Using potential performance theory to analyze systematic and random factors in enumeration tasks

Prior research has shown that as the number of items being enumerated increases, performance decreases, especially when the amount of time is limited. Researchers studying nonverbal enumeration have found that random noise increases as a function of the number of items presented. Over a series of 2 experiments, the authors used potential performance theory to expand these findings and discover precisely how much random noise actually influences observed performance and what performance might look like in the absence of random factors. Participants briefly viewed a visual stimulus comprising a set of 4 to 9 dots presented horizontally (Experiment 1) or randomly (Experiment 2) on a computer monitor. Findings from both experiments indicate that the decrease in performance for larger set sizes resulted almost entirely from a reduction in consistency (or an increase in random noise), whereas potential performance remained fairly constant until the maximum set size.