Individual Differences in Attention During Category Learning

Michael D. LeeUC Irvine

Ruud WetzelsUniversity of Amsterdam

Kruschke (1993) Condensation Experiment

8 stimuli varying in their box height and interior line position

Divided into 2 categories, so that both dimensions are relevant

40 participants did 40 blocks of trials with corrective feedback

Generalized Context Model

Results of Standard GCM Analysis

Marginal posterior over the attention parameter indicates both dimensions are important Familiar story, and a strong temptation to stop

there …

Posterior Predictive

“Violin plots” of posterior predictive for each stimuli, together with aggregated data (black line) and individual data (broken lines)

Types of Individual Differences

Allowing for Individual Differences

Continuous individual differences are modeled by drawing subject parameters from an over-arching hierarchical distribution

Discrete individual differences are modeled as a latent mixture, so different subjects can be drawn from different group distributions

Let WinBUGS do the heavy lifting, check chains for convergence, etc, …

Results of Individual Differences Analysis

Suggests there are two groups, with different attention

Bayes Factor

Savage-Dickey method gives approximate Bayes Factor of 2.3 in favor there being two groups (rather than one)

“artist’s impression”

Posterior Predictive Distribution

Posterior predictive distributions of categorization behavior are qualitatively different tracks people’s behavior at both the sub-group

and individual level

Interpretation of Groups

The two groups are shown in the panels The bars show the number of “A” vs “B”

category decisions made for each stimulus

Interpretation of Groups

The group on the left pays attention to position, and so makes mistakes with stimuli 4 and 5

Interpretation of Groups

The group on the left pays attention to position, and so makes mistakes with stimuli 4 and 5

The group on the right pays attention to height, and so makes mistakes with stimuli 2 and 7