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P M Rabbitt

Publications and source records attributed to P M Rabbitt.

At least 19 recordsLinked to original sources
PubMed1992

Effects of alcohol, practice, and task complexity on reaction time distributions.

The effects of alcohol (1.0 ml/kg body weight) and practice (2 sessions) were investigated in 2-, 4-, and 8-choice reaction time (RT) tasks with 24 male subjects. The number of errors increased with alcohol, practice, and increasing task complexity (choice). Mean RT decreased with practice, but increased with alcohol and complexity. Both the alcohol and practice effects on mean RT increased as complexity increased. The effects of alcohol, practice, and complexity were all larger for the higher percentiles of the RT distributions than for the lower percentiles. RT distributions were further analysed at each level of choice by plotting percentiles (5th, 10th, ... , 95th) for alcohol conditions against corresponding percentiles for no-alcohol conditions, and percentiles obtained early in practice (Session 1) against those obtained later in practice (Session 2). These plots revealed that whereas at all levels of choice the effect of alcohol could be expressed as a simple linear transformation of all RTs, the effect of practice required a more complex curvilinear transformation. Thus, alcohol produces a general slowing of all RTs, whereas practice produces a disproportionate improvement at the slower end of the RT distribution.

Adolescent↗
PubMed1992

Effects of age-related reductions in processing resources on text recall.

Available processing resources are presumed to determine the amount of deep, elaborative processing people can carry out, with reduced resources resulting in poor integration of details from texts, but preserved selection of main points. Two experiments examined whether experimentally reducing resources and levels of processing eventually results in a failure of selection and also whether it produces in younger people the pattern of recall normally observed in elderly people. Experiment 1 examined the effect of the added demand of selecting for preferential recall of a primary theme from a two-theme text. Subjects who putatively had greater processing resources ("younger" elderly in their 60s and those with high intelligence test scores) began to behave like older and lower intelligence test score individuals in that they recalled well main points from both themes but showed reduced recall of details from the secondary theme. In a sentence recognition task, subjects in their 70s more often accepted distractor sentences that did not preserve the meaning of the original text. In Experiment 2, encouraging subjects to process text more elaborately improved recall, especially the recall of the elderly, who began to produce recall protocols resembling those of younger and higher intelligence test score individuals. However, discouraging depth of processing did not have the converse effect of reducing quality of recall by younger and high intelligence test score individuals to resemble that of the old and less able. Instead, recall was generally depressed, with recall of main points being especially affected, suggesting that the oldest, lowest ability subjects were beginning to show a failure of selection here.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1991

Ageing memory: use versus impairment.

An uncued recall technique was used to compare recall of autobiographical events by two groups of elderly volunteers of equivalent general intelligence (assessed by unadjusted scores on the AH4 intelligence test). One group lived in residential care, and the other led independent lives. Residential care subjects recalled and spontaneously rehearsed more memories from their early than their recent lives, whereas the reverse was true for the independent elderly. The effects of senile confusional states were also investigated by testing a subgroup of cognitively impaired subjects, also in residential care. Although unimpaired elderly in care produced more early than recent memories, they were still able to produce substantial numbers of recent memories. Impaired subjects produced very few memories, those they did produce were mainly early ones. Frequency of rehearsal (or reminiscence) seemed to affect the probability of elicitation of a memory. People in institutions more often rehearse memories of early events. Frequency of rehearsal is thus a function of the use which people in different situations make of their memories. Cognitive impairment due to organic neurological changes in the elderly had a characteristic effect on the abundance of recall from recent life.

Activities of Daily Living↗
PubMed1990

Autobiographical and text recall in the elderly: an investigation of a processing resource deficit.

This study examined different explanations of age-related impairments in recall of details from text and autobiographical events. An interpretation of Central Executive Capacity Deficit was supported and explored further. This suggests that details are more demanding of capacity than main points, and that ability to appropriately integrate details with context is likely to be impaired. An implication was that irrelevant and false information may occur, and this was supported in both autobiographical and text recall. The effects were then examined in relation to various measures of ability. The aim was to determine whether declining capacity (as indicated by "Fluid Intelligence" measures) predicted ability to recall in a detailed manner. The difficulty with details was predicted independently by chronological age and by measures of fluid (e.g. AH4 intelligence test) and the more crystallized verbal ability (Mill Hill vocabulary test). Only a measure of the specificity of autobiographical recall was predicted solely by measures of fluid intelligence. Decreased specificity was not a result of faster decay of memory for details, as there was little difference across the lifespan. The resource deficit appears to affect retrieval and appropriate implementation of detail. It was concluded that lower-ability elderly subjects have decreased Central Executive resources, which leads to poor (often inappropriate) integration of details with central thematic points, but that subjects' verbal ability, which does not decline with age, still has an important part to play.

Aged↗
PubMed1990

Comparing the effects of alcohol and intelligence on text recall and recognition.

