Biomedical subjects

J Myerson

Publications and source records attributed to J Myerson.

At least 19 recordsLinked to original sources

PubMed2001

Area under the curve as a measure of discounting.

We describe a novel approach to the measurement of discounting based on calculating the area under the empirical discounting function. This approach avoids some of the problems associated with measures based on estimates of the parameters of theoretical discounting functions. The area measure may be easily calculated for both individual and group data collected using any of a variety of current delay and probability discounting procedures. The present approach is not intended as a substitute for theoretical discounting models. It is useful, however, to have a simple, univariate measure of discounting that is not tied to any specific theoretical framework.

Animals↗

PubMed2000

Behavioral evidence for brain-based ability factors in visuospatial information processing.

The present study examined possible parallels between the structure of human visuospatial abilities and the organization of the neural systems. Forty-eight participants were tested on seven speeded visuospatial tasks. Three of these tasks were constructed so as to rely primarily on known ventral stream functions and four were constructed so as to rely primarily on known dorsal stream functions. Both sets of tasks spanned approximately the same range of difficulty as indexed by both the speed and accuracy of decision making. Factor analysis of response times on the seven tasks revealed only two significant factors. The putative ventral stream tasks all loaded heavily on one factor (mean loading=0.843) but only weakly on the other factor (mean loading=0.222); the putative dorsal stream tasks showed the opposite pattern in that they all loaded heavily on the second factor (mean loading=0.828) but only weakly on the first factor (mean loading=0.229). These findings are consistent with the hypothesis that human visuospatial abilities can be classified using categories based on the specializations of underlying neural structures and systems.

Adult↗

PubMed2000

Converging evidence that visuospatial cognition is more age-sensitive than verbal cognition.

In 3 separate experiments, the same samples of young and older adults were tested on verbal and visuospatial processing speed tasks, verbal and visuospatial working memory tasks, and verbal and visuospatial paired-associates learning tasks. In Experiment 1, older adults were generally slower than young adults on all speeded tasks, but age-related slowing was much more pronounced on visuospatial tasks than on verbal tasks. In Experiment 2, older adults showed smaller memory spans than young adults in general, but memory for locations showed a greater age difference than memory for letters. In Experiment 3, older adults had greater difficulty learning novel information than young adults overall, but older adults showed greater deficits learning visuospatial than verbal information. Taken together, the differential deficits observed on both speeded and unspeeded tasks strongly suggest that visuospatial cognition is generally more affected by aging than verbal cognition.

Adolescent↗

PubMed2000

Age and individual differences in visuospatial processing speed: testing the magnification hypothesis.

Forty young adults and 40 older adults performed seven visuospatial information processing tasks. Factor analyses of the response times (RTs) yielded a single principal component with a similar composition in both age samples. For both samples, regressing the mean RTs of fast and slow subgroups for the seven tasks (18 conditions) on the corresponding mean RTs for their age group accounted for 99% of the variance. Taken together, these findings suggest that individual differences in processing time were largely task independent. The magnification hypothesis, a simple mathematical model of the interaction between age and ability, is presented. This model correctly predicts the finding that in both the young and the older adult groups, individual differences increased systematically with task difficulty. The magnification hypothesis also explains the regression parameters describing individual differences among young adults and predicts correctly that equivalent parameters describe individual differences among older adults. According to the magnification hypothesis, the RTs of slower individuals are more affected by aging than those of faster individuals, and slower individuals may be more at risk with respect to other biological insults (e.g., changes in health status) as well.

Adult↗

PubMed1999

Amount of reward has opposite effects on the discounting of delayed and probabilistic outcomes.

Previous research has shown that the value of large future rewards is discounted less steeply than is the value of small future rewards. These experiments extended this line of research to probabilistic rewards. Two experiments replicated the standard findings for delayed rewards but demonstrated that amount has an opposite effect on the discounting of probabilistic rewards. That is, large probabilistic amounts were discounted at the same or higher rates than small amounts. Although amount had opposite effects on the discounting of delayed and probabilistic rewards, nevertheless, the same form of mathematical function accurately described discounting of both types of reward. The findings suggest that fundamentally similar, but not identical, processes are involved in decision making regarding delayed and probabilistic rewards. The implications of these findings for impulsivity and self-control are discussed.

Adolescent↗

PubMed1999

Selective interference with verbal and spatial working memory in young and older adults.

Young and older adults were administered digit and location memory span tasks with and without verbal and spatial secondary tasks. Age differences were greater in location span than in digit span; however, there were no age differences in either the magnitude or pattern of effects of secondary tasks. There were also no age differences in the effects of secondary tasks on a combined (digit and location) task. On the digit and location span tasks, both young and older adults showed only domain-specific interference: naming colors selectively interfered with memory for digits, leaving memory for locations unaffected; pointing to matching colors selectively interfered with memory for locations, leaving memory for digits unimpaired. The results of the present study suggest a greater age deficit in spatial working memory than in verbal working memory, but provide no evidence of an age deficit in susceptibility to interference by secondary tasks in either domain.

