Holyoak Pilot Specs

Categorization Task

Stimuli: Each stimulus is a 10X10 grid of red or black squares against white background. Should measure about 1 cm per square (total size 10 cm X 10 cm).

Categories: Stimuli fall into 3 categories, designated A, B, and C. For each category, at the very beginning separately generate a prototype (same prototype is used for every subject). To generate a prototype, simply assign each of the 100 squares to be either black or red (p=0.5, independently). Do this only one time when you make the program, rather than at run time. So now you have prototype A, prototype B, and prototype C and those are fixed across the whole experiment. (Save them because we may use them in followup experiments.)

Generating stimuli: All stimuli are generated by copying the prototype and then randomly perturbing the stimulus as follows:

1. Determine whether the stimulus should be A, B, or C (independent prob=1/3 for each).

2. Now create a stimulus as follows:

for x = 1 to 100;

with probability perturb_prob flip the square from its color in the prototype to the other value red->black or black->red;

end;

Thus, each square within the stimulus is the same as its prototype with a probability (1-perturb_prob). To start with, let’s set perturb_prob to .15. This is a pilot to determine if that number works well.

Procedure for an individual categorization trial:

1. select stimulus

2. present plus sign in center for 500 msec

3. present stimulus until response

4. present feedback (confirmation tone if right; error tone if wrong together with “The Correct Answer was A” or whatever it was).

5. Pause 1 second before next trial.

Trials.

This is a pilot experiment. We just want to have 6 subjects do this experiment for 300 trials with feedback and see how they do.

Data File

One row per trial:

<Trial#; What prototype was used, A, B, or C; Subject’s response; Correct vs. Wrong>