From the American Speech-Language Hearing Association (www.asha.org)
"Behaviors that should trigger an SLP referral:
By age 3 years cannot: be understood by family and/or caregivers correctly produce vowels and such sounds as p, b, m, w in words repeat when not understood without becoming frustrated
By age 4 years cannot: be understood by individuals with whom they do not associate regularly be understood by family and/or caregivers correctly produce t, d, k, g, f be asked to repeat without becoming sensitive
By age 5 years cannot: be understood in all situations by most listeners correctly produce most speech sounds be asked to repeat without exhibiting frustration
Disturbance in neuromuscular control causes difficulty learning to produce sounds appropriately speech is usually slurred; difficulty controlling respiration for speech; abnormal loudness, rhythm, or vocal quality exhibits difficulty learning sounds to form words; may sound nasal, strangled and/or breathy exhibits frustration and/or avoidance of speech due to extreme difficulty forming sounds or difficulty being understood
Disturbance in programming, positioning, and sequencing of muscular movements sound errors are prevalent but variable (i.e., "dog" could be produced "dog," "tog," "gog," "god" by same child) varies from rarely being able to produce sounds to ongoing speech that is rarely understood, or speech that is usually understood with frequent sound errors unaware of sound variations or exhibits varying degrees of frustration and/or anxiety regarding inability to "control speech"
Disturbance in performing voluntary movements with mouth and vocal mechanism cannot produce movements for sound production or sounds are produced without voice (whispered speech) varies from inability to produce any words to extreme difficulty being understood exhibits frustration and/or avoidance of speech due to difficulties"