Auditory lateralization for speech in language-impaired children.

The ability of five language-impaired (LI) children and five matched controls, aged 7-10 years, to discriminate natural pairs of consonant-vowel syllables contrasted on place of articulation and voicing, presented to the right or left ear with white noise in the contralateral ear, was investigated. The general pattern of errors indicated that LI children had more difficulty than controls in discriminating place of articulation contrasts only when they were presented to the left ear, as well as a difficulty in discriminating voice contrasts selective to the right ear. The results are discussed in terms of acoustic integration and suggest that bihemispheric dysfunction is a basis for specific language impairment.     

Cerebral lateralization for speech in deaf and normal children

The cerebral lateralization pattern for speech production in normal hearing and congenitally deaf children was studied using the dual-task paradigm. Performance under the verbal task conditions showed predicted left hemispheric dominance for speech production in the normal hearing children. No developmental trends in asymmetry were found, suggesting that speech lateralization is present in normal 3-year-old children. These data support the developmental invariance hypothesis of cerebral organization. Deaf children showed more symmetrical patterns of cerebral control for speech production. No developmental trends in functional brain organization were observed among prepubescent deaf children.     

Information processing and speech lateralization in learning-disabled children

The relationship between information processing and speech lateralization was investigated in learning-disabled children. The Kaufman Assessment Battery for Children (K-ABC) assessed simultaneous and successive processing while a dichotic listening paradigm with free recall and directed attention conditions assessed speech lateralization. A three-factor ANOVA design conducted on the dichotic data revealed that normal children demonstrated stronger right ear advantage (REA); whereas learning-disabled showed weaker right ear advantage. Further, lambda analyses conducted on individual subjects revealed that the learning-disabled did not demonstrate the REA, were not biased attenders, and did not get more right ear than left ear items when attention was directed to one ear. Multiple-regression analysis was used to predict sequential processing from the dichotic data for both groups. Learning-disabled children demonstrated a substantial deficit in sequential processing as compared to normal children. These results indicate that learning-disabled children may not have adequate cerebral lateralization of receptive speech processes, shift their attention more readily, and are more inadequate in sequential processing that presumably subserves language functioning. Perhaps learning-disabled children have deficiencies of processor capacity of salient areas of the left (language) hemisphere.     

The effects of linguistic experience on cerebral lateralization for speech production in normal hearing and deaf adolescents

The cerebral lateralization patterns for speech production in 57 normal hearing and deaf adolescents were studied using the dual-task paradigm. Normal hearing subjects showed left hemispheric dominance for speech production, whereas both the congenitally deaf and those with early acquired deafness showed atypical cerebral representation for speech production. Deaf subjects whose hearing loss occurred after 2 years of age displayed a pattern of mixed cerebral dominance related to complexity of speech production or task difficulty. These results are interpreted as evidence for a relationship between linguistic/cognitive stage of development and the ontogenesis of cerebral lateralization. A parallel lateralization hypothesis of left cerebral dominance for speech production is offered.     

P300 stimulus sequence effects in children and adults

Immediate memory capability for 12 children (8 years) and 12 adults (21 years) was assessed electrophysiologically by using P300 event-related brain potential (ERP) stimulus sequences. These were derived from an auditory discrimination paradigm in which participants detected target stimuli in a series of target (T) and standard (S) tones that were varied by randomly presenting one of four sequence patterns (SSSS, TTTT, TTTS, SSST). Short-term memory capability was assessed behaviorally by recall performance of a 20-word list. Children and adults showed virtually identical P300 amplitude sequence patterns, such that for both groups component size increased systematically as the discrepancy between standard and target stimuli increased across sequence patterns. P300 latency evinced similar, albeit weaker, stimulus sequence effects, with children having longer component peak latencies. Memory recall performance was substantially weaker for the children than for adult participants, especially for recency effects. The findings suggest that immediate memory for stimulus sequences is fully developed in young children, although long-term memory is not.     

