Interpreting Visual Preferences in the Visual Paired-Comparison Task Jenny Richmond Children’s Hospital Boston Michael Colombo and Harlene Hayne University of Otago Performance on the visual paired-comparison (VPC) task has typically been interpreted with E. Sokolov’s (1963) comparator model of the orienting response; novelty preferences are interpreted as evidence of retention, whereas null preferences are interpreted as evidence of forgetting. Here the authors capitalized on the verbal nature of human adults to clarify the interpretation of visual preferences in VPC performance. In 2 experiments, adults were tested on either the VPC task or a forced-choice recognition task after delays of 3 min to 12 months. In Experiment 1, adults tested on the VPC task exhibited novelty preferences after short delays, null preferences after intermediate delays, and familiarity preferences after long delays. In Experiment 2, adults tested on the forced-choice recognition task exhibited high levels of accuracy irrespective of delay, but the latency with which they recognized the stimuli increased systematically over the retention interval. These data are inconsistent with a simple Sokolovian inter- pretation of VPC performance and instead suggest that memory may be expressed as a novelty preference, null preference, or familiarity preference depending on the accessibility of the representation. Keywords: visual recognition, novelty preference, null preference, familiarity preference, memory The task of measuring memory in human infants is one that is fraught with difficulty. Unlike human adults, preverbal infants cannot draw on language to express their memory of a past event. As a result, researchers typically use infants’ nonverbal behavior as an index of their memory, relying on them to “show” us rather than “tell” us what they remember. Unfortunately, because of their limited motor skill, young infants can make use of only a small number of behaviors (e.g., sucking, leg kicking, visual fixation) to express their memory (for review, see Hayne, 2004). In addition, infants are often unpredictable research participants; their attention span is typically short, and their emotional state changes rapidly. For these reasons, nonverbal memory tasks must be brief; when the experimental session is long, attrition rates are often high. Further- more, rapid developmental changes in language, motor skill, and attention that occur over the first 2 years of life have made it difficult to design a single task that can be used to study memory development in infants of different ages. The visual paired-comparison (VPC) task is one memory task that can be used to study memory development across the infancy period. Although the VPC task was originally designed to study perception in developing primates (Fantz, 1956, 1958b) and hu- man infants (Fantz, 1958a; Fantz & Ordy, 1959), it has since been adapted to assess memory (Fantz, 1964). The VPC procedure typically involves two phases: a familiarization phase and a test phase. During the familiarization phase, the participant is pre- sented with a pair of identical visual stimuli for a fixed period of time or until a fixed amount of looking time has been accumulated. Following a delay, the participant is tested with another pair of visual stimuli; this time one stimulus is the same as the familiar- ization stimulus and one stimulus is novel. The amount of time that infants spend looking at each stimulus during the test is the primary dependent variable. Traditionally, retention in the VPC task has been inferred when participants look longer at the novel stimulus than at the familiar stimulus during the test (i.e., exhibit a novelty preference), and forgetting is inferred when participants look at both stimuli equally (i.e., exhibit a null preference). These inferences are derived from Sokolov’s (1963) comparator theory of the orienting response. According to this theory, novel stimuli elicit an orienting response; visual fixation is one component of that orienting response. During the familiarization phase of the VPC task, the participant presum- ably forms an internal representation of the target stimulus. With continued exposure to the stimulus, further detail is added to the representation until encoding is complete. Once the participant’s internal representation matches the external stimulus exactly, the stimulus ceases to elicit an orienting response and the participant no longer attends to that stimulus. During the test phase of the VPC task, the familiarization stimulus is paired with a novel one and looking at both is com- pared. According to Sokolov’s theory, the degree to which each stimulus elicits attention during the test is a function of the dis- crepancy between the internal representation of that stimulus and its external reality (Sokolov, 1963). Provided that the familiariza- tion period was sufficient for the participant to form a complete representation, the familiar stimulus should no longer elicit an orienting response and the bulk of the participant’s attention should be directed toward the novel stimulus. Thus, when a fa- miliar and a novel stimulus are presented together, the participant Jenny Richmond, Laboratory of Cognitive Neuroscience, Children’s Hospital Boston; Michael Colombo and Harlene Hayne, Department of Psychology, University of Otago, Dunedin, New Zealand. This research was supported by Royal Society of New Zealand Marsden Grants UOO-014 and UOO-040 awarded to Harlene Hayne and Michael Colombo and a Bright Future Top-Achiever Doctoral Scholarship awarded to Jenny Richmond. Correspondence concerning this article should be addressed to Jenny Richmond, Laboratory of Cognitive Neuroscience, Children’s Hospital Boston, 1 Autumn Street #713, Boston, MA 02215. E-mail: jenny.richmond@childrens.harvard.edu Journal of Experimental Psychology: Copyright 2007 by the American Psychological Association Learning, Memory, and Cognition 2007, Vol. 33, No. 5, 823– 831 0278-7393/07/$12.00 DOI: 10.1037/0278-7393.33.5.823 823