What is the DAYC-2? The Developmental Assessment of Young Children explained

The DAYC-2, or Developmental Assessment of Young Children, Second Edition, is a "norm-referenced" developmental assessment, meaning it compares a child's development with that of a large national sample of same-age peers. Published by PRO-ED and authored by Judith K. Voress and Taddy Maddox, it evaluates children from birth through 5 years, 11 months across five domains: cognition, communication, social-emotional development, physical development, and adaptive behavior. Because those five areas match the areas named in federal special education law, the DAYC-2 is widely used to help determine whether infants, toddlers, and preschoolers qualify for early intervention or early childhood special education services. This article explains what each domain covers, how the test is given and scored, how it fits into eligibility decisions, and how it differs from a quick developmental screener.

According to PRO-ED, each of the five DAYC-2 domains reflects an area mandated for assessment and intervention for young children under the Individuals with Disabilities Education Act, usually shortened to IDEA. The domains can be assessed independently, so a team may test only the areas of concern, or administer all five when a picture of general development is needed.

• Cognition: early thinking skills such as attention, memory, purposeful play, and problem solving, the abilities that later assessments measure as reasoning.

• Communication: how a child understands language and expresses ideas. The publisher reports separate subdomain scores for "receptive language" (understanding) and "expressive language" (producing words and sentences).

• Social-emotional development: how a child relates to caregivers and other children, manages emotions, and responds to social cues.

• Physical development: body control and movement, with subdomain scores for "gross motor" skills (large movements such as sitting, walking, and climbing) and "fine motor" skills (small movements such as grasping and stacking).

• Adaptive behavior: practical self-help skills such as feeding, dressing, and toileting, the same territory covered in more depth by instruments like the Vineland-3.

The DAYC-2 is unusually flexible about where its information comes from. PRO-ED states that examiners may gather evidence about a child's abilities through observation, interview of caregivers, and direct assessment. In practice, that means an evaluator can credit an item because a parent reliably reports the skill, because the examiner watches the child do it naturally during play, or because the child performs a task on request. The Early Childhood Technical Assistance Center, a federally funded center at the University of North Carolina, notes that the DAYC-2 can be based on observation in natural settings and includes instructions for the parent's role.

This design suits very young children, who often will not perform on demand for a stranger. It also supports what the publisher calls "arena assessment," in which professionals from several disciplines (for example, a speech-language pathologist and an occupational therapist) evaluate the child together, each scoring the domain relevant to their specialty. PRO-ED lists testing time at about 10 to 20 minutes per domain, so a full five-domain evaluation typically runs about an hour to an hour and a half, often split across the session in a way that follows the child's lead.

Each domain yields a "standard score," a score expressed relative to the performance of same-age children in the norm sample. Training materials from Thomas Jefferson University's Child and Family Studies Research Programs state that all DAYC-2 standard scores have a mean of 100 and a "standard deviation," a measure of how spread out scores are, of 15. That is the same metric used by major IQ tests, so a domain score of 100 is exactly average for the child's age, and most children score between 85 and 115. Percentile ranks and age equivalents are also provided, and when all five domains are administered the domain scores combine into an overall composite, described in training materials as the General Development Index.

The publisher reports that the DAYC-2 was normed on a national sample of 1,832 children, with characteristics that approximate the 2010 United States census, and that all normative data were collected between 2009 and 2011. PRO-ED also reports validity studies including the test's "sensitivity" and "specificity," the rates at which a measure correctly flags true delays and correctly clears typical development.

Two cautions apply here, as with any standardized score. First, a single score always carries measurement error, so evaluators interpret scores as ranges rather than exact points. Second, age equivalents are the weakest score type; a 30-month-old scoring at a "24-month level" has not simply lost six months, and decisions should rest on standard scores instead.

Federal regulations for IDEA "Part C," the early intervention program for children under age 3, define an eligible infant or toddler as one experiencing developmental delay, measured by appropriate diagnostic instruments and procedures, in one or more of five areas: cognitive, physical, communication, social or emotional, or adaptive development. The DAYC-2's five domains map directly onto that list, which is a major reason states adopt it.

How much delay is required is set by each state, commonly expressed as a percentage delay or as standard deviations below the mean. Texas offers a concrete, citable example: the state's Part C performance plan states that when determining eligibility based on developmental delay, evaluation teams may use the DAYC-2 or the Battelle Developmental Inventory as their standardized tool. Jefferson University training materials for Pennsylvania's early intervention program similarly walk examiners through checking whether a DAYC-2 domain score falls 1.5 standard deviations below the mean, which on this scale means a standard score below 78.

