Flexible Processing in Procedural-Based CategorizationW. Todd Maddox1, J. Vincent Filoteo23 & Grant C. Baldwin1

1University of Texas; 2Veterans Medical Research Foundation, and 3UCSD

Introduction

– Much evidence supports the existence of neurobiologically distinct category learning systems [e.g., 1 – 4].

– Procedural-based system: mediated by the tail of the caudate nucleus and best suited for (nonverbalizable) information-integration category learning.

General Methods

Conclusions

References[1] Ashby, F. G., Alfonso-Reese, L. A., Turken, A. U., & -Waldron, E. M., (1998). A neuropsychological theory of multiple systems in category learning. Psychological Review, 105, 442-481.[2] Ashby, F. G., & Maddox, W. T. (2005). Human Category Learning. Annual Review of Psychology, 56, 149-178.[3] Maddox, W. T., & Ashby, F. G. (2004). Dissociating explicit and procedural-learning based systems of perceptual category learning. Behavioural Processes, 66(3), 309-332.[4] Smith, E.E., Patalano, A.L., & Jonides, J. (1998). Alternative strategies of categorization. Cognition, 65, 167-196.[5] Ashby, F. G., & Gott, R. E. (1988). Decision rules in the perception and categorization of multidimensional stimuli. J Exp Psychol Learn Mem Cogn, 14(1), 33-53.

http://homepage.psy.utexas.edu/homepage/group/MaddoxLAB/

Aims of Study

– (A; see above) Category representation component: Many-to-one mapping from visual areas to the tail of the caudate.

– (B; see above) Stimulus-label compatibility component: System associates a response label with a region of perceptual space

– Caudate to globus pallidus

– To determine whether there are different stages of procedural-based category learning.

–To determine whether these stages are differentially impacted by:

– Stimulus shifts in the perceptual space

– Stimulus-label switches

– Both

– To determine the flexibility of re-learning following these experimental manipulations.

– Participants: Healthy young adults.

– Task: Perceptual categorization task [5].

– Single line stimulus. Length and orientation vary across trials.

– Trial procedure:

– Session Procedure:

– 3 100-trial “pre-change” blocks

– 3 100-trial “post-change” blocks

Stimulus Response Feedback"Correct, that was an A"

or

"Wrong, that was an A"

Post-Change Information-Integration Categories

– Pre-change performance equated.

– More post changes lead to better re-learning.

Perceptual Shift Exp.

– Different stages of procedural-based categorization are differentially impacted by perceptual shifts and stimulus-label switches.

– Breaking cortico-caudate connectivity (through perceptual shifts) leads to a large initial performance cost, and slowed re-learning.

– Breaking the caudate–pallidal connectivity (through stimulus-label switches) leads to a small initial cost, and slowed relearning.

– Breaking the cortico-caudate-pallidal connectivity leads to a large initial performance cost, but fast relearning.

Summary– Perceptual shift cost larger than stimulus-label switch cost.

– The more “locked in” the larger the cost for perceptual shift, but not stimulus-label switch.

– Despite larger initial costs, the more post changes, the better post-change learning.

Results

Pre-Change Information-Integration Categories

Response Keys

A B C D

AB

Post-Change Cost

0

0.1

0.2

0.3

PerceptualShift

Stimulus-Label Switch

Shift/Switch

Post-Change Condition

Pos

t-C

hang

e C

ost

(Pre

3 -

Pos

t1)

ns

* *

Pre-Change/Post-Change Learning

0

0.1

0.2

0.3

PerceptualShift

Stimulus-Label Switch

Shift/Switch

Post-Change Condition

Lea

rnin

g

Pre-Change (Pre3-Pre1)Post-Change (Post3-Post1)

Pre-Change Training

Length

Ori

enta

tion

Post-Change Control

Length

Ori

enta

tion

Perceptual Shift

Length

Ori

enta

tion

Stimulus-Label Switch

Length

Ori

enta

tion

Shift/Switch

Length

Ori

enta

tion

Perceptual Shift (Close)

Length

Ori

enta

tion

Perceptual Shift (Far)

Length

Ori

enta

tion

Post-Change Cost

0

0.1

0.2

0.3

Close Medium Far

– Perceptual shift leads to bigger cost than stimulus-label switch.

– Is pre-3 accuracy predictive of cost?

– Yes, if a perceptual shift (rPS = .55, rSS = .41)

– No, if stimulus-label switch (rSLS = -.14)

Performance Curves

0.40.50.60.70.80.9

1

Pre1 Pre2 Pre3 Post1 Post2 Post3Block

P(C

orr)

ControlPerceptual ShiftStimulus-Label SwitchShift/Switch