Distortion product otoacoustic emissions in geriatric dogs.

Recordings of distortion product otoacoustic emissions (DPOAE) were taken from 28 geriatric dogs aged 12.2 ± 2.2 years and 15 control dogs aged 5.9 ± 3.0 years (mean ± standard deviation) to demonstrate frequency-specific changes in cochlear responses. Recordings were performed for primary frequencies of 2-12 kHz in 2 kHz increments. Brainstem auditory evoked response (BAER) recordings were also made from geriatric dogs for comparison with DPOAE responses. Significant decreases in DPOAE response amplitudes were observed at frequencies of 6-12 kHz in geriatric dogs compared to control dogs, reflecting loss of cochlear outer hair cells along the length of the cochlea. Significant decreases in response amplitudes were not seen at frequencies of 2 or 4 kHz. Decreases in BAER response amplitudes subjectively paralleled the depressed DPOAE amplitudes. No significant linear regression relationships were found for DPOAE response amplitude vs. age despite the progressive nature of age-related hearing loss. The reductions in response at all frequencies starting at the age where dogs are considered geriatric indicate that age-related hearing loss begins earlier in the life span. DPOAE recordings provide a means to assess cochlear function across different portions of the auditory spectrum for assessing hearing loss associated with aging, and potentially for losses from other causes of decreased auditory function.

Variation in the human lymphocyte sister chromatid exchange frequency as a function of time: results of daily and twice-weekly sampling.

The variation in lymphocyte sister chromatid exchange (SCE) frequency was investigated in healthy nonsmokers who were not taking any medication. Two separate studies were undertaken. In the first, blood was drawn from four women twice a week for 8 weeks. These donors recorded the onset and termination of menstruation and times of illness. In the second study, blood was obtained from two women and two men for 5 consecutive days on two separate occasions initiated 14 days apart. One donor participated in both studies. Analysis of the mean SCE frequencies in each study indicated that significant temporal variation occurred in each donor, and that more variation occurred in the longer study. Some of the variation was found to be associated with the menstrual cycle. Peaks in the SCE frequency were observed at times that corresponded approximately to ovulation and to the beginning and end of menstruation. In the daily study, most of the variation appeared to be random, but occasional day-to-day changes occurred that were greater than those expected by chance. To determine how well a single SCE sample estimated the pooled mean for each donor in each study, we calculated the number of samples that encompassed that donor's pooled mean within 1 or more standard errors. For both studies, about 75% of the samples encompassed the pooled mean within 2 standard errors. An analysis of high-frequency cells (HFCs) was also undertaken. The results for each study indicate that the proportion of HFCs, compared with the use of Fisher's Exact test, is significantly more constant than the means, which were compared by using the t-test. These results coupled with our previous work suggest that HFC analysis may be the method of choice when analyzing data from human population studies.

Acquisition of prototype-based information about social groups in adulthood.

Two experiments examined adult age differences in the ability to acquire prototype-based information about a fictitious social group. Young and older adults were presented with 60 descriptions of people who varied in their similarity to a prototypical group member along 12 (Experiment 1) or 10 (Experiment 2) feature dimensions. The prototype represented either an arbitrary combination of features or a coherent set of features based on evaluative content. Younger adults generally performed better than the older adults in learning the arbitrary prototype, whereas age differences were absent or in favor of the older adults when the prototype consisted of evaluatively consistent features. The authors argue that the results can be explained by the age-related variations in the reliance on automatic processing mechanisms and the congruence of these processes with the demands of the task across prototype conditions.

Age-related priming effects in social judgments.

Two experiments investigated adult age differences in the impact of previously activated (and thus easily accessible) trait-related information on judgments about people. The authors hypothesized that age-related declines in the efficiency of controlled processing mechanisms during adulthood would be associated with increased susceptibility to judgment biases associated with such information. In each study, different-aged adults made impression judgments about a target, and assimilation of these judgments to trait constructs activated in a previous, unrelated task were examined. Consistent with the authors' hypotheses, older adults were likely to form impressions that were biased toward the primed trait constructs. In contrast, younger adults exhibited greater awareness of the primed information and were more likely to correct for its perceived influence, especially when distinctive contextual cues regarding the source of the primes were available.

Aging and impression formation: the impact of processing skills and goals.

Two studies assessed age differences in representations and judgments about people. Our specific interest was in examining how presumed age-related changes in processing efficiency and motivation affected performance in an impression formation task. Consistent with age-related declines in processing efficiency, we found that increasing age was associated with: (a) no change in the processing of evaluative information; (b) less use of specific traits to organize impressions; (c) poorer memory for behavioral information, especially when it contradicted expectations; and (d) less systematic relationships between memory and judgments. We also found, however, that more meaningful task goals and a focus on individual behaviors resulted in reduced age differences in the nature of representations about the target person.