Solitary fibrous tumour of the pleura: a rare cause of digital clubbing

A woman in her early 70s was found to have incidental finger clubbing at a fracture clinic consultation for an unrelated problem. She reported no associated respiratory symptoms and was referred back to her General Practitioner for further investigation. A chest radiograph revealed a large left-sided mass. This was characterised as a pleural-based mass on CT, resulting in localised atelectasis and mediastinal shift. A CT guided biopsy revealed histology consistent with a solitary fibrous tumour of the pleura and the patient was referred for thoracotomy and resection.

Diagnosis of spontaneous secondary tension pneumothorax following apparent recovery from coronavirus disease 2019 pneumonitis: a case report

BACKGROUND

Coronavirus disease 2019 has been associated with a plethora of different manifestations of systems affected (including pulmonary, gastrointestinal, and thrombotic disease) and time to presentation of complications. Pneumothorax has been established as a complication in the literature. However, tension pneumothorax remains a rare presentation with higher mortality. We report a case of secondary tension pneumothorax in a patient following apparent recovery from coronavirus disease 2019 pneumonitis.

CASE PRESENTATION

Eight days after resolution of coronavirus disease 2019 pneumonitis symptoms, a 51-year-old Caucasian man with no pre-existing pulmonary disease was brought into the emergency department following 48 hours of progressive shortness of breath. Further clinical assessment revealed reduced breath sounds in the right lung, blood pressure was 116/95 mmHg, and jugular venous pressure was not elevated. Chest x-ray showed right-sided tension pneumothorax with mediastinal shift. Insertion of a chest drain led to rapid resolution of symptoms, and the patient was discharged following full re-expansion of the lung.

CONCLUSIONS

The period of recovery from coronavirus disease 2019 is variable. Clinicians should consider tension pneumothorax as a possible complication of coronavirus disease 2019 pneumonitis in patients presenting with type 1 respiratory failure, even after resolution of pneumonitis symptoms and a considerable time period following initial contraction of coronavirus disease 2019.

Discounting of delayed rewards across the life span: age differences in individual discounting functions

The present effort addressed both the issue of the generality of choice models and the issue of possible qualitative developmental change in temporal discounting by examining behavior at the individual level across the life span. Data from individual children, young adults, and older adults who participated in two previous studies were analyzed [Green, L., Fry, A.F., Myerson, J., 1994. Discounting of delayed rewards: a life-span comparison. Psychol. Sci. 5, 33-36; Green, L., Myerson, J., Lichtman, D., Rosen, S., Fry, A., 1996. Temporal discounting in choice between delayed rewards: the role of age and income. Psychol. Aging 11, 79-84]. At all ages, a hyperbola-like function originally proposed by Green et al. (1994) based on group data, provided the best description of individual discounting functions. Two developmental trends were observed. The rate at which individuals discounted the value of delayed rewards decreased with age, and there was a systematic change in the shape of the discounting function. Each of these trends was reflected in a separate parameter of the model. The fact that the same mathematical model described the behavior of individuals of different ages suggests that age and individual differences in the discounting of delayed rewards are primarily quantitative in nature and reflect variations on fundamentally similar choice processes.

Thrombin-inhibiting perfluorocarbon nanoparticles provide a novel strategy for the treatment and magnetic resonance imaging of acute thrombosis

BACKGROUND

As a regulator of the penultimate step in the coagulation cascade, thrombin represents a principal target of direct and specific anticoagulants.

OBJECTIVE

A potent thrombin inhibitor complexed with a colloidal nanoparticle was devised as a first-in-class anticoagulant with prolonged and highly localized therapeutic impact conferred by its multivalent thrombin-absorbing particle surface.

METHODS

PPACK (Phe[D]-Pro-Arg-Chloromethylketone) was secured covalently to the surface of perfluorocarbon-core nanoparticle structures. PPACK and PPACK nanoparticle inhibition of thrombin were assessed in vitro via thrombin activity against a chromogenic substrate. In vivo antithrombotic activity of PPACK, heparin, non-functionalized nanoparticles and PPACK nanoparticles was assessed through intravenous (i.v.) administration prior to acute photochemical injury of the common carotid artery. Perfluorocarbon particle retention in extracted carotid arteries from injured mice was assessed via (19) F magnetic resonance spectroscopy (MRS) and imaging (MRI) at 11.7 T. Activated partial thromboplastin time (APTT) measurements determined the systemic effects of the PPACK nanoparticles at various times after injection.

