On-line catalogs are replacing card catalogs in libraries. This paper reviews research covering the catalog's human-machine interface with emphasis on the difficulties of subject searching. Study 1 replicates previous findings that subject searching, though most often used, is the most problematic type of searching. In Study 2, the organization of the Library of Congress Subject Headings is compared with the knowledge structures of subject experts, subject novices, and librarians. Experts and novices in cognitive psychology differ from each other and from the subject heading structure, but librarians fall in between the two groups. The structures derived are used in Study 3 to predict the success of searching done by subject area novices and experts as well as by librarians. Experts in cognitive psychology find target books more easily than novices, but differences between librarians, subject experts, and subject novices are due to system experience, not subject expertise.

Consumer product risk perception research has traditionally employed adult subjects assessing adult risk, but little work has explored children's perceptions. Because adults structure the environment of children, it is important to understand not only how children assess risk for themselves, but how adults assess risk for children and how adults think children assess risk. This study examined the risk perceptions of 7-8 year old children and the perceptions which parents and non-parents have for and attribute to children. It was found that adults see the world as more hazardous for children than for adults, but predict that children do not see the hazards. Children do recognize product hazards, but do not see the world as hazardous as adults see it for them, nor do they see it as hazard-less as adults predict they will. This suggests that adults' mental framework, while inaccurate, is still likely to encourage children's safety.

Piloting and many related control activities, especially remote manipulation via teleoperations and robotics, stand to benefit substantially from better means of communication between controller and controlled. We have investigated one such approach: the use of augmented displays on a cathode ray terminal (CRT) for controlling simulated motion in microgravity. Such displays, which have been shown to be highly effective in a variety of applications, provide information to the operator which goes beyond that which is found in nature, and thereby emphasize important aspects of a task and minimize irrelevant ones. Using this approach, we attempted to develop stylized graphical displays, incorporating augmented feedback by distorting the background of the scene under display, for purposes of flight control and/or control of a robotic arm. Besides attempting to utilize transformations of the scene itself for informational purposes, the displays we developed represent significant departures from previous methods in two notable respects. First we have attempted to design our instrumentation to make use of peripheral rather than exclusively foveal vision, thus broadening the bandwidth of perception by vision. Second, we attempted to incorporate optical illusions intended to enhance the perception of depth and apparent motion to provide better and more compelling feedback for the operator performing the task. Data from a small group of subjects suggest that the illusion of depth produced significantly better performance in that this was faster, had fewer errors, and interfered less with a secondary task (all correlations were significant, with p $<$.0001), while the main effect for peripheral vision was not significant but other evidence suggests it improved performance nonetheless. A second experiment indicated that while pilots' acquisition of task skills differed significantly from nonpilots' (p =.00078), optical illusions augmenting the effect of depth and of motion induced profound differences in performance (p =.000006), although masked by practice effects, etc., and in control motion (p =.000006) where this augmented feedback eliminated any tendency to overcontrol in pilots and nonpilots both.

It has been hypothesized that social influence processes are altered in computer-mediated-communication (CMC) due to the lack on non-verbal information available across a computer. In these three studies, confidence ratings were used in an attempt to replace some of the non-verbal cues lost in CMC. Subjects participated in group decision making tasks in which the distribution of preferences and confidences were simulated. The results of these three experiments suggest that confidence ratings do not have an effect on an individual's preference decision but may be used to assess one's probability of persuading the other members of the group. The confidence ratings did not increase the probability of a group reaching a consensus decision. In addition, the results suggest that communication patterns in CMC are altered and, together with the lack of non-verbal cues, may result in changes in the social influence process.

It has been theorized that leadership recognition is the product of an automatic categorization process in which individuals compare a set of observed behaviors to a leadership prototype and then, given a sufficient match, automatically recognize the target individual as a leader (Lord, Foti, & DeVader, 1984). The first goal of this research was to test this theory. A second goal was to investigate three potential moderators of the cognitive processes mediating leadership recognition: information load, need for leadership, and time delay. Three experiments were conducted in which subjects assumed the role of a work team coordinator for a small computer company. Their task was to identify an individual to fill an opening in a work team. During a study phase, subjects read a series of behavioral descriptions that were taken from recommendations written about former employees and one job candidate. A test phase followed in which the primary task was Jacoby's (1991) process-dissociation procedure (PDP), a recognition memory that generates estimates of automatic and controlled processes. Results from the experiments revealed that leadership recognition was mediated by a combination of automatic and controlled processes, with the balance clearly favoring automatic processes. That is, individuals operated in a primarily unintentional, unavoidable, and effortless manner when processing and integrating behavioral information about a potential leader. This balance of automatic and controlled cognitive processes was moderated by subjects' perceptions of the extent to which the work team needed a leader (Experiment 2 - Need for Leadership). Specifically, high-need-for-leadership subjects employed a more focused strategy of information processing than did their low-need counterparts. They appeared to expect and to give less scrutiny to behaviors that were consistent with leadership (increase in automatic processes), and to work more diligently to make sense of and integrate behaviors that were irrelevant to leadership (increase in controlled processes). The general primacy of automatic processes found in these experiments suggests that individuals are adept at forming impressions of potential leaders. This ability to identify leaders in a primarily effortless fashion is largely adaptive in light of the attentional scarcity that characterizes much of everyday life.

