Decline In Intelligence Research Articles

Expertise and age-related changes in components of intelligence.

In a sample of 263 male GO players at 48 levels of expertise and ranging from 18 to 78 years of age, it was found that factors of expertise deductive reasoning (EDR) and expertise working memory (EWM) were independent of factors of fluid reasoning (Gf) and short-term working memory (STWM) that, along with cognitive speed (Gs), have been found to characterize decline of intelligence in adulthood. The main effects of analyses of cross-sectional age differences indicated age-related decline in EDR and EWM as well as in Gf, STWM, and Gs. However, interaction and partialing analyses indicated that decline in EDR and EWM decreased to no decline with increase in level of expertise. The results thus suggest that with increase in factors known to raise the level of expertise--particularly, intensive, well-designed practice--there may be no age-related decline in the intelligence that is measured in the abilities of expertise.

Time-varying spectral change in the vowels of children and adults.

Recent studies have shown that time-varying changes in formant pattern contribute to the phonetic specification of vowels. This variation could be especially important in children's vowels, because children have higher fundamental frequencies (f0's) than adults, and formant-frequency estimation is generally less reliable when f0 is high. To investigate the contribution of time-varying changes in formant pattern to the identification of children's vowels, three experiments were carried out with natural and synthesized versions of 12 American English vowels spoken by children (ages 7, 5, and 3 years) as well as adult males and females. Experiment 1 showed that (i) vowels generated with a cascade formant synthesizer (with hand-tracked formants) were less accurately identified than natural versions; and (ii) vowels synthesized with steady-state formant frequencies were harder to identify than those which preserved the natural variation in formant pattern over time. The decline in intelligibility was similar across talker groups, and there was no evidence that formant movement plays a greater role in children's vowels compared to adults. Experiment 2 replicated these findings using a semi-automatic formant-tracking algorithm. Experiment 3 showed that the effects of formant movement were the same for vowels synthesized with noise excitation (as in whispered speech) and pulsed excitation (as in voiced speech), although, on average, the whispered vowels were less accurately identified than their voiced counterparts. Taken together, the results indicate that the cues provided by changes in the formant frequencies over time contribute materially to the intelligibility of vowels produced by children and adults, but these time-varying formant frequency cues do not interact with properties of the voicing source.

Relation between age-related decline in intelligence and cerebral white-matter hyperintensities in healthy octogenarians: a longitudinal study

White-matter hyperintensities are commonly found on magnetic resonance imaging (MRI) of elderly people with or without dementia. Studies of the relation between severity of white-matter hyperintensities and cognitive impairment have had conflicting results. We undertook a longitudinal study of age-related decline in intellectual function and MRI at age 80 years. From a cohort of 698 people born in 1914 and living in seven municipalities in Denmark, 68 healthy non-demented individuals had been tested with the Wechsler adult intelligence scale (WAIS) at ages 50, 60, and 70, and they agreed to further WAIS testing at age 80, and cerebral MRI at age 80-82 (mean age 82.3 years). We scored separately the numbers of periventricular and deep white-matter hyperintensities. Scores for periventricular hyperintensities in this sample included all possible degrees of severity, but no participant scored more than 75% of maximum for deep white-matter hyperintensities. Neither type was related to the WAIS IQs of the 80-year assessment, but both were significantly associated with decline in performance IQ from age 50 to age 80 years (bivariate correlation coefficients 0.32, p=0.0087, and 0.28, p=0.0227, respectively). An analysis based on two WAIS subtests showed that the association between white-matter hyperintensities and cognitive impairment was significant only for cognitive decline in the decade 70-80 years. Both periventricular and deep white-matter hyperintensities are related to decline in intelligence but, in healthy octogenarians, the cumulative effect of these features alone explains only a small part of the large differences among individuals in age-related decline in intelligence. Interpretation of the presence and severity of white-matter hyperintensities in a diagnostic context must be done cautiously.

補聴器による語音聴取に対する衝撃音の影響

The purpose of this investigation was to examine how speech intelligibility is affected by an impact noise for listeners wearing a hearing aid. In this experiment, the subjects consisted of 10 sensorineural hearing-impaired and five normal hearing listeners. Sentences mixed with a single impact noise or without noise were presented randomly to subjects wearing a hearing aid. The hearing aids used in this experiment were digital hearing aids (TD-1) which compress the signals in the time domain, and conventional analog hearing aids with peak clipping (PC) or automatic gain control (AGC). The results demonstrated that the intelligibility of sentences mixed with an impact noise decreased when the hearing-impaired subjects wore the analog hearing aid. Interestingly, the decline in intelligibility arose in the phrases not only after the impact noise, but also before the noise. On the other hand, there was none or only a slight decrease in intelligibility, regardless of the impact noise, in the normal hearing subjects and the hearing-impaired wearing TD-1. These results indicate that the compression method adopted by TD-1 is useful for patients with sensorineural hearing loss even under conditions with impact noises. We believe that incompletely suppressed impact noises mask the speech signal, and thus causes a decrease in the speech recognition of hearing-impaired subjects wearing analog hearing aids.

