Are the Effects of Familiarity with the Size of a Novel Object on the Perception of Distance the Result of a Cognitive or Perceptual Process?

This study investigates the effects of familiarity and the size of a novel object on perception of depth. Familiar size is a visual depth cue that provides information about the distance of an object. This project explores if the familiar size illusion is a result of an automatic perceptual process or an intellectual thought process. This data was collected in two phases, a familiarization phase and a testing phase. The experimental participants were familiarized for 30 seconds with a novel object, while the control group was not shown any objects prior to presentation of test objects. The novel test stimuli were constructed in 5 sizes and participants in the familiar group were familiarized with the medium size object. Participants were then asked to indicate the perceived distance of different sized objects by moving a rod with a pointer at the end to match the distance. The smaller comparison objects subtended visual angles that participants had not previously experienced, while larger comparison objects produced a larger visual angle than the participants had seen during the familiarization phase. The testing phase was identical for both familiar and unfamiliar control groups. Apparent distance was influenced by the size of the objects. Larger objects were judged to be closer than the smaller objects. Participants not familiarized showed smaller effects of stimulus size than the familiarized group. The effect of familiarity was not significant for the smaller stimuli but was very significant for the larger stimuli. The results were not consistent with the cognitive theory which argues that familiar size is a result of a conscious thought process. These outcomes are predicted under the model of familiar size being an automatic perceptual process.