Visual search and immediate memory.

Abstract

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.

Strategies and Models of Selective Attention

“…However, he allowed high error rates, which may have changed the nature of the task to some extent. Very similar experiments Carvellas 1965, Kaplan, Carvellas, andMetlay 1966) have shown serial rather than parallel functioning. Neisser's task also showed an e¤ect of the number of targets when Ss were asked to search for their absence (''which line has no Q or H'') as if they had to check the presence of each of the set of targets serially, while in the earlier tasks their absence could be noted in parallel for the whole set.…”

“…If Ss were unable to set themselves for particular targets in a search task, the number of relevant targets should have no e¤ect on search time. Since such an e¤ect has been clearly demonstrated, for example, by Sternberg (1966) and by Kaplan et al (1966), we must conclude that Ss can restrict their analysis to features relevant to the task. The ability to do this often improves considerably with practice, provided that the target chosen makes it possible potentially to select a subset of tests for critical features (Rabbitt 1964).…”

Perceptual Selection and Integration

“…One is from experiments on scannin g, which has an obvious affinity to type (c) tasks : the subject scans through a list of, say, letters or words to note the presence or absence of particular items. The time taken has been found to increase with the number of different possible items from amongst which those actually shown are drawn (Oostlander andde Swart 1966, Gordon 1968), with the number of different items being sought in anyone scan (Kaplan and Carvellas 1965, Kaplan et al 1966, Nickerson 1966, and when the definition of a class of words or other items sought is wide rather than narrow (Foster 1962, Neisser andBeller 1965).…”

Searching for Multiple Targets and Age

“…In other studies, many exemplars of targets occur in a list and the task is to cross out each of them. With unpracticed subjects, search time slows with an increase in the number of targets (Kaplan, Carvellas, & Metlay, 1966) although the increase in time is not always linear. Neisser, Novick, and Lazar' (1963) and Shurtleff and Marsetta (1968) have shown that after large amounts of practice, search time is independent of the size of the target set.…”