Deaf signers and serial recall in the visual modality: Memory for signs,fingerspelling, and print

This study investigated serial recall by congenitally, profoundly deaf signers for visually specified linguistic information presented in their primary language, American Sign Language (ASL), and in printed or fingerspelled English. There were three main findings. First, differences in the serial-position curves across these conditions distinguished the changing-state stimuli from the static stimuli. These differences were a recency advantage and a primacy disadvantage for the ASL signs and fingerspelled English words, relative to the printed English words. Second, the deaf subjects, who were college students and graduates, used a sign-based code to recall ASL signs, but not to recall English words; this result suggests that well-educated deaf signers do not translate into their primary language when the information to be recalled is in English. Finally, mean recall of the deaf subjects for ordered lists of ASL signs and fingerspelled and printed English words was significantly less than that of hearing control subjects for the printed words; this difference may be explained by the particular efficacy of a speech-based code used by hearing individuals for retention of ordered linguistic information and by the relatively limited speech experience of congenitally, profoundly deaf individuals.     

Recall of order information by deaf signers: Phonetic coding in temporal order recall

To examine the claim that phonetic coding plays a special role in temporal order recall, deaf and hearing college students were tested on their recall of temporal and spatial order information at two delay intervals. The deaf subjects were all native signers of American Sign Language. The results indicated that both the deaf and hearing subjects used phonetic coding in short-term temporal recall, and visual coding in spatial recall. There was no evidence of manual or visual coding among either the hearing or the deaf subjects in the temporal order recall task. The use of phonetic coding for temporal recall is consistent with the hypothesis that recall of temporal order information is facilitated by a phonetic code.     

Short-term recall by deaf signers of American Sign Language: implications of encoding strategy for order recall

Two experiments were conducted on short-term recall of printed English words by deaf signers of American Sign Language (ASL). Compared with hearing subjects, deaf subjects recalled significantly fewer words when ordered recall of words was required, but not when free recall was required. Deaf subjects tended to use a speech-based code in probed recall for order, and the greater the reliance on a speech-based code, the more accurate the recall. These results are consistent with the hypothesis that a speech-based code facilitates the retention of order information.     

Sign recall by hearing signers: Evidences of dual coding

Deaf participants' sign recall is affected by sign similarity, sign length, irrelevant signing and manual articulatory suppression, suggesting the existence of a phonological loop for signs. In two experiments we explore whether hearing signers (who have learned Spanish Sign Language as second language) use a phonological loop for signs, whether they use their phonological loop for words or whether they use both when recalling sign lists. Articulatory suppression (manual and vocal) and list similarity (word similarity and sign similarity) were manipulated in two experiments. Results clearly suggest that our participants recode orally the signs and use those representations to recall sign lists, but visuospatial information is also used in this task.     

Silent reading: Insights from second-generation deaf readers

Previous studies indicate that hearing readers sometimes convert printed text into a phonological form during silent reading. The experiments reported here investigated whether second-generation congenitally deaf readers use any analogous recoding strategy. Fourteen congenitally and profoundly deaf adults who were native signers of American Sign Language (ASL) served as subjects. Fourteen hearing people of comparable reading levels were control subjects. These subjects participated in four experiments that tested for the possibilities of (a) recoding into articulation, (b) recoding into fingerspelling, (c) recoding into ASL, or (d) no recoding at all. The experiments employed paradigms analogous to those previously used to test for phonological recoding in hearing populations. Interviews with the deaf subjects provided supplementary information about their reading strategies. The results suggest that these deaf subjects as a group do not recode into articulation or fingerspelling, but do recode into sign.     

Processing of formational, semantic, and iconic information in American sign language

Three experiments examined short-term encoding processes of deaf signers for different aspects of signs from American Sign Language. Experiment 1 compared short-term memory for lists of formationally similar signs with memory for matched lists of random signs. Just as acoustic similarity of words interferes with short-term memory or word sequences, formational similarity of signs had a marked debilitating effect on the ordered recall of sequences of signs. Experiment 2 evaluated the effects of the semantic similarity of the signs on short-term memory: Semantic similarity had no significant effect on short-term ordered recall of sequences of signs. Experiment 3 studied the role that the iconic (representational) value of signs played in short-term memory. Iconicity also had no reliable effect on short-term recall. These results provide support for the position that deaf signers code signs from American Sign Language at one level in terms of linguistically significant formational parameters. The semantic and iconic information of signs, however, seems to have little effect on short-term memory.     

