Judging the urgency of nonvocal auditory warning signals: perceptual and cognitive processes

Previous research has identified acoustic properties modulating the perceived urgency of alarms. The authors conducted 3 experiments using a multidimensional approach in which participants made acoustic dissimilarity judgments and urgency dissimilarity judgments for pairs of sequences. Experiment 1 confirmed the validity of acoustic parameters in urgency perception of experimental alarms. Experiment 2 confirmed the role of these acoustic parameters with real alarms but suggested the importance of additional factors. Experiment 3 compared the relative degrees of urgency of alarms from Experiments 1 and 2, highlighting the role of both sequence structure and associated mental representation. The authors conclude that the design of alarms should not be based exclusively on acoustic factors but should also take into consideration the acquisition of an appropriate mental representation.     

A role for hemispheric asymmetry in human behavioral variability

A model is presented in which functional lateral specialization and selective hemisphere priming combine to provide a mechanism for behavioral variability. The model is tested and supported by two experiments in which lateral attentional priming produces significant reductions in between-subject and within-subject variability. These findings help us to understand the source of behavioral variability, broaden our knowledge of the gross structures and functions of the brain, provide information about the manipulation of perceived control, and offer a technique for increasing statistical power in a wide variety of research settings.     

Perceptual attenuation of nonfocused auditory streams

The aim of this study was to measure the perceptual attenuation, measured in decibels, resulting from the focusing of attention on one stream within a multistream auditory sequence. The intensity of a nonfocused stream was increased until the accuracy of detecting a temporal irregularity in this stream was the same as in a focused stream. Eight subjects were required to detect a temporal irregularity created by delaying or advancing one tone which could be situated in one of three temporally regular streams played simultaneously to create a multistream sequence. The three streams differed in tempo and frequency. Subjects’ attention was focused on one of the streams by preceding the multistream sequence with one of the single streams (a cue). We first established the size of temporal irregularity detected at a 90% level in cued streams, confirming that subjects were able to focus on one particular stream. Second, an irregularity of this size was not detected above chance level in noncued streams, demonstrating that listeners focus only on the cued stream. Third, for 5 subjects, a 15-dB increase in the level of one of the noncued streams was necessary to bring detection up to that found in the cued streams. This gain provides an equivalent measure of the perceptual attenuation of nonfocused streams. For 3 other subjects, detection in the noncued stream remained at chance performance whatever the level. For all subjects, detection in the cued stream decreased slightly as the level of the noncued stream increased. We conclude that the attenuation of nonfocused auditory streams can attain as much as 15 dB, at least for some subjects.     

Group versus individual reinforcement contingencies within the context of group study conditions

We investigated the effects of two teaching variables on students' Spanish vocabulary quiz performance: (a) group study and (b) individual versus group contingencies. In Experiment 1, we compared students' quiz scores under conditions in which students either studied independently and received no programmed reinforcement or studied in groups and received individual rewards for high scores. The results showed that, on average, the group-study individual-reward condition produced superior quiz scores. In Experiment 2, we compared individual (i.e., the superior condition in Experiment 1) and group contingencies within the context of the group study condition. On average across the class, group contingencies produced performance superior to individual contingencies. In both studies, however, benefits for the classes as a whole were mitigated by effects on individual students. These results extend the literature on the effects of group-based instructional activities and reinforcement contingencies. Educators who choose such procedures may encounter conflicting findings depending on whether they examine results at the group or individual level.     

Generating multivariate data from nonnormal distributions: Mihal and Barrett revisited

An algorithm described by Graybill (1969) factors a population correlation matrix, R, into an upper and lower triangular matrix, T and T′, such that R=T′T. The matrix T is used to generate multivariate data sets from a multinormal distribution. When this algorithm is used to generate data for nonnormal distributions, however, the sample correlations are systematically biased downward. We describe an iterative technique that removes this bias by adjusting the initial correlation matrix. R, factored by the Graybill algorithm. The method is illustrated by simulating a multivariate study by Mihal and Barrett (1976). Large-N simulations indicate that the iterative technique works: multivariate data sets generated with this approach successfully model both the univariate distributions of the individual variables and their multivariate structure (as assessed by intercorrelation and regression analyses).     