RESULTS

 An optical assay verified that PPACK nanoparticles exceeded PPACK's intrinsic activity against thrombin. Application of an in vivo acute arterial thrombosis model demonstrated that PPACK nanoparticles outperformed both heparin (P=0.001) and uncomplexed PPACK (P = 0.0006) in inhibiting thrombosis. (19) F MRS confirmed that PPACK nanoparticles specifically bound to sites of acute thrombotic injury. APTT normalized within 20 min of PPACK nanoparticles injection.

CONCLUSIONS

 PPACK nanoparticles present thrombin-inhibiting surfaces at sites of acutely forming thrombi that continue to manifest local clot inhibition even as systemic effects rapidly diminish and thus represent a new platform for localized control of acute thrombosis.

Automaintenance without stimulus-change reinforcement: Temporal control of key pecks

Yoked pairs of experimentally naive pigeons were exposed to a modified autoshaping procedure in which key pecking by the leader birds postponed both keylight termination and access to grain for the leader and the follower bird. Key pecking developed and was maintained in all birds and continued through two reversals of roles in the yoked procedure. Although temporal control developed more slowly in follower birds, asymptotic temporal distributions of key pecking were similar for all birds in both leader and follower roles; maximum responding occurred soon after keylight onset and decreased to a minimum prior to reinforcement. Response distributions for both leader and follower birds were described by Killeen's (1975) mathematical model of temporal control. Follower birds received response-independent reinforcement, and the development by these birds of temporal distributions which are minimal immediately prior to reinforcement is without precedent in Pavlovian appetitive conditioning. However, maintenance of key pecking by the leader birds, whose responses postponed both stimulus-change and food reinforcement, supports an interpretation of autoshaped and automaintained key pecking as responding elicited by signaled grain presentation.

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.

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.

Choice in transition: A comparison of melioration and the kinetic model

Transition-state choice behavior of pigeons was examined in two experiments designed to test predictions of melioration and the kinetic model. Both experiments began with an initial training condition during which subjects were maintained on concurrent variable-interval schedules. In Experiment 1, subjects were then exposed to concurrent variable-ratio schedules, whereas in Experiment 2, subjects were then exposed to concurrent extinction. Contrary to the predictions of melioration, but consistent with the kinetic model, acquisition of preference on concurrent variable-ratio schedules followed a negatively accelerated logistic trajectory, and preference remained stable in concurrent extinction. Predictions made by the kinetic model concerning rates of switching between alternatives were also supported.

Practical implications of the matching law

Many problem situations in applied settings are best conceptualized as choice situations. In addition, applied behavior analysts create choice situations when they reinforce a competing response to decrease inappropriate behavior. When such situations are analyzed using the matching law, variable interval (VI) schedules of reinforcement prove to be a superior intervention strategy regardless of the nature of the schedule maintaining other, less appropriate behavior. This conclusion is robust in that VI schedule superiority is observed in situations in which choice behavior is highly biased or shows pronounced undermatching as well as those in which the matching law holds precisely. Our analysis demonstrates the potential practical value of mathematical descriptions of behavior.

Histology classification is not a predictor of clinical outcomes in advanced non-small cell lung cancer (NSCLC) treated with vinorelbine or gemcitabine combinations

BACKGROUND

Until recently, histology has not been clearly or consistently described in the literature as a prognostic or predictive variable in advanced NSCLC studies. We have categorised patients treated with vinorelbine and gemcitabine based first line chemotherapy regimes for advanced NSCLC as either squamous or non-squamous, and also as either adenocarcinoma and non-adenocarcinoma, and compared outcome.

MATERIAL AND METHODS

420 patients treated with platinum/gemcitabine, platinum/vinorelbine or single agent gemcitabine or vinorelbine as first line chemotherapy for advanced NSCLC were identified. The influence of pathology on progression free survival (PFS) and overall survival (OS) has been investigated by means of a Cox regression analysis. Hazard ratios with 95% CIs have been given for each pathological type after adjusting for the effects of age, gender, stage (III vs. IV), PS (0/1 vs. 2/3) and treatment type (platinum doublet vs. single agent).

