Relevant and Irrelevant Saliency in Concept Learning

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Two concept-learning experiments are reported. The first compared performance under three stimulus configurations: with the two relevant dimensions highly salient; with two irrelevant dimensions highly salient; and with no highly salient dimensions. Performance was best when the relevant dimensions were highly salient, next best when two irrelevant dimensions were highly salient, and poorest when there were no highly salient dimensions. The second experiment explored several possible explanations of these results, which are contrary to existing notions of the effects of irrelevant saliency. Its results suggest that the presence of highly salient irrelevant dimensions improved performance because the subjects examined them in the early trials of the experiment and then could permanently eliminate them from further consideration. It is now generally accepted that variations in the saliency, vividness, or obviousness, of the stimulus materials have an important influence on human learning.1 Several different methods have been used in the attempt to manipulate saliency. One common method, called perceptual isolation, is to make some aspect of the stimulus material stand out by making it perceptually or conceptually unique. The effects of isolation are commonly identified with the name of von Restorff, who introduced isolation in a seriallearning task by embedding a single number in a list of nine syllables.2 The number was learned faster and retained better than the same number embedded in a more heterogeneous list containing other numbers, syllables, and nonsense forms. Received for publication March 9, 1970. This research was supported in part by Research Grants MH-11283 and MH-18249 from the National Institute of Mental Health, United States Public Health Service. 1 T. Trabasso and G. H. Bower, Attention in Learning, 1968; W. P. Wallace, Review of the historical, empirical, and theoretical status of the von Restorff phenomenon, Psychol. Bull., 63, 1965, 410-424. 2 H. von Restorff, Ueber die Virkung von Bereichsbildung im Spurenfeld, Psychol. Forsch., 18, 1933, 299-342.