Autism prevalence following prenatal exposure to hurricanes and tropical storms in Louisiana.

Hurricanes and tropical storms served as natural experiments for investigating whether autism is associated with exposure to stressful events during sensitive periods of gestation. Weather service data identified severe storms in Louisiana from 1980 to 1995 and parishes hit by storm centers during this period. Autism prevalences in different cohorts were calculated using anonymous data on birth dates and parishes of children diagnosed with autism in the state mental health system, together with corresponding census data on all live births in Louisiana. Prevalence increased in dose-response fashion with severity of prenatal storm exposure, especially for cohorts exposed near the middle or end of gestation (p < 0.001). Results complement other evidence that factors disrupting development during sensitive gestational periods may contribute to autism.

Production operations and the use of nonfinite verbs by children with specific language impairment.

Recent evidence from structural priming studies suggests that children with specific language impairment (SLI) are more likely to produce verb morphemes such as auxiliary is when their previous sentence contained an auxiliary than when it did not. The same paradigm was employed in the present study to determine whether failures to include auxiliary is might be due to prior use of nonfinite sentences (e.g., The mouse eating the cheese). Preschoolers with SLI and a group of younger normally developing children were more likely to produce auxiliary is to describe target pictures when the preceding sentence contained auxiliary are than when it contained past tense. Use of is in the target sentence was least likely when the preceding sentence was nonfinite. The implications of these findings for current accounts of SLI and current models of sentence production are discussed.