Stimulus structure, discrimination, and interference.

Subjects learned lists of consonant trigram word pairs varying in intralist formal stimulus similarity. On test trials, subjects were tested with all but one stimulus, then presented either the missing stimulus or one previously tested. Subjects had to correctly identify this stimulus, then recall its associated word. Both recall and recognition performance varied with the difficulty of discovering and utilizing a discriminated element. However, when subjects were instructed as to list structure, recall was improved without improvement in recognition in one condition, and recognition was improved without recall in another. This indicates that stimulus discrimination is neither necessary nor sufficient to reduce intralist interference.