Beckman HPP members report on role of memory in visual searches

A paper in the August issue of Psychology Press by several Beckman faculty members takes issue with the notion of memory free searches for items or locations within a display that have already been inspected.

A paper in the August issue of Psychology Press by several Beckman faculty members takes issue with the notion of memory free searches for items or locations within a display that have already been inspected.

The paper's co-authors include Beckman faculty Jason McCarley, Art Kramer, Ranxio Wang, and David Irwin, and graduate student Walter Boot. Basing their findings on eye-tracking data, they report in Oculomotor behaviour in visual search for multiple targets that test subjects do in fact use memory while performing these searches.

"Our eye-movement data showed that they are very much guided by some memory of where they've been, or at least their eyes are guided by where they've been," said McCarley, the paper's lead author. "What we showed was that what looked like the absence of memory or a memory-free search was actually a reduction in the size of the useful field of view, the functional field of view (FOV)."

The paper reports on test subjects' sampling behavior changes during oculomotor (the nerve that controls eye movements) scanning of images on a display screen.

"The oculomtor scanning is very much driven by memory, at least in our data," McCarley said. "The sampling changes, as we increase the task load or manipulate the tasks to make it a bit more demanding, show subjects tend to space their fixations more finely. They scan more coarsely, more broadly in the easier conditions and they sample the image more carefully in the higher load conditions."

Their findings contrast with a 2001 paper that hypothesized for memory-free searches.

"In our data we produced reaction times that were very similar to the data according to this other paper, but we showed that their original interpretation was inconsistent with the eye movement," McCarley said. "So I don't know if you can say it disproved their model but we've got an alternative and much more plausible explanation, and we've got eye movement data to back up our accounts."

The paper is part of a broader, long-term research line by those same Beckman faculty members, who are all members of the Human Perception and Performance group, involving the role of memory in guiding attention.