THE REPRESENTATIVENESS OF OBSERVATIONAL SAMPLES OF DIFFERENT DURATIONS

The representativeness of behavioral observation samples with durations of less than the whole time of interest was investigated. A real-time recording system was developed to quantify the behavior of 5 profoundly mentally retarded physically handicapped adult students in an institutional training setting. Behavior was observed using six mutually exclusive and exhaustive categories during 2.5-hr observation sessions. Sample observation sessions with durations ranging from 15 to 135 min were computer simulated from the whole-session (150-min) records. It was found that the representativeness of these samples, when compared to whole-session records, was a function of the relative duration of the behavioral categories and of sample duration. The occurrence of relatively high-duration behaviors (lasting for more than 50% of the session) was estimated to within 20% error by samples of less than 60 min, but low-duration behaviors (1 to 3% of the session) were inadequately quantified even from 135-min samples. Increasing irregularity of bouts of behavior in the low-duration behaviors is suggested as the cause of the functions obtained. Implications of the findings for applied behavior analysis are discussed, with the recommendation that the adequacy of observational session durations be empirically assessed routinely.     

Studies in auditory timing: 1. Simple patterns

Listeners' accuracy in discriminating one temporal pattern from another was measured in three psychophysical experiments. When the standard pattern consisted of equally timed (isochronic) brief tones, whose interonset intervals (IOIs) were 50, 100, or 200 msec, the accuracy in detecting an asynchrony or deviation of one tone in the sequence was about as would be predicted from older research on the discrimination of single time intervals (6%-8% at an IOI of 200 msec, 11%-12% at an IOI of 100 msec, and almost 20% at an IOI of 50 msec). In a series of 6 or 10 tones, this accuracy was independent of position of delay for IOIs of 100 and 200 msec. At 50 msec, however, accuracy depended on position, being worst in initial positions and best in final positions. When one tone in a series of six has a frequency different from the others, there is some evidence (at IOI = 200 msec) that interval discrimination is relatively poorer for the tone with the different frequency. Similarly, even if all tones have the same frequency but one interval in the series is made twice as long as the others, temporal discrimination is poorer for the tones bordering the longer interval, although this result is dependent on tempo or IOI. Results with these temporally more complex patterns may be interpreted in part by applying the relative Weber ratio to the intervals before and after the delayed tone. Alternatively, these experiments may show the influence of accent on the temporal discrimination of individual tones.     

Expected performance at the human/computer interface as a function of user proficiency and system power

How do managers expect the proficiency of users and the power of the computers to determine overall performance? Five different models are proposed: (a) a matching model in which optimal performance is achieved when the power of the system is judged to be compatible with the proficiency of the user, (b) an averaging model in which expected performance is the average of the values of user proficiency and system power, (c) a multiplying model in which performance is the product of the values of user proficiency and system power, (d) a human/computer ratio model in which performance is determined by the ratio of system power over total effort, and (e) a computer/human ratio model in which performance is determined by the ratio of user proficiency over total effort. The applicability of these models was assessed by having managers and students of management predict performance in human/computer systems from information about the user's proficiency with computers and the power of the system. Participants rated 16 combinations of user proficiency and system power from a 4 × 4 factorial design. The pattern of ratings indicated that 51 per cent used a multiplying model and 25 percent used an averaging model; whereas, only 6 percent used the matching model and 4 percent used a ratio model. The remaining 14 percent did not follow any model clearly. Implications of these results were discussed for the design of the human/ computer interface, training and selection of users, and the cost-benefit tradeoffs for investment in user training versus equipment acquisition.     

Crossing the Threshold: The Spillover of Community Racial Diversity and Diversity Climate to the Workplace

We examined the spillover of community diversity to the workplace using a sample of 2,045 professionals living in communities across the U.S. Spillover effects were examined using 2 measures of community diversity: the degree to which employees were racially or ethnically similar to others in their community and perceptions of their community's diversity climate. Aligned with theories of group threat and racial segregation, Whites who were racially dissimilar to their communities expressed stronger intentions to leave their communities, and ultimately their workplaces, than those living in primarily White communities. However, community diversity climate offset these relationships; Whites who lived in communities that were racially dissimilar to them, but experienced the climate as inclusive, had lower moving intentions than those in communities that were experienced as racially intolerant. In contrast, for people of color, community diversity climate, rather than racial similarity to the community, predicted moving intentions. For both groups, the diversity climate in the community predicted moving intentions, which in turn predicted work turnover intentions, job search behaviors, and physical symptoms of stress at work. These findings suggest that the intention to leave one's community, and ultimately one's workplace, is influenced by community experiences and the community's perceived diversity climate.