Patrick Rabbitt

What does a man do after he makes an error? an analysis of response programming

When people make errors during continuous tasks they temporarily pause and then slow down. One line of explanation has been that they monitor feedback to detect errors, that they may make incidental responses when errors occur (e.g. they may swear) and that they may pause to analyse their errors. In all these cases they may be assumed to act as single channel information processing systems of limited capacity, and to be unable to recognise any new signal until these processes have been completed. Analysis of response after errors shows that this cannot be the case. Responses after errors are inaccurate, but are not slow when they require the subject to make the response which he should have made on the previous trial (i.e. to make an error correction response). Subjects thus must recognise new signals as soon as they occur. The present results require a new model of error detection and correction, and a model for response programming and priming.

Brain-derived neurotrophic factor polymorphism Val66Met influences cognitive abilities in the elderly.

A functional brain‐derived neurotrophic factor (BDNF) gene polymorphism (Val66Met) that alters activity‐dependent secretion has previously been reported to influence cognitive functioning. A large proportion of these reports suggest that the Met allele, which results in reduced secretion of BDNF, impairs long‐term memory as a direct consequence of its influence on hippocampal function but has little influence on working memory. In contrast, other studies have found that the Met allele can also play a protective role in certain neurological conditions and is associated with improved non‐verbal reasoning skills in the elderly suggesting effects that appear disease, domain and age specific. We have investigated six haplotype‐tagging single nucleotide polymorphisms (SNPs) using a cohort of 722 elderly individuals who have completed cognitive tests that measured the domains of fluid intelligence, processing speed and memory. We found that the presence of the Met allele reduced cognitive performance on all cognitive tests. This reached nominal significance for tests of processing speed (P = 0.001), delayed recall (P = 0.037) and general intelligence (g) (P = 0.008). No association was observed between cognitive tests and any other SNPs once the Val66Met was adjusted for. Our results support initial findings that the Met allele is associated with reduced cognitive functioning. We found no evidence that the Met allele plays a protective role in older non‐demented individuals. Magnetic resonance imaging data collected from a subgroup of 61 volunteers showed that the left and right hippocampus were 5.0% and 3.9% smaller, respectively, in those possessing the Met allele, although only a non‐significant trend was observed.

An elementary preliminary taxonomy for some errors in laboratory choice RT tasks

Abstract A model derived from demonstrations of speed-error trade-off in choice RT experiments (S CHOUTEN and B EKKER , 1967; R ABBITT , 1969a) is discussed as an explanatory basis for all types of error in all choice RT tasks. This discussion is conducted in the context of a preliminary taxonomy of errors distinguishing errors of perceptual discrimination from three types of errors in the selection and execution of responses (i.e. motor sequence programming errors, motor set errors and motor confusion errors). It is clear that speed-error trade-off functions differ between these classes of errors. It must be concluded that while speed-error trade-off functions allow detailed analysis of sequential operations between perceptual discrimination and response selection within individual tasks, they do not provide a valid means of distinguishing between performance in different tasks. The constraints and the advantages implicit in the use of such functions are further discussed.

Detection of Errors by Skilled Typists

Abstract Skilled typists are able to detect and correct many errors which they make in copy text, even when they cannot see their copy; (Long 1976. West, 1967). The present investigation shows that they can also do this when they see neither their copy nor the keyboard they use; and that when they detect that they have made errors they arc usually also able to specify precisely what these have been. Typists sometimes make one, or even two additional correct keystrokes before pausing to signal that they have committed an error. They are nevertheless sometimes still able to report precisely what these errors were When copy obtained from a typewriter using mechanical linkages is examined, the density of impressions of different characters may be taken to indicate how hard particular keys have been struck. A second experiment shows that errors, more frequently than correct responses, are executed with light keystrokes. This, in line with previous work by Megaw (1972). suggests that typists sometimes become aw...

The changing pattern of perceptual analytic strategies and response selection with practice in a two-choice reaction time task

In the experiment reported here the primary hypothesis proposed, which was supported by the data, was that subjects performing a two-choice self-paced serial RT task would learn to change their strategy of perceptual analysis of signals presented to them as they became progressively more practised. Early in practice each signal is identified as a particular state of the display and an appropriate response is then made. Well practised subjects, however, select their responses by reference to the change or constancy between successive displays. This strategy implies that the assumptions made by the generally accepted simple S-R connectionist model of two-choice serial RT may be quite misleading, since the choice of any particular response must be determined not only by the display state but also by what the previous response had been.