Beyond eligibility, programs also use DAYC-2 results for federal reporting on child outcomes and for planning goals, and the assessment appears alongside tools such as the Bayley-4 when teams need a deeper look at infant and toddler development. A low DAYC-2 score is not a medical diagnosis. It documents a measurable delay for service purposes, and questions about conditions such as autism or genetic disorders still require a clinical diagnostic evaluation.

Parents often first meet developmental testing through a brief screener at a pediatric checkup, such as the Denver II. A screener's job is narrow: quickly sort children into "probably fine" and "worth a closer look." Screeners are short, are often scored pass/fail, and are deliberately tuned to over-refer rather than miss children.

The DAYC-2 sits at the next level. As a norm-referenced eligibility assessment, it produces standard scores precise enough to compare against a state's numeric eligibility criteria, something a screener cannot do. It samples each domain in more depth, took its norms from a national standardization sample, and supports subdomain comparisons, such as a gap between receptive and expressive language. When a team needs still more detail in one area, it may add a specialized instrument, for example the Vineland-3 for adaptive behavior. A sensible pathway is screener first, DAYC-2 or a similar eligibility measure second, and targeted diagnostic tools third.

The DAYC-2 measures emerging abilities during the years when development is fastest and least stable, so its scores describe a child's current standing rather than fix a lifelong trajectory. Early scores on developmental measures correlate only modestly with later intelligence test scores, which is one reason evaluators re-test as children grow and why early intervention itself can change the picture.

For adults who are curious about their own cognitive abilities, the appropriate instrument is an adult IQ test rather than a developmental scale. The RIOT IQ test, the Reasoning and Intelligence Online Test developed by RIOT IQ with psychometrician Dr. Russell T. Warne, is designed for adults 18 and older. It includes 15 subtests across six cognitive indices (verbal reasoning, fluid reasoning, spatial ability, working memory, processing speed, and reaction time), takes about 52 minutes, and reports scores on the same mean-100, standard-deviation-15 scale the DAYC-2 uses. It offers a rigorous, normed estimate of adult cognitive ability, though like any online measure it does not replace an individually administered diagnostic evaluation. You can take it at riotiq.com.

PRO-ED states the DAYC-2 is designed for children from birth through 5 years, 11 months, spanning both the Part C early intervention years (under 3) and the preschool special education years.

No. It is a developmental assessment. Its cognition domain samples early thinking skills, and its scores use the familiar mean-100, standard-deviation-15 scale, but it measures developmental status across five domains rather than intelligence.

In part, yes. The publisher's format lets examiners credit items through caregiver interview and natural observation as well as direct testing, which is one of the test's distinctive strengths with very young children.

About 10 to 20 minutes per domain according to the publisher, so roughly 50 to 100 minutes if all five domains are administered.

Each state sets its own eligibility threshold. A common criterion in early intervention practice is a domain score about 1.5 standard deviations below the mean, which corresponds to a standard score below 78 on this scale.

Not by itself. A low score documents a measurable delay that can qualify a child for services. Diagnosing a specific condition requires a broader clinical evaluation, and many children who receive early intervention catch up with support.

1. PRO-ED. (2013). DAYC-2: Developmental Assessment of Young Children, Second Edition, complete kit. proedinc.com

2. Pearson Assessments. (n.d.). Developmental Assessment of Young Children, Second Edition (DAYC-2). pearsonassessments.com

3. Child and Family Studies Research Programs, Thomas Jefferson University. (2013). Using the Developmental Assessment of Young Children, 2nd Edition (DAYC-2): Online class self-study workbook. jeffline.jefferson.edu

4. Early Childhood Technical Assistance Center. (2026). Developmental Assessment of Young Children, Second Edition (DAYC-2): Crosswalk to the three child outcomes. ectacenter.org

5. Texas Health and Human Services Commission. (n.d.). Part C state performance plan / annual performance report (FFY 2023-24). hhs.texas.gov

6. Legal Information Institute, Cornell Law School. (n.d.). 34 CFR § 303.21: Infant or toddler with a disability. law.cornell.edu

Photo: Markus Spiske, via Wikimedia Commons / Unsplash (CC0)