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.     

Central deafness and subcortical motor aphasia

Clinical and autopsy studies were made on a right-handed man who had central deafness and subcortical motor aphasia, and the literature on central deafness and on subcortical motor aphasia was analyzed. Central deafness is due to bilateral destruction of the primary auditory cortex. It is sometimes difficult to distinguish from word deafness and from auditory agnosia, which are due to pathology in other parts of the temporal lobes. There is almost always some preserved hearing in central deafness, possibly from some auditory pathway other than the classical pathway. In this patient the subcortical motor aphasia was due to bilateral destruction of the motor cortex for the mouth and throat. In some other cases subcortical motor aphasia was due to the same pathology that usually causes Broca's aphasia; in these cases the unexpected preservation of writing was perhaps related to some difference in how language functions were organized in the brain.     

The role of imagery in the representation of linear orderings

Two experiments were carried out to investigate whether visual imagery was used in representing transitive linear ordering relationships. Subjects were presented with passages describing either a linear ordering or a set inclusion relationship, while being subjected to either visual or verbal interference. Performance was tested by asking subjects to judge the truth or falsity of statements concerning both the information presented in the passages and inferences that could be drawn from this information. In neither experiment was there any evidence for the linear ordering material being selectively disrupted by the visual interference task, as would have been predicted by the imagery theory. Thus it is concluded that linear orderings are probably not represented as visual images.     

Contrasts in visual responsiveness and emotional arousal between rhesus monkeys raised with living and those raised with inanimate substitute mothers.

Rhesus monkeys were raised with dogs or inanimate surrogates in outdoor cages which provided them with complex, highly varied visual surroundings. Visual responsiveness to a variety of colored transparencies was investigated in three experiments, completed when the monkeys were between 18 and 30 mo old. Results indicated that the frequency and duration of looking at slides was significantly higher for dog-raised than for inanimate-surrogate-raised monkeys and that dog-raised monkeys were much more responsive to the novelty, complexity, ansal were obtained during the final experiment. Heart rate, vocalization, and changes in plasma cortisol were higher for monkeys raised with dogs. The frequency of most self-directed behaviors, however, was higher for monkeys raised with inanimate surrogates. Differences between rearing groups can only be the result of contrasts in attributes of the substitute mothers.     

Long-term retention of a visually cued poison-based aversion in monkeys.

Retention of a poison-based aversion after a 3-yr. period by 8 vervet monkeys (Cercopithecus aethiops) was found. The color of the visual cue appeared to effect the retention of the aversion.     

Effects of selective forebrain noradrenaline loss on behavioral inhibition in the rat.

Virtually total depletion of cortical and hippocampal noradrenaline by stereotaxic injection of 6-hydroxydopamine into the fibers of the dorsal noradrenergic bundle produced no impairment in acquisition learning of a runway response for food reward. Extinction of this response, once learned, was markedly slower in the treated group than in controls, the treated animals perseverating in rapid running to the goal box even with no food present there. Similarly, no impairment was found on acquisition of a continuously reinforced lever-pressing response for food. Extinction of this response, however, was again slower in the treated group. Subsequent acquisition of a successive light-dark discrimination task was also slower in the treated group, with these animals perseverating in responding to the negative stimulus. Although selective forebrain noradrenaline loss does not impair the acquisition of appetitive responses, the suppression of responses in the absence of reward is impeded. A parallel is drawn with those effects found classically after surgical lesion to the hippocampus.