Abstract
The perception of dynamic visual stimuli can be influenced by various factors. For example, auditory input can alter the perceived timing of a visual stimulus (Recanzone, 2009; Welch & Warren, 1980). Leibowitz (1985) suggested that larger real-life objects were perceived to be moving more slowly. The current study investigated the impact of the stimulus size (Experiment 1) and the presence of a pure tone auditory stimulus and its frequency (Experiment 2) on the perceived speed. In both experiments, two random dot kinematograms (RDKs) appeared sequentially for 200 milliseconds with a 500 milliseconds gap. The sizes and speeds of the dots in the reference RDK were constant, while the speed in the test RDK varied across trials. The task was to report which of the RDKs was perceived to be consisting of faster-moving dots. The dot sizes (small, medium, big) in the test RDK and the auditory stimulus accompanying the test stimulus (high-frequency pure tone, low-frequency pure tone, no sound) were manipulated across trials in experiments 1 and 2 respectively. The percentages of trials that test RDKs were reported to be faster than reference RDKs were fitted to a psychometric function for each level of the dot size (Experiment 1) and the auditory stimulus (Experiment 2). The main dependent variable was the point of subjective equality (PSE). The dot size had a significant effect: the mean PSE in the big-dot condition was lower than in the small-dot condition (Experiment 1). The effect of the auditory input was not statistically significant (Experiment 2). Contrary to the previous findings (Barton & Cohn, 2007; Clark et al., 2013, 2016; Leibowitz, 1985), we concluded that bigger objects, such as dots, were perceived to be moving faster than smaller objects. However, the presence of an auditory stimulus, or its frequency, did not influence the perceived speed.