Processing Speed

Your result, the one DNA position behind it, and what the research says.

5/10 confidence.

About Processing Speed

The symbol-digit substitution test is a simple timed puzzle: match symbols to digits using a key, as many as you can in a couple of minutes. It measures how quickly someone takes in and acts on simple information, and it is used in very large studies because it takes minutes and works in any language. This position sits inside APOE and came out attached to baseline scores in a study of several hundred thousand people. The difference is tiny.

Good to know: The measured difference is about two hundredths of a standard deviation. The test measures speed on a simple clerical puzzle, not general ability. Practice on the task moves the score far more than this variant does.

Fun fact: The symbol-digit test is used worldwide partly because it needs no language at all: it is symbols, digits and a key.

Discovery: Symbol-digit performance was mapped in very large population cohorts.

The Variant

The single variant behind this trait

Gene: APOE

Variant (rsID): rs440446

Location: Chr 19:44,905,910

dbSNP rs440446

The studies

Combining cross-sectional and longitudinal genomic approaches to identify determinants of cognitive and physical decline (Schoeler T et al., Nature communications, 2025)

Other lifestyle traits

Empathy & Bonding: A variant in the oxytocin-receptor gene, studied for its links to empathy, warmth, and social bonding. Its effect on any one person is small.

Reward & Motivation: A variant near the dopamine D2-receptor gene, studied for its role in the brain's reward and motivation system.

Stress & Focus: A common variant in the COMT gene that affects how quickly your brain clears dopamine - studied for its links to focus and how you handle stress.

Back to All Traits

Content updated September 2026.

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