Non-target Item Research Articles

Picture Recognition: A Human Factors Study of Four Illustration Types

Documentation and job aids for the installation and assembly of mechanical apparatus have traditionally made extensive use of figures and illustrations. Evidence suggests that using illustrations to supplement text instructions will be effective only if the illustrations they contain can be quickly and accurately understood. Surprisingly, there has been little research on what makes a good technical illustration. The present study was designed to see what effect illustration type has on performance in a task which primarily involves recognition. Twenty individuals with education or work experience in mechanical drawing and twenty individuals without such experience took part in the study. Each group consisted of equal numbers of male and female participants. Stimulus materials for the experiment were 16 geometric objects of uniformly high colorfulness assembled from two or more Playskool® Bristle Blocks in various combinations and four 35-mm slides depicting four illustration types for each of the 16 stimulus objects. The slides showed the four types of illustration of each stimulus object: a color photograph, a black and white photograph, an isometric line drawing, and a perspective line drawing. Objects were evenly divided among four complexity levels according to a pilot scaling study. Sixteen blocks of slides were presented tachistoscopically on a back projection screen. They appeared in the same orientation and subtended approximately the same visual angle as the objects. In each block, half of the slides showed one of the four illustration types, a target item, and half depicted a non-target item. Before each block, the participant studied one object for 10 seconds. After each slide, the participant was asked to judge from memory whether or not the slide depicted an object just seen. Response time to each slide as well as ‘yes’ and ‘no’ responses were recorded. Results showed that all the interesting effects occur for target items. Of greatest interest is the significant effect of illustration type on recognition time. Photographs resulted in faster recognition than line drawings and color photographs were faster than black and white photographs. We also found that increasing object complexity increased the time to recognize illustrations of that object.

Information processing in a binary classification task.

Three choice-reaction time studies were conducted to investigate whether information processing is exhaustive or self-terminating, serial or parallel, and N-dependent or N-independent. A total of 54 subjects were required to make key-pressing responses to one, two, or three digits presented in a circular display; one key was pressed if the display contained one or more target digits and another key was pressed if the display contained only nontarget digits. The first two studies utilized within-subjects designs in which the displays were constructed from only one target and one nontarget item (Study 1) or from three target and seven nontarget items (Study 2). The third study used a between-subjects design in which different groups of subjects responded to one-, two-, or three-element displays. In general, the results indicate that CRTs increased as the total number of display elements increased and decreased as the number of target elements (or the ratio of target to nontarget items) increased for a given display size. When only target elements were presented, CRT was independent of the number of elements displayed, and when only one target was presented, CRT increased as total number of elements increased. Theses combined results are interpreted as support for the inference that information processing in visual search tasks tends to be self-terminating, serial, and N-dependent (of limited capacity).

Processing of repeated letters in search and matching tasks

Several published experiments have used a variant of the matching or “same”-“different” paradigm in which the subject indicates whether or not all of the items in a visual array are the same. Contrary to the results of most paradigms in which subjects process multiple items, reaction time (RT) in this matching task is independent of the number of items in the display (N). One possible explanation of this independence holds that subjects respond to some overall property of the display, such as its general symmetry, and not to the individual items. I tested this hypothesis with a visual search task in which subjects searched a circular display of N=2, 4, or 6 letters for a specified target letter under three stimulus conditions. In the varied condition, the nontarget letters were all different from each other. In the repeated condition, the nontargets were repetitions of the same letter, but a single discrepant letter was always present in the display. The uniform condition also used repeated nontargets, but the negative (target-absent) displays contained N repetitions of a single nontarget item. I found that RT increased at a rate of 27 msec/item for the varied condition, but at only 13 and 8 msec/item in the repeated and uniform conditions, respectively. The slopes in the latter conditions were significantly lower than the slope for the varied condition, and they also differed significantly from each other. Hence, there was some advantage attributable to properties of the overall patterns associated with positive and negative responses, suggesting that at least some responses were based on these properties. There was a much larger advantage, however, attributable to the use of repeated nontargets, regardless of whether the overall patterns differed. This latter observation implies that the flat RT functions observed in matching studies must be interpreted primarily in terms of responses to individual items rather than to the pattern as a whole.