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Biomedical subjects

R A Barr

Publications and source records attributed to R A Barr.

9 recordsLinked to original sources
PubMed1991

Recent changes in driving among older adults.

Driving statistics comparing drivers aged at least 65 years with all drivers are examined for the years 1980 and 1989. In that time older driver fatalities had increased substantially despite a decrease in total driver fatalities. Analyses of size of population, numbers of licensed drivers, estimates of miles driven, and crash rates for these two years imply that the rise in total older driver deaths is related to increasing numbers of older adults who are licensed to drive and an increase in likelihood of fatality following a motor vehicle crash. This latter effect may be associated with a very substantial rise in the numbers of licensed drivers age 70 and older.

Accidents, Traffic↗
PubMed1990

Age-related decrement in auditory selective attention.

Young (n = 30), middle-aged (n = 32), and old (n = 28) adults repeated (shadowed) words presented to the left ear at 60 words per minute with and without distracter words presented to the other ear. Dichotic shadowing error rate increased with age. An attempt to eliminate the age effect by adjusting for age differences in monaural shadowing errors, fluid intelligence, and pure-tone hearing loss did not succeed. When the analyses were confined to subjects who made no monaural shadowing errors, dichotic shadowing errors still increased linearly with age. These results showed that there are selective-attention deficits in older adults that cannot be accounted for by the uncertainty of the target location.

Adult↗
PubMed1989

An observational study of driver behavior at a protected railroad grade crossing as trains approach.

Observations were made of 57 drivers who approached a rural rail grade crossing in the presence of activated warning flashers signalling an approaching train. Two thirds of the drivers crossed the tracks in front of the approaching trains. All but four drivers, however, slowed perceptibly or stopped prior to crossing. The probability of crossing was seen to vary reliably with distance of the trains from the crossing and the time available to cross (safety margin). It was concluded that, as a group, the drivers' decision to cross was a considered one that was based on an accurate perception of available evidence.

Accident Prevention↗
PubMed1989

On the relationship between category intensions and extensions in children.

We contrasted four theories of natural language category acquisition by investigating the relation between category intensions and extensions in children (kindergarteners, second graders, fifth graders) and in college students. Everyone was asked to define a category term, to make category membership judgments of possible exemplars, and to judge whether the possible exemplars possessed features generated by them and by previous adult subjects. Adult judges were also asked to judge whether the possible exemplars possessed the features generated by the subjects. Children's intensions and extensions were very consistent. In addition, children's extensions were reliably smaller than adults', and the features which children generated were more specific than those generated by adults. None of the existing theories discussed can explain this pattern of results. An exemplar-based model is proposed to do so.

Adolescent↗
PubMed1981

How do we focus our attention?

A shadowing experiment investigated subjects' ability to focus their attention in the presence of two irrelevant messages. The subjects shadowed a binaurally presented message while attempting to ignore two monaurally heard distractors, one on each ear. In one condition, the distractors were normally spoken messages. In a second condition, the distractors were reversed speech (normal speech played backwards). In a third condition, subjects shadowed a binaural message while attempting to ignore a single binaurally presented, reversed-speech distractor. The subjects combined both locational cues and the forward/reversed cue to help them to select the appropriate message. This result implies that the discriminability of the relevant message from the background is an important factor in selection. It exerts an effect in addition to any influence of the number of groups into which attended and background messages are segregated.

Adolescent↗
PubMedDate not supplied

Does retention of order require verbal labelling?

Older and younger adults attended to lists of either pictures or words presented one at a time. At the end of each list, they attempted to recall the serial position of each member of the list. There was a pronounced effect of primacy. No recency was observed, however, except when the very last item was tested first. The usual pictorial superiority effect was abolished when pictures were drawn from a conceptually homogenous set. It was reinstated when pictures were conceptually distinctive. Number of errors on pictures was highly correlated with the judged similarity of the items in a list. The younger subjects' performance uniformly exceeded that of the older ones; but chronological age failed to interact with any experimental variable. The results imply that pictures need not be verbally labelled in order for their serial positions to be retained.

Adolescent↗