Generality of the summation effect in human causal learning

Considerable research has examined the contrasting predictions of the elemental and configural association theories proposed by Rescorla and Wagner (1972) and Pearce (1987), respectively. One simple method to distinguish between these approaches is the summation test, in which the associative strength attributed to a novel compound of two separately trained cues is examined. Under common assumptions, the configural view predicts that the strength of the compound will approximate to the average strength of its components, whereas the elemental approach predicts that the strength of the compound will be greater than the strength of either component. Different studies have produced mixed outcomes. In studies of human causal learning, Collins and Shanks (2006) suggested that the observation of summation is encouraged by training, in which different stimuli are associated with different submaximal outcomes, and by testing, in which the alternative outcomes can be scaled. The reported experiments further pursued this reasoning. In Experiment 1, summation was more substantial when the participants were trained with outcomes identified as submaximal than when trained with simple categorical (presence/absence) outcomes. Experiments 2 and 3 demonstrated that summation can also be obtained with categorical outcomes during training, if the participants are encouraged by instruction or the character of training to rate the separately trained components with submaximal ratings. The results are interpreted in terms of apparent performance constraints in evaluations of the contrasting theoretical predictions concerning summation.     

Effects of interlimb practice on coding and learning of movement sequences

An interlimb practice paradigm was designed to determine the role that visual–spatial (Cartesian) and motor (joint angles, activation patterns) coordinates play in the coding and learning of complex movement sequences. Participants practised a 16-element movement sequence by moving a lever to sequentially presented targets with one limb on Day 1 and the contralateral limb on Day 2. Practice involved the same sequence with either the same visual–spatial or motor coordinates on the two days. A unilateral practice condition (control) was also tested where both coordinate systems were changed but the same limb was used. Retention tests were conducted on Day 3. Regardless of the order in which the limbs were used during practice, results indicated that keeping the visual–spatial coordinates the same during acquisition resulted in superior retention. This provides strong evidence that the visual–spatial code plays a dominant role in complex movement sequences, and this code is represented in an effector-independent manner.     

Choosing optimal causal backgrounds for causal discovery

In two experiments, we studied the strategies that people use to discover causal relationships. According to inferential approaches to causal discovery, if people attempt to discover the power of a cause, then they should naturally select the most informative and unambiguous context. For generative causes this would be a context with a low base rate of effects generated by other causes and for preventive causes a context with a high base rate. In the following experiments, we used probabilistic and/or deterministic target causes and contexts. In each experiment, participants observed several contexts in which the effect occurred with different probabilities. After this training, the participants were presented with different target causes whose causal status was unknown. In order to discover the influence of each cause, participants were allowed, on each trial, to choose the context in which the cause would be tested. As expected by inferential theories, the participants preferred to test generative causes in low base rate contexts and preventative causes in high base rate contexts. The participants, however, persisted in choosing the less informative contexts on a substantial minority of trials long after they had discovered the power of the cause. We discuss the matching law from operant conditioning as an alternative explanation of the findings.     

Positive and negative mediation as a function of whether the absent cue was previously associated with the outcome

After presenting two cues, A and B, together, later pairings of one of the cues alone with an outcome can generate changes in the associative value of the absent cue. These changes can be in the same direction as the present cue (i.e., positive mediation) or in the opposite direction to the present cue (i.e., negative mediation). We found both mediational effects in a human contingency task. In addition, we found that the direction of the change was determined by the existence of a prior association between the absent cue and the outcome. When a prior association exists, the absent cue tends to change its value in the opposite direction to the present cue, whereas when there is no prior association, the absent cue tends to change its value in the same direction as the present cue. Recent associative models (Stout & Miller, 2007 Stout, S. C. and Miller, R. R. 2007. Sometimes-competing retrieval (SOCR): A formalization of the comparator hypothesis. Psychological Review, 114: 759–783.  [Google Scholar]) can explain our results.     

Age differences in contingency judgement linked to perceptual segregation

We demonstrate large differences in judging positive and null contingencies between younger and older adults with a task commonly used to explore cue competition in both contingency and causality judgements. The one-phase blocking task uses two cues, with separate contingencies with the same outcome. The age differences persisted even when participants knew in advance which of the two contingencies to judge. The age differences disappeared, however, when the stimulus display contained markers aiding perceptual segregation. We suggest that the age differences elicited in the one-phase blocking task are linked to decrements in perceptual segregation.     

