Effects of training procedure on memory formation using a weak passive avoidance learning paradigm.

One-day-old chicks will learn, in one trial, to avoid pecking a bead that tastes aversive. This procedure is used widely as a model for learning and memory, although a variety of training procedures and bead types are used in different laboratories. Here we report that the decay of memory following training on a weak (10% methylanthranilate) avoidance task is dependent on the training procedure rather than the characteristics of the beads or the strain of chick used. Chicks that have been presented with a bead in pretraining and a similar bead coated in MeA during training fail to avoid the bead when tested 2 h posttraining, whereas chicks presented with a bead of particular color and size for the first time at training demonstrate high levels of avoidance at 2 h posttraining. These results resolve the differences in the time course of memory formation for a weak passive avoidance task described by the groups at Monash University (Crowe, Ng, & Gibbs, 1989) and the Open University (Sandi & Rose, 1994).