Curve estimation shows linear decline in processing speed after age 30, quadratic trajectories for category fluency and IQ, and no age change in letter fluency¶
Claim · All claims
Evidence · 1 study · associationalr2·q2
Currency · newest study 2011 · not yet checked against its sources · not reviewed by a person · overdue for a recheck since 2016: baselines and conditions change
Subclaims¶
Reading the evidence codes
q is the design tier, i the impact, n the sample, and the kind with its r
the rigour judged within that kind: what each code means.
This claim: no standardized effect is recorded in observations/ for it yet, so no benchmark reading is possible.
q2 i? Curve estimation across the 17–78 age range showed processing speed unchanged until about age 30 then declining linearly, category fluency improving until about age 35 then declining, IQ improving until about age 50 then declining gradually, and letter fluency showing no change with age. → Safa A. Elgamal 2011
Evidence¶
Safa A. Elgamal 2011¶
Safa A. Elgamal, MBBCh, PhD, Eric A. Roy, PhD, Michael T. Sharratt, PhD. (2011). Age and Verbal Fluency: The Mediating Effect of Speed of Processing. Canadian Geriatrics Journal, Volume 14, Issue 3. https://doi.org/10.5770/cgj.v14i3.17
q2 · i? · associational · r2
Curve estimation analysis of the cross-sectional data relating age to each cognitive measure. The results section states processing speed "remains unchanged until about the age of 30 years, after which it declines linearly" and that category fluency and IQ are "best represented by a quadratic curve"; letter fluency plotting "did not show any change with age" (Figure 1).
"Plotting the data using curve estimation showed that processing speed remains unchanged until about the age of 30 years, after which it declines linearly. However, the changes in category fluency and in IQ are nonlinear and best represented by a quadratic curve."
Discussion¶
Related Claims¶
- Age correlates negatively with processing speed and category fluency and positively with IQ, but not with letter fluency — a broader claim this one bears on
- Young adults outperform older adults on category fluency and processing speed, while older adults outperform young adults on premorbid IQ (NART) — related
- Category fluency declines with age and remains significantly impaired after controlling for processing speed and IQ — related
- Letter fluency shows no age-group difference in ANOVA, but older adults outperform young adults once processing speed and IQ are controlled — related
- Processing speed has a significant effect on both letter and category fluency in older adults, while IQ does not — related
- Decline in letter fluency beyond normal age expectations warrants further evaluation for neurological or mental disorder — related
- Cross-sectional age relations show monotonic decline in fluid cognition (age-reasoning correlation about −0.40) but stability followed by decline for acquired knowledge — related
- When relevant knowledge can be drawn upon, age trends in performance can reverse, with older adults outperforming younger adults on crossword puzzles — related
Page metadata
| Field | Value |
|---|---|
type |
claim |
id |
curve-estimation-differential-age-trajectories |
title |
Curve estimation shows linear decline in processing speed after age 30, quadratic trajectories for category fluency and IQ, and no age change in letter fluency |
description |
Curve estimation shows linear decline in processing speed after age 30, quadratic trajectories for category fluency and IQ, and no age change in letter fluency |
status |
review |
evidence_strength |
moderate |
newest_evidence |
2011 |
recheck_by |
2016 |
generated |
by process:wiki-ingest on 2026-10-17 |
trust |
unverified — no one has confirmed this page's content |
sources |
1 — safa-a-elgamal-2011 |
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