Behavioral influences of proximal alarms.

Confidence in and responses to an unreliable test alarm were studied in the presence of nearby unspecified alarms. The test alarm's reliability rate was represented as averaging "true" only 50% or 60% of the time. Confidence or response rates ranged proportionately from 23% to 97% with the number of active alarms within 5, 6, 7, or 9 annunciator arrays. Adjacent alarms resulted in confidence estimates that were higher (by about 10%) than those with the same number of active alarms spaced up to 3 positions away. Simultaneously activated alarms resulted in a more than 20% increase in "true" responses compared with the same number of alarms offset in time by up to 32 s, regardless of which came first. Active alarms "known" to be functionally related to, or independent of, the test alarm substantially raised or lowered responding but did not completely overcome prior effects. These findings indicate that presumptions that operators' responses are not influenced by nearby alarms, regardless of their function, may be unwarranted. Applications of this research include suggestions to improve responding and training recommendations.

Linguistic cues and memory for synthetic and natural speech.

Past research has demonstrated that there are cognitive processing costs associated with comprehension of speech generated by text-to-speech synthesizers, relative to comprehension of natural speech. This finding has important performance implications for the many applications that use such systems. The purpose of this study was to ascertain whether certain characteristics of synthetic speech slow on-line, real-time cognitive processing. Whereas past research has focused on the phonemic acoustic structure of synthetic speech, we manipulated prosodic, syntactic, and semantic cues in a task requiring participants to recall sentences spoken either by a human or by one of two speech synthesizers. The findings were interpreted to suggest that inappropriate prosodic modeling in synthetic speech was the major source of a performance differential between natural and synthetic speech. Prosodic cues, along with others, guide the parsing of speech and provide redundancy. When these cues are absent or inaccurate, the additional burden placed on working memory may exceed its capacity, particularly in time-limited, demanding tasks. Actual or potential applications of this research include improvement of text-to-speech output systems in warning systems, feedback devices in aerospace vehicles, educational and training modules, aids for the handicapped, consumer products, and technologies designed to increase the functional independence of older adults.

Ataxia following exposure to a virtual environment.

BACKGROUND: Virtual environment (VE) technology has many promising applications in a variety of areas that may likely lead to widespread use as technology progresses and cost decreases. Recent research has demonstrated that simulator sickness, a well-established effect of simulator exposure, can occur with VE exposure as well. Because ataxia (postural unsteadiness) is known to occur following simulator exposure, it might also occur following VE exposure. Simulator sickness and after-effects, such as ataxia, pose severe safety risks and raise serious liability questions. METHOD: A PC-based VE system was used to investigate the occurrence of ataxic decrements in postural stability following a 20-min exposure to a commercially available game. There were 20 male and 20 female undergraduate students who served as participants. Postural stability was assessed using a sensitive, reliable measure of stance involving the velocity of head movement sway along the y-axis. Data on the occurrence of simulator sickness were also collected. Based on findings in other simulators, ataxia was hypothesized to occur. RESULTS: Ataxic decrements in postural stability were not found although simulator sickness did occur. CONCLUSIONS: Several possible factors possibly involved in the lack of ataxia were considered: statistical power; aspects of the postural test; participants' VE adaptation, exposure time, and immersion position; and the task performed. Ataxia may not be associated with short exposures to VEs for tasks which are not highly dynamic and individuals who are not experienced with the system.

Human probability matching behaviour in response to alarms of varying reliability.

The goals of this research were to substantiate the existence of the cry-wolf effect for alarm responses, quantifying its effect on operator performance. A total of 138 undergraduate students performed two blocks of a cognitively demanding psychomotor primary task; at the same time, they were presented with alarms of varying reliabilities (25, 50 and 75% true alarms) and urgencies (green, yellow and red visual alarms presented concurrently with low-, medium- and high-urgency auditory civilian aircraft cockpit alarms). Alarm response frequencies were observed and analysed, and t-tests and repeated-measures MANOVAs were used to assess the effects of increasing alarm reliability on alarm response frequencies, speed and accuracy. The results indicate that most subjects (about 90%) do not respond to all alarms but match their response rates to the expected probability of true alarms (probability matching). About 10% of the subjects responded in the extreme, utilizing an all-or-none strategy. Implications of these results for alarm design instruction and further research are discussed.

Some effects of alcohol on various aspects of oculomotor control.

Recent studies have shown that alcohol interferes with visual control of vestibular nystagmus. The present study was designed to assess three partially independent systems of oculomotor control. Performance on three tasks was measured before and after mild alcohol dosage. One task involved visual suppression of vestibular nystagmus; a second involved smooth oculomotor tracking of a moving target; and a third required repetitive rapid voluntary shifts in gaze. Oculomotor control was degraded on the first two tasks with recovery toward the initial performance level 4 h after drinking. Performance on the third task was not obviously degraded, although it is possible that improvement with practice was retarded. Results are discussed in terms of neurological systems involved and kinds of flight tasks potentially affected.