Being wary of strangers
Many babies start showing caution or shyness with strangers at around 6 months, and this usually grows until about their first birthday. Children vary a lot.
How sure are we?
Not sure yet. Only one study has measured when it starts so far. How we know this
What it’s a sign of
Your baby can tell familiar people from unfamiliar ones and is being careful.
The four countries ranged from about 4 months in South Africa to about 7 in Argentina. In a large US study of twins, wariness rose from 6 to 12 months and then levelled off, but children followed different paths: some rose steeply, some slowly, and some were wary from early on.
We don't yet know the age by which nearly all babies show this.
A main source for the ages
Similarities and differences in child development from birth to age 3 years by sex and across four countries: a cross-sectional, observational study
Ilgi Ozturk Ertem, Vibha Krishnamurthy, Mphelekedzeni C. Mulaudzi, Yanina Sguassero, Hakan Balta, Ozlem Gulumser · 2018 · Lancet Global Health
- Children
- About 4,900 healthy children
- Where
- Argentina, India, South Africa and Turkey
- Ages
- Birth to 3½ years
- How
- Trained staff asked parents open questions about what their child could do, at health clinics
- What it found
- Found the age by which half of children reached more than 100 milestones. Most came at similar ages in all four countries, and for boys and girls. For example, half of children waved bye-bye by about 11 months and said a first word by about 9 months.
- Limits
- Only four countries and no rural areas, children from city clinics, and only healthy children (about half of those who came were left out for health reasons). It gives the age for half of children, not the full spread.
A main source for the ages
The development of stranger fear in infancy and toddlerhood: normative development, individual differences, antecedents, and outcomes
Rebecca J. Brooker, Kristin A. Buss, Kathryn Lemery‐Chalfant, Nazan S. Aksan, Richard J. Davidson, H. Hill Goldsmith · 2013 · Developmental Science
- Children
- About 1,300 twins
- Where
- Wisconsin, United States
- Ages
- 6 months to 3 years
- How
- Parents' questionnaires and researchers' observations as children grew
- What it found
- Wariness of strangers rose on average from 6 to 12 months and then levelled off. Children followed different paths: about 4 in 10 rose steeply, about a third rose slowly, and about 1 in 4 started high.
- Limits
- It describes how wariness changes, not the age it starts. Mostly white families in one state.
A classic study on this
Wariness of Strangers and the Study of Infant Development
L. Alan Sroufe · 1977 · Child Development
- Children
- Not given in the summary we read
- Where
- Not given in the summary we read
- Ages
- First year
- How
- A review of earlier studies
- What it found
- Wariness of strangers is rare in the first half year and common by about 8 or 9 months, with wide differences between babies.
- Limits
- We have only read the summary of this review.
If you’re worried about your child, talk to your child and family health nurse or GP.
Last checked 2 November 2026