Failure of acute and chronic administration of Δ9-tetrahydrocannabinol to affect the repeated acquisition of serial position responses in pigeons

Pigeons were trained to acquire a new four-response position sequence each day by pecking three response keys in a predetermined order. The key color varied after each correct response prior to food delivery. Acute administration of Γ⁹-tetrahydrocannabinol (Δ⁹-THC) up to a dose that completely eliminated responding, had no effect on total acquisition errors, or on within session patterns of error elimination. Chronic administration of Δ⁹-THC (3–10 mg/kg/day), either before or after the session for 4–7 weeks, also did not affect these error measures, although rates of responding were markedly suppressed and at times no responding occurred Discontinuation of Δ⁹-THC administration for periods of 4–6 weeks also was without effect on errors. These experiments suggest that neither acute nor chronic Δ⁹-THC produce specific effects on the repeated acquisition of serial position responses in pigeons.     

Long latency auditory evoked potentials

Experiment 1 elicited the P1, N1, P2, and N2 components of the long latency auditory evoked potential (AEP) using a 1000 Hz tone presented at 30, 50, or 70 dB SPL and 1-, 3-, or 5- second inter-stimulus intervals to assess the relative effects of the combination of these variables on component amplitude and latency. Four blocks of 16 tone presentations each were recorded from each subject to determine if changes in the AEP would occur because of short-term habituation. Both stimulus factors interacted significantly in a systematic fashion for the amplitude measures, with increases in latency also associated with increases in intensity and inter-stimulus interval. Only minor changes across the four trial blocks for either the amplitude or latency measures were observed over the various stimulus presentation conditions. Experiment 2 employed the same tone stimulus presented at 50 dB SPL and a 3-second inter-stimulus interval. Eight blocks of 64 trials were recorded from each subject on each day for four days to investigate long-term habituation effects. No substantial changes in any of the component amplitudes or latencies were obtained across the 32 trial blocks. It was concluded that intensity and inter-stimulus interval interact to determine AEP amplitude as well as latency values and that the constituent components do not change appreciably with repeated stimulus presentations, even after several days.     

A rapid and sensitive method for measuring the conditional emotional response II: On-the-baseline excitatory conditioning and extinction

The present study outlines a rapid and sensitive on-the-baseline conditional emotional response (CER) procedure. Using rats as the experimental subject, the method detects delay conditioning, incubation, extinction and spontaneous recovery. In addition, the method detects conditional responding using electric shock ranging from 0.23 to 0.50 mA as the unconditional stimulus. Because of its speed and sensitivity, the method shelters the subject from unnecessary long-term deprivation and pain.     

Verbal conditioning of stimulus significance in the orienting response context

The manipulation of stimulus significance, by instructions from the experimenter, may be taken as an example of verbal conditioning. Consideration of such a mechanism suggested that personality effects previously found in conditioning studies should be apparent in instructional manipulations of significance in a study of the orienting response (OR) to words. Because of recent changes in dimensioning of the personality structure, some of the items originally used to define Eysenck’s extraversion (E) dimension are now used to assess the new dimension of psychoticism (P), suggesting that at least some of the established effects of E upon conditioning may be associated now with P. Hence the P scale was focused on in this study. Words differing on the evaluative dimension of the semantic differential were presented in three blocks, the first under indifferent instructions, the second under instructions to rate the words for their affective impact, and the third under indifferent instructions again. These blocks correspond to baseline, conditioning, and extinction conditions respectively. Electrodermal activity indicated enhanced conditioning, together with greater carry-over effects in the extinction phase, for low-P compared with high-P subjects. The results indicate the importance of personality effects in studies of stimulus significance and illustrate the value of the verbal conditioning mechanism in this area of the OR field. They also suggest the need to re-examine previously obtained E-effects in conditioning studies in light of changing personality tests.     

Developmental versus sensory deficit effects on perceptual processing in the reading disabled

Thirty children and 5 adults participated in two experiments designed to compare visual processing in normal and reading disabled children. The children were aged 8, 10, and 12 years. In Experiment 1, subjects were asked to detect the temporal order of two briefly presented stimuli. In Experiment 2, subjects sorted cards containing bracket stimuli that did or did not produce perceptual grouping effects. Poor readers required more time to make accurate temporal order judgments and showed stronger perceptual grouping effects. For both good and poor readers, the amount of time necessary to make a correct temporal order judgment decreased, and perceptual grouping effects became weaker with age. However, the magnitude of the difference between the groups did not lessen with age. These results suggest that there are visual processing differences between good and poor readers that do not appear to correct by age 12.     

Using direct and indirect measures to study perception without awareness

Many studies directed at demonstrating perception without awareness have relied on the dissociation paradigm. Although the logic underlying this paradigm is relatively straightforward, definitive results have been elusive in the absence of any general consensus as to what constitutes an adequate measure of awareness. We propose an alternative approach that involves comparisons of the relative sensitivity of comparable direct and indirect indexes of perception. The only assumption required by the proposed approach is that the sensitivity of direct discriminations to relevant conscious information is greater than or equal to the sensitivity of comparable indirect discriminations. The proposed approach is illustrated through an evaluation of Avant and Thieman’s (1985) recent claim that an indirect measure of perception based on judgments of apparent visual duration provides a more sensitive indicator of perception than does a direct measure based on forced-choice recognition. Contrary to this claim, when direct and indirect indexes are measured under comparable conditions, an indirect measure based on judgments of perceived duration provides a less sensitive index of perceptual processing than do comparable direct measures. The proposed approach provides a general conceptual/methodological framework for using the dissociation paradigm in studies directed at establishing unconscious processes.     

Differences in school behavior and achievement between children from intact, reconstituted, and single-parent families.

Differences in school behavior and achievement between students from intact, reconstituted, and single-parent families were analyzed. Students from intact two-parent families had fewer absences and tardies, higher grade point averages, and fewer negative and more positive teacher behavioral ratings than did those from reconstituted and single-parent families.     

Individual differences in afterimage persistence: relationships to hypnotic susceptibility and visuospatial skills.

To investigate the moderating role of individual differences in hypnotic susceptibility and visuospatial skills on afterimage persistence, we presented a codable (cross) flash of light to 40 men and 46 women who had been dark adapted for 20 min. In an unrelated classroom setting, subjects had previously been given two standardized scales of hypnotic susceptibility (Harvard Group Scale of Hypnotic Susceptibility, Shor & Orne, 1962; Group Stanford Hypnotic Susceptibility Scale, Form C, Crawford & Allen, 1982) and the Mental Rotations Test (Vandenberg & Kuse, 1978). The first afterimage interval and the afterimage duration correlated significantly with hypnotic responsiveness, supporting Wallace (1979), but did not show the anticipated relationships with mental rotation visuospatial skills. Individuals in the high hypnotizable group had (a) significantly longer afterimage intervals between its first appearance and first disappearance than did those in medium or low groups, as well as (b) significantly longer afterimages between the first appearance and the final disappearance than did those in low groups, but those in medium groups did not differ significantly from the other groups. Discriminant analysis using the afterimage persistence measures classified correctly 65.2% of high hypnotizables, 37.5% of medium hypnotizables, and 54.8% of low hypnotizables. Hypothesized cognitive skills that assist in the maintenance of afterimages and underlie hypnotic susceptibility include abilities to maintain focused attention and resist distractions over time and to maintain vivid visual images.