In the present study we investigated the effects of school starting time on daytime behavior and sleep. Eight-hundred and eleven 5th grade pupils (10-12 years old) from 28 classes in 18 schools throughout Israel were divided into "early risers" (N = 232) who started school at 07:10 (42%) at least 2 times a week, and "regular risers" (N = 340) who always started school at 08:00 (58%). The remaining 239 pupils started school between 7:20 and 07:55 (and also after 08:00), and were not included in the study. Self-administered questionnaires concerning sleep habits during school days, weekends, and holidays, daytime fatigue, sleepiness, and difficulties concentrating and paying attention in school were completed by all children. Mean sleep time of the "early risers" was significantly shorter than that of the "regular risers." Early risers complained significantly more about daytime fatigue and sleepiness, and about attention and concentration difficulties in school. Their complaints were independent of the reported hours of sleep. We conclude that early starting of school negatively affects total sleep time and, as a consequence, has a negative effect on daytime behavior. The implications of these findings to the ongoing controversy concerning sleep need in contemporary society are discussed.

The present study investigates the association between sleep disturbances in shift workers and their general adaptation to the shift system. Three hundred and sixteen refinery, and 55 aluminium factory shift-workers participated in this study. In both plants, sleep disturbances were significantly associated with age, with dissatisfaction with working conditions and the quality of domestic life, with increased morbidity and increased high blood pressure. The association between high blood pressure and morbidity and sleep disturbances remained significant after adjusting for age. Shift workers complaining about their sleep also had higher blood pressure values than day workers with sleep disturbances.These findings suggest that periodic evaluation of sleep quality in rotating shift workers can provide useful information regarding their general adaptation level to the shift system.

Time-shared tasks may conceivably be separable or integral. A case in which the question of separability seems quite relevant is dual-axis tracking. To test the interaction between tracking dimensions, we first studied whether they interfere with each other. Practiced subjects performed tracking on one or two axes, with or without feedback indicators and with or without a requirement to allocate resources unevenly between axes. They also performed with or without a concurrent binary classification of visually presented digits which were presented within a moving square that served as the target for tracking. Small deficits were found in the performance of both tracking and digit classification when performed together. However, the conditions of tracking did not have a discernible effect on either tracking or digit classification. Hence, the introduction of a second tracking axis probably does not have harmful consequences either on tracking itself or on any other task time-shared with tracking. Further studies were conducted to examine whether the absence of an effect of number of tracking axes is dues to their integrality. Ordinary position tracking was paired either with another similar task on the other axis or with a novel sort of tracking in which subjects had to continually match sizes of moving rectangles. Tasks were paired under both divided-attention and focused-attention instructions. No interference on position tracking was observed even when the types of task on the two axes differed, and no other evidence for integrality of the homogeneous task pairs was found.

The present paper develops the argument that an effective evaluation of performance under time-sharing conditions requires a joint manipulation of tasks difficulty and operator's resources allocation. An experiment is presented in which each of the dimensions in a two dimensional pursuit tracking task waS manipulated and controlled seperately. Single and dual task conditions were created by presenting one dimension or two dimensions sL~ultaneously. Time-sharing efficiency was assessed under a joint manipulation of tracking difficulty on each dimension and their relative priorities. Subjects' tracking ability was individually calibrated by adaptive procedures. Regression equations and performance functions wers obtained to describe the joint effects of the experimental variables. Results are discussed in terms of their implications to the problem of measuring capacity, and their contribution to the understanding of tracking behavior. Performance on any given task can be expressed as a function of two sets of variables. One set includes such variables as the sensory quality of stimuli; predictability of stimulil availlability and completeness of relevant memory codes, SR compatibility, response complexity, amount of practice etc. etc. Norman and Bobrow (1975) seem to subsume all those parameters under the title data aualitv. As we feel that the connotation of this term is too limitted, we prefer the name Subiect-TRBk-ParSlllleters (m). The STP are the constraints imposed on performance by the task (or more percisely, the encounter of a specific task and an individual subject). Wi thin those constraints the human operator being an aCtive system is free to mobilize his various resources. These resources are the second set of variables which determin the level of task performance.In concurrent performance the joint demands of tasks very often exceed the ability of the operator to supply resources. When this happens an internally or externally determined "tradeoff" or "Priorities" function must be established to efficiently control the allocation of resources. Norman and Bobrow (1975) propose the term Performance Operating Characteristics (PCC) curves, to describe the tradeoff of performance levels on two tasks under time sharing conditione as a function of the relative allocation of resources. A whole family of different poe curves, each representing one STP combination, can be created for any pair of tasks.If thia approach is accepted, it is apparent that a comprehansive description of performance limitations under time-sharing conditions on any given pair of tasks, requires a joint assessment of the tradeoff function between task difficult,y 118 and resource allocation. This requirement represents a marked deviation from the traditional secondary task techniques that completely ignore the manipulation of resource allocation and concentrate exclusively on STP manipulations. We therefore, percieve the pressnt study as a pioneering effort towards the development of methodological techniques that enable a joint manipula...

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