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.

译文

如果获得的关联要准确地表示真实的关联关系,则存在这样的假设的动机,即在某些情况下,学习将被更适当地建模,而不是作为直接依赖,而是作为条件独立性。在连续复合条件调节实验中,向两组大鼠提供了条件刺激 (CS1),该条件刺激不完全 (50%) 预测食物,而cs2本身则不完全预测食物。组在CS2呈现的比例上有所不同,最终跟随食物 (25% 与75%)。因此,关于CS2与食物相关性的信息在直接依赖和条件独立性之间是模棱两可的 (给定CS1)。如果大鼠得知食物有条件地独立于CS1,则两组的受试者此后应与单独的CS2类似。与条件性假设相反,受试者关注了CS2的直接食物可预测性,这表明大鼠甚至将CS序列中的远端刺激视为与食物立即相关,而不是以中间刺激为条件。这些结果敦促在将间接关联表示为条件关联时要谨慎,在图形模型中强调马尔可夫条件的理论权重,并挑战理论以阐明期望动物学习条件关联的条件 (如果有的话)。

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