Understanding language without ability to speak

In 1962 Eric Lenneberg published an interesting case report of an 8 year old boy who had a congenital disorder that prevented him from developing the ability to speak. He could perform many oro-facial behaviors like chewing, swallowing, blowing, licking and he spontaneously made noises "that sound somewhat like Swiss yodeling" but he could not speak. With intensive speech therapy he eventually achieved the ability to "repeat a few words after his speech therapist or his mother but the words are still barely intelligible" (p. 420). In contrast, his speech comprehension had been judged as fully normal by the author as well as by neurologists and speech pathologists over the course of 20 or so visits. Lenneberg goes on to report a more systematic examination of the boy's comprehension which revealed it to be well preserved.

Lenneberg couched his case report, which he indicated is typical of a larger category of patients, in the context of theories of speech development which held that babbling and speech output was critical to the normal development language abilities including receptive (comprehension) skills. He argued that this type of case argues against the view that speech production is critical to the development of receptive speech.

Today, Lenneberg might have highlighted the relevance of his case for mirror neuron/motor theories of speech perception. These theories claim that speech is perceived by mapping acoustic speech sounds onto motor representations coding the production of speech. For example, Rizzolatti and Arbib (1998) stated,

mirror neurons represent the link between sender and receiver that Liberman postulated in his motor theory of speech perception as the necessary prerequisite for any type of communication (p. 189)

Such a theory would seem to predict that if an individual failed to develop motor systems underlying speech production they should not be able to perceive and comprehend speech. Lenneberg's report demonstrates that this prediction is incorrect.

Are there more recent cases of the development of normal language comprehension in the face of failures to develop speech production. Yes, here is a case I recently came across (Case 1 from Christen et al. 2000).

A three month old girl had an acute febrile illness (possibly meningitis) with epileptic seizures. After recovery from the acute illness, her motor development was delayed, she exhibited constant drooling, took only pureed food, and never acquired expressive language. She attended a school for disabled children, but made normal progress in writing and reading. She was examined at 15 years old by the paper authors. The patient presented with pseudobulbar palsy (difficulty with orofacial movements such as chewing, swallowing, speech), her “mental state” was normal but she could communicate only by non-verbal means as she was unable to produce identifiable speech sounds. However her language comprehension was reported as normal. An MRI showed bilateral lesions of the anterior opercular region which the authors believed were acquired at age three months during the child's illness and which damaged speech output systems. Bilateral lesions in this region in adults produce a similar disruption of speech output, without affecting comprehension abilities, so called Foix-Chavany-Marie syndrome.

Again, we have a clear demonstration of preserved receptive speech abilities despite a complete lack of development of motor speech capacity. This kind of result is not straightforwardly explained by theories which hold that speech production is critical for speech perception.

References

Christen HJ, Hanefeld F, Kruse E, Imhäuser S, Ernst JP, Finkenstaedt M. (2000). Foix-Chavany-Marie (anterior operculum) syndrome in childhood: a reappraisal of
Worster-Drought syndrome. Dev Med Child Neurol., 42, 122-32

Lenneberg, E. (1962). Understanding language without ability to speak: a case report. Journal of Abnormal and Clinical Psychology, 65, 419-425.

G Rizzolatti, M Arbib (1998). Language within our grasp Trends in Neurosciences, 21 (5), 188-194 DOI: 10.1016/S0166-2236(98)01260-0