Variability of neuropsychological deficits associated with carbon monoxide poisioning: four case reports

Carbon monoxide (CO) poisoning is associated with variable neuropsychological deficits, depending on levels of CO exposure and individual differences. Studies to date have reported variable findings, as their subjects have been exposed to different levels of CO from different poisoning sources. Four unique case studies are presented, all of whom experienced the same level of CO poisoning (17-29%) in the same accident. Two of the individuals were brothers with an identical genetic disorder (i.e. syndactylism) and the other two were brother/sister. The results indicated: (1) variable neuropsychological deficits despite similar levels of CO poisoning; (2) consistent estimated decline in intelligence; (3) similar memory decline for the two brothers, but not for the brother and sister; and (4) consistent late-onset emotional-behavioural difficulties. The results also suggested that the neuropsychological and emotional-behavioural deficits had an impact on the individual's ability to work.

Is age kinder to the initially more able?: differential ageing of a verbal ability in the Healthy Old People in Edinburgh study

Studies that examine whether there is differential age-related decline in intelligence test scores according to initial cognitive status, social class and education are reviewed. We tested the differential ageing hypothesis which states that decline in ability scores over time will be lower in those with superior mental ability, more education and higher social class at the time of original testing. 387 healthy old people were tested at baseline and followed up 4 years later. The National Adult Reading Test (NART) was administered on both occasions. NART-estimated IQ fell by a mean of 2.1 points over 4 years ( p<0.001). Subjects in higher social class categories had higher NART scores overall ( p<0.001), and had smaller NART decrements over 4 years. Ex-professional and -secretarial groups fell by a mean of 1.4 points in this period, versus 3.2 points for skilled manual, semi-skilled and unskilled groups. In addition, those who fell more in NART were older ( p=0.001), were less educated ( p<0.001), and had lower NART ( p<0.001) scores at baseline. In summary, those with higher baseline ability, in higher social class groups, with more education and who are younger are relatively protected from decline in this verbal ability with age. Possible mechanisms of differential decline in this verbal intelligence with age are discussed.

Terminus brain: the environmental threats to human intelligence

According to the author of this study, millions of people are suffering a decline in intelligence due to pollution, the absence of environmental micro-nutrients and a degraded psycho-social environment. This decline can range from severe intellectual disability to a variety of mild, sub-clinical dysfunctions experienced by most people in the population. Up to 90% of children in some African cities are tangibly affected by one pollutant - lead. In response to these fears, the US Congress declared the 1990s the Decade of the Brain. This study offers a wider, more comprehensive picture of the problem, ranging across the medical, social and environmental sciences, including evolutionary theory, disability studies, education, law and ethics.

Determinants of cognitive disorders in Autosomal Dominant Cerebellar Ataxia type 1

We assessed neuropsychological performances of 22 patients affected by Autosomal Dominant Cerebellar Ataxia type 1. All subjects completed a comprehensive battery of standardized tests requiring a verbal response, without time constraints. In order to verify the hypothesis that disease severity is the major factor in determining the cognitive status in this syndrome, patients were divided into three groups according to the severity of the clinical picture, as evaluated by the Inherited Ataxias Progression Scale (IAPS). Statistical analysis of the three groups' raw scores showed a significant decrement in patients with more severe clinical pictures on verbal short-term memory tasks. A similar trend, but not significant, was seen for general intelligence tests and verbal learning tasks. The decrement of verbal short-term memory could be related to motor speech problems. On the other hand, the decline of cognitive abilities over the course of the Autosomal Dominant Cerebellar Ataxia type 1 was not homogeneous enough to ensure statistically reliable trends. Therefore, this cross-sectional study suggests that the progression of the disease is a necessary factor in determining cognitive decline, but it is not sufficient. Other disease-related factors (age at onset, genotypic variety) could play a critical role: among these, the size of the expanded CAG repeats is significantly related to a decline of verbal intelligence and short-term memory in SCA2 patients.

