Processing time as influenced by the number of elements in a visual display

Abstract

In a visual-detection experiment. a display of severalletters was presented. and S was to report the presence or absence of a given target letter. Results clearly are incompatible with a selfterminating visual-scanning process as hypothesized by Sternberg (1967). Two models are considered. a serial exhaustive scanning process and a parallel exhaustive process, but findings from the present study do not provide a basis for differentiating between them.In several experiments, Taylor (1964, 1966) have studied the visual-detection process for the case in which S searches for one of a predesignated pair of letters (signal or critical elements) imbedded within a tachistoscopically presented display of noise letters. A forced-choice design was used with S responding that he saw one or the other of the critical elements on every trial, even if the detection was uncertain. The models proposed to account for the results assume S samples a proportion of the letters present on each trial, and then serially scans through them to determine which target letter was included in the display. If the target letter is among the letters sampled, S makes the appropriate response after processing the critical element. If, however, the target letter is not included among the elements sampled on that trial, S guesses one of the two alternatives. These models accurately predict an increase in error rate with an increase in the number of noise elements in the display, but a deeper analysis of the scanning process is difficult to achieve using their data primarily because of the somewhat random placement of letters within the display and the lack of latency measures.By measuring response latencies in a similar experiment, Estes and Wessel (1966) were able to demonstrate that error latencies remain essentially constant across display sizes, indicating that S continues processing elements in searching for a match with one of the target letters until some temporal criterion is reached (perhaps the point at which the registered image of the display has decayed beyond usefulness in extracting information), at which point S guesses. The data also indicated that the search process might terminate with a correct response as soon as the target letter is processed. Estes and Wessel based both of these latter inferences upon latency data that had been corrected for guessing, admittedly leaving definite conclusions about the nature of the scanning process for further research.Using a different paradigm, Sternberg (1966) has presented evidence for serial and exhaustive scanning of elements stored in memory. On each trial S was given a list of one to six digits to remember. A single test digit was then presented, and S responded by pulling an appropriate lever to indicate whether or not the test digit matched any of those in memory. In this experiment there were virtually no errors, allowing latency scores to be used without correction. Plotting latency against memory set size, Sternberg was able to draw two important conclusions: (a) The data could be...

Visual search through color displays: Effects of target-background similarity and background uniformity

“…An angular target letter was more easily detectable in a context of curved letters than of other angular letters, but this advantage was reversed when a curved target letter was specified. The effects of visual confusability between target and background have been confirmed in several more recent studies (e.g., Atkinson, Holmgren, & Juola, 1969;Corcoran & Jackson, 1977; Estes, 1972; Kaplan, Yonas, & Shurcliff, 1966;McIntyre, Fox, & Neale, 1970).…”

Response latency in visual search with redundancy in the visual display

“…The error rates at all display sizes were negligible. These results suggest that the visual processing involved in the Atkinson et al (1969) task includes some type of exhaustive comparison process; i.e., Ss compare all items in the display with some internal representationof the critical item regardless of whether or not the display contains a 123 critical letter. In contrast, Estes's assumption of a primary detection response implies that on at least a portion of the trials a response occurs before all items are processed.…”

“…investigate latencies in a yes-no task with a very low error rate. Atkinson, Holmgren, and Juola (1969) have used this type of task to look at the effect of number of letters, in a visual display on response latency. The Ss were shown a critical letter at the beginning of each trial.…”

Role of outcome conflict in dual-task interference.

“…One variable was display size: Ther were one or two words presented on each channel. This manipulation was expected to influence the difficulty of each single task in isolation, based on the standard result that search arme increases with the number of items to be searched (e.g., Atkinson, Holmgren, & Juola, 1969). V The second inc. oendem variable was the semantic relatedness of the nontarget words to the target categories.…”