmed to a 5 if preceded by Lincoln and the opposite for Australians? If that happens, that would suggest that these cultural expectations are percolating down to these really early stages of division and affecting how edges are bound together to form objects.

Q:  When you talk about culture, this is not race, but more about what country they were raised in? This is nurture, not nature.

A: You are right. I am looking at nurture, life experiences and cultural experiences and would they play a role. But that does not mean there is no role of nature but there is no data that suggests that or if gender might play a role.

Q: Not yet, anyway.

A:  Right. That could be future studies.

Q:  Even if it not immediately applicable to clinical use, what do we take forward from your work?

A:  It will tell vision researchers that the long standing dogma that culture doesn’t assert an influence on vision is wrong but also let us gain a better understanding of where in the visual processing stream culture exerts its role.

It is really basic science. When we think of psychology, we tend to look for applied significance where we might not look at that for other sciences. If we are studying the rings around Saturn or a fish that lives at the bottom of the ocean, people don’t wonder how that is going to affect their lives. Whenever we talk about people, the natural tendency is to ask – what are the applied aspects of that work?

Maybe it does have an application at some point, if people are having problems in vision or with Alzheimer’s or long-term memory. Those are super interesting questions which haven’t been explored yet.

But, my work is stages before that. 

By Catherine Robertson Souter

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