Assessing interactive causal influence

The discovery of conjunctive causes--factors that act in concert to produce or prevent an effect--has been explained by purely covariational theories. Such theories assume that concomitant variations in observable events directly license causal inferences, without postulating the existence of unobservable causal relations. This article discusses problems with these theories, proposes a causal-power theory that overcomes the problems, and reports empirical evidence favoring the new theory. Unlike earlier models, the new theory derives (a). the conditions under which covariation implies conjunctive causation and (b). functions relating observable events to unobservable conjunctive causal strength. This psychological theory, which concerns simple cases involving 2 binary candidate causes and a binary effect, raises questions about normative statistics for testing causal hypotheses regarding categorical data resulting from discrete variables.     

Human pulling strengths in different conditions of exertion

This study tested 29 young Taiwanese men and 31 young Taiwanese women to examine the effects of pulling type (one-handed and two-handed) and height (48 cm, 84 cm, 120 cm, and 156 cm) on maximum horizontal isometric pulling strengths. Analysis showed differences in pulling strength between one-handed and two-handed efforts were surprisingly small for free pulling postures. The pulling strength decreased significantly with pulling height. The highest pulling strength was approximately two to three fold the lowest pulling strength across the four pulling heights. The women's pulling strength was approximately 59% to 67% of men's pulling strength. The test-retest correlations for pulling strength were satisfactory. The correlations between pulling strength and subjects' anthropometry were not sufficiently high to justify the prediction of strength. Most correlations between strengths in any two different pulling conditions were high and significant.     

Does the information content of an irrelevant source differentially affect spoken word recognition in younger and older adults?

To determine whether older adults find it difficult to inhibit the processing of irrelevant speech, the authors asked younger and older adults to listen to and repeat meaningless sentences (e.g., "A rose could paint a fish") when the perceived location of the masker (speech or noise) but not the target was manipulated. Separating the perceived location (but not the physical location) of the masker from the target speech produced a much larger improvement in performance when the masker was informational (2 people talking) than when the masker was noise. However, the size of this effect was the same for younger and older adults, suggesting that cognitive-level interference from an irrelevant source was no worse for older adults than it was for younger adults.     

Age and subjective well-being revisited: a discrepancy perspective

The hypothesis that the age effect on subjective well-being was entirely mediated by goal discrepancies (GDs) was tested with structural equation modeling. Six GDs grouped into 3 broad categories (relationships, health, and others) were differentially related to age. Whereas GD relationships and GD others (e.g., materials) decreased with age, GD health increased with age. GD health had smaller effects on subjective well-being than GDs in relationships and other life domains. Hence, the net effect of all the GDs on well-being was positive. GD variations because of age could completely explain the age trends in life satisfaction and positive affect, and partially the age trend in negative affect.     

冯友兰人生境界论的审美维度

冯友兰特别重视心的觉解功能 ,并依据心灵觉解的程度将人生区分为自然、功利、道德、天地四种境界 ,其天地境界有着深厚的审美意蕴。达到这一境界必须运用有别于逻辑分析的直觉方法 ,即冯友兰所说的讲形而上学时的“负的方法” ,而“近于道的诗”正是形而上学“负的方法”之一。所以 ,冯友兰新理学中的人生境界论与审美理论非常接近。这一理论显示出从思维方式上融合中西的学术努力 ,对于 2 0世纪中国文艺境界论有着一定的影响。     

alpha7 Nicotinic acetylcholine receptors and temporal memory: synergistic effects of combining prenatal choline and nicotine on reinforcement-induced resetting of an interval clock

