Assessment of the relative importance of S+ and S− in rats using differential training on intercurrent discriminations

The present studies assessed the degree of stimulus control exerted by S+ and S? without confoundings of stimulus novelty and stimulus ambiguity. In Experiment 1, rats were trained on two intercurrent simultaneous discrimination problems with nine times more training given on one than the other. Then the animals were given transfer tests with re-paired stimuli. The results showed that S? exerts greater stimulus control than S+ in a two-choice simultaneous discrimination. Experiment 2 provided a test of the possibility that the relative degree of control by S? varies with different amounts of training. Three groups were trained on two intercurrent simultaneous discrimination problems; each group was given 7, 11, or 15 times more training on one problem than the other. Then transfer tests were given with re-paired stimuli. Again the results showed that S? exerts greater stimulus control than S+ in a two-choice simultaneous discrimination.     

Accessibility of the voicing distinction for learning phonological rules

In three experiments a series of nonsense syllables ending in consonants was presented to adult subjects who had to discover or learn a rule classifying the syllables into two groups. The rule was based either on the voicing of the final consonants or on an arbitrary division of them. Subjects performed better with the voicing than with the arbitrary rule only when there was a straightforward relationship between the voicing rule and the plural formation rule in English or, more generally, when voicing assimilation with an added consonant was involved and attention was focused on the sound and articulation of the syllables. We conclude that the voicing distinction is not ordinarily accessible and that individuals easily learn and use phonological rules involving voicing assimilation because of articulatory constraints on the production of consonant clusters.     

Conceptual memory for picture and prose episodes

In two experiments, subjects decided whether probes were true or false of one of some previously studied picture and prose episodes. The results indicated that response times to probes depicting explicit events were faster when they were in the same modality (picture or prose) as their episodes than when they were in the opposite modality, but response times to probes depicting implicit events were as fast when they were in the opposite modality as when they were in the same modality. These results suggest that the conceptual representations of picture and prose episodes are identical in form. The second experiment indicated that probes could be evaluated as fast from long as from short episodes. This result is consistent with the notion that retrieving information from episodes is done, not by scanning all the events of an episode, but by restricting the search only to the relevant slot in the schema into which the episode is assimilated.     

Shift of visual field preference for Hebrew words in native speakers learning to read

Lateralization for Hebrew words was tested in both the visual and auditory modalities in Israeli children learning to read their native language, Hebrew. A left visual field preference for tachistoscopically presented words was found in the second graders in contrast to a right visual field preference for the same words in the third graders. Children in both grades showed a right ear dominance for similar words presented dichotically. These data suggest right hemisphere involvement in acquiring reading skills of a native language.     

Auditory processing of brain-damaged adults under competitive listening conditions

Right CVAs, mild left CVAs, and non-brain-damaged adults received the Token Test under three conditions: quiet, white noise, and speech babble. Left CVAs performed most poorly of all groups in all conditions experiencing difficulty with subtests III, IV, and V. Right CVAs were inferior to controls on each of these three subtests in the speech babble condition only. Thus, right CVA difficulty with both memory and syntactic tasks was demonstrated in speech babble. These results are explained by the hypothesis that both hemispheres are necessary to process auditory information under complex listening conditions. Total brain capacity of right CVA patients may be overloaded if either memory load or linguistic complexity is increased in the presence of certain types of listening competition.     

Verbal and nonverbal recognition memory in aphasic and nonaphasic stroke patients

The ability to retain lists of verbal and nonverbalizable items across recurrent recognition tasks was tested in three groups: (1) stroke patients with a left-brain lesion and aphasia, (2) stroke patients with a right-brain lesion and left hemiplegia, and (3) nonneurologically impaired outpatients. As determined with signal detection measures, aphasics were deficient in discriminating words that were to be remembered from those that were not; their recognition of nonverbal visual (geometric art) or auditory (bird calls) patterns, however, was unimpaired. Left hemiplegics showed the opposite pattern. After a long-term interval (<10 min), correct recognition of words was diminished in all groups whereas recognition of visual patterns increased. Both groups of stroke patients adopted material-specific decision criteria which in part accounted for the dissociation of verbal and nonverbal recognition memory by laterality of lesion. Item analysis indicated that aphasics' verbal memory difficulties were affected by acoustic-semantic confusion of list words.     

A further evaluation of the limitation of wholistic visualization

In a previous study on the limitation of wholistic visualization, Beech (1976) found that when using a between subjects design, the limitation was an inverted-U function as presentation rate was varied. In the present study a within subject design was employed and it was found that as before, the limitation in visualization increased across the 0.5 to 3.0 sec/object presentation rates, but in contrast to Beech (1976), the limitation remained at an asymptote of 6.6 objects at the slower rates. This result excludes the hypothesis of image decay which was proposed previously. In the second experiment, the speed of visualizing each successively described object was monitored up to the point of the limitation. This showed that subjects took progressively longer to visualize as the array size increased. Furthermore, faster latencies for the first objects were related to subjects visualizing more objects both at the level of individual subjects and in terms of mean performance. Finally it was found that subjects who visualized more objects also remembered more objects on a recall test suggesting that visualization may aid recall.