Inductive Reasoning in Alzheimer''s Disease

We evaluated knowledge of basic level and superordinate semantic relations and the role of cognitive resources during inductive reasoning in probable Alzheimer's disease (AD). Nineteen mildly demented AD patients and 17 healthy control subjects judged the truthfulness of arguments with a premise and a conclusion that contain familiar concepts coupled with "blank" predicates, such as "Spiders contain phosphatidylcholine; therefore all insects contain phosphatidylcholine." Like healthy control subjects, AD patients were relatively insensitive to the typicality of the premise category when judging the strength of arguments with a conclusion containing a basic-level concept, but were relatively sensitive to typicality during judgments of arguments containing a superordinate in the conclusion. Moreover, AD patients resembled control subjects in judging arguments with an immediate superordinate in the conclusion compared to arguments with a distant superordinate. AD patients differed from control subjects because they could not take advantage of two premises in an argument containing basic-level concepts. We conclude that semantic knowledge is sufficiently preserved in AD to support inductive reasoning, but that limited cognitive resources may interfere with AD patients' ability to consider the entire spectrum of information available during semantic challenges.     

What is typical about the typicality effect in category-based induction?

Research on category-based induction has documented a consistent typicality effect: Typical exemplars promote stronger inferences about their broader category than atypical exemplars. This work has been largely confined to categories whose central tendencies are also the most typical members of the category. Does the typicality effect apply to the broad set of categories for which the ideal category member is considered most typical? In experiments with natural and artificial categories, typicality and induction-strength ratings were obtained for ideal and central-tendency exemplars. Induction strength was greatest for the central-tendency exemplars, regardless of whether the central tendency or the ideal was rated more typical. These results suggest that the so-called “typicality” effect is a special case of a more universal central-tendency effect in category-based induction.     

Expertise and category-based induction

The authors examined inductive reasoning among experts in a domain. Three types of tree experts (landscapers, taxonomists, and parks maintenance personnel) completed 3 reasoning tasks. In Experiment 1, participants inferred which of 2 novel diseases would affect "more other kinds of trees" and provided justifications for their choices. In Experiment 2, the authors used modified instructions and asked which disease would be more likely to affect "all trees." In Experiment 3, the conclusion category was eliminated altogether, and participants were asked to generate a list of other affected trees. Among these populations, typicality and diversity effects were weak to nonexistent. Instead, experts' reasoning was influenced by "local" coverage (extension of the property to members of the same folk family) and causal-ecological factors. The authors concluded that domain knowledge leads to the use of a variety of reasoning strategies not captured by current models of category-based induction.     

The Effects of Prior Processing Episodes on Basic level Superiority

Four experiments were conducted to investigate the effects of prior processing episodes on people's preference for categorizing objects at the basic level (e.g. dog) relative to their preference for categorizing at the superordinate (e.g. animal) and the subordinate (e.g. Dalmation) levels. The prior processing episode in Experiment 1 was designed to induce subjects to activate representations at the superordinate level, and those in the remaining experiments were designed to induce subjects to differentiate objects at the subordinate level. After the prior processing episodes, subjects performed either a free naming or a picture categorization task that required them to decide whether an illustrated object belonged to a specified category. Results showed that prior processing episodes modestly reduced the superiority of basic level to superordinate level and subordinate level in categorization but not in free naming. The results suggest that the basic-level advantage is subject to the effects of context, but the effects are not as strong as the context effects on other aspects of categorization behaviour (e.g. rating typicality of a category member). Hence, the preference for the basic level is a somewhat more stable, invariant aspect of conceptual representation. Possible determinations of this stability are discussed.     