Forty male subjects were divided into two groups on the basis of their scores on a computerized intelligence test administered in a preliminary session. They then participated in a text recall and recognition experiment in which they received alcohol (1.0 ml/kg body weight) in one session and no alcohol in another session (the order being counterbalanced). Subjects were required to read a short passage, immediately recall as much of it as possible and then select from sets of four sentences the ones that appeared in the original passage (recognition). Although two different passages were used, and subjects knew about the memory tasks in advance, there was nevertheless a significant practice effect: subjects recalled 10.6 per cent more propositions on the second occasion than on the first, but this could be at least partly explained by the fact that they spent 10.0 per cent longer reading the second passage. There was also a significant 7.8 per cent slowing of reading time due to alcohol. Practice did not interact with either intelligence or alcohol on any measure of performance. Alcohol impaired the performance of high intelligence test scorers more than low scorers. The effects of intelligence and alcohol on free recall were quantitatively similar: high intelligence test scorers recalled 8.7 more propositions than low scorers; with alcohol, subjects recalled 8.3 fewer propositions than without alcohol. However, the effects were qualitatively different. The effect of intelligence was primarily on the recall of lower level propositions, whereas alcohol impaired the recall of both higher and lower level propositions. Furthermore, while there was no effect of intelligence on recognition, alcohol impaired performance such that more incorrect sentences were erroneously recognized, particularly those which altered the meaning of the original sentence, rather than merely its surface structure. In terms of Kintsch & van Dijk's (1978) model of text processing, the results are interpreted as suggesting that, while both intelligence and alcohol affect the capacity of the short-term memory buffer, there is an additional impairment with alcohol in the ability to select between higher and lower level propositions prior to filling the buffer.

Adolescent↗
PubMed1990

Effects of alcohol and extended practice on divided-attention performance.

The effects of alcohol and extended practice on divided attention were investigated using a visual tracking task and an auditory detection task. Subjects performed the tasks with and without alcohol, under single-task (S) and dual-task (D) conditions, both before and after they had received extended practice under single-task conditions without alcohol. Tracking accuracy improved with practice and was impaired under divided-attention conditions but was not affected by alcohol. Speed of detection was impaired by alcohol, improved by practice, and impaired by divided attention. Extended practice did not reduce the influence of alcohol. The effects of both alcohol and practice on speed of detection were significantly greater under dual-task conditions than under single-task conditions. Analysis of detection-task reaction times in terms of relative divided-attention costs, (D-S)/S, showed no effect of alcohol, but a highly significant reduction in costs with extended practice. It is concluded that (1) alcohol and practice can have quantitatively, but not qualitatively, similar effects on speeded performance, and (2) the effect of alcohol is not influenced by the attentional requirements of the task.

Alcohol Drinking↗
PubMed1989

Reflexive and voluntary orienting of visual attention: time course of activation and resistance to interruption.

To study the mechanisms underlying covert orienting of attention in visual space, subjects were given advance cues indicating the probable locations of targets that they had to discriminate and localize. Direct peripheral cues (brightening of one of four boxes in peripheral vision) and symbolic central cues (an arrow at the fixation point indicating a probable peripheral box) were compared. Peripheral and central cues are believed to activate different reflexive and voluntary modes of orienting (Jonides, 1981; Posner, 1980). Experiment 1 showed that the time courses of facilitation and inhibition from peripheral and central cues were characteristic and different. Experiment 2 showed that voluntary orienting in response to symbolic central cues is interrupted by reflexive orienting to random peripheral flashes. Experiment 3 showed that irrelevant peripheral flashes also compete with relevant peripheral cues. The amount of interference varied systematically with the interval between the onset of the relevant cue and of the distracting flash (cue-flash onset asynchrony) and with the cuing condition. Taken together, these effects support a model for spatial attention with distinct but interacting reflexive and voluntary orienting mechanisms.

Adult↗
PubMed1989

Spatial cueing and the relation between the accuracy of "where" and "what" decisions in visual search.

To study the processes underlying selective attention in visual search, the relation between the accuracy of "where" (location) and "what" (same/different orientation matching) decisions was analysed under various display conditions. Target-non-target discriminability was varied by contrasting single and multiple element displays; further, attention was directly manipulated by spatial cueing. In Experiment 1, analyses for both single and multiple displays showed that localization accuracy remained above chance when same/different matching failed; the inverse also obtained. It seems that accurate matching is not a prerequisite for target localization, nor is accurate localization a prerequisite for same/different matching. However, localization is a prerequisite for the accurate recognition of target orientation (Experiment 2). In this case, it seems that features critical for localization "call" attention to a particular candidate location. This facilitates further (shape) analysis of the stimulus that is found there. This orienting process is by-passed if attention is cued to the location in advance.

Adult↗
PubMed1989

Variation in meals and sleep-activity patterns in aged subjects; its relevance to circadian rhythm studies.

