An associative-mediation hypothesis predicts that associations between stimuli sharing a common response will facilitate learning, while the same associations between stimuli or responses paired with different responses or stimuli will interfere with learning. An experiment was conducted to test each of these predictions. In Exp. I, four pairs of strong bi-directional associates were learned as ... [Show full abstract] stimuli to digit responses; the members of each pair were assigned a common response. Control lists were constructed by substituting a nonassociated word for one member of each pair of associates. Intralist association significantly facilitated learning. In Exp. II, the same words were employed as stimuli or responses to digits, but each word was paired with a unique digit. Under these conditions, intralist association significantly retarded learning.