Lockdown four-year-olds score well on language and poorly on executive function

Design

Observational cross-sectional study against published pre-pandemic norms with an internal non-verbal reasoning benchmark

Population

205 four-year-olds born during England's first COVID-19 lockdown (analyses on 189–205)

Primary outcome

Language, executive function, motor skills and non-verbal reasoning on standardised measures

Effect

Versus norms: sentence structure d = 0.59, receptive vocabulary d = 0.47, executive function d = −0.46. Versus own non-verbal reasoning: executive function d = −0.72 and −0.63, motor skills d = −0.33

The BICYCLE study assessed 205 children born during England's first COVID-19 lockdown at age four, using standardised measures with published pre-pandemic norms. Against those norms the children did better than expected on sentence structure (d = 0.59), receptive vocabulary (d = 0.47), non-verbal reasoning (d = 0.42) and expressive vocabulary (d = 0.24). Caregiver-reported executive function was well below norms (global executive composite d = −0.46).

The more informative comparison is internal. Benchmarked against each child's own non-verbal reasoning, executive function was substantially lower (d = −0.72 and −0.63 on the two subscales), and word structure (−0.35), expressive vocabulary (−0.22) and motor skills (−0.33) also lagged behind cognitive potential. Sentence structure and receptive vocabulary matched it.

That internal benchmark matters because a cross-sectional sample of 205 volunteer families is not the general population — these children were above pre-pandemic norms on general cognition, which is the signature of a selected sample. Comparing each child against their own reasoning score removes some of that selection. What survives the correction is a consistent executive function gap: self-regulation, working memory and flexible attention, not vocabulary.

• Ask about attention, self-regulation and flexibility at the four-year review in this cohort, not only about language milestones.
• Reassure parents who ask about lockdown and speech — expressive and receptive language held up against norms in this sample.
• A child struggling at school reception in this age group may have an executive function problem rather than a language one.
• Be cautious about generalising: this was a volunteer sample whose general cognition sat above pre-pandemic norms.
• Executive function here was caregiver-reported on a questionnaire, not directly tested.

Why it matters

The lockdown worry has been about speech, and in this sample speech was the thing that held up.

Don't overread it

This is a cross-sectional volunteer sample compared against historical norms — it cannot show that lockdown caused the executive function gap.

The statistics, in plain English

Cohen's d expresses a difference in standard deviations: 0.2 is small, 0.5 moderate, 0.8 large. The executive function gap against the children's own non-verbal reasoning (d = −0.72) is therefore substantial, and larger than the gap against population norms (−0.46) — which is the point of the internal benchmark. A cross-sectional comparison against historical norms cannot separate a pandemic effect from a sampling effect; the within-child comparison partly can.

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