Public Release: 

The human visual system is 'smart,' drawing on experience to interpret visual information

American Psychological Association



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WASHINGTON -- Every student of introductory psychology has seen figure-ground pictures, those ambiguous illustrations that demonstrate the flexibility of human perception. Is it a light goblet or two dark profiles? An elegant lady with a feather in her hat, or a vase? These figure-ground pictures are important to understanding how people make sense out of their visual environments, and act on what they perceive. Now, three University of Iowa psychologists have systematically documented that people usually see what falls in the lower region of a figure-ground picture as the "figure," not the "ground."

They report their findings in the June issue of the Journal of Experimental Psychology: General, published by the American Psychological Association (APA). The article covers eight experiments whose results consistently confirmed that people pick what constitutes the lower, not upper, region of a display as the "figure," not the "ground," at rates greater than chance.

The findings reveal the ongoing power of perception to guide us through a world in which everyday visual scenes contain multiple objects that often overlap and partly occlude one another. The perceptual system gives figures special treatment: People hold figures in short- and long-term memory longer than grounds; figures seem more salient than grounds; figures have a definite shape but grounds are shapeless; and figures are perceived as being closer to the viewer.

The researchers, led by Shaun Vecera, Ph.D., ran groups of five to 12 participants through a series of eight experiments that used two-color figure-ground displays to assess figure-ground preferences and investigate their source. The researchers found that lower-region preference was independent of whether the figure-ground display was placed in the upper or lower visual field; participants continued to defined "lower" relative to the horizon line.

Vecera and his colleagues suspect that the lower-region preference arose because in the real world, regions that fall below the horizon are physically closer. The perceptual system then uses this knowledge to interpret figure-ground displays. "The shared contour that separates upper and lower regions acts as a horizon," says Vecera, "and we perceive the lower region as the figure because it falls below the horizon line."

He adds, "Many perceptual phenomena are easily overlooked in everyday life because our visual systems are extraordinarily efficient. The lower-region preference provides a glimpse at one part of this behind-the-scenes work."

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Article: "Lower Region: A New Cue for Figure-Ground Assignment," Shaun P. Vecera, Ph.D.; Edward K. Vogel, Ph.D.; and Geoffrey F. Woodman, Ph.D., University of Iowa; Journal of Experimental Psychology - General, Vol 131, No. 2.

Full text of the article is available from the APA Public Affairs Office and at http://www.apa.org/journals/xge/press_releases/june_2002/xge1312194.html

Shaun Vecera can be reached by email at shaun-vecera@uiowa.edu or by phone at (319) 335-0839.

The American Psychological Association (APA), in Washington, DC, is the largest scientific and professional organization representing psychology in the United States and is the world's largest association of psychologists. APA's membership includes more than 155,000 researchers, educators, clinicians, consultants and students. Through its divisions in 53 subfields of psychology and affiliations with 60 state, territorial and Canadian provincial associations, APA works to advance psychology as a science, as a profession and as a means of promoting human welfare.

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