Very Long Chain Fatty Acid Analysis of Dried Blood Spots on Filter Paper to Screen for Adrenoleukodystrophy

Adrenoleukodystrophy (ALD) is an X-linked recessive disorder characterized by progressive demyelination of cerebral white matter and adrenal insufficiency. ALD is the most common peroxisomal disease, afflicting 1 in 20 000 male newborns. Patients with childhood ALD manifest changes of character or behavior and a decline of intelligence and visual or motor dysfunction as the first symptoms during school age. Most of them lapse into a vegetative state and die within several years of onset (1). Patients with all clinical subtypes, including childhood ALD, adolescent ALD, adult ALD (cerebral type), adrenomyeloneuropathy, and Addison disease without neurological symptoms, have defects in the ALD gene (2). Defective activity of peroxisomal lignoceroyl-CoA ligase is considered to lead to the accumulation of very long chain fatty acid (VLCFA) in various tissues and fluids as a secondary phenomenon (3)(4). Dietary erucic acid (C22:1) therapy may help prevent neurological deterioration in presymptomatic boys (5)(6). Patients in the early or presymptomatic stages may be candidates for bone marrow transplantation (5)(7). Gene therapy may also become possible. Screening for ALD, especially in the presymptomatic stage, will be important when these therapeutic methods are established, as in the cases of phenylketonuria or maple syrup urine disease. ALD is usually diagnosed by plasma VLCFA analysis (1)(8), sometimes followed by measurement of β-oxidation activity in cultured skin fibroblasts (9) and mutation analysis of the ALD gene (2)(10)(11)(12)(13)(14)(15)(16). However, screening requires a simpler and more economical method to deal with a large number of subjects. Utilization of a dried blood spot on filter paper …

‘Much more at home with 3.999 pupils than with four’1: The contributions to psychometrics of Sir Godfrey Thomson

Godfrey Thomson's writings cover many areas of psychology, education and statistics but the most influential aspects of his work were at the interfaces between these three fields. His work revolved around the concept of intelligence: its nature, how to measure it, how far it was genetically determined and whether on average it was increasing or decreasing in society over time. His earlier work on the factorial nature of intelligence was dominated by a debate with Charles Spearman, who promoted the notion of general intelligence not only as one explanation of test data but as the only permissible explanation. It was this claim of uniqueness which Thomson contested. Initially the debate was conducted in terms of alternative competing theories but subsequently it was overtaken by the development of factor analysis as a statistical technique and a recognition that the debate concerned the merits of different methods of analysing data rather than deciding empirically between mutually exclusive theories. Thomson's views on the role which selective tests should play in education are contrasted with the role which he did play as the author of the Moray House tests, which were widely used by education authorities throughout Britain. The development of these tests enabled Thomson to collect data to show that larger families score lower on standardised tests, suggesting that there might be a long‐term decline in national intelligence. His role in the 1932 and 1947 Scottish Mental Surveys illustrates his concern with this possibility, though the surveys did not produce evidence of any such decline.

Stroke Signs and Symbols: The Psychological Significance of Focal Neurologic Deficits and Its Relevance for Rehabilitation

Early psychological signs and symptoms of stroke are generally attributed to focal brain disease. These include aphasia (dominant hemisphere), memory loss (hippocampal involvement), and poststroke depression (left hemisphere more likely than right; anterior more likely than posterior). Changes in global, nonfocal psychological categories, such as self-identity and personality, are not typically observed or addressed in the stroke’s early stages. However, an analysis of medically naive discourse about stroke suggests that patients and observers conceptualize and internalize three important, long-term psychological sequelae of stroke: (1) the dehumanization of the patient, (2) the onset of senescence, and (3) the decline of intelligence. These psychological sequelae represent changes in the otherwise more enduring features of psychological structure. They are part of the disease burden of stroke and need to be addressed in long-term rehabilitation programs.

Brief report: Changing perspectives on aging and intelligence: An empirical update

This study updated the examination of a four-phase, chronological progression model of published research perspectives on aging and intelligence. Phase I research emphasized the inevitable decline of intelligence during adulthood. Phase II research described aging intelligence as a complex multidirectional process with different functions increasing, decreasing, or remaining stable across the life span. Phase III research entailed interventions to enhance aging intelligence. Phase IV research viewed intelligence as continuing to develop and improve throughout adulthood. It was hypothesized that Phase I and Phase II research would decrease during 1986–1995 compared to 1966–1975 and 1976–1985, while Phase III and Phase IV research production would increase in 1986–1995 compared to the previous two decades. A review of 277 articles and 50 dissertations supported the predicted evolution from the unidirectional inevitable decline model toward perspectives describing the plasticity of adult intelligence and the further development and improvement of intelligence across adulthood.

Effect of long-term glycemic control on cognitive function.