范畴变量对虚假记忆的影响

以中文词为材料,考察范畴样例重复,样例熟悉性、典型性和范畴大小对虚假再认的影响。实验1表明,随着范畴样例增加,虚假再认也增加。实验2表明,对高熟悉的样例虚假再认多。实验3表明,对高典型样例更易虚假再认。实验4表明,和大范畴样例比,对小范畴样例有更多的虚假再认。整个结果可以用激活扩散理论统一地加以解释     

Conceptual Hierarchies in a Flat Attractor Network: Dynamics of Learning and Computations

The structure of people's conceptual knowledge of concrete nouns has traditionally been viewed as hierarchical ( Collins & Quillian, 1969 ). For example, superordinate concepts ( vegetable ) are assumed to reside at a higher level than basic-level concepts ( carrot ). A feature-based attractor network with a single layer of semantic features developed representations of both basic-level and superordinate concepts. No hierarchical structure was built into the network. In Experiment and Simulation 1, the graded structure of categories (typicality ratings) is accounted for by the flat attractor network. Experiment and Simulation 2 show that, as with basic-level concepts, such a network predicts feature verification latencies for superordinate concepts ( vegetable ). In Experiment and Simulation 3, counterintuitive results regarding the temporal dynamics of similarity in semantic priming are explained by the model. By treating both types of concepts the same in terms of representation, learning, and computations, the model provides new insights into semantic memory.     

Are rating-based procedures reliable for derivation of typicality judgments from children?

The aim of the present study was to examine whether a rating-based procedure that has already been used by other investigators can be used for derivation of typicality ratings from children. The evidence reported in the study establishes that such a procedure cannot be reliably used for this purpose. The results show that children rated category items in terms of personal preferences rather than as a function of how representative they considered the items to be of their superordinate category. On the basis of these findings, an alternative method based on the family resemblance scores of the category members was proposed in order to derive typicality ratings from young children. This family resemblance method of obtaining typicality judgments may be useful to investigators interested in assessing how children process categorical information.     

Prototypicality in sentence production

Three cued-recall experiments examined the effect of category typicality on the ordering of words in sentence production. Past research has found that typical items tend to be mentioned before atypical items in a phrase—a pattern usually associated with lexical variables (like word frequency), and yet typicality is a conceptual variable. Experiment 1 revealed that an appropriate conceptual framework was necessary to yield the typicality effect. Experiment 2 tested ad hoc categories that do not have prior representations in long-term memory and yielded no typicality effect. Experiment 3 used carefully matched sentences in which two category members appeared in the same or in different phrases. Typicality affected word order only when the two words appeared in the same phrase. These results are consistent with an account in which typicality has its origin in conceptual structure, which leads to differences in lexical accessibility in appropriate contexts.     

归纳推理的抽样理论

作者提出归纳推理的抽样理论,认为归纳推理实质是根据与归纳特征有关的抽样样本情况来推断结论类别具有归纳特征的可能性,其中的抽样可分为类别抽样和特征抽样两种。以大学生为被试的两个实验结果一致支持抽样理论而不是别的归纳推理理论。对于归纳推理的主要现象,抽样理论比其它的相似性解释具有更大的解释范围,特别是能够解释其它理论严格不能解释的归纳推理非对称性现象     

Hemispheric effects of canonical views of category members with known typicality levels

Is there a preferred hemispheric canonical view of a concept? We investigated this question in a natural superordinate category membership decision task using a hemifield paradigm. Participants had to decide whether or not an image of an object lateralized in the left (LVF) or right (RVF) visual half-field is a member of a predesignated superordinate category. The objects represented high, medium, or low typicality levels, and each object had six different perspective views (front, front-right, front-left, side, back-left, and back-right). The latency responses revealed a significant interaction of Hemi Field X View X Typicality (there wasno hemifield difference in accuracy). The findings confirm the presence of asymmetry in stored concepts in long-term memory and suggest, in addition, a hemispheric canonical view of these concepts, a view strongly related to typicality level.     

