Characteristics of frontal lispers clustered according to severity.

The purpose of this investigation was to determine the relationship among frontal lisping, protrusive lingual force, and lingual diadochokinetic rates when subjects are grouped according to severity of lisping. Results revealed that when compared to normal speaking counterparts: (1) lispers in each severity subgroup exhibited significantly weaker protrusive lingual forces and that the significance of such differences increased with the severity of lisping; and (2) all but the moderately severe lispers displayed significantly slower lingual diadochokinetic rates. These findings suggest that clustering lispers into homogeneous severity subgroups before examining the relationships between their misarticulations and the lingual factors studied may offer important information regarding the diagnosis, treatment, and prognosis of their articulatory problems.