Possible response strategies
The same–different categorization task can be performed in many different ways. First, the participants could separately categorize each stimulus on the screen and then
compare their category labels. If both stimuli are assigned to the same category, the participant responds ‘‘Same’’. Otherwise, the participant responds ‘‘Different’’. This
strategy could lead to perfect accuracy if the categories are learned correctly. However, it is also possible that participants will not categorize the stimuli separately—either because they are unable to learn the adequate category representations or because they simply opt for another,possibly simpler, strategy. Two strategies that do not require separately categorizing each stimulus are similarity-
based strategies and guessing strategies. One way for participants to use a similarity-based strategy is to compare the distance between the two stimuli in perceptual space to a threshold. Distances smaller than the threshold would elicit a ‘‘Same’’ response, whereas distances greater than the threshold elicit a ‘‘Different’’ response. This strategy is likely to be suboptimal because with many categories,there will be stimuli that are more similar to some stimulus in the contrasting category than to other stimuli in the same category. Another strategy, which is obviously suboptimal,
but exceedingly simple, is to just guess. Our analysis includes fitting computational models that will attempt to identify which of these strategies was used by each
participant.