Stability of performances of individual stutterers on oral reading adaptation tasks

This study aimed to determine whether individual oral reading adaptation task performances are sufficiently reliable to be used as predictive indicators of improvement in stuttering behavior by testing the stability of individual stutterers' adaptation scores. Results demonstrated that all stutterers are not stable in their individual adaptation scores and therefore individual adaptation scores may be insufficiently reliable for predicting and classifying. Theoretical and clinical implications are discussed.     

Modeling semantic memory: Effects of presenting semantic information in different modalities

How is semantic information from different modalities integrated and stored? If related ideas are encountered in French and English, or in pictures and sentences, is the result a single representation in memory, or two modality-dependent ones? Subjects were presented with items in different modalities, then were asked whether or not subsequently presented items were identical with the former ones. Subjects frequently accepted translations and items semantically consistent with those presented earlier as identical, although not as often as they accepted items actually seen previously. The same pattern of results was found when the items were French and English sentences, and when they were pictures and sentences. The results can be explained by the hypothesis that subjects integrate information across modalities into a single underlying semantic representation. A computer model, embodying this hypothesis, made predictions in close agreement with the data.     

Short-term memory in deaf and hearing children in relation to stimulus characteristics

Experiment 1 examined short-term memory with a serial probe task in 20 younger (mean age: 6 years, 3 months) and 20 older (mean age: 8 years, 8 months) deaf children. Four sets of stimuli were used: familiar animals, unfamiliar nonsense forms, fingerspelled letters, and lower-case print. In contrast to earlier research with hearing children, strong primacy effects were found with all stimuli at both ages, with frequent gestural and/or oral labeling but little cumulative rehearsal evident. To determine whether results were uniquely tied to deafness, identical procedures were used in Experiment 2 with 20 younger (4 years, 9 months) and 20 older (5 years, 10 months) hearing children. Again, overt activity was common, with strong primacy effects on animals and nonsense forms in the older group and on animals in the younger group. Contrasts between present and earlier findings suggest the need to consider the degree to which stimulus labels are overlearned, the role of nonverbal mediators in rehearsal, and the effects of changing educational experiences.     

Effects of differential reinforcement and task difficulty on preschoolers' compliance with teacher instructions

Preschool children in day schools were given instructions to complete certain tasks. Four tasks were given of two types and two levels of difficulty. In each condition compliance with at most one instruction (one task) was reinforced. In two similar experiments, with six children, general results were: compliance with easy tasks was maintained without reinforcement when any task compliance was reinforced; compliance for hard tasks remained high only when that specific task was reinforced. Thus, generalization of compliance with instructions varied with task difficulty. The setting and procedure for both studies were designed to reduce possible coercive features of laboratory studies of generalized performance. Results show generalized performance can occur under naturalistic conditions. The effect of effort, as a response characteristic affecting generalized performance, is discussed.     

Structural complexity as a determinant of serial pattern learning

A new methodology extends the study of serial pattern learning to nonhuman organisms by constructing patterns using elements that are both familiar and motivationally meaningful to animals. Two experiments examine the ability of rats to anticipate various quantities of food as measured by running times in a runway when the quantities occur in a serial order. In Experiment 1, a serial monotonic pattern (14-7-3-1-0 food pellets) produced more rapid learning and more accurate anticipation of the various quantities (“tracking”) than a serial nonmonotonic pattern (14-1-3-7-0 food pellets), particularly with respect to the final 0-pellet element. In Experiment 2, the same monotonic pattern generated faster learning and more accurate anticipation of pattern elements than a weakly monotonic pattern (14-5-5-1-0 pellets). Associative explanations including simple excitatory or inhibitory effects, temporal anticipation, reinforcement contrast, and the number and discriminability of pairwise associations are not adequate to account for the data. Rather, the formally defined structural complexity of each pattern adequately predicts its relative difficulty.     

Preference for shock signals as a function of the temporal accuracy of the signals

Three groups of rats were exposed to pairs of three different contingencies on two sides of a shuttlebox. One signaled contingency provided 10-min danger and safety cues plus an additional 10-sec cue immediately preceeding shock (P-S), another signaled contingency provided 10-min danger and safety cues but random 10-sec cues with respect to shock (R-S), and an unsignaled contingency provided no safety period, but only a 20-min danger period during which shock could occur (NS). Signaled P-S and R-S contingencies were preferred in a choice test to the unsignaled NS contingency, and P-S was preferred to R-S. Independent tests of the fear-eliciting properties of the cues made in an off-baseline test of suppression of ongoing exploration indicated more freezing (fear) to the 10-sec cue in rats experiencing the P-S contingency. The results were interpreted as indicating a preference for cues providing more precise information about the temporal location of shock even when those cues were fear-eliciting.     

Numerical taxonomy of aphasia

Two hundred consecutively seen aphasics, 142 of them with infarcts, were examined by tests of fluency, comprehension, repetition, naming, and information content. The language scores were subjected to a minimum variance clustering algorithm separately for the total and for the infarct groups. The latter generated 10 clusters on a dendrogram. Attribute analysis of each cluster provided a clinically meaningful profile of language performance for these groups. The degree of correlation of most computer generated clusters with clinically recognized groups was high, and the homogeneity of some of the clusters is striking. An exception appears to be “conduction aphasia,” which is bimodally distributed. One of these clusters, with high fluency and low comprehension scores, was renamed “afferent conduction” aphasia, and the other, with lower fluency and higher comprehension, was renamed “efferent conduction” aphasia. The Principal Components Analysis was used to evaluate the discriminatory value of language characteristics, and the Nearest Neighbor Network Analysis was used to evaluate the significance of clustering. The dendrogram for all aphasics showed a less specific and less homogenous six clusters.     

Stimulus control of free-operant avoidance: The contribution of response rate and incentive relations between multiple-schedule components

The associations formed in the components of a multiple schedule can be classified as (1) stimulus-response (S-R) associations and (2) stimulus-reinforcer (S-S^R) associations. The present experiments sought to determine the individual contribution of these S-R and S-S^R associations to stimulus control by manipulating them independently. Responses postponed shocks by 25 sec in the presence of a tone alone and a light alone in all experiments. The contingencies programmed in the absence of both tone and light established a reference for the S-R and S-S^R associations in tone and in light. All four possible combinations of signalling response increase or decrease together with incentive increase or decrease were studied. Although the influence of the contingencies operating in the absence of tone and light was difficult to detect from response rates in tone or light, presenting tone and light together revealed clear effects. Response rates in tone and light together relative to those in either alone depended upon the contingency operating in the absence of tone and light. Stimulus-response and stimulus-reinforcer associations appeared to counteract each other when in opposition and combine together to enhance each other when in agreement. This suggested that the associations of a stimulus to response and to incentive combine algebraically in determining stimulus control. An algebraic analysis in terms of the S-R and S-S^R associations conditioned to the stimulus elements comprising the training and test stimuli accounted for the observed patterns of data.