Temporal processing in deaf signers

The auditory and visual modalities differ in their capacities for temporal analysis, and speech relies on more rapid temporal contrasts than does sign language. We examined whether congenitally deaf signers show enhanced or diminished capacities for processing rapidly varying visual signals in light of the differences in sensory and language experience of deaf and hearing individuals. Four experiments compared rapid temporal analysis in deaf signers and hearing subjects at three different levels: sensation, perception, and memory. Experiment 1 measured critical flicker frequency thresholds and Experiment 2, two-point thresholds to a flashing light. Experiments 3-4 investigated perception and memory for the temporal order of rapidly varying nonlinguistic visual forms. In contrast to certain previous studies, specifically those investigating the effects of short-term sensory deprivation, no significant differences between deaf and hearing subjects were found at any level. Deaf signers do not show diminished capacities for rapid temporal analysis, in comparison to hearing individuals. The data also suggest that the deficits in rapid temporal analysis reported previously for children with developmental language delay cannot be attributed to lack of experience with speech processing and production.     

Linguistic encoding in short-term memory as a function of stimulus type

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. Phonologically 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.     

Sign-based short-term coding of American Sign Language signs and printed English words by congenitally deaf signers

A short-term serial recall task consisting of lists of five American Sign Language signs and lists of five printed English words was administered to eight congenitally deaf subjects. For both modes of presentation, the stimuli in a given list were (1) high in phonological relatedness, (2) high in cherological relatedness (i.e., they were similar in terms of the formational attributes of their sign-equivalents), or (3) low in both phonological and cherological similarity (control). For both modes of presentation, recall accuracy was significantly lower on cherologically related lists than on both phonologically related lists and control lists. Phonologically related lists did not differ significantly from control lists. These results suggest the possibility that ways of looking at human memory which rely on a preference for phonological coding in short-term memory processes may reflect the audiocentricity of the experimenter rather than the inherent nature of such processes.     

Ordered short-term memory differs in signers and speakers: implications for models of short-term memory

Capacity limits in linguistic short-term memory (STM) are typically measured with forward span tasks in which participants are asked to recall lists of words in the order presented. Using such tasks, native signers of American Sign Language (ASL) exhibit smaller spans than native speakers ([Boutla, M., Supalla, T., Newport, E. L., & Bavelier, D. (2004). Short-term memory span: Insights from sign language. Nature Neuroscience, 7(9), 997-1002]). Here, we test the hypothesis that this population difference reflects differences in the way speakers and signers maintain temporal order information in short-term memory. We show that native signers differ from speakers on measures of short-term memory that require maintenance of temporal order of the tested materials, but not on those in which temporal order is not required. In addition, we show that, in a recall task with free order, bilingual subjects are more likely to recall in temporal order when using English than ASL. We conclude that speakers and signers do share common short-term memory processes. However, whereas short-term memory for spoken English is predominantly organized in terms of temporal order, we argue that this dimension does not play as great a role in signers' short-term memory. Other factors that may affect STM processes in signers are discussed.     

听力正常人与聋人长时记忆的比较研究

以视觉系列呈现,序列回忆和自由回忆的方法比较了音、形、义三维编码维量在听力正常人与聋人短时记忆和长时记忆加工过程中的相对效用。结果是听力正常组产生了明显的语音相似性效应,聋人组突出地显示出形码的相似性干扰。在短时记忆和长时记忆加工过程中两组被试都显示出了形义两维编码维量的作用最强,而音码的作用相对比较弱。两组被试也都显示出了明显的系列位置效应及大体相同的长时保持。     