A positive patterning advantage with complex but not simple patterning: A cue constellation approach

Determinants of a positive patterning advantage (that is, an advantage for positive patterning over negative patterning) in human causal reasoning were examined in an experiment that compared simple patterning discriminations (A, B vs. AB) to complex patterning discriminations (AB, BC, AC vs. ABC). As predicted by a cue constellation analysis of complex discriminations, a positive patterning advantage was found with complex patterning but not with simple patterning discriminations. This result may explain why some recent studies have found a positive patterning advantage where earlier studies had failed to find one. The interaction of patterning complexity with the positive patterning advantage appears to pose problems for rule-based accounts of patterning. The results support the view that associative theories of human causal reasoning are more easily distinguished from rule-based approaches when applied to conditions that make simple rules difficult to identify or implement.     

An investigation of the interaction between cognitive style and context reinstatement on the memory performance of eyewitnesses

The power of context reinstatement to improve recall is well established, but the degree of effect obtained varies widely between studies. Exploring possible causes for this variation, this paper examines the relationship between cognitive style and the efficacy of context reinstatement in improving free and cued recall in an eyewitness paradigm. Experiment 1, using a live staged event and a 1 week delay, indicated a significant improvement in free recall with the reinstatement of context and, as expected, no such improvement in cued recall. However, analysis of the data according to field dependency, as measured by Witkin, Oltman, Raskin, and Karp's [A manual for the Embedded Figures Test (1971) Palo Alto, CA: Consulting Psychologists Press] Group Embedded Figures Test (GEFT) revealed that, in free recall, field dependent witnesses' scores improved significantly with context reinstatement, whilst the scores of field independent witnesses did not. In cued recall, however, the field independent witnesses scored significantly higher overall than field dependent witnesses. Experiment 2 sought replication of these findings again utilised the GEFT and the Riding [Cognitive Styles analysis (1991) Birmingham: Learning and Training Technology] Cognitive Styles Analysis (CSA). Analysis of the data according to the Wholist-Analytic (W-A) dimension of the CSA, indicated no interaction with either context reinstatement or memorial performance. However the GEFT analysis produced similar results to that obtained in Experiment 1. The meaning of the interaction between the GEFT and both free and cued recall, and the failure of the CSA to similarly interact are discussed, together with the implication of these findings for establishing the value of reinstating context for individual eyewitnesses.     

Online measurement of mental representations of complex spatial decision problems: Comparison of CNET and hard laddering

This paper introduces the online Causal Network Elicitation Technique (CNET), as a technique for measuring components of mental representations of choice tasks and compares it with the more common technique of online ‘hard’ laddering (HL). While CNET works in basically two phases, one in open question format and one as guided linking of attributes and benefits, HL works completely structured with revealed attributes and benefits. Mental representations of two activity travel tasks were collected with both techniques among members of a nationwide Dutch household panel. The results confirm the hypothesis that the revealed format of variables in HL has an effect on the indication of variables as the elicited mental representations are almost twice as big for HL than for CNET. Furthermore, it turned out that CNET is more sensitive in measuring shifts among attributes in the mental representations for situational changes of the activity-travel task.     

Successive independence and behavioral contrast in a closed economy.

Two pigeons had access to multiple concurrent schedules of reinforcement for 24 hours per day in their home cages. The variable-interval schedules comprising the multiple concurrent schedules were varied across 16 conditions. In three sets of conditions, one schedule was varied while its concurrent alternative and the concurrent schedules in the other component were held constant. Behavioral contrast was observed; that is, as the rate of reinforcement arranged by the varied schedule decreased, response rates on the constant schedules typically increased. These conditions formed part of two larger sets of conditions in which the concurrent schedules in one multiple-schedule component remained constant while the concurrent schedules in the other component were varied. Successive independence was found, in that behavior allocation during the constant component did not vary as a function of the reinforcer ratios in the varied component. Successive independence between components in multiple concurrent schedules is a robust result that occurs in closed economies and under conditions that promote behavioral contrast.     

A test for conditional independence between response time and accuracy

An important distinction between different models for response time and accuracy is whether conditional independence (CI) between response time and accuracy is assumed. In the present study, a test for CI given an exponential family model for accuracy (for example, the Rasch model or the one‐parameter logistic model) is proposed and evaluated in a simulation study. The procedure is based on the non‐parametric Kolmogorov–Smirnov tests. As an illustrative example, the CI test was applied to data from an arithmetics test for secondary education.