Repetitive Behaviour in Young Children Has Four Distinct Types

What the research found

The children were observed in three ways. Some sat in a clinic room with a standard set of toys while a trained examiner scored what they did with them. Some were filmed at home and coded afterwards for how often a hand moved or an object was turned. For the rest, a parent worked down a questionnaire, marking which behaviours occurred and how often. All were under the age of four.

Pang Chaxiong, Adele Dimian and Jason Wolff, at the University of Minnesota, gathered 41 such studies into a systematic review published in the journal Frontiers in Psychology in 2022. The studies appeared between 1999 and 2020 and covered 5,816 children between them, with samples ranging from 20 to 760. The reviewers registered their search protocol before beginning.

Restricted and repetitive behaviour is one of the two domains required for an autism diagnosis, and the less studied of the two. The fifth edition of the diagnostic manual, in 2013, set out four patterns under that heading: repetitive movement or use of objects or speech; insistence on sameness, meaning rituals, routines and resistance to change; interests fixed narrowly on one subject; and unusual responses to sensory input, whether over-reactive, under-reactive or actively sought. The last of those was new that year. Sensory response had not previously counted as repetitive behaviour at all, and its arrival widened the term considerably.

Because research groups define and measure these things differently, the reviewers sorted every finding into a global score plus four kinds: repetitive motor behaviour, insistence on sameness, self-injury, and sensory response. That scheme is the review’s own, adopted to make studies comparable.

Across birth to age three, global scores and repetitive motor behaviour were significantly higher in autistic children than in typically developing children and than in children with other developmental delays, whether the measure was direct observation or parent report. Insistence on sameness and sensory response gave mixed results, with some studies finding autistic children similar to the comparison groups and others finding them higher. Not one study found autistic children showing less of either.

Twelve studies followed the same children over time, and their trajectories diverged. Several reported rising frequency, duration and severity in the autistic groups, while others reported global levels that fell or held steady across the same interval.

The level of repetitive behaviour was largely unrelated to autism severity in this age range. How much a two-year-old flapped, fixed on an object or resisted a change of routine told the clinician’s overall severity rating very little, which reverses what has been reported in older children.

What it means for you and your child

A line in a report about significant restricted and repetitive behaviour may therefore refer to any of four unlike things. The reviewers found no standard instrument, and the choice of one moved the result. A study measuring global repetitive behaviour with the Repetitive Behavior Scale-Revised found it negatively correlated with adaptive functioning, while another measuring the same domain by diagnostic interview found no relation. Which behaviour was scored, and with which tool, is a fair thing for a parent to ask.

For a child under three, the amount of repetitive behaviour appears useful for identifying autism and weak for predicting how that child will do. Relations with cognitive ability, language and adaptive function were mixed throughout the review, though no study reported that more repetitive behaviour accompanied better adaptive function. The reviewers read this as a developmental effect, with the associations consolidating later, once children reach preschool age and the ordinary repetitive behaviour of early childhood recedes. That reading is their interpretation of a mixed literature rather than a result.

On distress the evidence is thin and divided. Two of the 41 studies examined self-regulation. In one, of children averaging 40 months, parent-rated insistence on sameness correlated with both internalising and externalising problems at a magnitude counted as large, with repetitive motor behaviour and self-injury somewhat lower. In the other, of children averaging 32 months, observed repetitive behaviour showed no correlation with a dysregulation profile. Two studies pointing opposite ways cannot say whether these behaviours accompany distress in a particular child.

The reviewers note, citing work with autistic adults rather than children, that repetitive behaviour is often described by the people doing it as a way of controlling stimulation and coping with stress. They also note that parents rate it among the hardest features of autism to live alongside. Neither observation was tested here, and the review carries the usual constraints: English-language publications only, which over-represents White and Western samples, and published work, where positive results appear more readily. No study in it observed children younger than twelve months, and too few examined self-injury for the reviewers to draw anything from it.

Between one and three, insisting on sameness is ordinary in children who are not autistic, which is part of why its level reads so poorly at that age. A child who lines up the same eight cars every afternoon is doing something specific, and it is not the same behaviour as flinching from a hand dryer. The field has not yet learned to keep those apart consistently. You already do.