Signs of Delayed Social Development: What Parents Need to Know

Social development delays are among
the most important developmental concerns
to identify early — because early
identification and intervention produce
significantly better outcomes than
delayed recognition. Research on social
development and early intervention
consistently finds that children whose
social development concerns are identified
early — and who receive appropriate
support promptly — show significantly
better long-term outcomes than those
whose concerns are identified later.

This article covers what the research
shows about signs of delayed social
development — what to look for at
each age, what may cause delays,
and what parents can specifically do.

What Social Development Delay Is

Research on social development and
developmental delay defines social
development delay as social development
that is significantly behind what
is typical for the child’s age —
in ways that are not explained by
normal developmental variation.

Research distinguishes:

Normal developmental variation —
the wide range of typical social
development — including shyness,
introversion, and slower social
development within the normal range.

Social development delay —
social development that is
significantly behind typical
development — in ways that
may reflect an underlying developmental
condition or that warrant professional assessment.

Research finding: not all
social development differences
are delays — and parental concern
about social development is
sometimes based on unrealistic
expectations rather than genuine delay.
Understanding the difference
between normal variation and
genuine delay is practically important.

Red Flags in Infants
(Birth to Twelve Months)

Research on infant social development
and early identification identifies
the following red flags — signs
that warrant professional assessment:

No social smiling by two months.

No response to voices or
faces by two months.

No back-and-forth cooing or
vocal exchanges by four months.

No reaching toward familiar
people by six months.

No recognition of familiar
faces by six months.

No pointing, waving, or showing
by twelve months.

No back-and-forth sharing
of sounds, smiles, or facial
expressions by nine months.

Loss of any previously acquired
social skill — at any age.

Research finding: these red
flags — particularly the loss
of previously acquired skills —
warrant immediate professional assessment.
Earlier identification produces
significantly better outcomes.

Red Flags in Toddlers
(One to Three Years)

Research on toddler social development
and early identification identifies:

No single words by sixteen months.

No two-word phrases by twenty-four months.

No interest in other children —
consistently ignoring or avoiding peers.

No imitation of others’ actions by eighteen months.

No pretend play by twenty-four months.

No pointing to share interest —
declarative pointing — by fourteen months.

Significant difficulty with
transitions and changes — beyond
what is typical for the age.

No empathic responses to others’
distress by eighteen months.

Significant preference for
solitary activities over any
social interaction — even with caregivers.

Loss of any previously acquired
social or language skill.

What these red flags may indicate:

Research finds that these
red flags may be associated
with autism spectrum conditions —
which affect social communication
and social interaction — or
with language delays, hearing
difficulties, or other developmental conditions.

Research strongly supports
seeking professional assessment
promptly when these red flags are present —
because early intervention for
autism and other developmental
conditions produces significantly
better outcomes than delayed intervention.

Red Flags in Preschoolers
(Three to Five Years)

Research on preschool social development
and identification identifies:

No interest in playing with
other children — consistently
preferring solitary play over
any peer interaction.

Significant difficulty with
cooperative play — unable to
sustain cooperative play even briefly.

No genuine friendships —
no specific preferred peers
by age four or five.

Significant difficulty understanding
others’ emotions and perspectives —
limited theory of mind development
by age five.

Consistently aggressive or
disruptive behavior in social
contexts — significantly beyond
what peers show.

Significant social anxiety —
extreme distress in social
situations that is impairing daily functioning.

No pretend play by age three.

Significant difficulty separating
from caregivers — beyond what
is typical for the age.

What these red flags may indicate:

Research finds these red flags
may be associated with autism
spectrum conditions, social anxiety,
ADHD, developmental language
disorder, or other conditions
that warrant professional assessment.

Red Flags in School-Age Children
(Six to Twelve Years)

Research on school-age social development
and identification identifies:

No genuine friendships —
no specific reciprocal peer
relationships by age seven or eight.

Consistent peer rejection —
actively disliked by peers
rather than simply not well-known.

Significant difficulty reading
social cues — consistently
misreading others’ emotions,
intentions, and social signals.

Consistent social conflict —
frequent significant peer conflict
that does not improve with support.

Significant social withdrawal —
consistently avoiding all peer
interaction in ways that are impairing.

Significant social anxiety —
school refusal, extreme distress
in social situations.

Significant bullying — either
as a target or as the child
who is bullying — that is not responding to intervention.

Consistent difficulty with
group activities and cooperation.

What these red flags may indicate:

Research finds these red flags
may be associated with social
anxiety, autism spectrum conditions,
ADHD, depression, or other
conditions that warrant professional assessment.

What Causes Social Development Delays

Research on the causes of social
development delays identifies several factors:

Autism spectrum conditions.
Research finds that autism spectrum
conditions — which affect social
communication and social interaction —
are the most common specific
cause of significant social
development delay. Research
strongly supports early identification
and intervention for autism —
with significantly better outcomes
when intervention begins before age three.

