If you've ever been captivated by an M.C. Escher drawing of stairways that lead to nowhere or a waterfall that starts and ends at the same place, then you are familiar with what Psychologists describe as "impossible" objects and scenes. These are pictures or illusions of three-dimensional images that do not make any visual sense. Inevitably, we end up gawking at the image for several moments, attempting to make sense of the impossible.

These images are, of course, mere deceptions that result from our ability to create three-dimensional objects from two-dimensional images. An artist will use techniques such as shading, shadow, texture and the like to give his or her image a three-dimensional quality and sometimes, as in Escher's case, to confuse our ability to perceive them.

So when do we develop this ability to perceive coherence in three-dimensional objects? New York University perception researcher Sarah Shuwairi and her colleagues are now attempting to use this natural propensity to gaze at images of impossible objects to pinpoint when human infants develop the ability to perceive three-dimensional shape information from two-dimensional images.

To do this, Shuwairi enlisted 30 4-month-old infants to take part in a series of related experiments. With the help of their parents, the infant subjects sat in front of a computer screen that displayed alternating "possible" and "impossible" three-dimensional images. In the process, the researchers recorded how long the infants looked at each of the objects. As the reasoning goes, if the infants are sensitive to the visual features that give images a three-dimensional quality, they will inevitably gaze at the images that make no sense just as adults do; that is, they will stare at impossible objects longer.

The result was that infants looked significantly longer at impossible figures, suggesting that that as young as 4-months-old, humans have the ability to detect at least some three-dimensional features that give rise to the perception of object coherence.

Shuwairi explains that these findings, the first to document such abilities so early in development, "provide important insights into the development of mechanisms for processing pictorial depth cues that allow adults to extract 3D structure from pictures of objects." Ultimately, the implications of the research extend beyond the ability to be perplexed by visual impossibilities as researchers now have an additional tool to explain how infants develop an understanding of the physical world around them.

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Psychological Science is ranked among the top 10 general psychology journals for impact by the Institute for Scientific Information. For a copy of the article "Discrimination of Possible and Impossible Objects in Infancy" and access to other Psychological Science research findings, please contact Catherine West at the Association for Psychological Science .

Contact: Sarah Shuwairi
Association for Psychological Science