Forging a morphological system out of two dimensions: Agentivity and number.

Languages have diverse strategies for marking agentivity and number. These strategies are negotiated to create combinatorial systems. We consider the emergence of these strategies by studying features of movement in a young sign language in Nicaragua (NSL). We compare two age cohorts of Nicaraguan signers (NSL1 and NSL2), adult homesigners in Nicaragua (deaf individuals creating a gestural system without linguistic input), signers of American and Italian Sign Languages (ASL and LIS), and hearing individuals asked to gesture silently. We find that all groups use movement axis and repetition to encode agentivity and number, suggesting that these properties are grounded in action experiences common to all participants. We find another feature - unpunctuated repetition - in the sign systems (ASL, LIS, NSL, Homesign) but not in silent gesture. Homesigners and NSL1 signers use the unpunctuated form, but limit its use to No-Agent contexts; NSL2 signers use the form across No-Agent and Agent contexts. A single individual can thus construct a marker for number without benefit of a linguistic community (homesign), but generalizing this form across agentive conditions requires an additional step. This step does not appear to be achieved when a linguistic community is first formed (NSL1), but requires transmission across generations of learners (NSL2).

Watching language grow in the manual modality: nominals, predicates, and handshapes.

All languages, both spoken and signed, make a formal distinction between two types of terms in a proposition--terms that identify what is to be talked about (nominals) and terms that say something about this topic (predicates). Here we explore conditions that could lead to this property by charting its development in a newly emerging language--Nicaraguan Sign Language (NSL). We examine how handshape is used in nominals vs. predicates in three Nicaraguan groups: (1) homesigners who are not part of the Deaf community and use their own gestures, called homesigns, to communicate; (2) NSL cohort 1 signers who fashioned the first stage of NSL; (3) NSL cohort 2 signers who learned NSL from cohort 1. We compare these three groups to a fourth: (4) native signers of American Sign Language (ASL), an established sign language. We focus on handshape in predicates that are part of a productive classifier system in ASL; handshape in these predicates varies systematically across agent vs. no-agent contexts, unlike handshape in the nominals we study, which does not vary across these contexts. We found that all four groups, including homesigners, used handshape differently in nominals vs. predicates--they displayed variability in handshape form across agent vs. no-agent contexts in predicates, but not in nominals. Variability thus differed in predicates and nominals: (1) In predicates, the variability across grammatical contexts (agent vs. no-agent) was systematic in all four groups, suggesting that handshape functioned as a productive morphological marker on predicate signs, even in homesign. This grammatical use of handshape can thus appear in the earliest stages of an emerging language. (2) In nominals, there was no variability across grammatical contexts (agent vs. no-agent), but there was variability within- and across-individuals in the handshape used in the nominal for a particular object. This variability was striking in homesigners (an individual homesigner did not necessarily use the same handshape in every nominal he produced for a particular object), but decreased in the first cohort of NSL and remained relatively constant in the second cohort. Stability in the lexical use of handshape in nominals thus does not seem to emerge unless there is pressure from a peer linguistic community. Taken together, our findings argue that a community of users is essential to arrive at a stable nominal lexicon, but not to establish a productive morphological marker in predicates. Examining the steps a manual communication system takes as it moves toward becoming a fully-fledged language offers a unique window onto factors that have made human language what it is.

Chronic auditory agnosia following Landau-Kleffner syndrome: a 23 year outcome study.

We report a 27-year-old woman with chronic auditory agnosia following Landau-Kleffner Syndrome (LKS) diagnosed at age 4 1/2. She grew up in the hearing/speaking community with some exposure to manually coded English and American Sign Language (ASL). Manually coded (signed) English is her preferred mode of communication. Comprehension and production of spoken language remain severely compromised. Disruptions in auditory processing can be observed in tests of pitch and duration, suggesting that her disorder is not specific to language. Linguistic analysis of signed, spoken, and written English indicates her language system is intact but compromised because of impoverished input during the critical period for acquisition of spoken phonology. Specifically, although her sign language phonology is intact, spoken language phonology is markedly impaired. We argue that deprivation of auditory input during a period critical for the development of a phonological grammar and auditory-verbal short-term memory has limited her lexical and syntactic development in specific ways.

Aphasic and parkinsonian signing: differences in phonological disruption.

Since movements of the articulators in sign, unlike in speech, are directly observable, we can investigate signing not only as linguistic behavior but also as motor behavior and directly contrast linguistic-representational and motor-execution disorders of signing. We compared the temporal sequencing characteristics (duration of segments, pausing, periods of change in handshape posture), intactness of distinctive features, and correct use of prosodic templates in three pairs of signers--two Deaf aphasic signers with posterior damage in the left hemisphere, two signers with Parkinson's disease, and two gender- and age-matched control signers. With respect to distinctive features, the aphasic signers exhibited selection errors in the American Sign Language (ASL) distinctive features system, while the Parkinsonian signers showed an intact distinctive feature inventory, but with disturbances in executing these features. The Parkinsonian signers, unlike the aphasic and control signers, showed marked disturbances in the temporal organization and coordination of what we argue are the two subsystems of the ASL sign stream--handshape and movement. The findings demonstrate a phonetic deficit in Parkinsonian signers, in contrast with aphasic signers who showed a disruption in the underlying representation and syllabification processes in the language.

The relative effects of three expressive methods upon the speech intelligibility of profoundly deaf speakers.

Two studies, conducted over a nine month interval, were designed to evaluate the relative effects of three expressive methods (speech alone, speech and signs, and speech with cues) upon speech intelligibility. Five profoundly deaf adults, who were receiving continuous speech training, were recorded reading lists of individual words under all three expressive modes. Listeners were required to identify through a multiple choice format the target stimuli from auditory presentations only. Study I results indicated that speech with cues produced the highest level of intelligibility, while speech and signs produced the lowest level. Study II, with an expanded set of word stimuli, found that speech alone produced a 65% rate of correct identification by listeners; speech and signs again produced the lowest rate of correct identifications. Implications for the assessment and understanding of speech intelligibility are considered.