In Brief

When switching from one task to another, people often fail to completely prepare to perform the new task, indicates research appearing in April's Journal of Experimental Psychology: Human Perception and Performance (Vol. 31, No. 2). The research challenges previous claims that people preparing for a task switch either completely--without cost to response time or accuracy--or not at all.

The study's authors, Oregon State University psychology professor Mei-Chen Lien, PhD, and NASA Ames Research Center colleagues Eric Ruthruff, PhD, Roger Remington, PhD, and James Johnston, PhD, hope their research will eventually aid astronauts who juggle multiple tasks--monitoring displays, working with computers and the like--when flying shuttles.

In one trial, researchers tested their "partial-mapping preparation" hypothesis by having 18 undergraduates view four boxes in a two-by-two grid on a monitor. A colored shape, such as a red triangle, would appear in one box for four seconds. Participants had to press one of three computer keys that corresponded with either the object's color (red, green or blue) or shape (diamond, square or triangle). Participants used the same three keys for both object and color tests.

For the top boxes, half the participants pressed a key corresponding with the object's color. For the bottom boxes, they pressed a key corresponding to the object's shape. The researchers explained to participants that the object would first appeared in top left box, then in subsequent trials would appear in the box clockwise from most recent trial. The design assured that participants had to switch between focusing on the object's shape and color after every two trials.

The authors hypothesized that, when switching to a new task, participants would prepare to process and respond to only a few of the possible stimuli. For example, when getting ready to switch from the shape task to the color task, people might just prepare a response to the color "red." If the stimulus were red, participants would respond fast, but if it were blue or green, their response would be nearly as slow as if they hadn't prepared at all.

The researchers found no switch cost for whichever stimulus was listed first in the instructions, but large switch costs for the other stimuli--results consistent with the hypothesis. Were the all-or-none preparation hypothesis correct, Lien says, participants should have produced similar results for each stimulus.

This is true when participants had a time deadline. In another experiment, the colored shape moved rapidly toward a dot in the center of the screen. Participants had to respond before it reached the center, yet they still performed slowly whenever the task switched between color and shape. The finding suggests participants aren't lazy--they simply can't fully prepare for a task switch.

"People prepare for a task much better by doing it rather than by thinking about doing it," Lien explains. The research is part of a larger program exploring how to help NASA crews perform better when multitasking, such as by modifying the display in the shuttle cockpit.