No abstract

Six nulliparous female mice were trained to bar press with bar pressing reinforced by the opportunity to retrieve pups to the nest. Then, responses on one bar produced the opportunity to retrieve pups, while responses on a second bar produced sensory contact with non-retrievable pups, presented behind a screen door. All subjects emitted more responses on the bar yielding retrievable pups. When the bar-pup contingency was reversed, five subjects learned to press the opposite bar for retrievable pups. The sixth subject showed extinction of responding on the bar that had previously yielded retrievable pups, but failed to press the other bar. A major portion of the reinforcing value of pup presentation resulted from the opportunity to perform the behavior of pup retrieving. This finding supports theoretical formulations wvhich state that the performance of species-typical consummatory behaviors should have reinforcing properties. Craig (1918) described the strengthening of appetitive behavior whenever it was followed immediately by the appeted stimulus and consummatory reaction. His formulation may be considered an operant conditioning paradigm, witlh appetitive behavior as the operant, and the appeted stimulus and consummatory reaction as the reinforcer. Recent theoretical articles lhave restated and expanded upon Craig's ideas, concluding that the performance of any species-typical consummatory behavior (Valenstein, Cox, and Kakolewski, 1970), or the activation of neural structures mediating stuch behavior (Glickman and Schiff, 1967) should be a reinforcing e-ent.Within the last several years, experiments have shown that a variety of species-typical behaviors will, in fact, serve as reinforcers. Although such behaviors as aggressive display (Tlhompson, 1963;1964), aggression (Van Hemel, 1972) reinforcers, few studies lhave attempted to use maternal behaviors in this way. This lack of research is somewlhat surprising, since it has long been observed that maternal behavior is strongly motivated and persistent, and it could thus be expected to be a strong reinforcer. Only two recent studies have used maternal behavior as a reinforcer, one using rats as subjects and one using mice. Since it is impossible to present a belhavior to a subject as a reinforcer, these experiments presented pups in a situation where retrieval was possible. Wilsoncroft (1969) showed that lactating rats will bar press for retrievable pups when eaclh bar press is followed by presentation of a pup, and that the pups are invariably retrieved to the nest. Frieman (1965) showed that lactating mice would learn a light-dark discrimination in a clhoice apparatus to reach pups, which they retrieved to the nest. Slhe also reported pilot data showing that botlh male and female mice would bar press for pups on a fixed-ratio schedule.2The present experiment attempted to confirm Frieman's pilot finding that non-lactating mice can be trained to bar press for pups. Also, since it is known that mice will perform operants reinforced by environmental stimulus c...

A survey was distributed to about 25,000 truck drivers in the United States and Canada to determine their knowledge of several fatigue-related topics; 4,833 responses were received and tabulated. Analysis by topic area indicated that the following topics are not well understood by respondents and should be considered for special emphasis in fatigue outreach and education programs. Sleep disorders, especially sleep apnea, appear to be poorly understood by the respondents, and younger drivers are least informed on this topic. Many respondents are not aware that apnea is treatable. Napping is recognized as an effective short-term countermeasure to fatigue by fewer drivers than might be desired. Those who do use napping as a fatigue countermeasure believe it is very helpful. Sleep requirements may be underestimated by many drivers. About 25 percent of the respondents believe that 5 to 6 hr of sleep per night is enough to maintain alertness. Circadian rhythm effects are not fully understood by the respondents, especially effects on mood and performance efficiency. Caffeine and its effects on the body are misunderstood by many drivers. A fairly large proportion of respondents appear unaware of the limitations on caffeine’s stimulant effects and of possible side effects of caffeine overuse. Melatonin, a hormone, may be another substance the drivers need to know more about. Many drivers did not respond to the item on melatonin safety, and many others responded incorrectly.

The relationship between physical and mental fatigue is not well understood or well documented, a lapse that affects understanding of the interaction between loading and unloading activities and safe operation in the trucking industry. This experiment addresses the effects of loading and unloading on driving performance by measuring driving impairment in volunteer truck drivers operating a truck-driving simulator. Ten drivers participated, each for 17 days, including 2 driving weeks of 5 days with 14-h duty cycles separated by two 58-h rest periods. During one of the driving weeks, participants were given a significant hand-loading task, 3 hours of hand-loading pallets of boxes on 3 of 5 days; during the remaining week, only driving tasks were scheduled. Performance measurement focused on driver responses to planned and unplanned crash-likely challenges and vigilance tasks, supported by simulator-mediated driving indicators, such as lane-keeping performance. Measures of subjective drowsiness also were maintained. The effects of the loading and unloading task were mixed. There was an initial improvement in alertness, apparently because of the break in activity and a period of exercise; however, this effect wore off as the day progressed and may have contributed to a decrease in overall performance after 12 to 14 h of duty.

The goal of this project, sponsored by the US Nuclear Regulatory Commission, is to identify “leading” indicators of nuclear power plant safety. Such indicators would allow early recognition, and perhaps avoidance, of impending safety problems before the problems themselves became evident. Because data are limited in the nuclear industry, CTA's approach to this objective is to look beyond the nuclear power industry, to other industries with safety concerns analogous to those of the nuclear power community, for sources of such indicator data.