As part of a continuing investigation of the conditions associated with operating irregularities in air traffic control (ATC), reports prepared during the investigation of 301 operating irregularities were analyzed in order to identify the factors most likely to precipitate air traffic control incidents. Operating irregularities were found to occur more frequently under conditions of moderate or low workload and normal complexity. A second objective of the work has been to develop a database system from which statistical data on operating irregularities and the various identified factors can be extracted. However, in order to enhance the integrity of the descriptive information in the database, the category structure that has been used to record the occurrence of ATC incidents is being revised to reflect the contemporary approaches to human error. A brief description of the proposed structure is included in the present paper.

This study examined the effects of arousal, induced by alcohol and white noise, on the free recall of intentionally learned words and incidentally learned word-locations, in the presence or absence of word-order cues. The Activation-Deactivation Adjective Check List, a self-report measure of arousal showed that noise affected the tension dimension of arousal, whereas the moderate alcohol dose primarily affected the energy dimension of arousal. That the low dose exerted an arousing effect was evidenced by an increase in tension but only when combined with noise. When word-order was randomized over trials, noise improved word-recall and counteracted the deleterious effect of the moderate alcohol dose. When order remained fixed, however, the moderate dose impaired recall, and at that dose recall was worse under noise. Location-recall was impaired by the moderate dose, and it was superior when word-order remained fixed. It was concluded that recall was influenced by arousal mechanisms and that perceived task demand and consequent effort were possible factors contributing to the obtained effects.

Two experiments investigated the effectiveness of four methods for coding the operational states of targets in a process control task, under different levels of display density and inspection load, with search and identification tasks. In Experiment 1 subjects monitored one parameter (temperature) that could have four coded states. In Experiment 2 subjects monitored two parameters (temperature and oil level), each of which could have two coded states. Compared with partially redundant color coding or shape coding, color + shape coding and color coding led to quicker response time (RT) in a search task and mitigated the detrimental effects of increased display density. In addition, RT was faster with partially redundant color coding than with shape coding. Coding, however, had no effect on RT for the identification task. These findings held true across experiments. The effects of increased inspection load on RT were less pronounced with color + shape coding and color coding compared with the other coding conditions, but only when two parameters were monitored. Finally, RT was faster and responses were more accurate with one than with two parameters.

It is proposed that alcohol and nicotine will affect free recall of relevant cues and that these effects are mediated by changes in level of arousal. Alcohol (0.0 ml, 0.97 ml, or 2.33 ml per kg of body weight) and nicotine (no cigarettes, or two cigarettes each containing 1.3 mg of nicotine) were administered either individually or jointly to six groups of 15 men, such that different combinations of alcohol and nicotine induced different levels of arousal. Since subjects performed at chance level on recall of word-color, which constituted the irrelevant cue, no conclusions regarding the effect of the drugs on recall of irrelevant cues could be drawn. Under conditions of high arousal, induced by the administration of nicotine or a low dose of alcohol, immediate free recall of 20 adjectives was superior to recall in the low-arousal conditions (a moderate dose of alcohol administered either singly or in conjunction with nicotine) and in the control group. This finding is in line with the prediction that arousal, induced by nicotine or a low alcohol dose enhances attention to high-priority task components.

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