Orthogonal stimulus-response compatibility effects emerge even when the stimulus position is task irrelevant

The above-right/below-left mapping advantage with vertical stimuli and horizontal responses is known as the orthogonal stimulus-response compatibility (SRC) effect. We investigated whether the orthogonal SRC effect emerges with irrelevant stimulus dimensions. In Experiment 1, participants responded with a right or left key press to the colour of the stimulus presented above or below the fixation. We observed an above-right/below-left advantage (orthogonal Simon effect). In Experiment 2, we manipulated the polarity in the response dimension by varying the horizontal location of the response set. The orthogonal Simon effect decreased and even reversed as the left response code became more positive. This result provides evidence for the automatic activation of the positive and negative response codes by the corresponding positive and negative stimulus codes. These findings extended the orthogonal SRC effect based on coding asymmetry to an irrelevant stimulus dimension.     

Congruency effects in conceptualizing for speech

In naming a picture at the basic level, a semantically related distractor word induces interference in comparison to an unrelated word. When the task is changed from basic-level naming to categorization, however, this effect reverses to semantic facilitation. In previous studies, this semantic facilitation effect was attributed to “message congruency” at the conceptual level. The present study examines the nature of this message congruency effect: Is it due to competition between two activated category concepts in the incongruent condition or is it due to convergence of activity on a single category concept in the congruent condition? Two experiments show that neither the strength with which the context stimulus activates an incongruent category concept nor the semantic distance between the category concepts activated by target and distractor affect target categorization speed. We conclude that the message congruency effect is most likely due to convergence on a single category concept in the category-congruent condition.     

The morphological asymmetry of the hemispheres and cerebral dominance for speech: A possible relationship

The asymmetry of the posterior Sylvian branches of the middle cerebral artery was examined on the carotid angiograms of 59 patients in whom the lateralization of speech representation was known from sodium amobarbital (Amytal) studies. The usual asymmetry of these vessels was found to be present in the group of patients with left-hemisphere speech representation but significantly reduced in patients with atypical cerebral dominance for speech. A model of the inheritance of handedness and cerebral dominance is extended to take account of these results.     

The effects of word length on memory for pictures: Evidence for speech coding in young children

In a series of three experiments children aged from 4 to 10 years old were presented with a serial recall task with pictures of common objects which had short or long names. Children of all ages showed consistently better recall of pictures with short names. This effect occurred without the pictures being named at presentation and was abolished by articulatory suppression. It is concluded, in contrast to some earlier studies, that children as young as 4 years are able to use a speech code as a means of memorizing pictures.     

Specific effects of the Trier Social Stress Test on speech fluency in young and older adults

The notion that speech becomes less fluent during stressful speaking conditions has received little empirical test, and no research has tested this relationship in older adult participants. We analyzed speeches produced during the Trier Social Stress Test (TSST) or during a less stressful placebo (pTSST) version of the task. We measured young and older adults’ speech fillers (e.g., um), unfilled pauses (at least 1 s in duration), and other disfluencies (e.g., repetitions, repairs). Neither young nor older adult participants rated themselves as having greater stress in the TSST than pTSST condition, but behavioral effects were obtained. Participants in the TSST condition produced more mid-phrase speech fillers and unfilled pauses than participants in the pTSST condition. Young adults produced more unfilled pauses than older adults overall, and older adults produced more mid-phrase fillers than young adults. Critically, age group interacted with experimental condition, such that older speakers produced disproportionately more mid-phrase fillers than young adults in the TSST compared to the pTSST condition. In sum, the negative effects of the TSST on fluency were generally similar across age, but this specific age-related increase in mid-phrase fillers indicates that older adults’ word retrieval may have been particularly negatively affected. Findings are generally consistent with previous research and add to understanding of how factors internal to the speaker (i.e., demographic, personality, and cognitive variables) and factors external to the speaker (i.e., variables regarding the situation, context, or content of speech) combine to affect speech fluency.     