The study was performed upon a sample of aged and non-institutionalized subjects. Information was obtained by questionnaires and diaries on personal factors during a typical week. A random subset was subjected to a more detailed analysis of the composition of their meals. Results showed that increasing age was correlated with: a decreased day-by-day variability in an individual's time of retiring, rising and eating meals; earlier sleep times; increased frequency of daytime naps and nocturnal awakenings; and decreased physical activity. These results occurred both in subjects living alone and in those living with company. Day-by-day differences in the composition of meals tended to decrease with age. When differences between individuals were considered then these tended to increase with age. Some implications of these findings for studies of circadian rhythmicity in aged subjects--in whom the timing of circadian rhythms becomes more erratic and amplitude falls--are discussed.

Aged↗
PubMed1989

Rate of processing and judgment of response speed: comparing the effects of alcohol and practice.

Both alcohol and practice affect choice reaction time. The present study was conducted to investigate the possibility that impairment from alcohol and improvement with practice could be attributed to changes in the efficiency of control mechanisms (Rabbitt, 1979a), some of which depend upon the ability to judge response speed accurately. Twenty subjects participated in a four-choice reaction time experiment in which they received no alcohol (NA) in Session 1 and either no alcohol (10 subjects) or 0.8 ml alcohol (A) per kilogram of body weight (10 subjects) in Session 2. The task was to respond as fast and as accurately as possible to each stimulus. In addition, subjects were required to press a fifth key after any response that they considered to be both fast and accurate. Subjects had no difficulty in performing this task: (1) there was a significant difference of 122 msec between the mean response time for correct responses indicated as fast and that for correct responses not indicated as fast, and (2) subjects indicated 1 in 4 correct responses but only 1 in 64 errors. Alcohol increased all response times by approximately 40 msec. In contrast, practice decreased response times less for correct responses not indicated as fast than for correct responses indicated as fast. The ability to distinguish between fast and slow responses was thus unaffected by alcohol, but was improved by practice. Responses indicated as "fast" were significantly faster than errors, and appeared to occur without warning (unlike errors, which tended to end a sequence of increasingly fast correct responses). The results suggest that alcohol and practice influence choice reaction time in qualitatively different ways: Alcohol impairs overall response speed but has no effect on the ability to judge response speed, whereas practice improves both.

Adult↗
PubMed1988

Effects of alcohol on lexical access.

Two experiments investigated the effect of alcohol on retrieval of lexical information. In each, volunteers received alcohol (1 ml per kg body weight) in one session and no alcohol in another in counterbalanced order. Experiment 1 was a computerised version of the Mill Hill vocabulary test in which subjects were required to define words by making multiple choice responses as fast as possible. As expected, correct decision time increased with item difficulty and tended to increase with alcohol, but there was no interaction between these effects. Experiment 2 was a lexical decision task involving words of low, medium and high frequency. Alcohol significantly increased correct response time but this did not interact with word frequency. In both experiments, decision times for individual items varied, indicating that lexical access is more difficult for rare than for frequent items. However, alcohol slowed easy and difficult decisions equally, which suggests that its locus of effect is not primarily on speed of access to semantic information, but rather on other aspects of the decision process.

Adolescent↗
PubMed1988

The role of selective attention in the visuo-spatial memory of patients suffering from dementia of the Alzheimer type.

The visuo-spatial memories of groups of dements suffering from Alzheimer's disease (DAT) and multi-infarct dementia (MID) were compared with those of low-IQ but non-dementing elderly volunteers. In contrast to the other two groups, the DAT subjects were hindered when extra visual information was available as a memory aid. Similarly, DAT subjects' performance on a visual search task was worsened when the displays were made more varied. The concept that DAT patients' visuo-spatial memory problems may be due to a failure of selective attention is discussed.

Aged↗
PubMed1987

Effect of alcohol on rate of forgetting.

The effect of alcohol (1 ml per kg body weight) on the rate of forgetting was investigated using a continuous recognition memory paradigm. Subjects were required to make a speeded old/new response to each of 200 items presented sequentially on a computer screen. Ninety-five items appeared twice. The numbers of items intervening between the first and second occurrence were 1, 4, 9, 19 and 49 (19 of each). With alcohol, subjects were less sensitive (decreased d-prime) and more conservative (increased beta). Recognition speed and accuracy were both impaired by alcohol and by increasing numbers of intervening items. In addition, an interaction between the effects of alcohol and of delay on recognition accuracy indicates that the impairment of memory with alcohol can be at least partly attributed to faster forgetting.

Adolescent↗
PubMed1987

Effects of alcohol on word categorization and recognition memory.

Thirty-six subjects were given no alcohol on one day and 1 ml alcohol/kg body weight on another (the order of administration being counterbalanced across subjects). In both sessions, they performed a word categorization task involving surface and semantic processing of lists of 50 words followed by a recognition task (the presentation of those words in addition to an equal number of new words for speeded recognition). For categorization, subjects were slower and less accurate with alcohol than without. For recognition, alcohol resulted in a decrease in d' and an increase in beta. Categorization was slower and recognition more accurate for semantic processing than for surface processing. There was no evidence that the detrimental effects of alcohol on recognition memory can be reduced by deeper processing of the to-be-remembered items.

Adolescent↗