3.1.2. Task

The task used in this study was an EEG analogue of the fMRI task used in the pilot. Stimuli in this task consisted of three categories of football defensive formations, with two categories being very visually similar to each other and one category being visually distinct from the other two. For the two similar categories, the subjects needed to discover an explicit counting rule to reliably categorize members of these two groups. For the visually distinct category, subjects could rely on a simple visual similarity analysis to recognize members of this category. Within each category, all of the players were shu ffled around the field of view with the exception of the players on the line of scrimmage, as the number of players on the line dictated category membership (Figure 10). This forced subjects to focus their attention to the line of scrimmage over time while ignoring irrelevant players that are positioned elsewhere on the field.

**Figure 10.** From bottom-left to top right: A fixation cross was shown for 2–3 s. Formations were shown for 2 s while subjects made their response. Immediately following a response, contingent feedback was shown for 1.5 s. Upon feedback termination, a fixation mark was shown for the duration of the inter-trial interval of 2–3 s before the next formation was presented.

Every category had three formations, each sharing the defining number of players on the line of scrimmage for that category, for a total of nine formations used throughout the experiment. On a given trial, the participants were randomly shown one of the nine formations for 2000 ms and they were

instructed to place the stimulus into one of the three categories by pressing a button on a response box within the stimulus exposure window. Once they made a response the stimulus disappeared, and the subject was presented with a corrective feedback screen, which indicated whether they were correct along with text describing the correct category for the stimulus (Figure 10). The feedback was on the screen for 1500 ms, after which a fixation cross with a variable inter-stimulus-interval was shown for 2000–3000 ms. The task was divided into eight training blocks that consisted of 90 trials (or 10 exposures per stimulus) per block, which totaled 80 exposures of every stimulus throughout training.

After the final training block, a generalization block was used, which tested each subject's ability to apply any rules they developed during training to novel stimuli similar to the fMRI pilot. During the training block, a mixture of the nine training stimuli and nine novel stimuli belonging to the same categories were used. The subjects were not told that the generalization block would include novel stimuli. No feedback was given to the participants after pressing a button to categorize each formation. Instead, a black screen was shown for 1500 ms after a response was made before the fixation cross appeared to begin the next trial. Each old and novel stimulus (18 total stimuli) was shown five times for a total of 90 trials in the generalization block.