Coherence masking protection for speech in children and adults

In three experiments, we tested the hypothesis that children are more obliged than adults to fuse components of speech signals and asked whether the principle of harmonicity could explain the effect or whether it is, instead, due to children's implementing speech-based mechanisms. Coherence masking protection (CMP) was used, which involves labeling a phonetically relevant formant (the target) presented in noise, either alone or in combination with a stable spectral band (the cosignal) that provides no additional information about phonetic identity and is well outside the critical band of the target. Adults and children (8 and 5 years old) heard stimuli that were either synthetic speech or hybrids consisting of sine wave targets and synthetic cosignals. The target and cosignal either shared a common harmonic structure or did not. An adaptive procedure located listeners' thresholds for accurate labeling. Lower thresholds when the cosignal is present indicate CMP. Younger children demonstrated CMP effects that were both larger in magnitude and less susceptible to disruptions in harmonicity than those observed for adults. The conclusion was that children are obliged to integrate spectral components of speech signals, a perceptual strategy based on their recognition of when all components come from the same generator.     

Temporal properties of memory for speech in preschool children

The ability of four-year-old children to remember syllables was investigated, both to determine the temporal properties of memory for speech in subjects who do not use sophisticated retention strategies, and to determine what speech memory is available in the late preschool period. In Experiments 1 and 2, children were to remember pairs of nonsense syllables for 5, 10, 15, or 20 sec filled with a silent, manual task. In both experiments there was an apparent decay of one type of speech memory across 10-15 sec. In Experiment 2, strong interference was obtained when there was a final speech suffix item. An additional phase of this experiment verified that children cannot rehearse during the postlist period. However, in Experiments 3 and 4, suffix effects were not obtained with adult subjects in similar tasks. The results suggest that memory for speech persists for at least 10 sec even in preschool children, but that adults, unlike preschool children, engage in an additional type of speech coding that increases the resistance of memory to speech interference.     

The effects of verbal feedback and listener type on the speech of preschool children

The present study simultaneously assessed the relative contributions of feedback indicative of comprehension and the apparent age of the listener, either an adult or a doll which resembled a toddler, in a 2 (listeners) × 2 (types of feedback, C = comprehension, NC = noncomprehension) design. Two groups of children, a 3-year-old (N = 13, 7 boys, 6 girls) and a 5-year-old group (N = 12, 6 boys, 6 girls) were asked to tell stories to both the adult and doll in both C and NC conditions. The doll was constructed with an internal speaker such that it could actually carry on a conversation with the children. The conversations were taped, transcribed, and scored for mean length of utterance (MLU), transitional utterance length to each C and NC signal, and the proportion of child questions, exact self-repetitions, repetition and reductions, and rephrases/elaborations. The data analysis revealed that all children appropriately modified the length of their utterances (MLU) in the doll condition but not in the adult condition, indicating that they were sensitive to both the feedback and the nature of their listeners. Older children were more likely than younger children, and girls more likely than boys to adjust the length of their utterances appropriately to each type of feedback, slightly increasing the length of the subsequent utterance to a C signal and decreasing the length to an NC signal. The younger children were also more likely to respond with a simple repetition to NC cues from the adult.     

Iconicity in the speech of children and adults

Iconicity – the correspondence between form and meaning – may help young children learn to use new words. Early‐learned words are higher in iconicity than later learned words. However, it remains unclear what role iconicity may play in actual language use. Here, we ask whether iconicity relates not just to the age at which words are acquired, but also to how frequently children and adults use the words in their speech. If iconicity serves to bootstrap word learning, then we would expect that children should say highly iconic words more frequently than less iconic words, especially early in development. We would also expect adults to use iconic words more often when speaking to children than to other adults. We examined the relationship between frequency and iconicity for approximately 2000 English words. Replicating previous findings, we found that more iconic words are learned earlier. Moreover, we found that more iconic words tend to be used more by younger children, and adults use more iconic words when speaking to children than to other adults. Together, our results show that young children not only learn words rated high in iconicity earlier than words low in iconicity, but they also produce these words more frequently in conversation – a pattern that is reciprocated by adults when speaking with children. Thus, the earliest conversations of children are relatively higher in iconicity, suggesting that this iconicity scaffolds the production and comprehension of spoken language during early development.     

