Eye-movements and search-time of four subjects were studied as they searched for a target-dial in a 4 x 4 array of dials which were differentiated either by (1) color, (2) shape, (3) a combination of color and shape, or (4) were uncoded. Search-time varied reliably between conditions: it was generally shortest in the colorcondition, followed by color-shape, shape, and the uncoded condition. Subjects were capable of using both shape and color simultaneously. There was no difference in ratios of increase of search-time for color and shape as the target was situated more peripherally, and there was evidence that shapes, if properly chosen, might be as effective a coding device as color. Searchtime was strongly associated with the average number of fixations required for target-detection but not with other measures of eyemovements. Subjects did not exhibit a reliable or characteristic scanpath, and method of scanning' did not relate to search-time.
Eye movements were recorded while subjects viewed ordinary portraits and photographic negatives of those portraits. Under both conditions they first studied sixteen portraits and then tried to decide which of forty-eight portraits they had just seen. They made more errors of recognition while viewing negatives, and their fixation patterns were significantly altered: there was a decrease in the percentage of fixations directed to the eyes, nose, and mouth, and an increase for such details as the ears, cheeks, chin, cap, and necktie. There was also a decrease in the ratio of fixations to the most fixated detail compared to the least fixated detail.
31. M. L. Hair (private communication) states that, at pressures of 16 torr and above, the very rapid increase in the amount of absorbed water makes it difficult to make precise measurements, and a fairly broad range of values for the number of molecules absorbed per hydrogen-bonded hydroxyl pair may be indicated. Hair's failure to produce anomalous water may have been due to the special nature of the surface treatment, which may prevent a clustering of hydroxyl pairs sufficient to form successive layers. Fortunately all that is needed for understanding the formation process is identification of hydrogen-bonded surface hydroxyl pairs with an increased absorption under the pressure condiitons favorable to the formation of anomalous water.Hair also proposed the anomalous water geometry given in Fig. 4h, but this has a higher energy than either squares or planar hexagons. 32. Even though the asymmetric cyclic hexamer has a per-bond binding energy comparable to, or slightly greater than, tetrahedral coordination, its geometry is not favorable for formation of the normal liquid because of its very low entropy relative to the tetrahedral arrangements. 33. There is a further decrease in the free energy, due to the lower vibration frequency, hence the higher entropy, of the symmetric hexamer over the asymmetric hexamer. 34. L. Pedersen and K. Morokuma, J. Chem. Phys. 46, 3941 (1967). 35. When an anomalous-water bond is broken, the energy of the conformation immediately after breakage is close to that of a symmetric bonded chain. A concerted motion of each. symmetric hydrogen to a corresponding asymmetric position is highly unlikely because of the between-layer interconnections.
Eye movements and search time of four subjects were studied as they searched for a target dial in a 4 x 4 array of dials which were differentiated by (1) color, (2) shape, (3) a combination of color and shape. or (4) were uncoded. Subjects did not exhibit a characteristic scanpath, and method of scanning did not relate to search time. Search time varied reliably among conditions; it was generally shortest in the color condition, followed by color shape, shape, and the uncoded condition. Subjects were capable of using both shape and color simultaneously. Search time was strongly associated with the average number of fixations required for target detection but not with other measures of eye movements. Fixation duration was a particularly inconsistent measure.Noton and Stark (1971 a. b) have reported that a given individual will show a reliable pattern of eye movements under different viewing conditions. Gould and Peeples (1970) have noted that each subject generally uses the same scanning pattern throughout n experiment. Locher and Nodine (1974) have found that at least some subjects exhibit a characteristic scanpath when perusing a given random shape. But it is not clear if differences in visual search patterns are related to differences in searching performance. That is. do individuals who can quickly search out targets have distinctive scanpaths compared to less efficient searchers '! A second set of questions is concerned with the effects of the stimulus variables. Is an individual who is good in one condition also good in other conditions? Little is known about how the character of the nontarget stimuli affects the search for the target. There have been a number of studies which have investigated search time as a function of the amount of information available or the amount of irrelevant information (Archer. 1954; Baker. Morris and Steedman. 1960:
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