Determination of a behavioral transfer function: White-noise analysis of session-to-session response-ratio dynamics on concurrent VI VI schedules

Six pigeons were exposed to concurrent variable-interval schedules in which the programmed reinforcer ratios changed from session to session according to a pseudorandom binary sequence. This procedure corresponded to the stochastic identification paradigm (“white-noise experiment”) of systems theory and enabled the relation between log response ratios in the current session and log reinforcer ratios in all previous sessions to be determined. Such dynamic relations are called linear transfer functions. Both nonparametric and parametric representations of these, in the form of “impulse-response functions,” were determined for each bird. The session-to-session response ratios resulting from the session-to-session pseudorandom binary variations in reinforcer ratios were well predicted by the impulse-response functions identified for each pigeon. The impulse-response functions were well fitted by a second-order dynamic model involving only two parameters: a time constant and a gain. The mean time constant was 0.67 sessions, implying that the effects of abrupt changes in log reinforcer ratios should be 96% complete within about five sessions. The mean gain was 0.53, which was surprisingly low inasmuch as it should equal the sensitivity to reinforcement ratio observed under steady-state conditions. The same six pigeons were subjected to a similar experiment 10 months following the first. Despite individual differences in impulse-response functions between birds within each experiment, the impulse-response functions determined from the two experiments were essentially the same.     

Molecular maximizing characterizes choice on Vaughan's (1981) procedure

Pigeons keypecked on a two-key procedure in which their choice ratios during one time period determined the reinforcement rates assigned to each key during the next period (Vaughan, 1981). During each of four phases, which differed in the reinforcement rates they provided for different choice ratios, the duration of these periods was four minutes, duplicating one condition from Vaughan's study. During the other four phases, these periods lasted six seconds. When these periods were long, the results were similar to Vaughan's and appeared compatible with melioration theory. But when these periods were short, the data were consistent with molecular maximizing (see Silberberg & Ziriax, 1982) and were incompatible with melioration, molar maximizing, and matching. In a simulation, stat birds following a molecular-maximizing algorithm responded on the short- and long-period conditions of this experiment. When the time periods lasted four minutes, the results were similar to Vaughan's and to the results of the four-minute conditions of this study; when the time periods lasted six seconds, the choice data were similar to the data from real subjects for the six-second conditions. Thus, a molecular-maximizing response rule generated choice data comparable to those from the short- and long-period conditions of this experiment. These data show that, among extant accounts, choice on the Vaughan procedure is most compatible with molecular maximizing.     

Hippocampal stimulation disrupts spatial working memory even 8 h after acquisition

The present experiment used hippocampal stimulation to determine the temporal gradient of consolidation of spatial working memory. Rats were trained to perform a spatial working memory task on a radial maze with 12 arms. Each rat went to the ends of 6 arms to obtain a food reward. After 8 h, the rat chose among all the arms to find the ones not previously chosen (and consequently still having food). During some test sessions, the hippocampus was stimulated electrically either at a current level just high enough to produce an electrophysiological seizure, or at a current level below this seizure threshold. Stimulation occurred at one of five intervals (0 to 8 h) following the completion of the first six choices. During other test sessions, the hippocampus was not stimulated. After seizure stimulation, the number of retroactive errors (returning to arms chosen prior to stimulation) increased at all delay intervals; the number of proactive errors (returning to arms chosen after stimulation) increased only with the delay of 8 h. Subthreshold stimulation had no influence on either type of error. These results indicate that normal hippocampal function is required for the maintenance of spatial information in working memory, and that the time course of consolidation of this information is significantly greater than that seen in other types of memory, or consolidation may not take place at all.     

Dispositional and situational moderators of female and male causal attributions

To increase understanding of the relationships between gender and causal attributions, dispositional and situational variables were examined to determine if they affected causal attributions differently if the subjects were females or males. Four dispositional variables—locus of control, neuroticism, achievement motivation, and self-esteem—and five situational variables—expectancy of success, self-reported commitment, perceived productivity, perceived task complexity, and actual performance—were examined for their moderating effects on the gender-causal attributional relationships. The dispositional variables did not moderate any causal relationships. By comparison, four situational variables—performance, commitment, productivity, and complexity—moderated at least one of the gender-attribution relationships. It was concluded that more attention should be directed to the identification of situational moderators.     

Do alcoholic Korsakoff's syndrome patients acquire affective reactions?

