Many of today's modern parents are striving to expose their baby to as many life-experiences as possible and are successfully teaching their babies simple sign language before they can even speak. Some studies voice caution to these eager parents warning that learning sign language in infancy may impact a child's speech development.
On one hand pre-spoken language lessons are reported in some studies to produce positive results and claims abound of signing babies becoming brighter children with potentially higher IQ scores and larger vocabularies into adult life. The pro side of the discussion of early sign-language communication pre-vocabulary argue that the benefits of early simple visual language clues and hand signing will encourage greater communication and understanding between baby and parent before the child can physically use spoken language. Many babies are successfully signing simple needs such as milk, hungry, sleep, and more in what is an obvious two way communication with their parent.
The contradictors present an equally solid argument with caution that for a hearing child taught early sign language pre-speech could have a negative impact on a child's speech development. The worry is that the ability to communicate a non-verbal need and have it understood and met will delay the need for the child to have to learn to speak.
Many web hits are available to support either side of the discussion and as always reader-beware and always confirm and consider your source when gathering web-based only documentation.
One such study found on the web is on the "Impact of Symbolic Gesturing on Early Language Development" by Susan W. Goodwyn, Linda P. Acredolo and Catherine A. Brown, found athttp://www.springerlink.com/ where the reports of the study of 103 infants divided into control groups and subjected to interval language testing over a period of three years. The study, like many similar and readily available to read and research on the web, reported that " ... These results provide strong evidence that symbolic gesturing does not hamper verbal development and may even facilitate it."
Much documented evidence exists that all parent interaction is rewarding and a positive to the boding of parent and child and the socialization and communication skills are successfully carried into adulthood. Many studies also disagree on how spoken language is formed in the early development of infancy. Attributing a negative when there is obvious much positive gained when successfully using sign language as a simple form of two way communications between parent and a pre-speech baby seems counter-productive. If simple early sign language learning of a baby's basic needs does nothing more than further open the lines of communication and bring parent and baby closer than it should hardly be considered a negative impact on development in any form.