Biomedical subjects

P A Allen

Publications and source records attributed to P A Allen.

At least 19 recordsLinked to original sources

PubMed1995

Influence of case type, word frequency, and exposure duration on visual word recognition.

The authors report 4 lexical decision experiments in which case type, word frequency, and exposure duration were varied. These data indicated that there is a larger mixed-case disadvantage for nonwords than for words for longer duration presentations of targets. However, when targets were presented for 100 ms (followed by a postdisplay pattern mask), a larger mixed-case disadvantage occurred for words than for nonwords. For word frequency, the data from Experiments 1, 2, and 3 revealed a slightly larger mixed- case disadvantage for higher frequency words than for lower frequency words. (There was additivity between word frequency and case type for experiment 4.) These results are consistent with a holistically biased, hybrid model of visual word recognition but inconsistent with analytically biased, hybrid models of word recognition, such as the process model (Besner & Johnston, 1989) and the interactive-activation model (McClelland & Rumelhart, 1981).

Decision Making↗

PubMed1995

Aging and the speed/accuracy relation in visual search: evidence for an accumulator model.

Two models of performance in visual classification tasks, the fast-guess model and the accumulator model, offer contrasting accounts of the relation between speed and accuracy. We attempted to distinguish these models in the context of age-related changes in visual search performance. Twenty-four young adults (mean age 21.50 years) and 24 older adults (mean age 66.17 years) performed a visual search task requiring the detection of an upright L among rotated L's. The results supported the accumulator model, in that mean reaction time (RT) was higher for error responses than for correct responses, and there was a positive relation between RT and error rate. Both of these effects were more pronounced for older adults than for young adults, even when visual acuity was covaried statistically. We conclude that age-related changes in visual search performance involve a decline in the efficiency of sampling the amount of evidence necessary to exceed a decision criterion.

Adolescent↗

PubMed1994

Hypnotic susceptibility, imaging ability, and the detection of embedded words within letters.

Two experiments were conducted to determine the role of hypnotic susceptibility level (high or low) and imaging ability (vivid or poor) in the performance of a visual search for words embedded within matrices of letters. In Experiment 1, subjects searched for target words from a list; however, distractor words were also embedded in the matrices. Results indicated that subjects judged both high in hypnotic susceptibility and vivid in imaging ability demonstrated the fastest search speed with a greater percentage of target words found. These subjects also made fewer false alarm errors (locating distractor words not on the target list). The poorest performance was exhibited by subjects judged both low in hypnotic susceptibility and poor in imaging ability. The amount of variance accounted for by hypnotic susceptibility and imaging ability was approximately equal for each dependent measure. In Experiment 2, when subjects searched for target words from a list without distractor words embedded in matrices, similar results to those reported for Experiment 1 were produced, except that the percentage of words found was equivalent across groups. This was attributed to the elimination of potential false alarm errors. The results are explained in terms of the use of either a holistic or a detail strategy in the performance of a visual search.

Adult↗

PubMed1994

Adult age differences in attention: filtering or selection?

We examined the effect of target letter redundancy for target-only (TO) and target-plus-noise (TPN) trials on a visual search, divided attention task where target letters were presented in one or two corners of a two-corner display. Half of the two-letter displays also included a noise letter. In both Experiment 1 (two-choice vs go/no-go) and Experiment 2 (all go/no-go), older adults showed larger redundancy gains than did young adults, and this effect did not interact with task type or visual similarity. However, for the "no-go" trials in both experiments, there were no age differences in overall errors. These results suggest that there are age differences in the activation of selective attention rather than age differences in inhibitory control. In Experiment 2, young adults under lower-luminance presentation conditions (18 cd/m2) showed a smaller redundancy gain than did older adults under higher-luminance presentation conditions (40 cd/m2). These results provided further support of the age differences in activation interpretation, as well as indicating that older adults' larger redundancy gain was not due to an age decrement in retinal illuminance.

Adolescent↗

PubMed1994

Influence of imaging ability on word transformation.

In the present study, we examined whether individual differences in imaging ability affect visual word recognition. Poor and vivid imagers performed a naming task that involved nonreversed (e.g., JUMP) and reversed (e.g., PMUJ) words (Experiment 1). Poor and vivid imagers were also tested on a naming task that was controlled for verbal ability; all the words were reversed and presentation time was varied (Experiment 2). In both experiments, imaging ability interacted with task difficulty, suggesting that individual differences in imaging ability affect visual word recognition. Specifically, the present data suggest that poor imagers may be less efficient than vivid imagers at processing words analytically. The data are interpreted within a limited-capacity, hybrid, word recognition model, in which words can be processed as either word-level or letter-level codes.

Adult↗

PubMed1992

On mental multiplication and age.

