NCDS – Age 50 – Timed Letter Search/Letter Cancellation Test

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The 1958 National Child Development Study (NCDS) assessed their cohort members (CMs) during the study’s age 50 sweep using the Timed Letter Search/Letter Cancellation Test.

Details on this measure and the data collected from the CMs are outlined in the table below.


Domain:Processing speed
Measures:Attention/concentration
Mental speed
Visual scanning
Domain:Gv (Visual Processing)
Gs (Processing Speed)
Administration method:Trained interviewer; pen and paper.
Procedure:Participants were given a page of random letters arranged in rows (N = 26) and columns (N = 30). They were asked to cross out as many target letters (“Ps” and “Ws”) as possible within a one-minute timeframe. Respondents were instructed to work across each row from left-to right as if they were reading a page and they were asked to perform the task as quickly and accurately as possible. Once the allotted time was over, they were asked to underline the last letter that reached their eye (any letter, target or otherwise). The total number of letters searched was summed to provide a measure of speed of processing, whereas the total number of target letters missed reflects level of accuracy.
Link to questionnaire:https://cls.ucl.ac.uk/wp-content/uploads/2017/07/NCDS_8_FINAL_MAINSTAGE_DOCUMENTATION.pdf (opens in new tab)
Scoring:Speed of processing: summed total of letters scanned (0 - 65)
Accuracy: summed total of target letters missed (0 - 65)
Item-level variable(s):None
Total score/derived variable(s):N8CFLET - N8CFRC
Descriptives:Processing speed (raw score)Processing accuracy (raw score)
N = 9,442N = 9,442
Range = 84 - 780Range = 0 - 49
Mean = 334.10Mean = 4.42
SD = 88.83SD = 4.12
(click image to enlarge)
(click image to enlarge)
Age of participants (months):Mean = 608.27, SD = 1.92, Range = 598 - 614
Other sweep and/or cohort:NCDS – Age 61-63 – Proposed repeat of tests at age 50
BCS70 – Age 46-47 – Timed Letter Search/Letter Cancellation Test
NSHD – Age 43 – Timed Letter Search/Letter Cancellation Test (3 trials)
NSHD – Age 60-64 – Timed Letter Search/Letter Cancellation Test
NSHD – Age 68-70 – Timed Letter Search/Letter Cancellation Test
Source:The letter cancellation test was initially developed for the NSHD 1946 birth cohort study and has also been used in the MRC Cognitive Function and Ageing Study (MRC CFA Study, 1998). All cognitive measures at this sweep were taken from the 2002 English Longitudinal Study of Ageing (ELSA; Taylor et al., 2007).
Technical resources:Banks, J., Breeze, E., Lessof, C., & Nazroo, J. (2006). Retirement, health and relationships of the older population in England: The 2004 English Longitudinal Study of Ageing (Wave 2).
Brown, M., & Dodgeon, B. (2010). NCDS cognitive assessments at age 50: initial results. London: Centre for Longitudinal Studies.
Reference examples:Dregan, A., & Gulliford, M. C. (2013). Leisure-time physical activity over the life course and cognitive functioning in late mid-adult years: a cohort-based investigation. Psychological Medicine, 43(11), 2447-2458.
Bowling, A., Pikhartova, J., & Dodgeon, B. (2016). Is mid-life social participation associated with cognitive function at age 50? Results from the British National Child Development Study (NCDS). BMC Psychology, 4(1), 58.

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This page is part of CLOSER’s ‘A guide to the cognitive measures in five British birth cohort studies’.