The mere exposure effect with real world objects: Exposure duration and prototypicality

The mere exposure effect refers to the phenomenon that simple repeated exposure to a stimulus is sufficient to enhance its affective evaluation (Bornstein, 1989). This preference for familiarity typically has been investigated in relation to meaningless stimuli, with application to real world objects a relatively neglected area of research. Real world objects vary on a number of dimensions other than prior exposure that influence affective appraisal, such as the degree of prototypicality. While it has frequently been found that people prefer stimuli that are prototypic over those that are not (Reber, Schwarz, & Winkielman, 2004), little attention has been given to the combined effects of prototypicality and repeated exposure on affective evaluations. The current research, therefore, aimed to examine the mere exposure effect to real world objects varying in prototypicality. Interestingly, the mere exposure effect has been found in instances where conscious recognition was precluded, with some suggestion that the effects produced by subliminal stimuli are stronger than those produced by stimuli that are clearly recognized (Bornstein, 1989). However, few studies have tested this directly, and the findings are mixed. To clarify the role of exposure duration in the exposure-affect relationship, a second aim was to compare subliminal versus supraliminal effects. It was found that existing methods of rapid visual stimulus delivery are unreliable at delivering stimuli at rapid durations. A new apparatus, a light-emitting diode (LED) tachistoscope, was constructed and verified as capable of accurately and reliably displaying visual images at durations as rapid as 1 ms (Thurgood, Patterson, Simpson, & Whitfield, 2010). The brief presentation time is achieved by a liquid crystal display (LCD) that is illuminated externally by a brief LED flash after LCD steady-state is reached, such that image onset and offset timing can be precisely controlled. The equipment was validated on a human sample through a visual perceptual task involving the identification of animals (Thurgood, Whitfield, & Patterson, 2011). In the current mere exposure study, participants were repeatedly exposed to pictures of prototypic and non-prototypic chairs for either 1 ms or 1000 ms. These ‘old’ stimuli were then presented again, together with similar but never-before-seen ‘new’ equivalents, and each stimulus was rated for liking and recognition. At both 1000 ms and 1 ms, old stimuli were liked more than new, providing evidence that the mere exposure effect typically displayed for meaningless stimuli also extends to meaningful stimuli. There was no differential effect of exposure duration and the effect of repeated exposure was the same for prototypic and non-prototypic stimuli; however, the means were generally in the direction for favouring prototypic stimuli. Unexpectedly, at both 1000 ms and 1 ms, old stimuli were rated significantly higher for recognition than new stimuli. Thus, the 1 ms stimuli were not actually subliminal. The findings indicate that when using accurate display equipment, the visual system is more efficient at extracting information than previously thought. Furthermore, the LED tachistoscope opens up new avenues for visual perceptual research and provides a means for uncovering the limits of human visual perception.