Objectives: To determine if a broader measure of early language skill (the Preschool Language Scale - Version 4; PLS-4) would reveal the same relationships as previously found for vocabulary. Research questions were: (1) Are PLS-4 Auditory Comprehension (AC), and Expressive Communication (EC) (a) standard scores lower than CA norms and (b) age-equivalent scores equal to or lower than those expected for NVMA and (2) What is the relationship between AC and EC on the PLS-4?
Methods: Participants were 296 newly-diagnosed children with ASD, aged 2-4 years, in a multi-site longitudinal study. Data are taken from the first assessment point. A battery of tests was administered, including the PLS-4 and the Merrill-Palmer-Revised Scales of Development (M-P-R). NVMA was taken from the age-equivalent score of the M-P-R Cognitive subscale. Participants were divided into age bands; one set based on CA and another based on NVMA. Average AC and EC standard scores in each CA band were compared to the normative average of 100. AC and EC age-equivalent scores were compared with participants’ mean NVMA, organized by NVMA band, using a series of paired sample t-tests, with alpha level corrected for multiple t-tests. The discrepancy between EC SS and AC SS at each NVMA band was also calculated and results inspected.
Results: Mean standard scores for AC and EC were at least 1 SD and in most cases 2 SD below the normative means. Average AC age-equivalent scores were significantly below average NVMA in the following NVMA bands: 12-17 (NVMA M=15.24; AC M=11.63; t(50)=5.92, p<.001), 18-23 (NVMA M=21.10, AC M=15.56; t(81)=11.001, p<.001) and 48-78 months (NVMA M=57.55, AC M=50.65, t(19)=3.78, p=.001). Mean EC age-equivalent score exceeded NVMA in the <12 month band (NVMA M=9.05, EC M=14.05, t(19)=5.724, p<.001), but was significantly lower than NVMA in the 18-23 month (NVMA M=21.10, EC M=9.09, t(81)=4.629, p<.001) and the 48-78 month (NVMA M=57.55, EC M=49.45, t(19)=4.378, p<.001) NVMA band. EC SS was in advance of AC at the younger NVMA levels (mean discrepancies of 5.11, 7.51, 9.12 and 5.24 at NVMA bands of <12, 12-17, 13-23 and 24-29 months). At older NVMA levels, AC was higher than EC (mean discrepancies of -1.65, -3.7, -.95 at NVMA bands of 30-35, 36-47 and 48-78 months).
Conclusions: As expected, AC and EC standard scores were significantly lower than CA norms and generally equal to or lower than scores expected for NVMA. Contrary to expectations, EC did not consistently exceed AC. For children with NVMAs of 30 months or more, AC was greater than EC.