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. 2017 Feb 8;4(2):160994.
doi: 10.1098/rsos.160994. eCollection 2017 Feb.

Do rats learn conditional independence?

Robert Ian Bowers  1 , William Timberlake  2
Affiliations

Do rats learn conditional independence?

Robert Ian Bowers et al. R Soc Open Sci. .

Abstract

If acquired associations are to accurately represent real relevance relations, there is motivation for the hypothesis that learning will, in some circumstances, be more appropriately modelled, not as direct dependence, but as conditional independence. In a serial compound conditioning experiment, two groups of rats were presented with a conditioned stimulus (CS1) that imperfectly (50%) predicted food, and was itself imperfectly predicted by a CS2. Groups differed in the proportion of CS2 presentations that were ultimately followed by food (25% versus 75%). Thus, the information presented regarding the relevance of CS2 to food was ambiguous between direct dependence and conditional independence (given CS1). If rats learnt that food was conditionally independent of CS2, given CS1, subjects of both groups should thereafter respond similarly to CS2 alone. Contrary to the conditionality hypothesis, subjects attended to the direct food predictability of CS2, suggesting that rats treat even distal stimuli in a CS sequence as immediately relevant to food, not conditional on an intermediate stimulus. These results urge caution in representing indirect associations as conditional associations, accentuate the theoretical weight of the Markov condition in graphical models, and challenge theories to articulate the conditions under which animals are expected to learn conditional associations, if ever.

Keywords: Markov condition; Rattus norvegicus; associative learning; causal reasoning; conditionality; graphical models.

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Figures

Figure 1.
Figure 1.
(a–c) Three network structures that predict responding to CS2, any of which may feasibly be acquired with serial compound conditioning (CS2, followed by CS1, followed by US). The analysis applies whether the edges are directed (left to right) or undirected.
Figure 2.
Figure 2.
Presence on the feeder platform over the 5 days of extinction during lever presentations, tone presentations (first day only), and baseline recordings for group 75%+ (hollow lines) and group 25%+ (filled lines). Bars show s.e.m.
Figure 3.
Figure 3.
Lever contact during lever presentations over the five days of extinction. Bars show s.e.m.
See this image and copyright information in PMC

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