Intelligence & cognition

Information processing speed


Contact: Hannie Comijs

The Coding task is used to measure speed of information processing and has also been appeared in another form: the Digit-Symbol Substitution subtest of the Wechsler Adult Intelligence Scale (WAIS-R; Wechsler, 1987). The Coding task is very sensitive for aging. Salthouse (1996) postulated that aging results in a decrease in the speed with which many elementary processing operations can be executed; this in turn results in impairments of higher order cognitive functions, such as memory and reasoning.
The Coding task is not pure a measure of information processing speed but also reflects a global measure of intellectual functioning. Various processes are involved, like attention processes, memory function, and perceptual organisation and speed (Bouma et al., 1996). Improvement on the task within the three trials is related more to memory than to age, reasoning and perceptual speed (Piccinin & Rabbit, 1999).

Measurement instrument in LASA
The Coding Task as used in LASA, is an adjusted version of the Alphabet Coding Task-15 (Savage, 1984), a letter substitution task described by Piccinin and Rabbitt (1999). In this task two rows of characters are shown, each character in the upper row belongs to a character in the bottom row. The test contains also two rows, one of them containing characters and the bottom row is empty. The respondent has to complete as many character combinations as possible, by naming the corresponding character. This was done in three cycles of one minute. The mean score for the three trials is mainly used in the analyses (range 1.0 to 42.7).

The original task in which the respondent had to write down the missing characters (written response) was adapted so that the respondent had to name the characters (verbal response), for both practical and conceptual reasons. From a pilot study it appeared that older respondents had difficulty in writing the letters. Furthermore, it was sometimes difficult for data entry assistants to read the handwriting of the respondents (van den Heuvel, 1994). With regards to the conceptual (construct) validity of the test, the motor speed component of the task could be omitted by using verbal rather than written responses so that the test mainly measures cognitive speed processes.

The descriptive statistics of the Coding Task at waves B to G: pdf.

Variable information
LASAB155 / LASAC155 / LASAD155 / LASAE155 / LAS2B155 / LASAF155 / LASAG155 / LASAH155 / LAS3B155 / LASAI155

Availability of information per wave1:

























1 More information is available on:

* 2B=baseline second cohort;
   3B=baseline third cohort;
   MB=migrants: baseline first cohort (Under Construction);
   I=not yet available

Me=data collected in medical interview

Previous use in LASA
Information processing speed and decline in information processing speed has previously been examined by e.g. Aartsen (2002, 2004), Comijs (2001, 2011), Dik (2000, 2003), Jonker (2003) Robitaille et al (2013) and Van den Kommer et al (2009).


  1. Aartsen, M.J., Smits, C.H.M., Van Tilburg, T.G., Knipscheer C.P.M. & Deeg, D.J.H. (2002). Activity in older adults: Cause or consequence of cognitive functioning? A longitudinal study on everyday activities and cognitive performance in older adults. Journal of Gerontology 2, 153-162.
  2. Aartsen, M.J., Martin, M, & Zimprich, D (2004). Gender differences in level and change in cognitive functioning: Results from the Longitudinal Aging Study Amsterdam. Gerontology 50, 35-38.
  3. Bouma A, Mulder J, Lindeboom J (1996) Neuropsychologische diagnostiek. Handboek. Swets & Zeitlinger Publishers, Lisse.
  4. Comijs HC, Jonker C, Beekman AT and Deeg DJ (2001) The Association Between Depressive Symptoms and Cognitive Decline in Community-Dwelling Elderly Persons. International Journal of Geriatric Psychiatry 16 (4): 361-367.
  5. Comijs, H.C., van den Kommer, T.N., Minnaar, R.W.M., Penninx, B.W.J.H., Deeg, D.J.H. (2011). Accumulated and differential effects of life events on cognitive decline in older persons: depending on depression, baseline cognition, or ApoE ε4 status? The Journals of Gerontology, Series B: Psychological Sciences and Social Sciences, 66B (S1), i111-i120.
  6. Dik MG, Deeg DJ, Bouter LM, Corder EH, Kok A, Jonker C (2000) Stroke and apolipoprotein E epsilon4 are independent risk factors for cognitive decline: A population-based study. Stroke 31 (10): 2431-2436.
  7. Dik MG, Pluijm SMF, Jonker C, Deeg DJH, Lomecky MZ, Lips P. (2003) Insulin-like growth factor I (IGF-I) and cognitive decline in older persons. Neurobiol Aging 24:573-581.
  8. Jonker C, Comijs HC, Smit JH (2003). Does aspirin or other NSAIDs reduce the risk of cognitive decline in elderly persons? Results from a population-based study. Neurobiology of Aging 24: 583-588.
  9. Piccinin AM, Rabbit PMA (1999) Contribution of cognitive abilities to performance and improvement on a substitution coding task. Psychology and Aging 14(4), 539-551.
  10. Robitaille A, Piccinin AM, Muniz G, Hoffman L, Johansson B, Deeg DJH, Aartsen MJ, Comijs HC, Hofer SM. Longitudinal Mediation of Processing Speed on Aging-Related Change in Memory and Fluid Intelligence. Psychology and Aging, 2013, 28(4):887-901.
  11. Salthouse TA (1996) The processing speed theory of adult age differences in cognition. Psychological reviews 103, 403-428.
  12. Savage RD (1984) Alphabet Coding Task 15. Unpublished manuscript. Western Australia: Murdoch University.
  13. Van den Kommer, T.N., Dik, M.G., Comijs, H.C., Fassbender, K., Jonker, C. (2009). Total cholesterol and oxysterols: Early markers for cognitive decline in elderly? Neurobiology of Aging, 30, 534-545.
  14. Van den Heuvel N. Information processing speed: Coding Task (1994). In: Deeg DJH, Westendorp-de Serière M, eds. Autonomy and well-being in the aging population I: report from the Longitudinal Aging Study Amsterdam 1992-1993. Amsterdam, The Netherlands: VU University Press, 59-63.
  15. Wechsler D (1987) Wechsler Adult Intelligence Scale-Revised. Manual. New York: Psychological Corporation.