Scientists sometimes have an idea, then spend years before they fully understand it or appreciate its importance. So it was with the idea that defined much of my career. I believed for many years that I had that idea sometime in 1973 or 1974, and that I immediately embarked on a program of research to explore and test it. Decades later, however, a colleague showed me that the idea was stated quite clearly in an article I had published in 1969; I was very surprised.

There was in the air at the time a notion that perception involves the separate analysis of different features, including shape, color, orientation, and motion, which could be separately attended to. The notion of separate analyzers raised a question, which is now known as the “binding problem”: how are the separate features recombined into representations of the objects that we perceive and recognize? For example, imagine a display consisting of a red T and a green X. The color analyzers register the presence of two colors and the shape analyzers register two shapes. How does the observer know which color goes with which shape?

The solution that occurred to me was that a spotlight of attention travels over the visual field, binding together the features that it finds in each location as it passes through it. The features that are present in that location are perceived as belonging to the same object. The features are known to be present even before the spotlight visits their location, but they are free-floating, not localized in space. If the scene contains yellow objects and squares, for example, I immediately know that there is yellow somewhere and a square somewhere, but I can only know that there is a particular yellow square in a particular place by bringing the spotlight of attention to that place.

Many psychological ideas can be understood by referring to our subjective experience, and psychologists often develop hypotheses by examining their mental life. This was not the case for my solution to the binding problem, which involved events that occur without any awareness and that are not directly represented in mental life. You are surely not aware of your attention scanning the visual scene at a very rapid rate, much faster than the rate at which you can move your eyes.