Age differences in implicit and explicit associative memory: exploring elaborative processing effects.

Research in memory processes suggests implicit memory is more resistant to the effects of aging than explicit memory. Two experiments examined how variations in level of processing affect memory for novel word-pair associations across age groups. The results indicate that new learning may rely on some degree of elàborate and even explicit processing and that older adults show deficits in any form of new learning. Explicit associative memory benefited from elaborative processing for both age groups and age differences appeared to relate to overall working-memory capacity rather than effective use of elaborative processes. These results support a model of associative memory that distinguishes automatic unconscious processes versus conscious controlled processes in which older adults exhibit deficits in associative memory tasks that actually rely on consciously controlled processes.

Inhibition and aging: similarities between younger and older adults as revealed by the processing of unattended auditory information.

The ability to selectively attend to an auditory stimulus appears to decline with age and may result from losses in the ability to inhibit the processing of irrelevant stimuli (i.e., the inhibitory deficit hypothesis; L. Hasher & R. T. Zacks, 1988). It is also possible that declines in the ability to selectively attend are a result of age-related hearing losses. Three experiments examined whether older and younger adults differed in their ability to inhibit the processing of distracting stimuli when the listening situation was adjusted to correct for individual differences in hearing. In all 3 experiments, younger and older adults were equally affected by irrelevant stimuli, unattended stimuli, or both. The implications for auditory attention research and for possible differences between auditory and visual processing are discussed.

Redirects: a strategy to increase peer initiations.

Preschoolers' verbal abilities influence their verbal interactions with play partners. Previous research has suggested that preschoolers with specific language impairment (SLI) are more likely to initiate conversations with adults than with peers, as compared to their typically developing peers. This study investigated a teacher-implemented procedure, redirects, as a means to facilitate initiations to peers. A redirect occurs when a child initiates to the teacher, and the teacher then suggests the child initiate to a peer, thereby redirecting the child from an adult to a peer. Four preschool boys with SLI participated in the study. The teacher training was successful in increasing the teacher's ability to redirect the children's initiations. The children consistently responded to redirects by initiating to peers, and most redirected initiations received conversational responses from peers. Generalization effects to spontaneous peer initiations following the intervention period were demonstrated for 2 of the boys.

Effects of lexical meaning and practiced productions on coarticulation in children's and adults' speech.

This investigation examined the effect of familiarity with a speech target on the magnitude of the coarticulation observed in children (aged 3, 5, and 7 years) and adults. For the purposes of this investigation, coarticulation was defined as the effect that a following vowel, /i/ or /u/, had on the frequency value of the second formant (F2) in the preceding fricative, /s/ or /f/. Familiarity with the spoken targets was examined through the manipulation of two factors: (a) the presence or absence of lexical meaning and (b) the extent to which speakers were allowed to practice an item prior to recording. Results of acoustic measurements confirm that the children exhibited a greater effect of a following vowel on the preceding fricative when compared to adults. Nonmeaningful production items appeared to exhibit a greater effect of the vowel on the preceding fricative than meaningful production items, regardless of age of the individual. Limited motor practice did not have an effect on degree of fricative-vowel coarticulation in production items for any of the age groups. For the productions in this investigation, the primary coarticulatory effect was intrasyllabic.

In vivo use of N-(4-hydroxyphenyl retinamide)-0-glucuronide as a breast cancer chemopreventive agent.

The inhibitory effects of N-(4-hydroxyphenyl) retinamide and its glucuronide derivative on the development and growth of 7,12-dimethylbenz (a) anthracene - induced rat mammary tumors in vivo were compared. The results indicate that the glucuronide had a greater chemopreventive potency than equimolar concentration of the free retinoid by all the criteria measured, mainly the inhibition of tumor incidence, multiplicity and tumor growth. HPLC analysis of the blood of the rats showed no hydrolysis of the glucuronide during its chronic consumption, indicating that the retinoid glucuronide is probably acting in vivo per se rather than through hydrolysis to the free retinoid. The higher potency and lower toxicity of the glucuronide suggests, for the first time, that the conjugate may have an in vivo chemopreventive advantage over the parent retinamide.

