One of our main concerns as a Speech Language Pathologist (SLP) is understanding the difference between developmental vs. disordered speech and making a diagnosis accordingly. In order to make an informed decision, we must fully understand typical speech sound development based on past research conducted by professionals within the field of Speech Language Pathology.
One way of figuring out if a speech error is developmental or not is by using what are called sound acquisition norms or speech sound norms.
Speech sound norms are one of the many tools that SLP's use to help guide them in determining which errors are developmental in nature, and which errors are truly disordered.
For more information regarding articulation/speech developmental milestones and to view developmental charts, please visit the following links below:
Speech and Language Milestones- http://www.ldonline.org/article/6313
Typical Expressive Language Development- http://www.speech-language-therapy.com/index.php?option=com_content&view=article&id=33:brown&catid=2:uncategorised&Itemid=117
Speech Sound Development Chart- http://www.talkingchild.com/speechchart.html
Information adapted from: http://www.asha.org/slp/schools/prof-consult/norms/nformation adapted from: http://www.asha.org/slp/schools/prof-