听力正常人与聋人短时记忆的比较研究

以视觉系列呈现,自由回忆的方法比较了听力正常人与聋人对分别被强化的厂类相似性汉语字表的短时记忆获得量。从总的平均获得量来看,两组结果没有显著差异,而从每一编码维量在短时记忆的加工过程中的作用来看,两组被试都显示出了形、义两维编码维量的作用最强,而音码的作用相对比较弱。两组被试也都显示出了明显的系列位置效应,但聋人组的次级记忆容量明显地低于听力正常组,而初级记忆容量两组没有显著差异。并对可能的机制进行了讨论。     

Effects of signability and imagery on word recall of deaf and hearing students

This study examined 40 deaf and 20 hearing students' free recall of visually presented words varied systematically with respect to signability (i.e., words that could be expressed by a single sign) and visual imagery. Half of the deaf subjects had deaf parents, while the other half had hearing parents. For deaf students, recall was better for words that had sign-language equivalents and high-imagery values. For the hearing students, recall was better for words with high-imagery values, but there was no effect of signability. Over-all, the hearing students recalled significantly more words than the deaf students in both immediate and delayed free-recall conditions. In immediate recall, deaf students with deaf parents reported using a sign-language coding strategy more frequently and recalled more words correctly than deaf students with hearing parents. Serial-position curves indicated several differences in patterns of recall among the groups. These results underline the importance of sign language in the memory and recall of deaf persons.     

Visual field asymmetries for motion processing in deaf and hearing signers

Recently, we reported a strong right visual field/left hemisphere advantage for motion processing in deaf signers and a slight reverse asymmetry in hearing nonsigners (Bosworth & Dobkins, 1999). This visual field asymmetry in deaf signers may be due to auditory deprivation or to experience with a visual-manual language, American Sign Language (ASL). In order to separate these two possible sources, in this study we added a third group, hearing native signers, who have normal hearing and have learned ASL from their deaf parents. As in our previous study, subjects performed a direction-of-motion discrimination task at different locations across the visual field. In addition to investigating differences in left vs right visual field asymmetries across subject groups, we also asked whether performance differences exist for superior vs inferior visual fields and peripheral vs central visual fields. Replicating our previous study, a robust right visual field advantage was observed in deaf signers, but not in hearing nonsigners. Like deaf signers, hearing signers also exhibited a strong right visual field advantage, suggesting that this effect is related to experience with sign language. These results suggest that perceptual processes required for the acquisition and comprehension of language (motion processing in the case of ASL) are recruited by the left, language-dominant, hemisphere. Deaf subjects also exhibited an inferior visual field advantage that was significantly larger than that observed in either hearing group. In addition, there was a trend for deaf subjects to perform relatively better on peripheral than on central stimuli, while both hearing groups showed the reverse pattern. Because deaf signers differed from hearing signers and nonsigners along these domains, the inferior and peripheral visual field advantages observed in deaf subjects is presumably related to auditory deprivation. Finally, these visual field asymmetries were not modulated by attention for any subject group, suggesting they are a result of sensory, and not attentional, factors.     

Atypical lateralization of memory for location: effects of deafness and sign language use

This paper examines the impact of auditory deprivation and sign language use on the enhancement of location memory and hemispheric specialization using two matching tasks. Forty-one deaf signers and non-signers and 51 hearing signers and non-signers were tested on location memory for shapes and objects (Study 1) and on categorical versus coordinate spatial relations (Study 2). Results of the two experiments converge to suggest that deafness alone supports the atypical left hemispheric preference in judging the location of a circle or a picture on a blank background and that deafness and sign language experience determine the superior ability of memory for location. The importance of including a sample of deaf non-signers was identified.     

