Tuesday 20 May 2014

Processing ability in the 8th decade of life: Stuart Ritchie


Stuart Ritchie is an up and coming researcher in the Deary gang who, as well as having organised the Processing Speed conference in Edinburgh, is penning a short introduction to intelligence, which I hope to review before too long.

Stuart has been looking at ageing in the eighth decade of life. It is only recently that one could gather together a reasonable and representative sample. Stuart has got 697 76-year olds of whom 628 have been tested and have completed all the data at 70, 73 and 76 years of age.

The Deary gang have many merits, but the brightest gold in their treasure chest is the Lothian Birth Cohort. As a result of a far-sighted decision to give every child in Scotland an IQ test at 11 years of age they have a glowing trace on intelligence through the life course, revealing its impact on scholastic and life attainments, health and behaviour. More about them here: http://www.ccace.ed.ac.uk/

An interest in intelligence is not altogether surprising in a small population which gave rise to the architect Robert Adam; the self-educated logician and founder of Mind Alexander Bain; the inventor Alexander Graham Bell; the biographer James Boswell; writer and historian Thomas Carlyle; bacteriologist Alexander Fleming; the philosopher David Hume; physicist Lord Kelvin; physicist James Maxwell; inventor of signal code Samuel Morse;writer Sir Walter Scott; economist Adam Smith whose Theory of Moral Sentiments may be even better than Wealth of Nations;  and writer Robert Louis Stevenson whose Treasure Island is an absolute gem. Was there ever better proof of Cold Winter Theory that bad weather dripping on granite is good for the intellect?

I have omitted Peter Higgs, he of the boson under whose portrait we sat, because a) he was born in England and b) he had a Scottish mother and English father, a condition I know well. One must be tough about these things, or we will have everyone claiming to be Scottish.  For reasons of tact I have omitted priests and politicians, have not mentioned clans, nor whether the luminaries ended up in Edinburgh or Abroad. A final word to Scots about how to increase their vast contribution to the modern world? Emigrate.

The full Powerpoint of the talk is here:


Slide 2 shows the basic proposition: if you can note even the slightest, most briefly presented stimuli in the environment, then you can behave more intelligently.

Slide 4 shows the sample sizes and the Inspection Time procedure. The latter is correctly named by its inventors, but one has to keep repeating that responses are not timed. With the benefit of hindsight, the test could have been called Brief Encounters, like the movie, or Brief Exposures though the latter might be subject to some misunderstandings. You are shown a visual cue that something is coming, then a very brief display of what I will describe as an unbalanced tuning fork without the handle but with different lengths of prong, then an irrelevant masking display so that the image on the retina does not last long, and then you have time to make a decision. Plenty of time. Are you perceptive enough to have noted whether the shorter leg of the design was on the left or the right? Exposures are varied in order to find out the shortest exposure you can reliably cope with.

Slide 5 is particularly good. Please show it to those Individual Differences Fundamentalists who will not accept any group differences findings because “Everyone is unique”.  This slide shows that over the 3 occasions of testing there are very different trajectories i.e. performance is variable. Nonetheless you can draw a slope on the data, and in the case of Inspection Time is a less scattered picture . Or in the language that Stuart might use, it is less hedge-hoggy. (See his unfair self-description @StuartJRitchie).

Slide 9 shows that though intelligence and inspection time have the entirely respectable correlation of .46 the slope of each (change over the six years of testing)correlate a very large  .78 which is impressive.

Inspection Time is a ratio measure in the SS Stevens sense, that being able to detect at almost zero exposure is a true zero, and the other inspection time durations are true time scores. The test does not have ceiling/floor effects in terms of item difficulty. It does not depend on response/movement speed which could be affected by age-related peripheral changes like in muscle tone.  It can be used across all age groups and with clinical patients because it is conceptually very simple. However, it does require equipment, and take some time. Nonetheless, it seems highly likely that as we age we take longer “to look at an object in order that we may see it.”

Processing = the mechanism that produces thought?


  1. Inspection time correlates with fundamentalist religiosity, too!


  2. While interesting, as I said to Ritchie, the key weakness in this is that this sample appears to be people who were still participating in the study at that age. You lose a bit via attrition.