Abstract
Memory rarely replicates exactly what we see; instead, it reconstructs past experiences with distortions and errors. In some cases, memories lose their clarity and detail as time passes; in other cases, however, memories “add” details that weren’t originally there. Though such biases are more commonly associated with naturalistic visual scenes (which may recruit higher-level knowledge or schemas), here we show how memory adds content to even the simplest of stimuli: ordinary geometric shapes. We generated a library of smooth-edged shapes, and manipulated their complexity by gradually simplifying their skeletal structure — essentially altering the “amount of information” in the shapes. On each trial of Experiment 1, subjects saw a novel shape; after a brief delay, a version of the same shape appeared at a different level of complexity, and subjects’ task was to “adjust” the new shape to match the one they had just seen, using a slider that altered the adjustable shape’s complexity. Surprisingly, subjects consistently misremembered the shapes as more complex than they really were (i.e., the shapes they produced had increasingly informationally-dense skeletons). Experiment 2 showed that this finding emerges even at wider ranges of complexity, and Experiment 3 expanded this phenomenon further using the method of serial reproduction. In a “telephone game”, one observer’s recalled shape became the presented shape of the next observer, and so on; these reproduction chains amplified our observed complexity biases, such that 300 observers’ chains converged onto shapes much more complex than had initially been presented. Finally, Experiment 4 ruled out certain forms of strategic responding, finding that the patterns remained no matter the subject’s guess about the effect’s expected direction. These findings reveal a new “complexity bias”, whereby even the most basic units of visual processing are remembered as being more information-dense than they really are.