RESULTS

Neither univariate nor multivariate analysis suggested that there was a significant difference in the response rates for adenocarcinoma vs. non-adenocarcinoma or between squamous and non-squamous pathology. There was no difference in PFS between adenocarcinoma and non-adenocarcinoma pathologies until 8 months (p = 0.98), and there was a statistically significant advantage in PFS for squamous vs. non-squamous pathologies (p = 0.04). Using multivariate Cox regression analysis to adjust for the effects of age, gender, stage, PS, and treatment type, the pathology subtype was not significant. There was no difference in OS in any group.

CONCLUSIONS

These results suggest that histology may not be considered as a predictor of clinical outcome using these drugs.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

General slowing in semantic priming and word recognition

Analyses of lexical decision studies revealed that (a) older (O) adults' mean semantic priming effect was 1.44 times that of younger (Y) adults, (b) regression lines describing the relations between older and younger adults' latencies in related (O = 1.54 Y-112 and unrelated conditions (O = 1.50 Y-93) were not significantly different, and (c) that there was a proportional relation between older and younger adults' priming effects (O = 1.48 Y-2). Analyses of word-naming studies yielded similar results. Analyses of delayed pronunciation data (Balota & Duchek, 1988) revealed that word recognition was 1.47 times slower in older adults, whereas older adults' output processes were only 1.26 times slower. Overall, analyses of whole latencies and durations of component processes provide converging evidence for a general slowing factor of approximately 1.5 for lexical information processing.

General cognitive slowing in the nonlexical domain: an experimental validation

Older and younger adults were tested on 4 nonlexical tasks: choice reaction time, letter classification, mental rotation, and abstract matching. A positively accelerated relation was observed between older and younger adults' latencies. Consistent with general slowing, the relation observed with the same subjects in each condition was more than 3 times as precise as in a comparable meta-analysis. Further analyses compared the ability of various models to describe the present data and also to predict the data on the basis of parameters estimated from a previous meta-analysis. Compared with linear models, the information-loss and overhead models provided more accurate accounts of general cognitive slowing in the nonlexical domain.

How general is general slowing? Evidence from the lexical domain

Three analyses are reported that are based on data from 19 studies using lexical tasks and a reduced version of the Hale, Myerson, and Wagstaff (1987) nonlexical data set. The results of Analysis 1 revealed that a linear function with a slope of approximately 1.5 described the relationship between the lexical decision latencies of older (65-75 years) and younger (19-29 years) adults. The results of Analysis 2, based on response latencies from 6 lexical tasks other than lexical decision, revealed a virtually identical linear relationship. In Analysis 3, it was found that performance on nonlexical tasks spanning the same range of task difficulty was described by a significantly steeper regression line with a slope of approximately 2.0. These findings suggest that although general cognitive slowing is observed in both domains, the degree of slowing is significantly greater in the nonlexical domain than in the lexical domain. In addition, these analyses demonstrate how the meta-analytic approach may be used to determine the limits to the external validity of experimental findings.

General cognitive slowing in the nonlexical domain: An experimental validation

Older and younger adults were tested on 4 nonlexical tasks: choice reaction time, letter classification, mental rotation, and abstract matching. A positively accelerated relation was observed between older and younger adults' latencies. Consistent with general slowing, the relation observed with the same subjects in each condition was more than 3 times as precise as in a comparable meta-analysis. Further analyses compared the ability of various models to describe the present data and also to predict the data on the basis of parameters estimated from a previous meta-analysis. Compared with linear models, the information-loss and overhead models provided more accurate accounts of general cognitive slowing in the nonlexical domain.

