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An example of a part of a training set in a patchy environment. To emphasize the patchy structure of the environment, elements that belong to the two groups (group A{a,b,c,d,e} and group B{v,w,x,y,z}) were underlined by a different line style. Circles (red in online version) mark the occurrences of the reinforcer ‘f’ (food). (Online version in colour.)
