Crystallized intelligence
LASA filenames:
LASA037 / LASA237
Contact: Almar Kok
Background
Crystallized intelligence is the ability to use skills, knowledge and experience, as demonstrated largely through one’s vocabulary and general knowledge. In older adults it is considered a stable characteristic, and only declines when people are seriously demented.
In most studies with cognitive outcome measures, the level of education is entered in the model in order to adjust for the premorbid or general level of intelligence. However, it is questionable if this is a reliable measure for the level of intelligence among the elderly, because many people were not able to follow suitable education at the time they were young. The associations between the level of intelligence and cognitive test performance was up to twice as strong as the association with level of education (beta’s varying between 0.30 and 0.50 for intelligence). The strongest associations were found between the level of verbal intelligence and the MMSE. This suggests that it is important to include the level of intelligence as a covariate in studies using the MMSE and any other cognitive test instead of the level of education.
Measurement instrument in LASA
Crystallized intelligence is assessed with the vocabulary test, a subtest of the Groninger Intelligentie Test (GIT; Luteijn & van der Ploeg, 1983). In this subtest, 20 words of increasing difficulty are presented, of which the respondent has to choose the synonym out of five alternatives. The total score ranged between 0-20, with higher scores reflecting a higher level of verbal intelligence. It is measured once, at the baseline of each cohort, because it is considered a stable characteristic in older adults.
Scale construction
The total GIT score equals the sum of the number of correct answers on the test (range 0-20).
Variable information
LASAC037 / LASAF037 /LASAI037 (Main interview). In LASA037 *GIT_A1 to A3 are used to practice the test. The variables *GIT_1 to *GIT_20 are the items that comprise the actual performance score. The sum scores of these items are provided in LASAC237, LASAF237, and LASAI237 for the first, second, and third cohort respectively.
Availability of GIT vocabulary test per wave ¹
| B | C | D | E | 2B* | F | G | H | 3B* | MB* | I | J | K | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| GIT-VT | - | Ma | - | - | - | Ma | - | - | - | - | Ma | - | - |
¹ More information about the LASA data collection waves is available here.
* 2B=baseline second cohort;
3B=baseline third cohort;
MB=migrants: baseline first cohort
Ma=data collected in main interview
Previous use in LASA
GIT was used as covariate in the study of Comijs et al. 2001 and 2004.
References
- Comijs HC, Jonker C, Beekman ATF, Deeg DJH. (2001) The association between depressive symptoms and cognitive decline in community-dwelling elderly persons. International Journal of Geriatric Psychiatry, 16: 361-367.
- Comijs HC, van Tilburg T, Geerlings SW, Jonker C, Deeg DJH, van Tilburg W, Beekman ATF. Do severity and duration of depressive symptoms predict cognitive decline in older persons? Results of the Longitudinal Aging Study Amsterdam. Aging Clinical and Experimental Research, 2004, 16 (3): 226-232.
- Luteijn F, van der Ploeg FAE.1983. Groninger Intelligentie Test. Handleiding (Groninger Intelligence Test. Manual). Lisse: Swets, Zeitlinger BV.
Date of last update: December, 2019
