Taking an IQ Test in a Second Language: Does It Lower Your Score?

A specific, practical question comes up constantly around IQ testing: if the test is taken in a second language, does the score come out lower than it should? The honest answer has two parts, and both matter. Some subtests are affected, meaningfully and predictably. Others are built specifically to avoid the problem. Treating "the test" as one undifferentiated thing obscures an answer that is actually quite precise.

Where language enters the test at all

A full IQ battery is not a single measurement instrument; it is a set of subtests grouped into index scores, and language plays a very different role in each group. Verbal Comprehension subtests ask a test-taker to define words, explain similarities between concepts, or draw on general knowledge — tasks that depend directly on vocabulary size and cultural exposure built up over years inside one linguistic and cultural environment. A person who acquired that vocabulary in a different language, or acquired it later in life, is being asked to perform a task that partly measures something other than reasoning: how completely a second language has been internalised.

Visual-Spatial and Perceptual Reasoning subtests sit at the other end of the spectrum. Arranging blocks to match a pattern, or identifying the relationship in a matrix of shapes, requires no vocabulary and very little culturally specific knowledge. Working Memory tasks such as digit span fall somewhere in between — instructions are verbal, but the content being remembered usually is not.

Why culture-fair tests exist

This is not a new problem, and testing has a decades-old, purpose-built response to it. Raven's Progressive Matrices — a largely nonverbal instrument built around abstract pattern completion — was specifically designed to reduce the influence of language and formal education on a reasoning score, making it more comparable across people from different linguistic and educational backgrounds. Our culture-fair test works on the same principle: the fewer words and culturally specific references a task requires, the less a second-language test-taker is penalised for something unrelated to reasoning ability.

• A verbal analogy question depends on knowing both words and the cultural context that makes their relationship obvious to a native speaker.
• A matrix-completion question depends on recognising a visual transformation — rotation, addition, shading change — that requires no vocabulary at all.
• A general-knowledge question assumes exposure to a specific culture's common facts, which a recent arrival to that culture may simply not have had the years to accumulate.
• A block-design or spatial task assumes none of that, which is precisely why these formats are favoured when comparing people across language backgrounds.

What actually predicts the size of the effect

The effect is not a flat penalty that applies equally to everyone tested outside their first language. Several factors change its size, and they matter more than the simple first-language-versus-second-language label:

• Age of acquisition. Someone who has spoken the test language since early childhood is affected far less than someone who began learning it as an adult, even if it is technically their second language.
• Years and depth of exposure. Vocabulary and idiom accumulate with sustained use; a few years of exposure closes much of the gap on verbal subtests specifically.
• Similarity of cultural reference points. A general-knowledge item assumes familiarity with a particular culture's common facts — the gap is larger when the test-taker's own background differs substantially from the one the test was normed on.
• Which subtests are weighted. A test administered and scored with full attention to verbal versus nonverbal splits gives a very different picture than one that reports only the Full-Scale total, a distinction covered in our piece on why the composite score can hide a real pattern underneath it.

What proper practice looks like

Professional testing guidelines have addressed this directly for decades, and the response is not to throw out verbal testing altogether — verbal reasoning is genuinely useful information when it is interpreted correctly. The response is procedural:

• Test in the person's strongest or most dominant language whenever that option exists, rather than defaulting to whichever language is administratively convenient.
• Weight nonverbal and visual-spatial indexes more heavily when interpreting results for someone tested outside their strongest language, rather than anchoring on the Full-Scale total.
• Note language history explicitly in the report — age of acquisition, years of exposure, and which language is used at home — so anyone reading the score later has the context.
• Where a fully bilingual or native-language-normed version of an instrument exists, prefer it over administering the standard version in a non-dominant language.

The same logic that applies to a formal clinical assessment applies, in a smaller way, to a general online test taken for curiosity. Our note on what to check before trusting an online score covers norming quality broadly; language match between test-taker and test is one more item on that checklist, easy to overlook because it is invisible unless you are the one it affects.

The precise version of the original question, then: does a second language lower a score? On verbal subtests specifically, it can, and the size of that effect depends on acquisition age, years of exposure and cultural overlap far more than on the simple fact of being a second language. On nonverbal subtests, the effect shrinks dramatically, which is exactly why those formats exist. Reading a cross-language result well means reading the profile, not the total — the same habit that matters for interpreting any IQ report, extended to one more variable that deserves to be named rather than ignored.

Common questions