Guided Search: The Effects of Learning

The previous report (Efron & Yund, 1996) offered an interpretation of the results of a number of search experiments within the theoretical context of the guided search model of Cave and Wolfe (1990) and Wolfe (1994). The present report extends this interpretation to the effects of extended practice when subjects search for a target defined by its orientation in the presence of a number of heterogeneous distractor items having differing orientations. Three experiments are described: The first revealed that over the course of 21 experimental sessions extending for a period of 6 weeks there were marked decreases in the magnitude of the reaction time gradient (RTG) and the right visual field superiority observed in the previous experiments. This learning persisted for more than 3 years. The second experiment revealed an interference in the capacity to learn to detect a target of one orientation when subjects had previously learned to detect a target of a different orientation at the same locations. The third experiment revealed that the learning was restricted to the area of the visual field where the target had been presented and that subjects could learn to detect two different targets concurrently. The results of these experiments indicate that the learning is orientation-specific and location-specific and is consistent with a localized increase in the selectivity of the top-down selection mechanism of the guided search model.