To investigate the relationship between recurrent hypoglycemia and cognitive impairment in insulin-dependent diabetic patients. Seventy patients who were diagnosed as diabetic at age 18 years or older, were under 55 years old, and had no condition likely to affect cognitive abilities were recruited from a diabetic register. Patients were interviewed to obtain information on the frequency of major and minor hypoglycemia. Their cognitive abilities were assessed on tests of premorbid intelligence, current intelligence, reaction time, concentration, memory, and information processing. There was a significant correlation between the apparent decline in intelligence, expressed as the discrepancy between the estimated premorbid and the actual performance intelligence quotient, and the frequency of major hypoglycemic attacks (rs = -0.30; P < 0.01). Comparison of patients with and without recurrent hypoglycemia showed few significant differences in cognitive ability. Results support previous work that suggests that major hypoglycemic attacks have a significant effect on some aspects of cognitive function, but the clinical importance of this finding remains to be determined.

Are the frontal lobes implicated in “planning” functions? Interpreting data from the Tower of Hanoi

Twenty adult patients with lesions in the prefrontal cortex were tested on the Tower of Hanoi puzzle. The performance of patients was significantly worse than that of controls. This difference could not be accounted for in terms of a general decline in intelligence or memory, or by the size of the lesion. The results further suggest that both patients and controls used the same general strategy to solve the problem and that patients' difficulties with the task have little to do with planning or “look ahead” deficits (as is generally assumed in the neuropsychology literature). Patient performance is best explained in terms of an inability to see or resolve a goal-subgoal conflict. This interpretation is compatible with several existing accounts of frontal lobe dysfunction that postulate a failure of inhibition of a prepotent response to explain poor performance on the Wisconsin Card Sorting task, the Stroop task, the Antisaccade task, the A-Not-B task, and the Delayed Alternation task.

Intelligence and brain myelination: A hypothesis

Many observations concerning intelligence could be explained if much variance in intelligence reflects myelination differences. More intelligent brains show faster nerve conduction, less glucose utilization in positron emission tomography, faster reaction times, faster inspection times, faster speeds in general, greater circumference and volume, smaller standard deviation in reaction times, greater variability in EEG measures, shorter white matter T 2 relaxation times, and higher gray-white matter contrast with magnetic resonance imaging. Also explainable are peculiarities of the increased reaction times and standard deviations with number of choices and complexity, reaction time skewness, the shorter latencies in evoked potentials, shorter latencies to the P300 wave, the high glial to neuron ratio in Einstein's brain, less glucose utilization per unit volume in large brains, certain results related to lipids, essential fatty acids, and cholesterol in adults and premature babies, and the survival of genes for lower intelligence. Children's improved performance with maturation might result from myelination. The slowing of response times with age, the decline in intelligence, and increased T 1 relaxation times could be explained. Differential myelination in the mouse brain might be able to explain the heterosis observed for myelination, brain size, caudal nerve conduction velocity, and maze performance observed.

The decline of intelligence in America: a strategy for national renewal

Acknowledgments Decline Introduction: Truth and National Survival Nations, Powerful and Wealthy America's Greatness Economics: Is the Sleeper a Giant? Our Educational Wreckage The Social Bond Unravels Ebb Tide The Free Market of High Intelligence The Tragedy of Low Intelligence Renewal Defensive Driving The American Family A Non-Hyphenated People W.E. Burghardt DuBois Immigration: Hot War Disestablishing State Schooling Middle-Class Economics and the Social Contract Natality: World War III Appendix: America, 2044 A.D. Notes For Further Reading Index

Ageing and the retrieval of specialized and general knowledge: Performance of Masterminds

Contestants in the television quiz show Mastermind attempt to answer correctly as many questions as possible in two minutes on: (1) A specialized subject of their own choosing and (2) general knowledge. In this study, past contestants were asked to provide details of their performance in the competition. It was predicted that younger contestants would outperform older contestants under the speeded conditions of Mastermind because of their superior fluid intelligence. The main results were as follows: (1) Higher scores and lower tip-of-the-tongue (TOT) rates were achieved in the specialized subject round than in the general knowledge round. (2) TOT rate was positively related across the two rounds. (3) There was no effect of age on performance in the specialized subject round. In the general knowledge round, age was positively correlated with both score and accuracy. Thus, contrary to predictions, the older contestants actually outperformed the younger contestants (at least in the general knowledge round), presumably because of their superior crystallized intelligence. The results are discussed in terms of 'limited impact' theories of ageing, such that age-related decline in fluid intelligence does not necessarily occur for (a) everybody or (b) everything.