We previously showed that prenatal choline supplementation could increase the precision of timing and temporal memory and facilitate simultaneous temporal processing in mature and aged rats. In the present study, we investigated the ability of adult rats to selectively control the reinforcement-induced resetting of an internal clock as a function of prenatal drug treatments designed to affect the alpha7 nicotinic acetylcholine receptor (alpha7 nAChR). Male Sprague-Dawley rats were exposed to prenatal choline (CHO), nicotine (NIC), methyllycaconitine (MLA), choline + nicotine (CHO + NIC), choline + nicotine + methyllycaconitine (CHO + NIC + MLA), or a control treatment (CON). Beginning at 4-mo-of-age, rats were trained on a peak-interval timing procedure in which food was available at 10-, 30-, and 90-sec criterion durations. At steady-state performance there were no differences in timing accuracy, precision, or resetting among the CON, MLA, and CHO + NIC + MLA treatments. It was observed that the CHO and NIC treatments produced a small, but significant increase in timing precision, but no change in accuracy or resetting. In contrast, the CHO + NIC prenatal treatment produced a dramatic increase in timing precision and selective control of the resetting mechanism with no change in overall timing accuracy. The synergistic effect of combining prenatal CHO and NIC treatments suggests an organizational change in alpha7 nAChR function that is dependent upon a combination of selective and nonselective nAChR stimulation during early development.     

Honeybees (Apis mellifera) holding on to memories: response competition causes retroactive interference effects

Five experiments on honeybees examined how the learning of a second task interferes with what was previously learned. Free flying bees were tested for landmark-based memory in variations on a paradigm of retroactive interference. Bees first learned Task 1, were tested on Task 1 (Test 1), then learned Task 2, and were tested again on Task 1 (Test 2). A 60-min delay (waiting in a box) before Test 2 caused no performance decrements. If the two tasks had conflicting response requirements, (e.g., target right of a green landmark in Task 1 and left of a blue landmark in Task 2), then a strong decrement on Test 2 was found (retroactive interference effect). When response competition was minimised during training or testing, however, the decrement on Test 2 was small or nonexistent. The results implicate response competition as a major contributor to the retroactive interference effect. The honeybee seems to hold on to memories; new memories do not wipe out old ones.     

Differences in automatic social information processing between nondepressed and subclinically depressed individuals

The present research examined individual differences in automatic social information processing. We hypothesized that because nondepressed and subclinically depressed persons have different interpersonal experiences, they may process social information in different ways. In this experiment, participants were asked to make judgments about social relationships after being reminded of a target person. They had to make these judgments under either a light or a heavy memory load. Results showed that when nondepressed participants were reminded of people with whom they had frequent pleasant interactions, they made a greater number of positive judgments about their social relationships than did subclinically depressed participants. When subclinically depressed participants were reminded of people with whom they had had frequent unpleasant interactions, they made a greater number of negative judgments about their social relationships than did their nondepressed counterparts. Moreover, performance in these experimental conditions was unaffected by memory load, suggesting that automatic thoughts about their social relationships had been evoked.     

Generalisation: mechanistic and functional explanations

An overview of mechanistic and functional accounts of stimulus generalisation is given. Mechanistic accounts rely on the process of spreading activation across units representing stimuli. Different models implement the spread in different ways, ranging from diffusion to connectionist networks. A functional account proposed by Shepard analyses the probabilistic structure of the world for invariants. A universal law based on one such invariant claims that under a suitable scaling of the stimulus dimension, generalisation gradients should be approximately exponential in shape. Data from both vertebrates and invertebrates so far uphold Shepard's law. Some data on spatial generalisation in honeybees are presented to illustrate how Shepard's law can be used to determine the metric for combining discrepancies in different stimulus dimensions. The phenomenon of peak shift is discussed. Comments on mechanistic and functional approaches to generalisation are given. Accepted after revision: 10 September 2001 Electronic Publication     

From covariation to causation: a test of the assumption of causal power

How humans infer causation from covariation has been the subject of a vigorous debate, most recently between the computational causal power account (P. W. Cheng, 1997) and associative learning theorists (e.g., K. Lober & D. R. Shanks, 2000). Whereas most researchers in the subject area agree that causal power as computed by the power PC theory offers a normative account of the inductive process. Lober and Shanks, among others, have questioned the empirical validity of the theory. This article offers a full report and additional analyses of the original study featured in Lober and Shanks's critique (M. J. Buehner & P. W. Cheng, 1997) and reports tests of Lober and Shanks's and other explanations of the pattern of causal judgments. Deviations from normativity, including the outcome-density bias, were found to be misperceptions of the input or other artifacts of the experimental procedures rather than inherent to the process of causal induction.