BLOCKING IN THE SPATIAL DOMAIN

An initial series of experiments with rats in a swimming pool establis hed that they could find a hidden platform the location of which was d efined in terms of 3 or 4 landmarks and that, when trained with all 4, any subset of 3 (or even, after a sufficient number of swimming trial s, 2) landmarks was sufficient to produce accurate performance. When o nly one landmark was present during testing, however, performance fell to chance. Two additional experiments demonstrated a significant bloc king effect: If rats were first trained to locate the platform with 3 landmarks, they did not learn to use a 4th landmark added to their ini tial set of 3.