Many-to-one matching with temporal and hedonic samples in pigeons

Pigeons were initially trained with either temporal samples (2- and 8-s key lights) or hedonic samples (food and no food) mapped to line-orientation (h orizontal and vertical) comparisons. Delay testing revealed marked retentio n asymmetries in both groups (i.e., a choose-short effect with temporal sam ples and a choose-no-food effect with hedonic samples). Next, while both gr oups continued training on the original task, a second set of samples was a dded, hedonic for birds originally trained with temporal samples and tempor al for birds originally training with hedonic samples. For all birds, food and short samples were associated with one comparison, and no-food and long samples were associated with the alternative comparison (many-to-one, MTO, mapping). This time, delay testing revealed symmetrical retention function s in both groups with both sets of samples, and mediated-transfer testing r evealed positive transfer. It was concluded that (1) a common code was used to represent samples associated with the same comparison in the MTO mappin g and (2) the content of the codes was unrelated to the identity of the sam ples. (C) 2001 Academic Press.