The apparent size of the path traversed by a rotating target during saccadic and smooth pursuit: New data on the shrinking circle illusion

Twelve subjects attempted to visually track a continuously or discretely moving target as it rotated through a path 20° in diameter at velocities ranging from .18 to 5.2 cps. Tracking error, resulting from the eye tracking a path inside that of the target, was an increasing function of velocity from .18 to 1.13 cps. Higher velocity targets could not be tracked consistently. Apparent path diameter and the tracking diameter of the eye were both a decreasing function of velocity (through 1.13 cps) in the condition requiring smooth pursuit of a continuously moving target. Tracking diameter was also a decreasing function of velocity for the condition requiring saccadic pursuit of a discretely moving target, but this was not associated with a corresponding decrease in apparent size. These results suggest that the retinal position error generated by undertracking the target is processed during saccadic, but not during smooth, pursuit.     

The effect of environment on visual cliff performance in the Mongolian gerbil

Depth perception in the Mongolian gerbil was investigated as a function of age and environment. Thirty-two gerbils were raised in either a cliff or flat environment, and half the gerbils in each condition were tested on the visual cliff from 21 to 57 days of age. All gerbils were tested at 60–61 days on a standard visual cliff, a barrier cliff which prevented movement along the centerboard, and a jumping platform. While the gerbils did not display a preference for the shallow side when tested at 21 days, those living in a cliff environment showed rapid acquisition of such a preference, whereas those living in a flat environment did not. By 60–61 days, however, all gerbils demonstrated a strong preference for the shallow side on both versions of the visual cliff, regardless of environment or pretesting experience.     

Toward an empirical subclassification of “learning disabilitiesℍ: A psychophysiological comparison of “hyperactiveℍ and “nonhyperactiveℍ subgroups

The diagnostic category of learning disabilities is a heterogeneous one, but few empirical attempts have been made to distinguish subgroups. Recent research, however, suggests that it may be meaningful to discriminate between hyperactive and nonhyperactive learning-disabled children. In the present study, 21 learning-disabled children identified as hyperactive through teacher nominations and ratings were compared to 15 learning-disabled children identified as nonhyperactive in the same manner. The two groups differed on rated behavior, birth order, amount of prescribed stimulant medication, amount of psychosocial stress, and Verbal, Performance, and Full Scale WISC-R IQ scores. They did not differ, however, on several demographic variables, the number of perinatal complications, reading achievement, and a number of tonic and phasic measures of autonomie activity. These findings support the distinction between hyperactive and nonhyperactive subgroups of learning-disabled children, but suggest that the two subgroups may have a similar biological substrate.We wish to express our sincere appreciation to Douglas Carmichael, Martha Stewart, Kay Richmond, and the teachers of Clarke County for their kind and sophisticated assistance, and to David Coleman and David Hammer for their technical assistance.     

Design and use of a U.S. census data computer laboratory for teaching undergraduate research methods

This paper discusses the design and development of an interdisciplinary social science computer laboratory for teaching undergraduate research methods courses and research components of applied and theoretical courses. The U.S. Census of the Population, a database commonly used in all of the social sciences, is used in order to give students research experience and to avoid ethical problems involved in working with animal and human subjects in an undergraduate course. Some issues in laboratory design and required changes in teaching methods are discussed.     

Selecting one of two regular sound sequences: perceptual and motor effects of tempo

This study assessed the influence of tempo on selecting a sound sequence. In Exp. 1, synchronization with one of the two regular subsequences in a complex sequence was measured. 30 participants indicated a preference for the fastest subsequence when subsequences were in a slow tempo range (> or = 500 msec. IOI), and with the slower subsequence when they were in the fast tempo range (< or = 300 msec. IOI). These results were replicated using a perceptual task (Exp. 2 and 3) in which the 30 listeners had to detect a temporal irregularity in one of the two subsequences. Detection was better when the temporal irregularity was in the fastest subsequence than in the slowest one when the complex sequence was in a slow tempo range (> or = 500 msec. IOI) and the reverse was obtained when the complex sequence was in a fast tempo range (< or = 180 msec. IOI). These results have implications for design of auditory alarms.