The complexity effect phenomenon is an epiphenomenon of age-related fluid intelligence decline

This paper employs the methods of covariance structure analysis to explore the relationship between complexity, age, and fluid intelligence. Fluid intelligence is defined by seven psychometric tests. Complexity is systematically varied by making two well-known measures of fluid intelligence progressively more simple. The model assumes the existence of three psychometric factors—fluid intelligence with loadings from all psychological tests including those whose complexity was manipulated, and two narrow factors (the Swaps and Triplets factors) representing only complexity levels of a given test. The results show that age is related to the general fluid intelligence factor—it does not seem to have direct links with different levels of complexity manipulations. It is argued that the often observed tendency for the magnitude of age differences in performance to increase as the task becomes more complex—known in the literature as the Complexity Effect Phenomenon—is a consequence of the fact that fluid intelligence correlates with age.

A study on speech intelligibility in traffic noise

In studying speech intelligibility in traffic noise, I was able to reproduce a sound field with considerable reality by reproducing both speech and traffic noises by the speaker method using a CD. As a result, the following conclusions were reached. 1) The influence of noise on speech intelligibility is similar for the single syllable and adult disyllable in normal persons. 2) The influence of the kinds of noises and changes with time in the sound pressure level on the intelligibility of the single syllable does not easily manifest itself in patients with sensorineural hearing loss. 3) The speech intelligibility depends largely on the blocking effect of the mid-high frequency components of the noise in both normal persons and patients with sensorineural hearing loss. 4) The intelligibility of the second sound of the adult disyllable is good in both normal persons and patients with sensorineural hearing loss. Furthermore, normal persons can understand a significant disyllable word to some extent by means of "uncertain understanding" even when they cannot hear each vowel and consonant clearly. 5) The intelligibility of the vowel is good in both normal persons and patients with sensorineural hearing loss. 6) As for the intelligibility classified by consonant in normal persons, the intelligibility of the nasal sounds (m, n) and voiced consonants (b, d, g, r, z) becomes low in the case of the S/N ratio being poor. 7) In patients with sensorineural hearing loss, the intelligibility of the bulldozer noise was the lowest, followed by motorway noise among the noises applied. The frequency spectrum distribution of the former consisted mainly of mid-high frequencies of 1 kHz or more. A serrated change with an amplitude of about 6 dB, 2 Hz was noted at the sound pressure level. A sine wave-like change with an amplitude of about 7 dB, 1 Hz was recognized at the sound pressure level of the latter. These are considered to be factors which account for a decline in intelligibility. The present study is part of an experiment I conducted at a sound field using TY-89. The results of this experiment suggest that the frequency spectrum intelligibility of noise as well as time-dependent changes in the sound pressure level of the noise exert an influence on communication disruption in patients with sensorineural hearing loss.

Whole-brain irradiation and decline in intelligence: the influence of dose and age on IQ score.

Decline in intelligence can occur after whole-brain cranial irradiation for childhood malignancy. The purpose of this analysis was to estimate better the impact of dose and age at time of irradiation on IQ decline. A total of 48 children were studied. We combined two previously reported studies that included 15 patients with pediatric acute lymphocytic leukemia (ALL) and 18 pediatric patients with medulloblastoma/posterior fossa primitive neural ectodermal tumors (PNETs) in whom serial IQ tests were administered. Another 15 patients (nine ALL and six PNET) were studied subsequent to these reports. This experience included ALL patients who were treated with whole-brain irradiation at doses of 18 Gy (n = 9) and 24 Gy (n = 15), and PNET patients who were treated with 18 Gy (n = 5), 22 to 24 Gy (n = 2), and 32 to 40 Gy (n = 17). Multiple regression models were constructed to estimate expected IQ score after treatment based on initial IQ score, age at treatment, and dose of whole-brain irradiation. Using a multiple linear regression model to correct for initial IQ and age at treatment, patients who received a dose of 36 Gy to the whole brain were estimated to score 8.2 points less on IQ testing than those with 24 Gy (95% confidence interval [CI], 1.8 to 14.6) and 12.3 points less than those who received 18 Gy (95% CI, 2.7 to 21.7). Older age at the time of irradiation resulted in less decline in subsequent IQ score. The predicted IQ decline is 11.9 points less in a 10-year-old patient than in a 3-year-old patient (95% CI, 4.2 to 19.6) for equivalent doses of irradiation. The model to predict IQ accounts for half the total variation in IQ score. There was no significant difference between the coefficients that reflected IQ decrease from radiation dose between subgroups who had ALL versus those with PNET. One can forecast final IQ score based on the initial IQ score, dose of irradiation, and age at time of irradiation. Our findings should aid in the selection of appropriate therapy when whole-brain irradiation is needed.