In this study we report two experiments that investigate the acquisition of affective reactions. In Experiment 1, unfamiliar melodies were played to Korsakoff's syndrome patients and alcoholic and nonalcoholic control subjects who were matched with them according to age and education. Following a retention interval of 5 min, subjects received a preference test on old and new melodies. Korsakoff's syndrome patients showed the same increase in preference for old melodies as a consequence of prior exposures as control subjects did, but their recognition of melodies was significantly impaired in comparison with controls. In Experiment 2, the same subjects saw photographs of two men. Fictional biographical information depicted one as a "good guy" and the other as a "bad guy." After a retention interval of approximately 20 days, Korsakoffs recalled virtually none of the biographical information; however, 78% preferred the good guy, and impression ratings were less favorable for the bad guy. Korsakoff patients developed preferences and impressions even though they did not have voluntary access to the information on which the preferences were based. However, their impression ratings were less extreme than those of controls. The pattern of results of the two studies is discussed in terms of Johnson's (1983) MEM model of memory.     

Direction- and velocity-specific responses from beyond the classical receptive field in the middle temporal visual area (MT)

The true receptive field of more than 90% of neurons in the middle temporal visual area (MT) extends well beyond the classical receptive field (crf), as mapped with conventional bar or spot stimuli, and includes a surrounding region that is 50 to 100 times the area of the crf. These extensive surrounds are demonstrated by simultaneously stimulating the crf and the surround with moving stimuli. The surrounds commonly have directional and velocity-selective influences that are antagonistic to the response from the crf. The crfs of MT neurons are organized in a topographic representation of the visual field. Thus MT neurons are embedded in an orderly visuotopic array, but are capable of integrating local stimulus conditions within a global context. The extensive surrounds of MT neurons may be involved in figure-ground discrimination, preattentive vision, perceptual constancies, and depth perception through motion cues.     

Effects of luminance and contrast on direction of ambiguous apparent motion

A study is reported of the role of luminance and contrast in resolving ambiguous apparent motion (AM). Different results were obtained for the short-range (SR) and the long-range (LR) motion-detecting processes. For short-range jumps (7.5 min arc), the direction of ambiguous AM depended on brightness polarity, with AM only from white to white and from black to black. But for larger jumps, or when an interstimulus interval (ISI) was introduced, AM was less dependent on polarity, with white often jumping to black and black jumping to white. Two potential AMs were pitted against each other, one carried by a light stimulus and the other by a dark stimulus. The stimulus whose luminance differed most from the uniform surround captured the AM. Visual response to luminance was linear, not logarithmic. When the stimulus was modified to give continuous AM in one direction it was followed by a negative aftereffect of motion only when the spatial displacement was 1 min arc. A larger displacement (10 min arc) gave good AM but no motion aftereffect. Thus only short-range motion adapts motion-sensitive channels.     

A longitudinal comparison of couples with sex-typical and non-sex-typical orientations to intimacy

The present study was designed to investigate the relationship experience of males and females who do not conform to sex-typical orientations to intimacy. One hundred sixty-three couples' and 88 nondating singles' (total N=414) responses to the Relationship World Index—Version 2 (RWI-2) were analyzed via discriminant analysis to determine if subjects' sex could be predicted accurately upon the basis of their RWI-2 scores. One discriminant function was found which was significant by the Wilks' lambda test [x²(60)=140.57, p<.001]; the procedure correctly classified 76% of the respondents. Those who were classified correctly were considered sex-typical and the remaining 24% of the sample was considered non-sex-typical in their orientations to intimacy. Additional analyses using data from a 6-month longitudinal study located qualities which significantly distinguished sex-typical from non-sex-typical subjects and couples in which at least one member was non-sex-typical from couples in which both members were classified as sex-typical.     

Reasons black african adults use to explain their acceptance of sex-role reversals

A structured questionnaire based on Rest's Defining Issues Test format was adopted to investigate the reasons used by 50 Black African males and 50 Black African females to explain their degree of acceptance of sex-role reversals. Both males and females showed little acceptance of sex-role reversals. The organization of the reasons they used to explain their degree of acceptance of sex-role reversals was most parsimoniously explained by Rest's complex stage model rather than the model suggested by Ullian, which is based on Piagetian stage criteria.     

Alternation behavior, spatial discrimination, and reversal disturbances following 6-hydroxydopamine lesions in the nucleus accumbens of the rat

The effects of dopaminergic depletion of the nucleus accumbens was tested in various behavioral tasks such as alternation, spatial discrimination, and reversal learning, and in an extinction paradigm in a T maze. Animals with lesions showed impairment of spontaneous alternation behavior, disturbances in the acquisition of spatial discrimination, and great difficulty in reversing previously learned habits. In the extinction phase, experimental animals are unable to adjust their behavior, and continue to choose the previously reinforced arm of the T maze. It is suggested that the nucleus accumbens plays an important role in the transition of motivation into action, and that dopamine has a facilitatory influence on the mediation of these processes.