Context Model Bayesian Exemplar Models Neural Networks Medin

Context Model, Bayesian Exemplar Models, Neural Networks

Medin and Shaffer’s ‘Context Model’ • No category information -- only specific items or exemplars. • Evidence for category A given probe p: EA, p = Si in a. S(p, i)/(Si in a. S(p, i) + Si in b. S(p, i)) • Where S(p, i) = Pj (Pj = Iij ? 1: aj) ; aj = c, f, s, p • Prob. of choosing category A given probe p: PA, p = EA, p

Medin and Shaffer’s ‘Context Model’ • No category information -- only specific items or exemplars. • Evidence for category A given probe p: • EA, p = Si in a. S(p, i)/(Si in a. S(p, i) + Si in b. S(p, i)) • Where • S(p, i) = Pj (Pj = Iij ? 1: aj) ; aj = c, f, s, p • Probability of choosing category A given probe p: • PA, p = EA, p

Some things about the model • Good matches count more than weak matches • An exact match counts a lot • But many weak matches can work together to make a (nonpresented) prototype come out better than any exemplar • Dimension weights like ‘effective distance’ (or maybe ‘log of effective distance? ’ • If weight = 0, we get a categorical effect • Dimension weights are important – how are they determined? – Best fit to data? – Best choice to categorize examples correctly?

Independent cue models For items 1, 2, 3 and 7:

Neural Network Model Similar to Context Model Within each pool, units inhibit each other; between pools, they are mutually exictatory if neti(t) > 0 else Choice rule:

What REMERGE Adds to Exemplar Models Recurrence allows similarity between stored items to influence performance, independent of direct activation by the probe. X

Bayes/Exemplar-like Version of the Remerge Model inpi Hedged softmax function: Logistic function: Choice rule:

Acquired Equivalence (Shohamy & Wagner, 2008) • Study: – – – F 1 -S 1; F 3 -S 3; F 2 -S 1; F 2 -S 2; F 4 -S 3; F 4 -S 4 • Test: – Premise: F 1: S 1 or S 3? – Inference: F 1: S 2 or S 4?

Acquired Equivalence (Shohamy & Wagner, 2008) • Study: – – – F 1 -S 1; F 3 -S 3; F 2 -S 1; F 2 -S 2; F 4 -S 3; F 4 -S 4 • Test: – Premise: F 1: S 1 or S 3? – Inference: F 1: S 2 or S 4? F 1 S 1 F 2 S 2 F 3 S 3 F 4 S 4

Acquired Equivalence (Shohamy & Wagner, 2008) S 1 S 2 S 3 S 4 • Study: – – – F 1 -S 1; F 3 -S 3; F 2 -S 1; F 2 -S 2; F 4 -S 3; F 4 -S 4 • Test: – Premise: F 1: S 1 or S 3? – Inference: F 1: S 2 or S 4? F 1 S 1 F 2 S 2 F 3 S 3 F 4 S 4

Acquired Equivalence (Shohamy & Wagner, 2008) S 1 S 2 S 3 S 4 • Study: – – – F 1 -S 1; F 3 -S 3; F 2 -S 1; F 2 -S 2; F 4 -S 3; F 4 -S 4 • Test: – Premise: F 1: S 1 or S 3? – Inference: F 1: S 2 or S 4? F 1 S 1 F 2 S 2 F 3 S 3 F 4 S 4

Acquired Equivalence (Shohamy & Wagner, 2008) • Study: – – – F 1 -S 1; F 3 -S 3; F 2 -S 1; F 2 -S 2; F 4 -S 3; F 4 -S 4 • Test: – Premise: F 1: S 1 or S 3? – Inference: F 1: S 2 or S 4?