Ernest M. Weiler

Effects of Sensory Modality and Task Duration on Performance, Workload, and Stress in Sustained Attention

The workload and stress associated with a 40-min vigilance task were examined under conditions wherein observers monitored an auditory or a visual display for changes in signal duration. Global workload scores fell in the midrange of the NASA Task Load Index, with scores on the Frustration subscale increasing linearly over time. These effects were unrelated to the sensory modality of signals. However, sensory modality was a significant moderator variable for stress. Observers became more stressed over time as indexed by responses to the Dundee Stress State Questionnaire, with evidence of recovery in the auditory but not the visual condition toward the end of the watch. This result and the finding that signal detection accuracy - although equated for difficulty under alerted conditions - favored the auditory mode, indicate that display modality and time on task should be considered carefully in the design of operations requiring sustained attention in order to enhance performance and reduce stress. Actual or potential applications of this research include domains in which monitoring is a crucial part, such as baggage screening, security operations, medical monitoring, and power plant operations.

Effects of sensory modality on cerebral blood flow velocity during vigilance

Transcranial Doppler sonography was used to measure cerebral blood flow velocity (hemovelocity, CBFV) from the left and right middle cerebral arteries during the performance of 40-min auditory and visual vigilance tasks. Reductions in stimulus duration were the critical signals for detection in both tasks, which were equated for stimulus salience and discrimination difficulty. Signal detection responses (correct detections and false alarms) and CBFV declined significantly over time in a linear manner for both modalities. In addition, the overall level of CBFV and the temporal decline in this measure were greater in the right than the left cerebral hemisphere. The results are consistent with the view that a right hemispheric system is involved in the functional control of vigilance and that this system operates in a similar manner in the auditory and visual channels.

Sex of listener and hormonal correlates of auditory thresholds.

The present study investigates changes in auditory threshold during 4-6 week intervals for men, women on birth control pills, and normal cycling women not on birth control pills. Thresholds were determined at 250, 500, 1,000, 2,000, 4,000, 6,000, 8,000 Hz. Normal cycling females had significantly lower thresholds during first half of the menstrual cycle than during the second half. Females on birth control pills showed significantly and consistently lower thresholds than other listeners at several frequencies. Explanations for the phenomena are proposed.

Sensory alternation and vigilance performance: the role of pathway inhibition

Posners theory of pathway inhibition leads to the expectation that stimulus heterogeneity should attenuate the event rate effect and the decrement function in sustained attention. These predictions were tested through a sensory alternation procedure in which stimulation was shuttled between the auditory and visual modalities. Subjects detected slight reductions in the duration of recurrent flashes of light or bursts of white noise at two event rates (5 and 40 events/min) during a 50-min vigil. Consistent with the model, sensory alternation eliminated the event rate effect. It did not, however, moderate the decrement function. Although pathway inhibition can account for the effects of event rate, other factors are probably responsible for the vigilance decrement.

Magnitude estimates of loudness adaption at 60 dB SPL.

Previous reports indicate that adaptation measured by the technique of successive magnitude estimations is not found above 30 dB SL (Fishken et al., 1977; and others). Although the present study confirmed this finding at 60 dB SPL for the original procedure, it was found that a modification of the magnitude estimation procedure resulted in significant loudness adaptation at this intensity. Introduction of a 20-dB increment for 5 s, every 30 s, resulted in a marked and statistically significant decline in successive loudness judgements of the 60-dB tone. In addition, the decline in reported loudness magnitude was cumulative and progressive throughout the 7-min duration of the monaural stimulus. This is typical of classical results found with simultaneous dichotic loudness balances.

Loudness Adaptation: Resolution of a Psychophysical Enigma

Traditional measurement of loudness adaptation based on binaural matching has been challenged by Scharf (1983) and others as an artifact of binaural interaction due to contrast effects. Weiler, Sandman, and Pederson (1981) addressed this problem by developing a monaural technique called the ipsilateral comparison paradigm (ICP), which demonstrates strong adaptation effects within the auditory system. The two experiments described in this report support the meaningfulness of that procedure. They show that the ICP is not confounded by psychophysical contrast as suggested by Canevet, Scharf, and Botte (1983); they also demonstrate that the results obtained with the ICP are robust--adaptation effects were noted across a broad range of intensities and were similar when psychophysical reports were made by magnitude estimation and graphic rating means.

Visual Evoked Potentials in Early Alzheimer's Dementia: An Exploratory Study

Topographical maps of visual evoked potentials (VEPs) were recorded from 10 possible Alzheimers disease (AD) patients and 10 control subjects. The purpose of the study was to determine if the two types of VEPs could function as a diagnostic screening for AD. Results of the statistical analysis did not reveal any latency differences between VEPs for the components elicited by either the pattern shift visual evoked potential (PSVEP)--or flash visual evoked potential (FVEP)--elicited components for AD patients compared with the control subjects; however, the information provided insight into results that are frequently lost with conventional evoked potential data. Statistically significant differences in amplitude were found between the P1 and the N2 of the PSVEP at 124, 126, and 130 ms, and at 116 ms for the FVEP.

Metapragmatic Awareness of Explanation AdequacyDeveloping Skills for Academic Success From a Collaborative Communication Skills Unit

A third-grade classroom participated in a communication skills unit (CSU) that was designed and implemented collaboratively by a teacher, speech-language pathologist, and student speech-language pa...

An improved model for loudness coding during auditory adaptation.

A comparison of loudness adaptation measured at four baseline intensities and at test values 10 and 20 dB above the baseline intensities revealed an orderly decline. The magnitude of the decline in loudness adaptation with the increasing difference between the test values and the baseline was shown to agree with earlier theories. A method for closely estimating the change in loudness adaptation is presented in convenient graphic form and in algebraic equations.

Monaural Auditory Adaptation as Measured by Simple Reaction Time

Pre- and post-reaction time measures were compared following 7 min of monaural auditory adaptation. The adapting stimulus utilised was a 500 Hz pure tone presented at an intensity level of 50 dB SPL for a period of 7 minutes. The pre- and post-adaptation reaction time measures were obtained for the frequences 400, 8000, and 10,000 Hz at intensity levels of 50, 60, and 70 dB SPL. The results revealed a significant increase in the post-adaptation reaction time measures for all of the frequencies and intensities tested and would suggest that reaction time measures can be utilised in the study of auditory adaptation phenomena.