Use of current explanations in multicausal abductive reasoning

In multicausal abductive tasks a person must explain some findings by assembling a composite hypothesis that consists of one or more elementary hypotheses. If there are n elementary hypotheses, there can be up to 2ⁿ composite hypotheses. To constrain the search for hypotheses to explain a new observation, people sometimes use their current explanation—the previous evidence and their present composite hypothesis of that evidence; however, it is unclear when and how the current explanation is used. In addition, although a person's current explanation can narrow the search for a hypothesis, it can also blind the problem solver to alternative, possibly better, explanations. This paper describes a model of multicausal abductive reasoning that makes two predictions regarding the use of the current explanation. The first prediction is that the current explanation is not used to explain new evidence if there is a simple (i.e., nondisjunctive, concrete) hypothesis to account for that evidence. The second prediction is that the current explanation is used when attempting to discriminate among several alternative hypotheses for new evidence. These hypotheses were tested in three experiments. The results are consistent with the second prediction: the current explanation is used when discriminating among alternative hypotheses. However, the first prediction—that the current explanation is not used when a simple hypothesis can account for new data—received only limited support. Participants used the current explanation to constrain their interpretation of new data in 46.5% of all trials. This suggests that context-independent strategies compete with context-dependent ones—an interpretation that is consistent with recent work on strategy selection during problem solving.     

Modellierung von Fehlkonzepten in einer algebraischen Wissensstruktur

An extension of the theory of knowledge spaces by Doignon &; Falmagne (1985) is presented that tries to account for subjects’ typical errors and wrong answers. This extension concerns two major points: The usual dichotomous item format (right/wrong) is generalized to polytomous response categories, and the theoretical structure (knowledge, skills, misconceptions) is clearly separated from the empirical structure (observable solution behavior, subject’s responses). Using examples from a set of questions about properties of simple electric circuits the general method is demonstrated. Axioms of an algebraic structure known as “information system” (Scott, 1982) are shown to provide an appropriate characterization of the theoretical domain. The structural properties of the data, on the other hand, can be derived from assumptions about the influence of knowledge and misconceptions on specific answers for a set of questions.     

On counteradaptation

Often adaptation to artificially altered stimulation takes place because veridical stimulation that produces the same perceptual property that is produced by the altered stimulation is also received. In these cases, an assimilation of the two perceptual processes produced by the two different stimulations (the altered and the veridical) is supposed to be responsible for the adaptation that is achieved. This hypothesis, which was formulated by Wallach and Karsh (1963), would be confirmed by demonstrating a modification of the perceptual process produced by veridical stimulation rather than the one produced by the altered stimulation. We demonstrated this by having S observe in the dark for 20 min a luminous figure that objectively expanded as it moved toward S and contracted as it moved away. But instead of testing for changes in size perception as such, we tested for a change in the relation between accommodation and convergence on the one hand and registered distance on the other. In one experiment, such a change was measured by obtaining estimates of perceived size and depth before and after the adaptation period. Highly significant changes of size and significantly greater changes of stereoscopic depth were obtained. Inasmuch as stereoscopic vision was totally absent from the adaptation conditions, the change in stereoscopic depth that was larger than the size change can only be ascribed to a change in registered distance. In another experiment, we tested for a change in distance by having S point from the side to a vertical line, before and again after the adaptation period, under conditions where only accommodation and convergence could serve as distance cues. Significant changes in the pointing distance were measured, indicating more directly a change in the relation between these oculomotor adjustments and perceived distance. We propose the term counteradaptation for such modification of a perceptual process away from veridicality.     

Primate learning tasks reveal strong impairments in patients with presenile or senile dementia of the Alzheimer type

Eight subjects with the likely diagnosis of presenile or senile dementia of the Alzheimer type were tested on two frequently used primate learning tasks: a concurrent object discrimination task and a delayed non-match-to-sample task. In addition, various tests for cognitive, mnemonic, perceptual, and language functions were applied. The results suggest a severe decline of the Alzheimer subjects in all measures when compared with 10 control subjects matched for age, gender, and education. The two animal learning tasks revealed strong impairments, thus demonstrating a high sensitivity for the detection and assessment of human amnesic disorders. Implications of these findings for human neuropsychological, and especially comparative neuropsychological, research are discussed.     

Summa psychologiae: A special review

In the first section of the review, the general features of this large reference work are described as well as the manner in which “eminence” has been defined. The principles of the selection of the references for the two volumes are noted and the potential uses of the bibliography are discussed. The second section is devoted to a critique of some stylistic matters (diacritical signs, symbols, and abbreviations) and of certain practices (choice of the edition of books, treatment of the secondary references published in several journals, translations) regarded as open to debate. The review closes with considerations of problems of professional identification of the eminent contributors, and the correctness and relevance of some of the entries. The bibliography is regarded by the reviewer as a sine qua non reference work indispensable to students, teachers, and scholars in or out of psychology.