Imagined pictures possess 3-D properties.

Imagined pictures possess 3-D properties

A vivid passage in a book often prompts a reader to paint a mental picture of the scene. Now a study in the March JOURNAL OF EXPERIMENTAL PSYCHOLOGY: GENERAL suggests these mental paintings are spontaneously rendered on a three-dimensional canvas. Moreover, objects lying in certain directions are easier to uproot from memory when a person searches an imagined landscape.

People mentally construct an imaginary space around themselves based on three dimensions, or axes, report Nancy Franklin of the State University of New York at Stoney Brook and Barbara Tversky of Stanford University. For an upright observer, imagined objects above or below the body run along a vertical axis from the head to the feet and are easiest to recall, followed by objects in front or behind the body running alone one horizontal axis and objects to the left or right running along a second horizontal axis.

"It looks like this is a powerful [mental strategy] to organize space that we use whenever we can," Franklin says.

The data contradict two theories of memory for three-dimensional information. One asserts memory is equally fast for objects in all directions, when the distance of each object from the observer is the same. The other theory holds that memory is quickest for objects in front of an observer, with more time needed as objects move to the sides and to the back.

Franklin and Tversky had 77 college students read narratives in which five objects are located around the reader along the three landmark axes. In one narrative, "you are standing next to the railing of a wide, elegant balcony" and objects are described above, below, in front, behind and to the right of the reader. The narrative was then presented again, one sentence at a time, on a computer screen. The computer periodically instructed the students to shift their orientation in the scene -- say, turn 90 degrees to the right -- and identify object locations by pushing specific numbers on the keyboard.

After discarding the few errors the study participants made on this task, the researchers found students were fastest to locate objects above or below the imagined observer, slower to locate objects in front of or behind the observer, and slowest to locate objects to the left or right. If the students imagined themselves reclining, rather than standing, the directional bias shifted, with objects in front and behind recalled faster than those along the head-to-foot axis, which were recalled faster than objects to the left and right.

For an upright observer, Franklin notes, the vertical dimension is defined by the environment--the ground and the sky -- and objects remain "above" or "below" as the observer moves about. The horizontal dimensions depend on more arbitrary reference points, thus creating some confusion when the body's orientation shifts. The reclining observer is not aligned along the vertical axis, so visible, easy-to-reach objects in front of the body and behind are easier to recall, Franklin maintains.

This research may spur the redesign of airplane cockpits to improve pilot performance and offer strategies to rewrite textbooks on subjects requiring the visualization of accompanying diagrams, such as physics, Franklin says.