How general is general slowing? Evidence from the lexical domain

Three analyses are reported that are based on data from 19 studies using lexical tasks and a reduced version of the Hale, Myerson, and Wagstaff (1987) nonlexical data set. The results of Analysis 1 revealed that a linear function with a slope of approximately 1.5 described the relationship between the lexical decision latencies of older (65-75 years) and younger (19-29 years) adults. The results of Analysis 2, based on response latencies from 6 lexical tasks other than lexical decision, revealed a virtually identical linear relationship. In Analysis 3, it was found that performance on nonlexical tasks spanning the same range of task difficulty was described by a significantly steeper regression line with a slope of approximately 2.0. These findings suggest that although general cognitive slowing is observed in both domains, the degree of slowing is significantly greater in the nonlexical domain than in the lexical domain. In addition, these analyses demonstrate how the meta-analytic approach may be used to determine the limits to the external validity of experimental findings.

The information-loss model: a mathematical theory of age-related cognitive slowing

A model of cognitive slowing is proposed with the following assumption: Information is lost during processing, processing occurs in discrete steps with step duration inversely related to the amount of information currently available, and the effect of aging is to increase the proportion of information lost per step. This model correctly predicts a positively accelerated relation between latencies of older and younger adults and provides a unified account of the effects of task complexity, practice, speed-accuracy tradeoffs, and fluctuations in individual performance. Strong support for the thesis that cognitive slowing is global, and not localized in specific age-sensitive components, is provided by the fact that the model accurately predicts the latencies of older adults on the basis of those of younger adults, without regard to the nature of the task, across a latency range of nearly 2 orders of magnitude.

Global increase in response latencies by early middle age: complexity effects in individual performances

Ten young women (age 20 to 22 years) and 10 middle-aged women (age 36 to 44 years) served as subjects in choice reaction time, letter classification, and abstract matching-to-sample tasks. In each of seven conditions, the older group responded more slowly than the younger group. Age differences showed a complexity effect. That is, differences between the latencies of young and old subjects increased as the latency of the young subjects increased. Both linear and power functions accurately described the relation between the latencies of the middle-aged and young adult groups. This was true not only for the relation between average latencies but also for the relation between corresponding quartiles of latency distributions. Similar results were observed at the individual level: All middle-aged subjects showed complexity effects, and, for each middle-aged subject, the relation between her latencies and those of the average young adult was well described by linear and power functions. These findings indicate that age-related slowing is apparent by age 40, and that complexity effects are observable in individual performances. This slowing is global and not specific to particular tasks, as indicated by the fact that the latencies of older adults can be predicted directly from those of younger adults without regard to the nature of the task.

Age, variability, and speed: between-subjects diversity

Two independent data sets were selected to examine the interrelations among reaction time (RT), between-subject variability or diversity (SD), and age. In both data sets, a strong correlation between RT and SD was obtained. This strong correlation was not affected when age was controlled in a partial correlation analysis. On the other hand, a weaker but significant correlation was obtained between age and SD. This correlation was eliminated when RT was controlled in a partial correlation analysis. Our analyses of the two data sets also indicated that the relation between RT and SD is identical for both young and elderly groups. Thus, the greater diversity often observed in performances of older groups is a direct consequence of slowing, rather than an independent effect of advancing age.

Age, variability, and speed: Between-subjects diversity

Two independent data sets were selected to examine the interrelations among reaction time (RT), between-subject variability or diversity (SD), and age. In both data sets, a strong correlation between RT and SD was obtained. This strong correlation was not affected when age was controlled in a partial correlation analysis. On the other hand, a weaker but significant correlation was obtained between age and SD. This correlation was eliminated when RT was controlled in a partial correlation analysis. Our analyses of the two data sets also indicated that the relation between RT and SD is identical for both young and elderly groups. Thus, the greater diversity often observed in performances of older groups is a direct consequence of slowing, rather than an independent effect of advancing age.

General slowing of nonverbal information processing: evidence for a power law

Data were analyzed from studies of nonverbal information processing in which the dependent measure was the latency of pressing or releasing a response key. Positively-accelerated power functions described the relationship between the response latencies of groups of older (50 to 60 years and 65 to 75 years) and younger adults (20 to 25 years) with extreme precision (r2 = .99). The exponent of the best-fitting power function increased with the age of the older group. The form of the relationship is allometric, and is consistent with a model (Botwinick, 1984) in which response latency increases exponentially with task difficulty. The present findings suggest that this model holds across a wide variety of information-processing tasks and over a very broad range of latencies.