Processing speed is one of those terms which is used in different ways, but which typically applies to performance on relatively simple tasks such as digit symbol substitution, simple and choice reaction time, letter cancelling and visual and auditory inspection time. They tend to be repetitive tasks, straightforward to explain and to carry out, not likely to be strongly influenced by school teaching or wider cultural factors, and somewhat clerical and dull when compared to more demanding intellectual tasks like solving matrix puzzles, analogies or defining vocabulary words.
Of course, just because a task looks basic does not mean that it is fundamental. Nonetheless, it is tempting to believe that understanding these simple tasks could help us decode the factors involved in higher cognitive abilities. Processing tasks could give us an estimate of the fundamental “clock speed” of each person’s brain.
By analogy, if these tasks are the building blocks of all cognitive abilities they would constitute a periodic table of cognition. We would rise above the confusion of multiple abilities and task dependent skills and be able to specify the real ingredients of thought. Ian Deary bemoans the fact that currently cognitive psychologists are all working on their own, personal, and very disparate periodic tables, and hopes they can come together to get a better understanding of simple processing.
First steps first. Can processing speed explain anything? Journeying to Edinburgh for the conference I speculated that processing is, almost by definition, an integral part of thinking. For example, is low level processing required to work out whether one needs a passport to travel from London to Edinburgh? In the current political climate I think this probably counts as a high level abstract problem. Conversely, estimating the time of departure from home should be a low level problem, but on examination in my case turned out to be another high level problem. From the stated departure time you must subtract the delay imposed by security, the further delay involved in parking a car and then taking a shuttle bus to the terminal, the further delay in driving to the airport imposed by a then-current Tube strike which will have a consequent overflow effect on car traffic and, by recourse to high level mathematics, you eventually prove that you should have left the previous day.
Low level processing involves those mundane tasks which are integral to driving, recognising signals, responding to traffic conditions and noticing features of the environment. By analogy, perhaps measuring the speed of completing simple tasks will reveal the mental horsepower we can bring to bear on more complicated tasks. Galton speculated that synaptic efficiency might explain why one individual is brighter than another, rather like the processing speed of a computer determines what degree of complexity it can cope with.
There are a number of problems with this view, not least that some notable researchers point out that it is a poor fit with the facts. Others, including a new wave of researchers, continue to find merit in the notion, and I will give pride of place to the most recent findings. Meanwhile, here is the programme of talks:
Expert Workshop on Processing Speed and Cognitive Ageing Edinburgh, 30 April 2014 “Is the world too fast when we’re slowing down?”
Session 1: Getting Up to Speed on Slowing
Ian Deary: ’10 Hard Questions about Processing Speed’
Patrick Rabbitt: ‘Reaction Times, Age, Intelligence and Memory’
Nicholas Mackintosh: ‘Correlations and Causes’
Paul Verhaegen: ‘General Slowing Yields to Major Dissociations, and Other Small Victories from the Brinley Front’
Session 2: Quick Summaries of New Data
Geoff Der: ‘Does the Relationship Between Reaction Time and Intelligence Vary
Stuart Ritchie: ‘Inspection Time and Fluid Intelligence in the Eighth Decade of Life’
Elliot Tucker-Drob: ‘Processing Speed and the Positive Manifold of Cognitive Ageing’
Discussant: Tim Croudace
Session 3: Axons and Alacrity
Mark Bastin: ‘What Does Diffusion MRI Tell Us about Relationships Between
White Matter and Information Processing Speed?’
Rogier Kievit: ‘Processing Speed(s), White Matter Integrity and Fluid Intelligence:
A Hierarchical Perspective’
Thomas Espeseth: ‘Processing Speed and its Components – Associations with Age
and Indices of Brain White Matter Microstructure’
Discussant: James Thompson
Session 4: General Discussion
Chair: Ian Deary
I will begin by posting up Ian Deary’s introduction to the conference, which follows soon.