S scanned a list of random letters looking for 1 to 5 target letters, which were read to him just before the list was presented. His scanning rate was estimated from a graph of the time required to find a target at different positions in the list. The more targets S was seeking, the more slowly he scanned. The time spent processing each non-target letter in the list increased in direct proportion to the number of targets for which S was searching.

The >S"' s task was to list all the 4-letter words he could make up from a set of 5-10 different letters. Responses occurred rapidly at first and then more slowly as S exhausted his store of words. When S had more letters to work with, he could generate a greater total number of words, but took longer to produce any given fraction of them. Thus with 5 letters, 5 found 80% of his limit of 8 words in less than 5 min., whereas with 10 letters, S took more than 15 min. to find 80% of his limit of 43 words. The results were analyzed in terms of a model that compared the retrieval of information from memory to a search process.

Magnitude estimates were obtained for the dissimilarity of pure tones varying in frequency and intensity. In Expt. 1, a spatial embedding for a set of seven tones was determined by assuming the magnitude estimates represented distances in a two-dimensional space whose coordinate axes were pitch and loudness. Embeddings were determined for both Euclidean and "city-block" distance functions. A linear relation was consistently observed between the projections of the tones on dimensions of pitch and loudness and their values on Stevens's mel and sone scales, with the city-block projections usually yielding higher correlations. In Expt. 2, 11 tones were used and the magnitude estimates of dissimilarity were compared to the tightly constrained "monotone" distances derived from the rank-order properties of the dissimilarities. The agreement observed between the magnitude estimates and the monotone predicted distances strongly supports a distance interpretation for the dissimilarities.

2 experiments examined the relationship between search time and number of targets searched for. The 1st experiment photographed S's eye movements as he compared 2 groups of letters to determine whether one was a subset of the other. The time spent searching the containing set increased in proportion to the number of target letters it contained. In this case, search time included the time spent recognizing all the targets. The 2nd experiment photographed S's hand movements as he canceled just-learned target letters in English text.Here search time was measured so that it excluded the accumulation of recognition times. Search time still increased with the number of targets being sought.