Representation and retention of three-event sequences in pigeons

The present experiments studied a three-event delayed sequence-discrimination (DSD) task: one arrangement (order) of two stimuli (red and yellow overhead lights) taken three in succession (e.g., red, yellow, red) was the positive sequence and the remaining seven arrangements were the negative sequences for responding and reward during the subsequent test stimulus. In Experiment 1, the final stimulus (recency) and the order of stimuli in the positive sequence controlled acquisition of discrimination. In Experiment 2, increasing the duration of memory intervals between stimuli reduced the discriminability of those negative sequences identical to the positive sequence after the delay. Three-event DSD performance in Experiments 1 and 2 was similar to two-event DSD performance in comparable published experiments. Models developed to explain pigeon performance in two-event DSD were extended to the three-event task. Results from both two- and three-event versions of the DSD task falsified a noncumulative model and several cumulative integration models (i.e., adding, averging, and some multiplying models), but corroborated one cumulative, multiplying model.     

Representativeness and fallacies of probability judgment

Representativeness is the name given to the heuristic people often employ when they judge the probability of a sample by how well it represents certain salient features of the population from which it was drawn. The representativeness heuristic has also been used to account for how people judge the probability that a given population is the source of some sample. The latter probability, however, depends on other factors (e.g., the population's prior probability) as well as on the sample characteristics. A review of existing evidence suggests that the ignoring of such factors, a central finding of the heuristics approach to judgment under uncertainty, is a phenomenon which is conceptually distinct from the representativeness heuristic. These factors (base rates, sample size, and predictability) do not always exert the proper influence on people's first-order probability judgments, but they are not ignored when people make second-order (i.e., confidence) judgments. Other fallacies and biases in subjective evaluations of probability are, however, direct causal results of the employment of representativeness. For example, representativeness may be applied to the wrong features. Most devastating, perhaps, is that subjective probability judgments obey a logic of representativeness judgments, even though probability ought to obey an altogether different logic. Yet although the role of representativeness judgments in probability estimation leaves a lot to be desired, it is hard to envision prediction and inference completely unaided by representativeness.     

Some determinants of inhibitory stimulus control

Interspersed reinforcement and extinction during discrimination learning generate a U-shaped gradient of inhibition about the stimulus correlated with extinction. The present work showed that extinction is not a necessary determinant of inhibitory stimulus control. In Exp. I, a reduction in the rate of reinforcement, through a shift from a multiple variable-interval 1-min variable-interval 1-min schedule to a multiple variable-interval 1-min variable-interval 5-min schedule, resulted in a post-discrimination line orientation gradient of inhibition about the stimulus correlated with the variable-interval 5-min schedule. In Exp. II, the rates of reinforcement, correlated with a pair of stimuli, were held constant during a shift from a multiple variable-interval 1-min variable-interval 1-min schedule to a multiple variable-interval 1-min differential-reinforcement-of-low-rate schedule. Inhibitory stimulus control about the stimulus correlated with the differential reinforcement of low rate was obtained. In both experiments, a reduction in the rate of responding during one stimulus and behavioral contrast during the other stimulus preceded the observation of inhibitory stimulus control.     

The effects of narrative context on French verbal inflections: A developmental perspective

This experiment examines how narrative context affects French subjects' selection of past imperfective (imparfait) vs. perfective inflections with different predicate types. Adults and 10-year-old children were asked to inflect verbs presented in their written infinitive form in two conditions: (a) in isolated sentences; (b) embedded in the beginning, middle, or end of narratives. Regardless of conditions, the adults rarely used theimparfait with punctual resultative predicates. In both conditions, the frequency ofimparfait was high with durative predicates, particularly with aresultative ones, but it varied with position in the narratives, being highest at the beginning and lowest at the end. Although the children also used the imparfait frequently with durative predicates, they overgeneralized it to punctual resultative ones, regardless of conditions and of positions. These results show that adult uses of the imperfective/perfective distinction are determined by both predicate properties and grounding in narrative context. The children are less sensitive to some predicate properties than the adults and they do not differentiate imperfective/perfective aspect consistently as a function of discourse context.     

An Attributional Analysis of Emotional Reactions to Schizophrenia in Mexican and Anglo American Cultures1

The present study uses attribution theory to identify factors that may lead to unfavorable emotional reactions toward patients with schizophrenia and to highlight factors that may contribute to the observed inverse relationship between industrial status of a country and schizophrenia outcome. University students from Mexico and the U.S., 2 countries differing in industrial status, served as participants. Eighty-eight Mexicans from Guadalajara and 88 Anglo Americans from Los Angeles, California read vignettes of a patient described to meet DSM-IV criteria for schizophrenia. In one vignette, the patient's disorder was characterized by predominantly positive symptoms (e.g., hallucinations, delusions), whereas in the other vignette negative symptoms (e.g., social withdrawal, apathy) predominated. In support of an attributional approach, negative symptoms were associated with greater perceived control than were positive symptoms. Correspondingly, negative symptoms were found to provoke more intense negative affect and less intense positive affect than were positive symptoms. Some national and gender differences were also found.     

Compassion: An east‐west comparison

Compassion is an emotion that occupies a central position in Mahāyāna Buddhist philosophy while it is often a neglected subject in contemporary western philosophy. This essay is a comparison between an Eastern view of compassion based upon Mahāyāna Buddhist perspectives and a western view of the same emotion. Certain principles found in Mahāyāna Buddhist philosophy such as the Bodhisattva Ideal, and suffering (dukkha) to name two, are explored for the information they contain about compassion. An essay by Lawrence Blum is taken as representative of a Western view (but not exclusively) and it is analyzed for its shortcomings in light of the Buddhist view. The conclusion briefly describes the value of understanding an eastern view on compassion as a means of filling the void one finds in western medical ethics discourse which focuses so heavily, and redundantly, upon issues such as patient autonomy and paternalism.     

Commentary on Wolford,Taylor, and Beck: The conjunction fallacy?

AlthoughP(A&B|X) can never exceedP(A|X) (the conjunction rule), it is possible forP(X|A&B) to exceedP(X|A). Hence, people who rankA&B as more probable thanA are not necessarily violating any normative rule if the ranking is done in terms of the probability of these events to yield an eventX. Wolford, Taylor, and Beck (1990) have argued that this indeed is what happens in some problems (e.g. Tversky& Kahneman’s [1983] Linda problem). The claim made here is that the Linda problem is hard to reconcile with this interpretation; that there is little if any evidence that subjects utilize this interpretation; and that in any case, representativeness can account for all Linda problem results.     

A faith for all seasons

A FAITH FOR ALL SEASONS:ISLAM AND WESTERN MODERNITY. By Shabbir Akhtar. London: Bellew Publishing, 1990. 251pp. Hb. £25.00. ISBN 0–947792–41–4.