MonkeyCantab User’s Guide
Publisher: Cambridge University Technical Services Ltd (distributed by Lafayette Instrument)
Pages: 100
Subject: CANTAB-style cognitive testing battery for non-human primates (touchscreen-based)
Relevant Section: Dimensional Shifting (pp. 65-68)
Dimensional Shifting in Humans
Typical dimensions might be colour, shape, and number. A famous example is the Wisconsin Card Sorting Test (Grant & Berg, 1948, J Exp Psychol 38: 404), in which subjects sort cards with a variable number of coloured shapes and must discover the sorting rule solely by reinforcement. The rule is then changed:
- Reversal: switch from “red correct, blue wrong” to “blue correct, red wrong”
- Intradimensional shift: new set of colours to learn (same dimension)
- Extradimensional shift: switch from “blue correct, red wrong” to “circles correct, squares wrong” (different dimension)
Dimensional Shifting in Non-Human Primates
Two typical dimensions are “blue shapes” and “white squiggly lines” (Dias, Robbins & Roberts, 1997, J Neurosci 17: 9285-9297). A large number of exemplars are used in each dimension.
Basic Test Sequence (General Case)
Two dimensions, A and B, with a large catalogue of objects. Each object has a value for each dimension (or “undefined”).
- Simple discrimination — objects possess dimension A but not B. A=1 correct, A=2 incorrect.
- Simple reversal — reverse: A=1 incorrect, A=2 correct.
- Compound discrimination — introduce dimension B but ignore it. Continue A discrimination.
- Reversal of compound — reverse A discrimination, still ignore B.
- Intradimensional shift — new values of A (A=3 correct, A=4 incorrect); B still ignored.
- Extradimensional shift — switch attention to dimension B, ignore A. B=1 correct, B=2 incorrect.
Irrelevant dimensions caveat: When a dimension is present but being ignored, ensure p(correct) does not depend on its value. A dimension can be made irrelevant by holding it constant (e.g., always purple background) or randomizing it (e.g., randomizing left/right position).
Required stimulus library categories:
- A=1; B=undefined
- A=2; B=undefined
- A=1; B=anything except undefined (constant or randomized)
- A=2; B=anything except undefined
- A=3; B=anything except undefined
- A=4; B=anything except undefined
- A=anything except undefined; B=1
- A=anything except undefined; B=2
Having many objects per category encourages extraction of general features (e.g., learning “red is correct” rather than “red triangle is correct”). This approach is used in primate tasks but not in rat tasks.
MonkeyCantab Test Sequence
| Stage | Stimuli |
|---|---|
| Simple discrimination | A1(+), A2(-) |
| Reversal | A2(+), A1(-) |
| Compound discrimination | A1/B1(+), A2/B2(-); A1/B2(+), A2/B1(-) |
| Reversal | A2/B1(+), A1/B2(-); A2/B2(+), A1/B1(-) |
| ID shift | A3/B3(+), A4/B4(-); A3/B4(+), A4/B3(-) |
| Reversal (optional) | A4/B3(+), A3/B4(-); A4/B4(+), A3/B3(-) |
| ED shift | B5/A5(+), B6/A6(-); B5/A6(+), B6/A5(-) |
| Reversal (optional) | B6/A5(+), B5/A6(-); B6/A6(+), B5/A5(-) |
Criterion: typically 6 consecutive correct responses (configurable). Left/right position randomised per trial. Presentation order of alternative pairs randomised in pairs of trials.
Rat Set-Shifting (Birrell & Brown, 2000)
Birrell & Brown (2000, J Neurosci 20: 4320-4) implemented a digging-bowl set-shifting task with dimensions of odour, filling medium, and surface texture. They used a “total change design” (all stimuli changed at ID/ED shifts). Medial frontal cortex mediates perceptual attentional set shifting in the rat.
Predefined Stimuli Style
The experimenter creates compound stimuli manually using arbitrary dimensions (colour/number, colour/shape, shape/line, etc.). Requires one object per category: A1, A2, A1/B1, A1/B2, A2/B1, A2/B2, A3/B3, A3/B4, A4/B3, A4/B4, A5/B5, A5/B6, A6/B5, A6/B6. If compound stimuli can be generated by superimposing simple stimuli, the Superimposed Stimuli Style saves work.