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Robert Nosofsky

October 10, 2012

Psychological and Brain Sciences Professor receives the 2012 Howard Crosby Warren medal for breakthrough research on categorization and memory

 

You may have had this experience: You are in a doctor’s office staring at a black and white photograph on a back-lit screen. The doctor is showing you an X-ray. Except that no matter how hard you look, you cannot make sense of what the doctor is pointing to. All you see is a blur of dark and light shadows.

The problem, Robert Nosofsky might tell you, is that to read an X-ray well, you need to look at hundreds of x-rays, thousands, maybe more, until finally you learn to “see” what is in them.That process of learning how to read an X-ray is a vivid instance of categorization–one of the fundamental ways our minds make sense of the objects, words, faces, and patterns in the world around us, how we learn to understand the thing we see. Learning to read X-rays is categorization writ large.

Nosofsky, a Distinguished Professor and Chancellor’s Professor of psychological and brain sciences at IU Bloomington, has constructed a highly influential mathematical model to explain and predict the mental operations by which categorization works.

According to his model, we store countless examples (of objects, words, faces, etc.) in our memory to form categories. Robins, sparrows, eagles, and hawks, for instance, are different things, but we learn to group them together. Like radiologists-in-training, we reach a point when we have seen enough examples of a certain category that making sense of a new object by placing it in a certain category becomes automatic. Categorization is a key facet of our mental architecture which enables us to make sense of what we see in a basic way.

In the laboratory, Nosofsky and his colleagues have determined the formal rules by which categorization works, developing mathematical models to explain and decipher the way our minds operate in those infinitesimal flashes of time in which we perceive an image. The models can predict, for example, how fast your mind will retrieve certain information as you categorize an object. The more similar an object in your memory is to the one perceived, for example, the faster it will be retrieved. By using sophisticated scaling techniques, Nosofsky’s research team can measure precisely the similarity between objects, and therefore use their models to predict the chances that a person will classify an object in a particular category.

They have also studied how people become experts, the process by which we learn to classify things automatically. Participants in the lab become quicker and quicker as they are shown more and more examples of a certain category, and as they accumulate these examples, like a radiologist, they become more skilled at classifying the objects shown to them.

In April this year Nosofsky traveled to Rice University in Houston to accept one of the oldest and most important awards given in experimental psychology, the Howard Crosby Warren Medal. The medal, “designed to honor and promote excellence in psychological science,” is awarded to scholars for research conducted over the past five years which forms the capstone of a prolific and influential career.

The award came in the wake of Nosofsky’s groundbreaking work in which he extended his model of categorization to another key domain in the fields of cognitive psychology and cognitive neuroscience: recognition memory.

While categorization involves placing an object in a particular category, recognition memory is the cognitive process by which we determine, “Is the object we are seeing old or new?” We look at a face, a word, or an object and determine whether or not we have seen it before. Like categorization, recognition memory is another cognitive function by which we perceive and make sense of the world around us in fundamental ways.

Previous theories hold that separate brain systems mediate categorization and recognition memory. Nosofsky has hypothesized that what goes on when people categorize things and when they recognize them are closely related. His theory proposes that “despite their different goals, the same mental processes are used to accomplish them. Categorization and recognition rely on similar mental representations and processes and on highly overlapping neural systems.”

Like an X-ray on the fluorescent screen, Nosofsky’s mathematical models of the psychological mechanisms by which we see or know the world offer up a new image of the mind.

“Memory is one of the most important processes in cognitive science. Likewise categorization,” Nosofsky says. “To have a model that understands both things in a unified way changes the way we understand the mind.”
–By Elizabeth Rosdeitcher

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