Acquisition of strategies depending on the opponents' competence level

The development of problem-solving skills from novices to advanced subjects in dependence of the competence level of the opponent is examined in a two-person zero-sum game (Othello). In a repeated-measurement design 18 Ss. (6 Ss in 3 groups) played 10 games against one of three opponent-strategies (implemented on a computer): one "expertlike" strategy, which uses domain specific knowledge and local heuristics (minimax-algorithm with alpha-beta pruning); one "novicelike" strategy, in which global, domain independent problem solving strategies (means-ends analysis, goal-reduction) are implemented; and one strategy, which contradicts the supposed heuristics of the novices, but which results in a "weak" performance (minimization in move-selection). Contrary to our assumptions no significant effects of experience could be verified (win versus loss during single runs). An experience dependent differentiation of global problem solving strategies could not be shown for any of the groups. Neither could a general improving effect of the model for acquiring local, task specific heuristics be proved.     

The effect of control and predictability in learned helplessness

The present 2 x 2 study deals with the influence of controllability and predictability of an aversive noise stimulus on a subsequent learning task. Eighty-four subjects participated in two experiments. In correspondence with the concept of learned helplessness, controllability was shown to be the dominant factor in the first experiment. In the second experiment, a modified test task was used in which both factors were shown to act in specific ways: The main influence of controllability is upon response measures (latency, omission), whereas unpredictability retardates learning of new predictive connections. The results are discussed in terms of contingency learning.     

Sensible reasoning in two tasks: Rule discovery and hypothesis evaluation

The hypothesis testing skills of undergraduates were measured in two tasks: the 2-4-6 rule discovery task in which students generate and assess hypotheses, and a hypothesis evaluation task, which requires only the assessment of hypotheses. The results of Experiments 1 and 2 show that the students consistently employed a disconfirmation strategy when assessing hypotheses, but employed a counterfactual inference strategy when they also were required to generate the hypotheses. The results of Experiment 3 suggest that the selection of the hypothesis testing strategy reflected a balance between the logical requirements of the task and the desirability of possible outcomes. Taken together, the findings support a more consistent picture of human rationality across tasks, and suggest alternatives to accounts of confirmation bias.     

Phoneme monitoring and lexical processing: Evidence for associative context effects

In this paper, we propose a new version of the phoneme monitoring task that is well-suited for the study of lexical processing. The generalized phoneme monitoring (GPM) task, in which subjects detect target phonemes appearing anywhere in the test words, was shown to be sensitive to associative context effects. In Experiment 1, using the standard phoneme monitoring procedure in which subjects detect only word-initial targets, no effect of associative context was obtained. In contrast, clear context effects were observed in Experiment 2, which used the GPM task. Subjects responded faster to word-initial and word-medial targets when the target-bearing words were preceded by an associatively related word than when preceded by an unrelated one. The differential effect of context in the two versions of the phoneme monitoring task was interpreted with reference to task demands and their role in directing selective attention. Experiment 3 showed that the size of the context effect was unaffected by the proportion of related words in the experiment, suggesting that the observed effects were not due to subject strategies.     

A neuroscience model of stuttering

Using motor control systems analysis and a reductionist approach, we provide a unified model of stuttering. This model views stuttering as a momentary instability in a complex multiloop control system. The model predicts the temporal conditions under which this instability will occur. Furthermore, these temporal conditions account for the efficacy of fluency-evoking maneuvers, therapy, and the variability of speech output in stutterers.     

The Additive Factor Method: A differential diagnostic tool in hyperactivity and learning disability

The Additive Factor Method assumes that task performance is the sum of sequential and independent processes. We studied the duration of the central processes (memory search and decision) and the motor decision process in hyperactive and learning-disabled children under socalled divided attention and S-R compatibility conditions. It was found that the learning-disabled were impaired in memory search and decision processes whereas hyperactives were impaired in the motor decision process.The authors wish to thank L. Leertouwer for making the drawings.     

Regional cerebral blood flow for singers and nonsingers while speaking, singing, and humming a rote passage

Two groups of singers (n = 12,13) and a group of nonsingers (n = 12) each produced the national anthem by (1) speaking and (2) singing the words and by (3) humming the melody. Regional cerebral blood flow (rCBF) was measured at rest and during each phonation task from seven areas in each hemisphere by the 133Xe-inhalation method. Intrahemisphere, interhemisphere, and global rCBF were generally similar across phonation tasks and did not yield appreciable differences among the nonsingers and the singers.     

The nature of prolonged word search

Two alternative hypotheses were considered concerning the process of prolonged search for an uncommon word in response to hearing its definition. One alternative is that a conscious retrieval effort brings the target progressively closer to threshold. The second is that the retrieval process is a random neural exploration outside of conscious control. A tachistoscopic probe was devised to compare word recognition thresholds after 10 sec versus 30 sec of presumed search time. Results failed to show a difference between the two delay conditions and were interpreted as inconsistent with the first alternative but consistent with the second.     

Neuropsychological functioning in hemiparkinsonism

A standardized neuropsychological battery including measures of intellectual cognitive, memory, attention-concentration, language, abstraction and mental flexibility, and sensory and motor functions was administered to 21 hemiparkinsonian patients (14 with right side and 7 with left side symptoms) and 17 controls matched for age and education. Patients were impaired in all functions except sensory. For motor functions, impairment was ipsilateral to the side of symptoms. For cognitive functions, right side symptoms were associated with verbal deficits whereas left side symptoms were associated with spatial deficits. Thus, a pattern of neuropsychological deficits consistent with the lateralization of motor symptoms may appear in the early stages of the disease.