Psychological refractory delay and response-stimulus interval duration in serial, choice-response tasks

Abstract It has been suggested that for some fixed period of time after making a response a human subject is unable to process further information because his single decision channel is occupied with an analysis of kinaesthetic or other feedback, validating the successful completion of his motor act ( Welford , 1952, 1959, 1967). On such assumptions it might be predicted that mean correct RT in serial choice tasks would vary inversely with the duration of the time-interval between the completion of each sequent response and the moment of onset of the subsequent signal (R-S interval duration). In three experiments performance was compared between conditions in which R-S intervals varied between 20 msec and 220 msec. The experiments also allowed examinations of the possibility of interactions between the effects of R-S interval duration and signal and response repetition effects; ( Bertelson , 1965; Rabbitt , 1968a). Experiment 3 also examined the possibility of interactions between the effects of R-S interval duration and the effects of variations in response information load. In experiments I and 2 data were analysed to compare delays to response following errors with delays to responses proceded by at least two correct responses. The expected inverse relationship of mean correct RT to R-S interval duration was observed, but the data do not allow the interpretation that a fixed refractory delay follows each sequent response. The other interactions examined were not significant. The results allow identification of some complex interactions which result in slow responses following errors in serial choice tasks.

Influence of serotonin transporter gene polymorphisms on cognitive decline and cognitive abilities in a nondemented elderly population.

Dysfunction of the serotonergic pathway disrupts normal cognitive functioning and is believed to be the underlying basis for a variety of psychiatric disorders. Two functional polymorphisms within the serotonin transporter (SLC6A4) gene (promoter 44 bp insertion/deletion (HTTLPR) and an intron two 16 or 17 bp variable number tandem repeat (VNTR2)) have been extensively studied in psychiatric conditions but not in the cognitive functioning of normal individuals. We have investigated these two polymorphisms for association with both the level of cognitive abilities and their decline with age using a cohort consisting of over 750 elderly nondemented individuals with a follow-up of up to 15 years. We found that volunteers homozygous for the VNTR2 12 allele had a faster rate of decline for all cognitive tests. This reached significance for both tests of fluid intelligence (novel problem solving) (AH1 P=0.002, AH2 P=0.014), the test of semantic memory (P=0.010) and general cognitive ability (P=0.006). No association was observed between the HTTLPR polymorphism and the rate of cognitive decline when analysed either independently or in combination with the VNTR2 polymorphism based on their influence on expression in vitro. No associations were observed between the two polymorphisms and the baseline level of cognitive abilities. This is only the second gene that has been reported to regulate the rate of cognitive decline in nondemented individuals and may be a target for the treatment of cognitive impairment in the elderly.

Effects of global atrophy, white matter lesions, and cerebral blood flow on age-related changes in speed, memory, intelligence, vocabulary, and frontal function.

Brain images were obtained from 133 healthy people of ages 61-85 years who completed 20 tests of information processing speed, intelligence, frontal and executive function, memory, and vocabulary. Structural equation models examined relationships between cognitive test scores, ages and measurements of global age-associated atrophy, white matter lesions, and cerebral blood flow. These neurophysiological measures jointly account for all age-related variance in information processing speed. Speed entirely mediated relationships between neurophysiological measures and memory and partly mediated relationships between neurophysiological measures and intelligence and frontal function. Neurophysiological measures, but not calendar age, accounted for vocabulary scores. Cognitive slowing was responsible for some, but not all, age-related declines in mental function. Age-related declines in intelligence, frontal function, and speed were due to changes in different functional systems.

Some errors of perceptual analysis in visual search can be detected and corrected.

This experiment tried to discover whether people can correct errors which occur because they incorrectly analyse a display to which they have to respond—whether, in fact, they can correct “perceptual” as well as “motor” errors. In a serial, self-paced visual search task, subjects made one response to indicate that a display of five or nine letters contained either of a pair of target letters, and another response when no target was present. Omission errors were much more common than False Identification Errors, but more of them were corrected. Omission errors were detected and corrected faster than False Identification Errors. Typically omission errors were slow responses while False Identification Errors were fast responses. It is possible to deduce that at least some errors resulting from incorrect analysis of a display can be detected and corrected, probably because of an extension of perceptual analysis during, or immediately after, the time when a response to the display is made.

Hand dominance, attention, and the choice between responses

Thirty pairs of matched right- and left-handed subjects carried out a serial C.RT task involving reaches between 2.4 cm square contact grids set at 2.4 cm intervals in a horizontal line. In one condition they responded with the right hand alone, in a second with the left and in a third they had to choose between hands on each trial responding to left side grids with the left hand and to right side grids with the right. All subjects took longer to respond when they had to choose between hands than when they used either hand alone. In the one-hand conditions neither group showed any effect of hand dominance. When choices had to be made between hands both groups responded faster with their dominant than with their nondominant hands. Analysis of the results was undertaken in terms of two hypothetical systems of instructions which might control machines designed to carry out similar tasks. It is concluded that in some tasks hand dominance can be described in terms of an attentional bias towards the field of operation of one effector rather than another. In the present task the effects of such possible attentional biases were shown not to interact with other effects, such as the facilitation of successive responses by repeated use of the same limb. These latter effects seem to depend on processes underlying execution of responses rather than choices between responding limbs.