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From: Dennis Drayna
Date: 17 Oct 2011
Time: 16:46:53 -0500
Remote Name: 165.112.47.66
The relative role of nature versus nurture in stuttering has been the subject of a great deal of research. This question is most often addressed by twin studies and adoption studies. A number of independent twin and adoption studies have been published for stuttering. While these studies differ from each other in many details, their results are surprisingly consistent. In twins shared genes explain about 50-70% of stuttering, while shared environment does not seem to explain much of stuttering. Unique environment (things that one twin experienced but not the other), which might include things like perinatal adverse events or random developmental factors, seem to account for the rest. So, genetics certainly does not account for all of stuttering. But there's no evidence for things like general family environment as a cause of stuttering, despite some half dozen good quality attempts to find it.