Adolescent↗

PubMed1999

Individual and developmental differences in working memory across the life span.

The effects of secondary tasks on verbal and spatial working memory were examined in multiple child, young adult, and older adult samples. Although memory span increased with age in the child samples and decreased with age in the adult samples, there was little evidence of systematic change in the magnitude of interference effects. Surprisingly, individuals who had larger memory spans when there was no secondary task showed greater interference effects than their age-mates. These findings are inconsistent with the hypothesis that age and individual differences in working memory are due to differences in the ability to inhibit irrelevant information, at least as this hypothesis is currently formulated. Moreover, our results suggest that different mechanisms underlie developmental and individual differences in susceptibility to interference across the life span. A model is proposed in which memory span and processing speed both increase with development but are relatively independent abilities within age groups.

Adult↗

PubMed1998

Cerebellar contribution to linguistic processing efficiency revealed by focal damage.

The cerebellum's role in cognitive skills was examined in a child (L.C.) with focal injury to the left cerebellum. Initial symptoms included aphasia and dysarthria. At 3 and 9 months post-injury, clinical neuropsychological tests revealed persistent psychomotor slowing as well as deficits in executive functions. Further cognitive testing at 13 and 16 months post-injury demonstrated that L.C. processed information from both the linguistic and nonlinguistic domains more slowly than age-, grade- and sex-matched controls. Notably, her linguistic processing was more than twice as slow as that of her peers, whereas her nonlinguistic processing was only approximately 20% slower. Within each domain the degree of cognitive slowing was approximately the same across diverse tasks. These results are consistent with the hypothesis of a cerebellar contribution to cognitive processing, particularly the processing of linguistic information.

Cerebellar Diseases↗

PubMed1997

The interleukin-1 beta converting enzyme family of cysteine proteases.

Interleukin-1 beta converting enzyme (ICE) is the first enzyme of a new family of cysteine endoproteinases to be isolated and characterized. An overview of the structure and activity of ICE is outlined together with highlights of salient features common to members of each of the family members.

Amino Acid Sequence↗

PubMed1997

General lexical slowing and the semantic priming effect: the roles of age and ability.

Older adults performed three lexical information-processing tasks approximately 1.3 times slower than young adults. Consistent with general lexical slowing, slopes of regressions based on individual subjects' RTs on two of the tasks (single lexical decision and category judgment) did not differ from slopes based on the third (double lexical decision) task. Moreover, slopes based on the single lexical decision and category judgment tasks accurately predicted the size of semantic priming effects on the third (double lexical decision) task. This was true for the older group as a whole, and also for subgroups of fast, medium and slow older adults, as well as for young adult subgroups. The size of the semantic priming effects for the fast old and slow young subgroups (who differed in age but not in processing speed) were approximately equal, consistent with the idea that the effect of age on priming is entirely attributable to slowing. Across all tasks, each old subgroup (fast, medium, or slow) showed the same degree of slowing relative to the corresponding young subgroup, so that the differences in RTs observed between subgroups in the young sample were magnified in the old sample. Taken together, the present findings suggest that ability-related differences in lexical processing speed may be functionally equivalent to age-related differences and that both factors interact to determine performance on speeded lexical tasks.

Adult↗

PubMed1997

Rate of temporal discounting decreases with amount of reward.

The present, subjective value of a delayed reward is a decreasing function of the duration of the delay. This phenomenon is termed temporal discounting. To determine whether the amount of the reward influences the rate of temporal discounting, we had subjects choose between immediate and delayed hypothetical rewards of different amounts ($100, $2,000, $25,000, and $100,000 delayed rewards). As predicted by psychological models of the choice process, hyperbolic functions described the decrease in the subjective value of the delayed reward as the time until its receipt was increased (R2s from .86 to .99). Moreover, hyperbolic functions consistently provided more accurate descriptions of the data than did exponential functions predicted by an economic model of discounted utility. Rate of discounting decreased in a negatively accelerated fashion as the amount of the delayed reward increased, leveling off by approximately $25,000. These findings are interpreted in the context of different psychological models of choice, and implications for procedures to enhance self-control are discussed.

Adolescent↗

PubMed1996

Temporal discounting in choice between delayed rewards: the role of age and income.

This study examined the effects of age and income temporal discounting (i.e. the decrease in the subjective value of a reward as the delay to its receipt increases). The value of delayed hypothetical monetary rewards was discounted at similar rates by adults of different ages but similar income levels, but at different rates by adults of similar age but different income levels. Specifically, lower income older adults showed a greater degree of temporal discounting than did either upper income older adults or upper income younger adults, but there were no age differences in discounting between the upper income groups. Comparison of these findings with those of a previous study (Green, Fry, & Myerson, 1994) suggests that impulsivity in decision making declines rapidly in young adulthood, reaching stable levels in the 30s. Further, age and income appear to interact in determining the impulsivity of decision making by adults.

Adult↗

PubMed1996

Toward the development of a gene index to the human genome: an assessment of the nature of high-throughput EST sequence data.