The present paper reviewed the literature supporting and contradicting three theories of categorical perception in speech; the specialized speech processor theory, the cue duration theory, and the acoustic percept theory. Three experiments were then carried out to further investigate these theories. The first experiment compared subjects' perception of speech and three types of nonspeech stimuli (simple nonspeech, complex nonspeech, and reverse speech) and the effect of training on subjects' ability to discriminate these stimuli. The second experiment, dealt with a failure to replicate Pisoni (1977) using complex speech stimuli with the same parameters. The third experiment, compared speech and nonspeech perception in aphasic patients. Results failed to lend support to the specialized speech processing theory. Support for the cue duration theory and acoustic percept theory was mixed.

In trouble-shooting, subjects choose the order in which they test hypotheses. This choice often involves a trade-off between the time it takes to test a hypothesis and the probability that the hypothesis is correct. In visual search, subjects may have to choose which of two displays they are going to search first. The trade-off is similar in that the display most likely to contain the target may take longer to search. A series of experiments investigated whether subjects are efficient in the way they trade-off the size of a visual display and the probability it contains the target. Subjects were presented with information about the size of each of two displays and their respective probabilities of containing the target. The task was to choose which display to search first and then conduct the search as rapidly as possible. The first experiment showed that subjects did follow specific patterns of display choice, and that subjects have a strong tendency to overweigh probability information. Experiment 1 also showed that subjects generally fail to take into consideration the effect of highlighting the target. When a target is highlighted, the size of the display has a negligible effect on search time and therefore should make the size of the display unimportant in choosing which display to search. The display choice of most subjects was uninfluenced by target highlighting. Experiment 2 used a wider range of display sizes to see if that would make display size more salient and possibly induce subjects to pay more attention to it. As in Experiment 1, subjects paid too much attention to the probability that a display contains the target and not enough attention to the time it takes to search the display. Three methods of training subjects to consider the time to test a hypothesis when choosing hypotheses were evaluated in Experiment 4. Even though the surface characteristics of the training materials and the visual search task differed, training did improve subjects' performance on the visual search task. The relative neglect of the time it takes to test hypotheses may be a general phenomenon.

Behavior as related to occupational danger was explored in this research by examining industrial workers' reactions to accidents they had on the job. An observational study was conducted using longitudinal data to investigate relationships between hypothesized antecedent conditions and the occurrence of accidents at a large petrochemical refining and manufacturing complex. Models were developed that indicated the extent to which job-related injuries affected the duration of subsequent accident-free periods prior to another accident. Results indicated that a worker's job category and cumulative accident history as well as characteristics associated with previous accidents reliably influenced accident propensity. The tendency to be involved in accidents was unrelated to seasonal or weekly influences. Results are discussed in terms of the relative magnitude of various system factors on accident liability. It is anticipated that the theoretical and analytical techniques employed will be useful in developing strategies for clarifying the mechanisms through which workers perceive, assess and respond to danger in the workplace and enhancing decisions with regard to the targeting of prevention efforts.

As the use of graphical user interfaces expands into new areas, icons are becoming an increasingly important aspect of GUIs. Oddly, little research has been done into the costs and benefits associated with using icons. A set experiments was conducted in which various attributes of icons were examined, including simple icon borders, icon "quality" and set size (number of "distractor" icons). An eye tracking study of the task was also conducted to examine the icon search strategies of computer users. Based on the results of the studies, two models were then constructed in ACT-R/PM to carry out the same task as in the experiments. The final iteration of the models was predictive of human performance in icon search tasks. Insights into icon design and computational modeling of icon search are discussed.

Research has shown that one type of common procedural error, postcompletion error, occurs systematically under high working memory load. Studying the effects of different interventions on this reproducible and well-explained error type may help extend our understanding of the underlying psychological mechanisms behind human error and interactive task behavior. Experiment 1 was an investigation of the error-reducing efficacy of a simple visual cue and a separate downstream error cost condition. While neither was found to be reliably effective, this inquiry provided valuable insight that led to a follow up study. In Experiment 2, a cue based on design guidelines and a mode indicator were implemented to explore possible reasons for why the previous interventions failed. Only the cue had a reliable effect, demonstrating the difficulty of designing a successful intervention. Finally, a computational model based in ACT-R was developed to provide theoretical demonstration of this finding.