Bayley Scales of Infant and Toddler Development, 4th Edition (Bayley-4) — Source

What is the Bayley-4?

The Bayley Scales of Infant and Toddler Development, now in their fourth edition, are widely regarded as the clinical reference standard for assessing development in the first three-and-a-half years of life. Administered by a trained clinician, the Bayley-4 produces detailed scores against a norming sample of 1,700 US children.

How it is structured

It spans seven subscales — Cognitive, Receptive and Expressive Communication, Fine and Gross Motor, Social-Emotional, and Adaptive Behavior. Together they give one of the most complete pictures of early development in clinical use.

How Learning Curve represents it

The Bayley-4 is a proprietary instrument, so Learning Curve holds none of its actual test items. What appears here is a representative set of paraphrased behavioural constructs across all seven subscales — plain-language descriptions grounded in published validation studies and widely-reported developmental norms, with attribution. It is a coverage sample, not the full test, and it serves as a normative reference point rather than a reproduction of the instrument.

The shape of Bayley Scales of Infant and Toddler Development, 4th Edition

Alternate visualizations

Bayley-4 milestones (72)

Social-Emotional (12)

infant seeks physical proximity to primary caregiver, especially when distressed

infant sustains eye contact during caregiver interaction

Settles or reduces distress when a familiar caregiver uses voice, touch, holding, or rocking.

infant smiles in response to caregiver's face or voice

infant participates in turn-taking exchanges of vocalisation, gesture, and affect with caregiver

Shows visible pleasure or anticipatory excitement when a familiar person approaches.

Uses gaze, body movement, or vocalizing to keep an adult socially engaged.

Responds differently to familiar people than unfamiliar people and enjoys reciprocal playful interaction.

Shows wariness with unfamiliar people or distress when a caregiver leaves, while seeking reassurance from familiar adults.

infant uses pointing or showing to direct caregiver's attention to a third object

child accepts caregiver soothing, uses simple strategies to manage frustration

Notices another person's distress and may pause, look concerned, approach, or attempt simple comforting.

Receptive Communication (9)

Changes state, startles, quiets, or turns attention when a loud environmental sound occurs.

Turns attention toward a familiar caregiver voice, especially when spoken to from nearby.

child consistently turns or vocalises in response to own name

Looks toward or attends to a familiar object or person when it is named in everyday context.

child follows simple one-step verbal directions without gestural support

Identifies several familiar body parts through looking, touching, or pointing when they are named.

child points to named body parts on themselves or a doll

Carries out two linked familiar actions from spoken language during a routine, without needing a full demonstration.

Understands simple object-function language, such as knowing which item is used for eating, drawing, wearing, or washing.

Expressive Communication (9)

Produces non-cry sounds that vary with comfort, interest, or social engagement.

Vocalizes during pauses in caregiver interaction, creating early back-and-forth sound exchanges.

Experiments with playful mouth sounds, squeals, and changing voice quality during alert play.

Produces repeated consonant-vowel sound strings with speech-like rhythm.

child combines gesture, vocalisation, and gaze to communicate intent

child combines two words to express a request or comment

child names common objects shown in pictures

Uses recognizable words or word approximations to request more, refuse, label an action, or mark recurrence.

Asks simple who, what, where, or why questions during everyday conversation.

Adaptive Behavior (11)

Coordinates sucking, pausing, alerting, and calming around feeding and caregiver soothing routines.

Signals readiness or refusal for feeding by opening the mouth, closing the lips, turning away, or stopping intake.

Brings manageable pieces of food to the mouth with the fingers during meals or snacks.

child uses a spoon to feed themselves

child drinks from an open cup independently

child engages in caring play with dolls or stuffed animals

Participates in dressing or handwashing by offering hands, pushing an arm through a sleeve, or lifting a foot.

child imitates familiar household actions in play (sweeping, cooking, talking on phone)

child cooperates with dressing, attempts simple self-care steps independently

Attempts to bring food from spoon to mouth with improving control, though spilling remains common.

Puts on simple loose clothing such as pants, jacket, or hat with limited help, even if orientation is imperfect.

Cognitive (11)

Maintains attention on a moving person or object and visually follows its path for several seconds.

child searches for an object hidden under a cloth or in a container after watching the hiding event

Shows recognition of feeding routines by preparing the mouth or body when a familiar bottle, breast, spoon, or meal cue appears.

Explores safe objects by looking, touching, turning, and mouthing them to learn their sensory properties.

child shifts attention between caregiver and a referent of mutual interest

Brings two objects together repeatedly to create sound or motion and observes the result.

child imitates simple gestures and actions modeled by the examiner

child marks paper after watching examiner make a stroke

Uses familiar household objects in a recognizable everyday way, such as treating a cup, phone, brush, or book according to its usual purpose.

child works out how to retrieve a small object from inside a container without demonstration

Uses one object to stand for another during pretend play, showing flexible symbolic thinking.

Fine Motor (9)

Briefly opens the hands and swipes or bats toward nearby objects with emerging voluntary control.

Maintains grasp on a placed object and brings it toward the mouth or body midline.

child picks up a small object using thumb and index finger

Passes a small object from one hand to the other while maintaining control.

Uses several fingers together in a raking motion to gather a small piece of food or object toward the palm.

child stacks small blocks into a tower

child turns pages of a book one or several at a time

Makes visible marks on paper by moving a crayon or marker with the hand.

Uses coordinated wrist and finger movement to turn one page at a time or rotate a lid, knob, or similar object.

Gross Motor (11)

Raises and steadies the head and upper chest while lying on the belly using forearm support.

infant lowers head with control from prone position

Rolls from belly toward the back or shifts the trunk enough to complete the turn.

infant assumes and maintains a hands-and-knees crawling position

Maintains a seated posture briefly by leaning forward and supporting the body with the hands.

Moves across the floor using crawling, creeping, or scooting to reach a desired place or object.

infant walks independently across a room without holding on for support

child climbs onto and off furniture and small play structures

child kicks a ball on the ground when prompted