In 2 experiments, younger and older adults were presented with simple multiplication problems (e.g., 4 x 7 = 28 and 5 x 3 = 10) for their timed, true or false judgments. All of the effects typically obtained in basic research on mental arithmetic were obtained, that is, reaction time (a) increased with the size of the problem, (b) was slowed for answers deviating only a small amount from the correct value, and (c) was slowed when related (e.g., 7 x 4 = 21) versus unrelated (e.g., 7 x 4 = 18) answers were presented. Older adults were slower in their judgments. Most important, age did not interact significantly with problem size or split size. The authors suggest that elderly adults' central processes, such as memory retrieval and decision making, did not demonstrate the typical age deficit because of the skilled nature of these processes in simple arithmetic.

Adolescent↗

PubMed1992

Adult age differences in attentional allocation during memory search.

Young and older adults performed a memory search task in which, before probe onset, a cue indicated which of 4 memory-set items the probe was most likely to be. The results were consistent with an attentional allocation model in which performance represents a weighted combination, across trials, of focused (i.e., selective) versus distributed attention. The model significantly underestimated the reaction time required by miscued trials, probably because of the response inhibition occurring on these trials. The degree to which Ss relied on focused attention was significantly greater for older adults than for young adults. The estimated time required to shift attention between memory-set items was equivalent for the 2 age groups.

Adolescent↗

PubMed1992

Age and ideal chunk size.

We tested young, middle-aged, and older adults for ability to organize six-letter sequences when these subjects were not externally induced to chunk the letter sets. In order to determine whether subjects would use optimal chunk sizes of two, three, or six letters, a serial recall task on which subjects were cued using digits was employed. From these data, the total number of correctly recalled sequences was computed, in addition to global and stop transitional error probabilities (TEPs). The results indicated that older adults recalled fewer correct sequences than did the young adults. However, both the global and stop TEP analyses demonstrated that all three age groups were chunking the six-letter sequences into two sets of three letters each. The present study (along with Allen & Coyne, 1988a, 1989) suggests that there are no appreciable age differences in functional chunk capacity, but that older adults exhibit poorer serial recall than younger adults.

Adult↗

PubMed1992

Impact of age, redundancy, and perceptual noise on visual search.

We examined adult age differences in the impact of redundancy and perceptual noise during visual search. Using a two-choice, visual search task, subjects responded to letters presented in one to four corners of an imaginary display square. On each trial, one, two, or three instances of a given target letter were presented. In the target-plus-noise condition, all nontarget corners of the imaginary square were filled with distractor (i.e., noise) letters. In the target-only condition, all nontarget corners were left blank. The results indicated that older adults showed relatively greater redundancy benefits than the young adults for the target-plus-noise trials than for the target-only trials. These results are interpreted within an internal noise framework.

Adolescent↗

PubMed1992

Age differences in short-term memory: organization or internal noise?

Older and young adults' letter search performances were examined on a short-term memory (STM) task where subjects compared a five-letter target sequence stored in short-term memory to a subsequently presented five-letter probe sequence. The same five letters were always presented on target and probe portions of a given trial, but on half of the trials, two letters were transposed in the first chunk, second chunk, or between the first and second chunks of the probe sequence ("No" trials). On the remaining half of the trials, the target and probe sequences were identical ("Yes" trials). Both young and older adults showed increases in reaction time (RT) when the chunk boundary for "yes" trials was different for the target and probe sequences of a given trial. This finding indicated that both age groups were organizing the sequences in STM in the same qualitative manner. However, older adults showed a relatively greater increase in RT and errors than young adults for second-chunk transpositions than for first-chunk or between-chunk transpositions, and this finding suggested that an age difference in task complexity could not account for this effect. We propose, though, that these data are consistent with an internal noise model.

Adolescent↗

PubMed1992

Impact of adult age and Alzheimer's disease on levels of neural noise for letter matching.

We tested healthy young and older adults as well as higher-scoring (Mini-Mental State Exam, MMSE, scores between 14-20) and lower-scoring patients diagnosed with probable Alzheimer's disease (AD) on a letter-matching task. Subjects were instructed to respond "same" if two simultaneously presented letters were identical, or "different" if the letters did not match. Healthy older adults showed a larger "fast-same" effect than healthy young adults. Also, higher-scoring AD patients showed a large "false-different" effect for errors, but lower-scoring AD patients showed a large "false-same" effect. These data indicate that older adults exhibit higher neural noise levels than younger adults. The cross-over error pattern for AD suggests that moderately demented AD patients show evidence of forming degraded visual percepts whereas more severely demented AD patients show evidence of forming incomplete percepts.

Adult↗

PubMed1991

Adult age differences in letter-level and word-level processing.

