Modality-specific interference with overt mediation by pigeons in a delayed discrimination task

Pigeons were trained on a delayed discrimination task in which they were rewarded for pecking a white terminal stimulus (TS) presented 5 sec after a green initial stimulus (IS) and for not pecking the white TS when it followed a red IS. Each bird bridged the memory interval (MI) with overt mediational behaviors. Nevertheless, sustained retroactive interference (RI) effects were produced by houselight illumination (Experiments 1 and 3), and mild shock pulses (Experiment 5) but not white noise (Experiment 2) presented during the MI. Although the magnitude of the light-induced RI effect was proportional to the duration of houselight illumination (Experiment 4), the beginning-end effect described by W. A. Roberts and D. S. Grant (Journal of Experimental Psychology: Animal Behavior Processes, 1978, 4, 219–236) was not observed. These results not only attest to the between-task robustness of both light-induced RI and modality-specific effects with pigeons, but also support the hypothesis that RI effects result from the disruption of mediational activities possibly analogous to rehearsal. The results further demonstrate that an event interpolated within the MI need not be unexpected or novel to produce RI. Furthermore, the interpolated event can produce modality-specific RI effects even though it effects a different sense than do the IS and TS.     

Discrimination of mirror-image shapes by young children

Experiments were conducted to examine the difficulty six-year-old children have in discriminating visually between a shape and its lateral reversal, relative to the difficulty in discriminating between a shape and its inversion. Contrary to results with simultaneous presentation, under successive presentation there was no difference between the difficulty of discriminating lateral reversals and difficulty of discriminating inversions. This was also the case for successive presentation with trial-to-trial variation in position of shapes. Spatial adjacency of the shapes to a reference feature of the visual background accounted for the variations in difficulty between discrimination of lateral reversals and discrimination of inversions which obtained under simultaneous presentation.     

Behavioral parameters of drug action: signalled and response-independent reinforcement

Four pigeons were initially trained under a multiple variable-interval 1-min variable-interval 1-min schedule of food reinforcement. For two of the pigeons, a signal was then presented whenever the reinforcer was available in one component; this resulted in positive contrast. For the other two pigeons, the reinforcer was presented independently of responding on a variable-time schedule in one component; this resulted in negative induction. After 30 to 50 sessions, however, a similar degree of differential responding occurred under both multiple schedules, i.e., high rates in the variable-interval component and low rates in the other component. Reinforcement frequency remained about the same in each of the schedule components. The stable performances then served as baselines for studying drug effects. In the high-rate component of both multiple schedules, small doses of d-amphetamine increased responding, whereas larger doses decreased responding. In the low-rate component of both multiple schedules, there was no rate-increasing effect at any dose of d-amphetamine; such an effect was found, however, with phenobarbital at a dose that decreased responding in the high-rate component. The drug effects thus depended on the interaction of pharmacologic variables (specific drug and dose) with behavioral variables (schedule components).     

Textbook preferences among trainers of school psychologists

A survey of trainers of school psychologists was conducted in order to determine which texts in each of 16 areas of psychology they felt to be most relevant to the training of school psychologists. Usable responses were obtained from 48 out of 143 training programs. A 69-item bibliography of ranked choices in each area was presented. Possible trends indicated by the trainers' choices were discussed.     

Enhancement of progressive-ratio performance by chlordiazepoxide and phenobarbital

The key pecking of two pigeons was reinforced with food on a progressive-ratio schedule, which required an increasing number of responses for each successive reinforcement: 8, 16, 24, 32, etc. When the subject failed to complete the next ratio in the sequence within 60 min, the session terminated. The number of responses in the final completed ratio was defined as the "breaking point". After the breaking point had stabilized (60 sessions), it served as a baseline to assess the effects of varying doses (5 to 80 mg/kg) of chlordiazepoxide and phenobarbital, administered intramuscularly 30 min before the sessions. Both drugs increased the breaking point. The dose-effect curves were inverted U-shaped, with maximum enhancement of performance occurring at 20 mg/kg for chlordiazepoxide and at 40 mg/kg for phenobarbital. A comparable enhancement was not obtained during a non-drug "probe" session, which was conducted after the subjects' body weights had been temporarily reduced from 80% to 70% of their free-feeding weights. The drug-induced enhancement of breaking point was related to the initial values of the performance and may represent a reduction in the aversiveness of the schedule.     

Monitoring animals’ movements using digitized video images

An animal’s movements can be monitored continuously using video digitization techniques. We outline the differences between video frame-grabbers and column-scan digitizers, and describe two applications using column-scanners: detecting episodes of spontaneous locomotion and tracking the position of a moving appendage. Strategies are discussed for increasing the speed of software and for compressing the information in the video images into an analog motion signal to be displayed and stored for later analysis. Finally, the advantages and limitations of frame-grabbers and column-scan digitizers are assessed.     

Comparative study of neurolinguistic variables in Alzheimer patients, traumatic aphasias and Korsakoff psychoses and normal control probands

There are few studies of the breakdown of language in specific dementias and there is some dispute that language pathology in brain failure is comparable to that of focal lesions. It is recognized that while aphasic language is a disturbance of receptive and propositional speech, disturbances of "InnerLanguage" disrupt the planning and regulatory basis of behavior. This paper presents a comparison of three pathological groups to match normal controls and suggest that in its initial stages reduced cognitive performances in Alzheimers type Dementia and Korsakow Psychosis on non verbal measures maybe a further of the regulatory role of inner speech comparison with traumatic Aphasia which more clearly exists on a deficit of verbal comprehension and expression.