The Language Development Survey (LDS) (Rescorla, 1989) uses parents’ reports of vocabulary and word combinations to identify language delays in children at ages 18-35 months. It can be completed independently by a parent in about 10 minutes and requires only fifth grade reading skills.

Over the past 20 years, the LDS has been used with thousands of children. Parents ranging widely in socioeconomic status and education have provided reliable and valid reports of their children’s early language development using the LDS (Klee, Carson, Gavin, Hall, Kent, & Reece, 1998; Rescorla, 1989; Rescorla & Alley, 2001; Rescorla, Hadicke-Wiley, & Escarce, 1993). The LDS can be completed in waiting rooms, daycare centers, preschools, and homes. A Latino Spanish language version is included with the Latino Spanish Child Behavior Checklist/1½-5 (CBCL/1½-5/LDS). Several studies report findings for Latino children (Patterson, 1998; Stelzer, 1995), and there are translations in several other languages.

The LDS includes 310 words arranged into 14 semantic categories (e.g., food, animals, people, vehicles). Parents are asked to circle each word the child uses spontaneously. They are also asked to indicate whether their child uses word combinations. If so, they are requested to write down five of their child’s longest and best phrases or sentences. The LDS words were chosen on the basis of diary studies of early vocabulary development. The LDS went through many revisions, with lengths ranging from 240 to 353 words. The current 310-word version, which has been used for more than a decade, contains many high frequency words (e.g., “daddy”), as well as less common words (e.g., “yellow”).

Most LDS research has been done with children around 24 months of age. In these studies, mean LDS vocabulary scores at 24 months have been between 175 and 195 words, with standard deviations in the range of 70 to 80 (Klee et al., 1998; Rescorla & Alley, 2001). Mean vocabulary scores have generally been higher for girls than boys. LDS vocabulary has been shown to be significantly related to socioeconomic status (SES) in samples where the SES range is wide (Rescorla, 1989).
LDS studies have indicated high test-retest reliability (.97-.99) (Patterson, 1998; Rescorla, 1989; Rescorla & Alley, 2001) and high Cronbach’s alpha internal consistency (.99) (Rescorla, 1989). Across many samples, correlations between LDS vocabulary score and number of objects and pictures named on various instruments have ranged from .66 to .87, indicating a high degree of congruence between parent-reported vocabulary scores on the LDS and tested vocabularies (Klee et al., 1998; Rescorla, 1989; Rescorla & Alley, 2001; Rescorla et al., 1993).

Several studies have used the LDS to assess the prevalence of expressive language delays at 24 months (Klee et al.,1998; Rescorla, 1989; Rescorla & Alley, 2001; Rescorla et al., 1993). These studies have typically used a cut-off of fewer than 50 words or no multi-word combinations at 24 months. Delay rates using this cut-off have ranged from 10-20%, with boys having higher rates of delay than girls. Concurrent validity of the LDS using “hit rate” analysis has also been reported, with the child’s performance on a directly administered language test used as the “gold standard” for “true” delay. Sensitivity (percent of “truly” delayed identified as delayed by the LDS) was 87% in Rescorla (1989), 90% and 100% in Rescorla et al. (1993), 91% in Klee et al. (1998), and 80% in Rescorla & Alley (2001). Specificity (percent of “truly” not delayed identified as such on the LDS) was 85% in Rescorla (1989), 90% and 95% in Rescorla et al. (1993), 87% in Klee et al. (1998), and 94% in Rescorla & Alley (2001).

Rescorla & Alley (2001) found that children identified as delayed by the LDS were more than 30 times as likely to be identified as delayed in subsequent testing with the Reynell Expressive Language Scale than were children who were not identified as delayed on the LDS (odds ratio of 34).

In the 1999-2000 National Survey of Children, Youths, and Adults (Achenbach & Rescorla, 2001), normative data for the LDS were obtained for 278 children ranging in age from 18 to 35 months. The survey sample was very diverse in SES level (19% lower, 48% middle, 33% upper-middle and upper) and ethnicity (57% white, 22% African-American, 13% Latino, 8% other). Girls had significantly higher vocabulary scores than boys in all age groups, but the gender difference was not significant for average length of phrases. SES had small but significant correlations with LDS vocabulary score and average length of phrases (.14, p < .05, and .18, p < .01, respectively).

Gender-specific norms for vocabulary are provided for ages 18-23, 24-29, and 30-35 months. Scores at or below the 15th percentile suggest delayed vocabulary development. For average length of phrases, norms are provided only for ages 24-29 and 30-35 months, because many children do not combine words into phrases prior to 24 months. Scores at or below the 20th percentile suggest delayed phrase development. 

References: Achenbach, T. M., & Rescorla, L. A. (2000) Manual for the ASEBA Preschool Forms & Profiles. Burlington, VT: University of Vermont Department of Psychiatry.

Klee, T., Carson, D. K., Gavin, W. J., Hall, L., Kent, A., & Reece, S. (1998). Concurrent and predictive validity of an early language screening program. Journal of Speech, Language, and Hearing Research, 41, 627-641.

Patterson, J.L. (1998). Expressive vocabulary development and word combinations of Spanish-English bilingual toddlers. Journal of Speech and Language Pathology, 7, 46-56.

Rescorla, L. (1989). The Language Development Survey: A screening tool for delayed language in toddlers. Journal of Speech and Hearing Disorders,54, 587-599.

Rescorla, L., & Alley, A. (2001). Validation of the Language Development Survey (LDS): A parent report tool for identifying language delay in toddlers. Journal of Speech, Language, and Hearing Research44, 434-445.

Rescorla, L., Hadicke-Wiley, M., & Escarce, E. (1993). Epidemiological investigation of expressive language delay at age two. First Language, 13, 5-22.

Stelzer, S. C. (1995). Adaptacion, normalizacion, y estudios de validez del “sondeo del desarrollo de lenguaje” (SDL) para la deteccion de retraso de lenguaje expresivo en niños Mexicanos de 15 a 31 meses de edad. Mexico City: Universidad de las Americas.