Tag Archives: Intelligence quotient

Do your siblings lower your IQ?

7 Jun

As the number of siblings increases, the fraction of parental resources received by each one declines. Thus, it has been suggested that larger sib size should be associated with lower IQ and lower school performance. A recent paper in the journal Intelligence looked at the evidence. Here is the abstract:

We examine the effects of child sibship size on intelligence, school performance and adult income for a sample of Swedish school children (n = 1326). These children were measured in grade three in 1965 (age 10) and in grades six (age 13) and nine (age 16), and the women and men were later followed up in adulthood at ages 43 and 47, respectively. Using Bayesian varying-intercept modeling we account for differences between school classes in each of our three response variables: IQ-scores, school grades and adult income, and control for background variables such as gender, socioeconomic status, and maternal- and paternal age. Consistent with previous research, we find patterns of decreasing IQ scores for increasing sibship sizes, specifically for an increasing number of older siblings. No relationships between sibship size and children’s school grades are found. We find, however, patterns of decreasing adult income for an increasing number of younger siblings. In addition, considerable amounts of variations in intelligence scores as well as school grades are found between school classes. Some implications of the findings and suggestions for future research are provided.

Ravens are just as smart as chimps

8 Jun

A paper in Royal Society Open Science:

“Given birds’ small brain size—in absolute terms—yet flexible behaviour, their motor self-regulation calls for closer study. Corvids exhibit some of the largest relative avian brain sizes—although small in absolute measure—as well as the most flexible cognition in the animal kingdom. We therefore tested ravens, New Caledonian crows and jackdaws in the so-called cylinder task. We found performance indistinguishable from that of great apes despite the much smaller brains. We found both absolute and relative brain volume to be a reliable predictor of performance within Aves. The complex cognition of corvids is often likened to that of great apes; our results show further that they share similar fundamental cognitive mechanisms.”

Here is the press release:

“A study led by researchers at Lund University in Sweden shows that ravens are as clever as chimpanzees, despite having much smaller brains, indicating that rather than the size of the brain, the neuronal density and the structure of the birds’ brains play an important role in terms of their intelligence.”

 

 

Age related cognitive decline is real

7 Mar

While we may be able to do some things to slow cognitive decline, a recent study published in the journal Intelligence reports evidence that age related cognitive decline is real:

“Processing speed is an important human cognitive capability that might underlie differences in other cognitive skills and their aging. We aimed to test aging-related processing speed differences using a novel cross-sectional design that adjusted for cognitive ability tested in youth. We examined aging differences on three different ways of assessing processing speed: psychometric, experimental, and psychophysical. We compared large narrow-age cohorts of 70- and 83-year-old people who were matched for cognitive ability in childhood. There were decrements of substantial effect size in all processing speed assessments in the older group that were not accounted for by prior cognitive ability, health, or fitness differences, though these factors also contributed to processing speed differences. These findings confirm age-related cognitive slowing using an unusual research design, and provide evidence against recent theories characterizing aging-related cognitive decline as a myth.”

Are our brains getting bigger?

17 Feb

A paper in Learning and Individual Differences:

“Secular increases in brain mass over nearly a century have been noted for both males and females in the UK and Germany. It has been argued that such trends may be associated with the Flynn effect. The IQ gain predicted on the basis of these trends is 0.19 and 0.08 points per decade for UK, and 0.2 and 0.15 points per decade for German males and females respectively, indicating a small contribution to the Fullscale IQ trends in these countries (2.95% of the German decadal gain and 12.73% of the UK gain). There is also a sex difference in the rates of brain mass gain in both countries, favoring males. Temporal correlations between the secular trend in UK brain mass and European Flynn effects on Fullscale IQ, Crystallized, Fluid and Spatial abilities reveal correlations ranging from 0.751 in the case of Fluid ability to 0.761 in the case of Crystallized ability. The brain mass increase may be an imperfect proxy for changes in specific neuroanatomical structures important for IQ gains. Its small contribution to these gains is also consistent with the influence of other contributing factors. Increasing brain mass is predicted by the life history model of the Flynn effect as it suggests increased somatic effort allocation into bioenergetically expensive cortical real estate facilitating the development of specialized cognitive abilities.”

 

Intelligence and brain size

16 Oct

Despite what you may have been told, there is a positive correlation between brain size and IQ score. A recent paper in the journal Intelligence looks at the correlations between IQ and specific brain structures. Here are the study highlights:

“Brain size is known to correlate with general intelligence (g).
It is unclear which other neuroimaging variables contribute beyond total brain size.
We model multiple brain measures and g in a large sample aged around 73 years.
All brain variables together account for around 20% of variance in g.”

 

BRAIN

 

Transcranial direct current stimulation decreases performance on intelligence test

7 May

The other day, I linked to a popular account of this story. Here is the abstract for the original paper:

Transcranial direct current stimulation (tDCS) modulates excitability of motor cortex. However, there is conflicting evidence about the efficacy of this non-invasive brain stimulation modality to modulate performance on cognitive tasks. Previous work has tested the effect of tDCS on specific facets of cognition and executive processing. However, no randomized, double-blind, sham-controlled study has looked at the effects of tDCS on a comprehensive battery of cognitive processes. The objective of this study was to test if tDCS had an effect on performance on a comprehensive assay of cognitive processes, a standardized intelligence quotient (IQ) test. The study consisted of two substudies and followed a double-blind, between-subjects, sham-controlled design. In total, 41 healthy adult participants completed the Wechsler Adult Intelligence Scale, Fourth Edition (WAIS-IV) as a baseline measure. At least one week later, participants in substudy 1 received either bilateral tDCS (anodes over both F4 and F3, cathode over Cz, 2 mA at each anode for 20 min) or active sham tDCS (2 mA for 40 s), and participants in substudy 2 received either right or left tDCS (anode over either F4 or F3, cathode over Cz, 2 mA for 20 min). In both studies, the WAIS-IV was immediately administered following stimulation to assess for performance differences induced by bilateral and unilateral tDCS. Compared to sham stimulation, right, left, and bilateral tDCS reduced improvement between sessions on Full Scale IQ and the Perceptual Reasoning Index. This demonstration that frontal tDCS selectively degraded improvement on specific metrics of the WAIS-IV raises important questions about the often proposed role of tDCS in cognitive enhancement.”

The study design seems strong and suggests that one should think twice before running electric currents through the brain.

 

tDCS, reason to reserve judgement

6 May

Many of the articles I read on transcranial direct current stimulation follow a similar pattern. The intrepid reporter is strapped with electrodes to the skull and, after reporting a tingling feeling, describes some cognitive benefit from the procedure.

A good piece by Kira Peikoff in The New York Times breaks that pattern and acknowledges the limits of our knowledge about tDCS:

“In January, the journal Brain Stimulation published the largest meta-analysis of tDCS to date. After examining every finding replicated by at least two research groups, leading to 59 analyses, the authors reported that one session of tDCS failed to show any significant benefit for users.”

 

 

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