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In two studies, we find that native and non-native acquisition show different effects on sign language processing. Subjects were all born deaf and used sign language for interpersonal communication, but first acquired it at ages ranging from birth to 18. In the first study, deaf signers shadowed (simultaneously watched and reproduced) sign language narratives given in two dialects, American Sign Language (ASL) and Pidgin Sign English (PSE), in both good and poor viewing conditions. In the second study, deaf signers recalled and shadowed grammatical and ungrammatical ASL sentences. In comparison with non-native signers, natives were more accurate, comprehended better, and made different kinds of lexical changes; natives primarily changed signs in relation to sign meaning independent of the phonological characteristics of the stimulus. In contrast, non-native signers primarily changed signs in relation to the phonological characteristics of the stimulus independent of lexical and sentential meaning. Semantic lexical changes were positively correlated to processing accuracy and comprehension, whereas phonological lexical changes were negatively correlated. The effects of non-native acquisition were similar across variations in the sign dialect, viewing condition, and processing task. The results suggest that native signers process lexical structure automatically, such that they can attend to and remember lexical and sentential meaning. In contrast, non-native signers appear to allocate more attention to the task of identifying phonological shape such that they have less attention available for retrieval and memory of lexical meaning.

In this study, we investigated bases for encoding linguistic stimuli in short-term memory. Past research has provided evidence for both phonological (sound-based) and cherological (sign-based) encoding, the former typically found with hearing subjects and the latter with deaf users of sign language. In the present experiment, encoding capabilities were delineated from encoding preferences, using 58 subjects comprising six groups differing in hearing ability and linguistic experience. Phonogically related, cherologically related, and control lists were presented orally, manually, or through both modalities simultaneously. Recall performance indicated that individuals encode flexibly, the code actually used being biased by incoming stimulus characteristics. Subjects with both sign and speech experience recalled simultaneous presentations better than ones presented orally or manually alone, which reveals the occurrence of enhanced encoding as a function of linguistic experience. Total linguistic experience appeared to determine recall accuracy following different types of encoding, rather than determining the encoding basis used.

This commentary supports MacNeilage's dismissal of an evolutionary development from sign language to spoken language but presents evidence of a feature in sign language (echo phonology) that links iconic signs to abstract vocal syllables. These data provide an insight into possible mechanism by which iconic manual gestures accompanied by vocalisation could have provided a route for the evolution of spoken language with its characteristically arbitrary form-meaning relationship.

This study replicated the 1984 work of Miller who reported a normal mean Verbal IQ of profoundly deaf students. To 27 profoundly deaf students the WISC - R Verbal Scale was administered using one of three signed language systems. The means do not support Miller's findings and raise some doubt about the mediating effects of language systems among profoundly deaf students.

The upper regions of the temporal lobe of the brain are important in hearing and comprehension of spoken language. The regions have been shown to be activated by sign language in congenitally deaf subjects, suggesting that the brain region for hearing could be activated by other sensory modalities, providing evidence of neural plasticity. Sign language was found to activate the 'language' areas, although not primary auditory cortex, and the sign language area was identified as the supratemporal gyri.

The critique by Petronio and Lillo-Martin 1997 of the argument that, in American sign language (ASL), WH-phases move rightward to a specifier CP position, proposes a leftward WH-movement. A new study suggests that Petronio and Lillo-Martin incorrectly interpreted the data and their analysis does not account for the facts of the language. Therefore, the argument that ASL WH-phases move to the right in ASL holds good.