A rigorous analysis of the Merck-sponsored EST data with respect to known gene sequences increases the utility of the data set and helps refine methods for building a gene index. A highly curated human transcript data base was used as a reference data set of known genes. A detailed analysis of EST sequences derived from known genes was performed to assess the accuracy of EST sequence annotation. The EST data was screened to remove low-quality and low-complexity sequences. A set of high-quality ESTs similar to the transcript data base was identified using BLAST; this subset of ESTs was compared with the set of known genes using the Smith-Waterman algorithm. Error rates of several types were assessed based on a flexible match criterion defining sequence identity. The rate of lane-tracking errors is very low, approximately 0.5%. Insert size data is accurate within approximately 20%. Reversed clone and internal priming error rates are approximately 5% and 2.5%, respectively, contributing to the incorrect identification of reads as 3' ends of genes. Follow-up investigation reveals that a significant number of clones, miscategorized as reversed, represent overlapping genes on the opposite strand of entries in the transcript data base. Relevance of these results to the creation of a high-quality index to the human genome capable of supporting diverse genomic investigations is discussed.

Algorithms↗

PubMed1995

PROFILER: a tool for automatic searching of internally maintained databases.

A new application program, the BIOINFORMATICS PROFILER, is described which simplifies the analysis of new genome sequence information appearing on a daily basis. Control tasks are defined through an intuitive graphical user interface and are executed at user defined nightly intervals. Electronic mail is sent to indicate that search results have been found. All task output is presented to users in the form of hypertext (HTML), allowing easy browsing. Currently supported tasks include BLAST and FastA sequence searching, keyword based searching of network news articles and WAIS databases, examination of GenBank sequence entries using regular expressions and boolean operations and protein sequence motif searching.

Amino Acid Sequence↗

PubMed1995

Converging evidence for domain-specific slowing from multiple nonlexical tasks and multiple analytic methods.

Older and young adults were tested on eight nonlexical tasks that overlapped extensively in complexity: disjunctive choice reaction time, line-length discrimination, letter classification, shape classification, mental rotation, visual search, abstract matching, and mental paper-folding. Performance on the first seven tasks was associated with equivalently low error rates in both groups, making it possible to directly compare their response times (RTs) on these tasks. Consistent with domain-specific slowing, the relationship between the RTs of the older adults and the RTs of the young adults was well described by a task-independent mathematical (Brinley) function. Evidence from this analysis and from analyses based on task-specific information-processing models leads to similar conclusions and provides converging support for general cognitive slowing in the nonlexical domain.

Adult↗

PubMed1995

Discounting of delayed rewards: Models of individual choice.

The present paper addresses the question of the form of the mathematical relation between the time until a delayed reward and its present value. Data are presented from an experiment in which subjects chose between hypothetical amounts of money available either immediately or after a delay (Green, Fry, & Myerson, 1994). Analyses of the behavior of individual young adults demonstrated that temporal discounting is better described by hyperbola-like functions than by exponential decay functions. For most individuals, the parameter that determines the rate of discounting varied inversely with amount. Raising the denominator of the discounting function to a power resulted in better descriptions of the data from most subjects. Two possible derivations of the temporal discounting function are proposed, a repeated choice model and an expected value model. These provide theoretical interpretations for amount-dependent discounting but amount-independent exponent parameters.

Journal Article↗

PubMed1994

Brinley plots, explained variance, and the analysis of age differences in response latencies.

Critics of Brinley plot analyses (e.g., Fisk, Fisher, & Rogers, 1992; Perfect, 1994) claim: (a) that lack of overlap between latencies on different tasks inflates r2 values; (b) that Brinley plots mask task-specific age differences; and (c) that measurement error in young adults' latencies precludes the use of regression techniques with Brinley plot data. We dispute these claims. We show that lack of overlap does not inflate r2 and that the possible presence of task-specific effects in Brinley plot data may be evaluated using standard regression techniques. These techniques are illustrated using data from the Fisk and Rogers (1991) study of visual and memory search. Analysis of their data reveals significant differences between the lexical and nonlexical domains, but not between types of search. Finally, the effect of measurement error on Brinley plot analyses is shown to be small and, if taken into account, leads to increased support for general cognitive slowing.

Adolescent↗

PubMed1993

Short-term and long-term effects of reinforcers on choice.

The relation between molar and molecular aspects of time allocation was studied in pigeons on concurrent variable-time variable-time schedules of reinforcement. Fifteen-minute reinforcer-free periods were inserted in the middle of every third session. Generalized molar matching of time ratios to reinforcer ratios was observed during concurrent reinforcement. Contrary to melioration theory, preference was unchanged during the reinforcer-free periods as well as in extinction. In addition to this long-term effect of reinforcement, short-term effects were observed: Reinforcers increased the duration of the stays during which they were delivered but had little consistent effect either on the immediately following stay in the same schedule or on the immediately following stay in the alternative schedule. Thus, an orderly effect of reinforcer delivery on molecular aspects of time allocation was observed, but because of its short-term nature, this effect cannot account for the matching observed at the molar level.

Journal Article↗