Friday, 30 May 2014

Religiosity, intelligence and cognitive decline

If there is any support for Pascal’s wager, older people should increasingly believe in God, if only as a precaution. Even if it does not get you on the right side of God, shuffling to church should provide good exercise, and believing several impossible things before breakfast should keep the mind supple.

Now the Deary gang have started treading on some traditional assumptions, not on the nature of the Trinity, but on the presumption (scientifically proven, ho ho) that church attendance is protective against later-life cognitive decline. They found that religious belief, but not attendance, was negatively related to intelligence. The effect size was smaller than in previous studies of younger participants. Longitudinal analyses showed no effect of either religious belief or attendance on cognitive change either from childhood to old age, or across the ninth decade of life.

Stuart J. Ritchie, Alan J. Gow, Ian J. Deary. Religiosity is negatively associated with later-life intelligence, but not with age-related cognitive decline. Intelligence 46 (2014) 9–17

Why? Individuals who are more religious tend to have lower intelligence, albeit by
only a small degree. Some previous studies had indicated that, in later
life, religiosity was protective against age-related cognitive decline. However, that earlier work used rather crude mental state tests with significant ceiling effects.

The authors used the Lothian Birth Cohort 1921 which was tested for their intelligence in 1932 at age 11 and again at age 79, 83, 87 and 90. Eat your hearts out, Scandinavian epidemiologists! Don’t mess with the Scots.

The subjects were Christians or non-believers, all healthy, and 9 with dementia excluded. Low rate, is it not, on a base of 129 nonagenarians? Old age does, mostly, not involve dementia. The authors measured church attendance and religious belief with detailed questionnaires.

They found that brighter people tend to be less religious. Or, more specifically, clever white Scots tend to be non-believers, less clever white Scots tend to believe in Christianity. Their estimates of the covariate-adjusted relation of general intelligence to religious belief (β = −.14, p = .02 for the general factor from the Religious Involvement Inventory, and β = −.12, p = .06 for the religious wellbeing factor from the Spiritual Wellbeing Scale) were on the lower end of the effect sizes taken from the meta-analysis of religion and intelligence by Zuckerman et al. (2013), which produced an overall effect
size of r = −.24.

Some of these findings may be due to cohort effects: for older cohorts, born at times of higher societal religiosity, attendance at religious ceremonies may be a weaker signal of cognitive ability. They are just doing the done thing. A longitudinal study testing both religiosity and cognitive ability multiple times from midlife into old age would be useful to test this.

Practical tip: brighter people take the view that god does not exist, and going to church does not prevent cognitive decline, so there is no need to make your way to the Kirk every Sunday. Not unless you fancy one of the congregation, that is.


  1. "Old age does, mostly, not involve dementia."

    I remember reading somewhere that half of all 90 year olds have dementia. Can't provide a cite, though...

    I think for old people, religious attendance is rewarding socially, and thus motivates old people to go to church, independent of their IQ and/or scoring points with god before mortal coils are shuffled.

    Hopefully, tough, they've picked the right denomination. Imagine wasting time in Christian churches-- and the eternal consequences that might follow-- if Allah is actually the one true god. (or vice versa; this is why I think Pascal's wager fails miserably). Perhaps the social aspect explains the relatively lower effect sizes this study reports?

    Nonetheless, we seem to be converging on about a -.20 effect size for religiosity and IQ.

    Disclosure: I was on peer reviewer for this study. It was an easy "accept".

  2. If you're going to be practical about it, church attendance probably does contribute to happiness, even if not to intelligence. I suppose that if you're convinced that it's all a bunch of hokum you might not find it as rewarding -- it would be interesting to see how much church attendance predicted intelligence when one controls for how sincere the attendant's beliefs are.