Dysarthria of motor neuron disease: longitudinal measures of segmental durations.

Motor neuron disease encompasses a group of terminal, demyelinating diseases affecting upper- and lower-motor neurons and producing muscular weakness resulting in a flaccid, spastic, or spastic-flaccid dysarthria of speech. The present study presents measurements of the temporal-acoustic characteristics of dysarthria in three subjects with Motor Neuron Disease over a two-year recording period. Changes seen over the course of the disease varied by type of motor neuron disease, though all types demonstrated some degree of neutralization of the prevocalic VOT, target vowel duration, and postvocalic closure duration. These changes are discussed with relation to physical manifestation and progression of the disease.

Dysarthria of motor neuron disease: clinician judgments of severity.

Motor Neuron Disease (MND) is a terminal, demyelinating disease affecting upper- and lower-motor neurons and producing muscular weakness resulting in a characteristic spastic-flaccid dysarthria of speech. The present study investigates the relationship between the temporal-acoustic parameters of the speech of 15 individuals with MND as they relate to the progression of the disease and clinicians' judgments of dysarthria severity. When temporal-acoustic parameters are used to predict the progression of MND, it becomes apparent that victims provide compensatory gestures to mark voicing distinctions. When the same acoustic parameters are used to predict clinician judgments of severity, it is found that clinicians tend to use the same temporal cues that mark actual disease progression. Differences between the two sets of predictions relate to the linguistic systems of both speaker and judge, and the implications of this are discussed.

Mandibular position during children's defective /s/ productions.

Mandibular displacement during /s/ production was monitored via a mercury strain gauge which was taped to the face of two normally articulating and six /s/-misarticulating children. Simultaneous audio and jaw displacement visicorder traces were produced from an FM-tape recording of each experimental session, and were subsequently analyzed. Results indicated that various /s/-misarticulating subgroups exhibit different mandibular positions during /s/-production, and phonetic contextual effects upon mandibular position also vary by articulatory type.

Children's identification of their own /s/ misarticulations.

Six /s/ misarticulating children, two normal-articulating children, and four adults identified a variety of /s/ productions as normal and defective. The /s/ samples were embedded in short segments of speech spliced from the sentence repetitions of the same eight children. Results indicate that each misarticulator could identify at least some of his or her own productions as defective. Although no statistically significant differences appeared between groups, the two lateralizing subjects exhibited poorer identification scores on defective /s/ items than did the other groups, possibly indicating somewhat poorer auditory monitoring abilities. Included is a discussion of procedural considerations important to research of this type.

Speech style modifications of language-impaired children.

Six language-impaired children, each having a mean length of utterance (MLU) greater than 3.0, were observed in dyadic interactions with (1) normal-language children of similar chronological ages and (2) normal-language children who were younger but exhibited similar MLUs. Eight measures analyzing overall sentence complexity, sentence form, and features of discourse were used to compare the subjects' linguistic behaviors in the two conditions. Across conditions, the subjects made changes in their speech that were consistent with the speech style modifications made by normal-language children observed in earlier interaction studies. Lower Mean Pre-Verb Length, a greater degree of conversational assertiveness, and a higher frequency of Internal-State Questions were characteristic of the subjects in the MLU-matched condition as compared to the age-matched condition. Diagnostic and therapy considerations are discussed in view of these findings.

Age and changes in vocal jitter.

Small cycle-to-cycle variations of voice fundamental frequency (vocal jitter) were examined for sustained phonations of vowels (/i,a,u/) produced by 20 young adults and 20 older adults. Jitter was measured by an automatic fundamental frequency tracking program which utilized a peak-picking method of voice analysis. Results showed that the average jitter of the older adults was significantly greater than that of the young adults. It was also found that the jitter magnitudes differed significantly among the vowels. Implications of the findings to aging effects on voice and early detection of laryngeal dysfunction were discussed.