Cross-cultural differences in colour vision: Acquired ‘colour-blindness’ in Africa

We report a study of the incidence of ‘colour-blindness’ in southern and central Africa, and we compare the African data with data from various European groups. There was a surprisingly high incidence of tritan errors (yellow–blue defect). The likelihood of making tritan errors increased with age, and was greater in rural areas than in towns. In Europe, no tritan errors were made by samples from the U.K., Eire or Spain, but some tritan errors were made by a sample from southern Greece. In contrast, most of a British sample of people over sixty-five years old makes tritan errors. Although tritan errors were the most frequent, they were often accompanied by protan and deutan errors. This mixed pattern of errors is consistent with the condition being acquired rather than congenital. Many languages of southern Africa categorise blues and greens with the same term. If the tritanopia we report has been endemic, it may have reduced the ‘perceptual pressure’ to split the blue-with-green categories into separate blue and green terms; a speculation consistent with Rivers, W. H. R. (1901. Introduction to A. C. Haddon (Ed.), Reports on the Cambridge Anthropological Expedition to the Torres Straits. Cambridge: Cambridge University Press) © 1998 Elsevier Science Ltd. All rights reserved..     

The influence of negative advertising frames on political cynicism and politician accountability

This research examined the influence of negative political advertising frames on the thoughts and feelings people generate in response to campaign advertising. Preparing and conducting this investigation involved the use of a multiple‐method strategy. Content analysis identified two advertising frames (i.e., candidate theme and ad hoc issue advertisements) and two experiments separately induced political cynicism and politician accountability. Three hundred and sixty people participated in the experimental studies, in which they read and responded, using a thought‐listing technique, to candidate theme or ad hoc issue negative advertisements. Results demonstrated that participants were more likely to generate cynical comments and hold politicians accountable for the country's ills when reading candidate theme advertisements than ad hoc issue advertisements. The results indicate that this contributes to a political climate of cynicism and may function to erode the electorate's overall trust in government.     

Structural awareness mitigates the effect of delay in human causal learning

Many studies have demonstrated that reinforcement delays exert a detrimental influence on human judgments of causality. In a free-operant procedure, the trial structure is usually only implicit, and delays are typically manipulated via trial duration, with longer trials tending to produce both longer experienced delays and also lower objective contingencies. If, however, a learner can become aware of this trial structure, this may mitigate the effects of delay on causal judgments. Here we tested this “structural-awareness” hypothesis by manipulating whether response–outcome contingencies were clearly identifiable as such, providing structural information in real time using an auditory tone to delineate consecutive trials. A first experiment demonstrated that providing cues to indicate trial structure, but without an explicit indication of their meaning, significantly increased the accuracy of causal judgments in the presence of delays. This effect was not mediated by changes in response frequency or timing, and a second experiment demonstrated that it cannot be attributed to the alternative explanation of enhanced outcome salience. In a third experiment, making trial structure explicit and unambiguous, by telling participants that the tones indicated trial structure, completely abolished the effect of delays. We concluded that, with sufficient information, a continuous stream of causes and effects can be perceived as a series of discrete trials, the contingency nature of the input may be exploited, and the effects of delay may be eliminated. These results have important implications for human contingency learning and in the characterization of temporal influences on causal inference.     

Temporal predictability facilitates causal learning

Temporal predictability refers to the regularity or consistency of the time interval separating events. When encountering repeated instances of causes and effects, we also experience multiple cause-effect temporal intervals. Where this interval is constant it becomes possible to predict when the effect will follow from the cause. In contrast, interval variability entails unpredictability. Three experiments investigated the extent to which temporal predictability contributes to the inductive processes of human causal learning. The authors demonstrated that (a) causal relations with fixed temporal intervals are consistently judged as stronger than those with variable temporal intervals, (b) that causal judgments decline as a function of temporal uncertainty, and (c) that this effect remains undiminished with increased learning time. The results therefore clearly indicate that temporal predictability facilitates causal discovery. The authors considered the implications of their findings for various theoretical perspectives, including associative learning theory, the attribution shift hypothesis, and causal structure models.     

Temporal predictability enhances judgements of causality in elemental causal induction from both observation and intervention

When the temporal interval or delay separating cause and effect is consistent over repeated instances, it becomes possible to predict when the effect will follow from the cause, hence temporal predictability serves as an appropriate term for describing consistent cause-effect delays. It has been demonstrated that in instrumental action-outcome learning tasks, enhancing temporal predictability by holding the cause-effect interval constant elicits higher judgements of causality compared to conditions involving variable temporal intervals. Here, we examine whether temporal predictability exerts a similar influence when causal learning takes place through observation rather than intervention through instrumental action. Four experiments demonstrated that judgements of causality were higher when the temporal interval was constant than when it was variable, and that judgements declined with increasing variability. We further found that this beneficial effect of predictability was stronger in situations where the effect base-rate was zero (Experiments 1 and 3). The results therefore clearly indicate that temporal predictability enhances impressions of causality, and that this effect is robust and general. Factors that could mediate this effect are discussed.     

The influence of temporal distributions on causal induction from tabular data

Two experiments investigated the joint influence of statistical and temporal information on causal inference from tabular data. Participants were presented with unambiguous data sets containing information about relative effect frequencies in cause-present and cause-absent situations. In addition to contingency information, the stimuli also revealed information about the temporal distribution of effects. The participants took this information into account when making causal judgments, so that the mere advancing or postponing of the effect in time was attached with causal significance, even when the cause did not increase the overall probability of the effect. These results cannot be reconciled with standard contingency accounts of causal induction.