Social anxiety. Research finds
that social anxiety — significant
fear and avoidance of social
situations — is a common cause
of social development difficulty
in older children — both limiting
social experience and producing
genuine social skill deficits.

ADHD. Research finds that
ADHD — through its effects
on impulse control, attention,
and emotional regulation —
significantly affects social
development — producing social
skill deficits and peer relationship difficulties.

Developmental language disorder.
Research finds that developmental
language disorder — significant
difficulty with language comprehension
and expression — significantly
affects social development —
because language is central
to social interaction.

Hearing loss. Research finds
that unidentified hearing loss —
which significantly affects
language development — can
produce social development delays
that resolve when hearing is
appropriately supported.

Adverse childhood experiences.
Research finds that adverse
childhood experiences — abuse,
neglect, domestic violence —
significantly affect social
development through their effects
on attachment, emotional regulation,
and trust in relationships.

Insecure attachment. Research
finds that insecure attachment —
produced by inconsistent, unresponsive,
or frightening caregiving —
significantly impairs social development.

What to Do If You Notice Red Flags

Research on early identification
and intervention consistently supports
the following approach:

Trust your instincts — and
seek assessment. Research finds
that parents’ concerns about
their child’s development are
frequently accurate — and that
seeking professional assessment
when concerns arise produces
significantly better outcomes
than waiting and hoping.

Start with your pediatrician.
Research supports beginning
with the child’s pediatrician —
sharing specific concerns and
requesting a developmental assessment.

Request a formal developmental assessment.
Research supports requesting
a comprehensive developmental
assessment — including assessment
of social communication, language,
and cognitive development —
when social development concerns are significant.

Access early intervention services.
Research on early intervention
consistently finds that intervention
beginning before age three —
through early intervention services —
produces significantly better
outcomes than intervention beginning later.

In the US — children under
three with developmental concerns
are entitled to free early
intervention assessment and
services through the Individuals
with Disabilities Education Act.

Do not wait and see for significant concerns.
Research on early intervention
consistently finds that earlier
intervention produces better
outcomes — and that the “wait
and see” approach delays access
to support that could make
a genuine difference.

Try This This Week

Practice 1 — The Red Flag Review
What it is: A deliberate honest
review of your child’s social
development against the age-appropriate
red flags — identifying any
concerns that warrant attention.

How to do it: This week review
the red flags for your child’s
current age — and honestly assess:

Are any of these red flags present?
Have I been noticing concerns
but hoping they would resolve?
Is there any sign that warrants professional assessment?

If yes — take one step toward professional assessment this week.

Why it works: Research on
early identification consistently
finds that earlier assessment —
and earlier intervention when
needed — produces significantly
better outcomes. A deliberate
honest review of red flags
is the most important first step.

Practice 2 — The Pediatrician Conversation
What it is: A deliberate preparation
for a specific developmental
conversation with your child’s
pediatrician — if concerns are present.

How to do it: If you have
concerns about your child’s
social development — this week prepare:

Write down specific behaviors
you have observed — with examples.
Note when concerns began.
Note whether development has
regressed — previously acquired
skills that are no longer present.
Note whether concerns are
present across settings — home,
preschool, with family.

Share this specific information
at your next pediatric appointment.

Why it works: Research on
pediatric developmental assessment
consistently finds that specific,
concrete parental observations —
with examples and timing —
produce significantly more accurate
assessment than general concern statements.

Practice 3 — The Early Intervention Step
What it is: A concrete commitment
to accessing early intervention
services — if your child is
under three and has significant social development concerns.

How to do it: If your child
is under three and you have
significant social development concerns —
this week contact your local
early intervention program:

In the US — contact your
state’s early intervention program —
through your pediatrician or
by searching “early intervention [your state].”
Request a free developmental assessment.
You do not need a physician
referral to request an early intervention assessment.

Why it matters: Research on
early intervention consistently
finds that intervention beginning
before age three produces significantly
better outcomes than intervention
beginning later — making early
access to assessment and services
one of the most important actions
parents can take when concerns are present.

The Bottom Line

Recognizing the signs of delayed
social development — and seeking
professional assessment promptly
when concerns arise — is one
of the most important things
parents can do for their child’s
long-term wellbeing. Research
is clear: earlier identification
produces better outcomes; parental
concerns are frequently accurate;
the wait-and-see approach delays
access to genuinely helpful
support; and early intervention —
particularly before age three —
produces significantly better
outcomes than later intervention.

If you have concerns about
your child’s social development —
please seek professional assessment.
Early support makes a genuine
and lasting difference.

Sources

American Academy of Pediatrics.
(2020). Identifying infants
and young children with developmental
disorders in the medical home.
Pediatrics, 118(1), 405–420.

Lord, C., et al. (2020).
Autism spectrum disorder.
Nature Reviews Disease Primers, 6(1), 1–23.

Shonkoff, J. P., & Phillips, D. A. (2000).
From Neurons to Neighborhoods.
National Academy Press.

Hartup, W. W. (1996).
The company they keep.
Child Development, 67(1), 1–13.