Semantic and formational clustering in deaf and hearing subjects’ free recall of signs

To investigate whether formational properties of sign language are used spontaneously to organize long-term memory, 16 deaf college students were given a free recall task with items that could be categorized either by shared semantic category or by shared sign language hand shape. Both presentation and response modes (signed or written) were varied between subjects. Analyses revealed no effects of mode on trials to criterion or number of items recalled at 1 week. The clustering that occurred was exclusively semantic, with significantly higher clustering scores during acquisition trials in subjects required to sign their responses. In Experiment 2, formational clustering was encouraged by including formational similarity as the only experimenter-defined basis of categorization, by increasing formational similarity within categories, and by testing only subjects with high signing skills. Input and output modes were again varied between subjects. Subjects were deaf college students with deaf parents (n = 10) or hearing parents (n = 16), and hearing adults with deaf parents (n = 8). Again, spontaneous clustering by formational similarity was extremely low. In only one case— deaf subjects with hearing parents given signed input—did formational clustering increase significantly across the eight acquisition trials. After the categorical nature of the list was explained to subjects at a 1-week retention session, all groups clustered output by formational categories. Apparently, fluent signers do have knowledge of the formational structure of signs, but do not spontaneously use this knowledge as a basis of mnemonic organization in long-term memory.     

Linguistic coding by deaf children in relation to beginning reading success

The coding of printed letters in a task of consonant recall was examined in relation to the level of success of prelingually and profoundly deaf children (median age 8.75 years) in beginning reading. As determined by recall errors, the deaf children who were classified as good readers appeared to use both speech and fingerspelling (manual) codes in short-term retention of printed letters. In contrast, deaf children classified as poor readers did not show influence of either of these linguistically based codes in recall. Thus, the success of deaf children in beginning reading, like that of hearing children, appears to be related to the ability to establish and make use of linguistically recoded representations of the language. Neither group showed evidence of dependence on visual cues for recall.     

The associative learning of the deaf: The effects of word imagery and signability

In two experiments, deaf and hearing subjects learned paired associate lists in which rated visual imagery and signability (a measure of the ease with which a word can be represented as a gestural sign) were orthogonally varied. Visual presentation of three alternating study-recall trials resulted in significant positive effects of imagery for both deaf and hearing subjects, whereas signability facilitated recall only for deaf subjects. Examination of the relation between item attributes and reported learning strategy indicated that both deaf and hearing subjects used imaginal mediators more frequently for high-imagery than low-imagery pairs. A gestural sign strategy was reported almost exclusively by deaf subjects, particularly for high-signability pairs. These results suggest that an examination of the effects of sign language variables will contribute to an understanding of the qualitative differences in the associative learning of the deaf and hearing.     

How grammar can cope with limited short-term memory: simultaneity and seriality in sign languages

It is known that in American Sign Language (ASL) span is shorter than in English, but this discrepancy has never been systematically investigated using other pairs of signed and spoken languages. This finding is at odds with results showing that short-term memory (STM) for signs has an internal organization similar to STM for words. Moreover, some methodological questions remain open. Thus, we measured span of deaf and matched hearing participants for Italian Sign Language (LIS) and Italian, respectively, controlling for all the possible variables that might be responsible for the discrepancy: yet, a difference in span between deaf signers and hearing speakers was found. However, the advantage of hearing subjects was removed in a visuo-spatial STM task. We attribute the source of the lower span to the internal structure of signs: indeed, unlike English (or Italian) words, signs contain both simultaneous and sequential components. Nonetheless, sign languages are fully-fledged grammatical systems, probably because the overall architecture of the grammar of signed languages reduces the STM load. Our hypothesis is that the faculty of language is dependent on STM, being however flexible enough to develop even in a relatively hostile environment.     

Memory for Faces and Objects by Deaf and Hearing Signers and Hearing Nonsigners

The memory of 11 deaf and 11 hearing British Sign Language users and 11 hearing nonsigners for pictures of faces of and verbalizable objects was measured using the game Concentration. The three groups performed at the same level for the objects. In contrast the deaf signers were better for faces than the hearing signers, who in turn were superior to the hearing nonsigners, who were the worst. Three hypotheses were made: That there would be no significant difference in terms of the number of attempts between the three groups on the verbalizable object task, that the hearing and deaf signers would demonstrate superior performance to that of the hearing nonsigners on the matching faces task, and that the hearing and deaf signers would exhibit similar performance levels on the matching faces task. The first two hypotheses were supported, but the third was not. Deaf signers were found to be superior for memory for faces to hearing signers and hearing nonsigners. Possible explanations for the findings are discussed, including the possibility that deafness and the long use of sign language have additive effects.