Cognitive components of naming in children: effects of referential uncertainty and stimulus realism.

The ease of picture naming in children was assessed as a function of two stimulus characteristics: (a) the number of available correct names for a picture (referential uncertainty) and (b) the degree to which a picture realistically represents the depicted object (stimulus realism). Two experiments employing different methods demonstrated that: (a) children named low uncertainty objects (those with a single dominant name, e.g., key, elephant) faster than high uncertainty objects (those with multiple possible correct names, e.g., lamp/light, stove/oven) and (b) this uncertainty effect arose at a stage of naming subsequent to object identification. Possible underlying mechanisms for the uncertainty effect include passive diffusion of activation over multiple object-name pathways or active inhibition among competing candidate names. Stimulus realism (colored photographs vs uncolored line drawings) did not consistently influence naming performance. Implications for understanding children's naming behavior are discussed.     

Importance of considering background factors when evaluating the effects of compensatory education programs designed for young children

A comparison was made of the intelligence and achievement of three groups of disadvantaged Negro kindergarten children: 27 who attended a summer Headstart program, 56 who attended a year-long Prekindergarten program, and 44 who had no preschool experience. No differences were found in test scores among the groups. When the socioeconomic background of the children was investigated, it was found that although the children were correctly classified as lower class, there were differecees among them in terms of socioeconomic status, and these differences were related to their test scores. The results suggest that the common practice of grouping all disadvantaged children in one category (lower class) may mask differences that may have an important effect on the children's ability to benefit from compensatory education programs. This may make it difficult to determine whether compensatory education has been effective.     

Hemispheric specialization for speech perception in language deficient kindergarten children

Twenty right-handed kindergarten children with superior language skills and twenty with deficient language skills (as defined by performance on an elicited sentence repetition task) were tested (1) for hemispheric specialization for speech perception with a dichotic CV syllable task and (2) for relative manual proficiency by means of a battery of hand tasks. Reading readiness and aspects of other cognitive abilities were also assessed. The superior children evidenced a mean right-ear advantage of 14.5%, which is consistent with normal values reported by other investigators using the same stimuli. The language deficient group evidenced essentially no mean ear advantage (0.5) with half of these subjects exhibiting left-ear superiority. The findings suggest relationships among cerébral dominance, language proficiency (including reading readiness), and general cognitive functioning.     

Durable partial reinforcement effects and social dominance in the rat

Following partial reinforcement (PRF) or consistent reinforcement (CRF) of an approach response in a straight runway and experimental extinction, rats were given the arena food-dominance test in Experiment 1 and both the arena test and the tunnel-dominance test in Experiment 2. PRF subjects were dominant in the tunnel test, but subordinate in the arena test, regardless of which dominance test was given first. These durable and pervasive effects of partial reinforcement training can be interpreted in terms of frustration theory.     

Evidence for stimulus-response compatibility effects in a divided visual field study of cerebral lateralization

The question addressed here was whether lateral asymmetry of processing might be influenced by response position, a factor which is usually considered irrelevant in divided visual field studies of cerebral lateralization. For this purpose a lexical decision task, which had previously been investigated with lateral unimanual two-finger choice reactions (Heister et al. 1983), was carried out under different manual and vocal response conditions so as to uncover possible S-R compatibility effects. In the first study, thirty-two subjects responded unimanually, with their responding hand held in a medial position. In the second study, twenty-four subjects responded vocally, i.e., in both cases the spatial (right/left) cues of the response position were eliminated. The reaction time advantage for compatible S-R pairings obtained with lateral hand position disappeared in the experiment with medial hand position, and the right-field superiority for vocal reactions was much smaller than the right-field superiority for right-hand reactions in the earlier lateral experiment. This indicates that an S-R compatibility effect contributed to the results of the earlier experiment. Thus, S-R compatibility can affect even unimanual reactions in lateralization studies.