Older and young adults' letter detection and lexical decision performance were examined as word frequency varied to determine whether there were age differences in word recognition. Allen and Madden (1989) found that older adults' pattern of reaction time (RT) across word frequency categories was different from young adults' pattern for a letter detection task. In this study, for both letter detection and lexical decision tasks, older adults exhibited a monotonically decreasing RT function as word frequency increased. However, young adults exhibited a nonmonotonic RT function across word frequency for the letter detection task but a monotonically decreasing RT function as word frequency increased for the lexical decision task. An expanded parallel input serial analysis model of word processing was hypothesized.

Adolescent↗

PubMed1991

Adult age differences in the rate of information extraction during visual search.

We investigated adult age differences in the function relating accuracy to speed during visual-search performance. Twenty-four young adults between 17 and 26 years of age, and 24 older adults between 59 and 75 years of age, participated. The level of accuracy at which performance was first improved by increasing RT was higher for older adults than for young adults. Independently of this age difference in accuracy, however, a significant age-related slowing was present in the rate of information extraction during visual-search performance.

Adolescent↗

PubMed1991

On age differences in processing variability and scanning speed.

This investigation examined adult age differences on a recognition memory taks for order information. Experiment 1 consisted of a modified memory-scanning task in which a memory set of four letters was presented in boxes. Subjects judged whether a subsequent probe letter was or was not transposed from its original presentation position. One block of primary memory trials (i.e., no distractor task) and one block of secondary memory trials (i.e., a 10-second distractor task) were used. Experiment 2 used basically the same task, except both blocks of trials were primary memory tasks, and acoustic similarity was manipulated. A processing variability model predicted that both experiments should show distance effects (i.e., transposing letters a distance of one box should result in more errors and/or longer reaction times than a transposition of two, or three boxes) for both right and left transposition directions. However, a generalized slowing model predicted that distance effects should only occur for left transpositions (because of left-to-right scanning order). The present data supported the processing variability model but not the generalized slowing model.

Adolescent↗

PubMed1991

Effect of imagery ability on letter-level and word-level processing.

In a letter-identification task, subjects matched a probe letter to the initial letter of a subsequently presented probe word. We varied word frequency and predicted that the performance of vivid imagers would resemble that of typical young adults, whereas the performance of poor imagers would fall in between that of typical young adults and of older adults, or would simply resemble the performance of typical older adults (a linear decrease in reaction time [RT] with word frequency; see Allen & Madden, 1989). The in-between function for young and older adults combined predicts a dip in RT for very-high-frequency words compared to medium-high-, low-, and very-low-frequency words. As predicted, vivid imagers exhibited increased latencies for medium-high-frequency words relative to the other three word-frequency categories, whereas poor imagers exhibited a dip.

Adult↗

PubMed1990

Evidence for a parallel input serial analysis model of word processing.

A parallel input serial analysis (PISA) model of word processing was developed and tested. The goal was to expand on the "critical processing duration" hypothesis of Johnson, Allen, and Strand (1989) so that both single-word and multiple-word presentation, letter detection data could be explained. In Experiments 1-3 four different word frequency categories on a single-presentation, letter detection task were used. These three experiments indicated that there was a curvilinear relationship between word frequency and letter detection reaction time (RT). That is, letter detection RTs for medium-high-frequency words were significantly longer than letter detection RTs for very-high-, low-, and very-low-frequency words. These results support the PISA model rather than the Healy, Oliver, and McNamara (1987) version of the unitization model. In Experiments 4-5 multiple-presentation (i.e., two words), letter detection tasks were used. The PISA model could also account for the results from these two experiments, but the unitization model could not.

Adolescent↗

PubMed1989

Improving aerobic capacity in healthy older adults does not necessarily lead to improved cognitive performance.

The effects of aerobic exercise training in a sample of 85 older adults were investigated. Ss were assigned randomly to either an aerobic exercise group, a nonaerobic exercise (yoga) group, or a waiting-list control group. Following 16 weeks of the group-specific protocol, all of the older Ss received 16 weeks of aerobic exercise training. The older adults demonstrated a significant increase in aerobic capacity (cardiorespiratory fitness). Performance on reaction-time tests of attention and memory retrieval was slower for the older adults than for a comparison group of 24 young adults, and there was no improvement in the older adults' performance on these tests as a function of aerobic exercise training. Results suggest that exercise-related changes in older adults' cognitive performance are due either to extended periods of training or to cohort differences between physically active and sedentary individuals.

Adult↗

PubMed1989

Are there age differences in chunking?

We examined the ability of younger and older adults to organize letter sequences in memory when no external inducement of chunking was used. In order to do so, subjects were tested on a paired-associate, serial recall task. From these data the number of completely recalled sequences was computed, as well as global and stop transitional error probabilities (TEPs). Older adults recalled fewer correct letter sequences than did the young adults, but the global and stop TEP data indicated that both age groups were chunking the four-letter sequences into two sets of two letters. Thus, the present study indicates that there are no age differences in primary organization, but that older adults exhibit an age deficit in serial recall.

Adult↗