Strategies of semantic categorization in the cerebral hemispheres

Strategies of semantic categorization in intact cerebral hemispheres were studied in two experiments by presenting names of typical and atypical category instances to the left visual field (LVF) (right hemisphere) or to the right visual field (RVF) (left hemisphere). The results revealed that the typicality of instances had a large effect on categorization times in the LVF in both experiments, suggesting that the right hemisphere relies strongly on a holistic, similarity-based comparison strategy. In Experiment 1, the typicality effect was weaker in the RVF than in the LVF. In Experiment 2, a typicality effect in the RVF was observed for the "four-footed animal" category but not for the "bird" category. The hypothesis that the left hemisphere employs a strategy based on defining or necessary features is not supported by the observed typicality effect in the "four-footed animal" category. Instead, it is suggested that the left hemisphere may be able to categorize on the basis of prestored instance-category knowledge. When such knowledge is not available (e.g., as for four-footed animals), a similarity-based comparison strategy is employed by the left hemisphere.     

The two faces of typicality in category-based induction

Studies of category-based induction using different methods have found somewhat contradictory results for whether typical items are a stronger basis for induction. Typical category items are generally more similar to other category items than are atypical ones, and they are also more likely to be categorized into the category in question. We propose that the first aspect (representativeness) influences induction, but the second (uncertainty about the correct category) does not. Two experiments using artificial categories found support for this prediction. Two further experiments manipulated pictures of objects and also found that representativeness in the category influenced the strength of induction, but uncertainty of classification did not. Thus, the two aspects of typicality have different effects on category-based induction.     

Towards tolerance: Representations of superordinate categories and perceived ingroup prototypicality

According to Mummendey and Wenzel (1999), group members tend to perceive their ingroup, relative to an outgroup, as more prototypical of the superordinate category encompassing both groups. Hence, they tend to regard the outgroup as deviating from the norms of the superordinate category. Factors that inhibit perception of relative ingroup prototypicality should thus promote intergroup tolerance. In two experiments, the representation of the superordinate category was manipulated. Both an undefinable prototype (Experiment 1; N=63) and a complex representation (Experiment 2; N=88) led to a decrease in relative ingroup prototypicality. Dual identification with the ingroup and the superordinate category increased relative ingroup prototypicality, which was negatively correlated with positive attitudes towards the outgroup. The findings supported Mummendey and Wenzel’s assumptions about the conditions that lead to intergroup tolerance.     

The role of familiarity in determining typicality

Ashcraft (1978b) found that people tend to know more properties of instances they rate as typical of a category than of instances they rate as atypical. This suggests that variations in typicality result from variations in familiarity. Three experiments are presented that challenge or qualify this suggestion. Experiment 1 showed that subjects sometimes produce more properties for items they rate as low in typicality. Experiment 2 showed that in a large, random sample of items, there was a tendency to produce fewer properties for atypical items, but Experiment 3 indicated that part of the reason for this result was a response bias to assign low typicality ratings to unfamiliar words, rather than a reflection of low perceived typicality of the referents themselves. These results suggest that variations in typicality can exist independent of variations in familiarity, although familiarity may also play a role.     

Exemplars and prototypes in natural language concepts: A typicality-based evaluation

Are natural language categories represented by instances of the category or by a summary representation? We used an exemplar model and a prototype model, both derived within the framework of the generalized context model (Nosofsky, 1984, 1986), to predict typicality ratings for 12 superordinate natural language concepts. The models were fitted to typicality ratings averaged across participants and to the typicality judgments of individual participants. Both analyses yielded results in favor of the exemplar model. These results suggest that higher-level natural language concepts are represented by their subordinate members, rather than by a summary representation.     

Inclusion in a superordinate category, in-group prototypicality, and attitudes towards out-groups

We hypothesized that group members’ attitudes towards an out-group are negatively related to the in-group’s perceived relative prototypicality for a superordinate category, but only if both the in-group and out-group are included in this superordinate category. In Experiment 1 (N=40), Germans’ attitudes towards Poles were negatively correlated with the relative prototypicality of Germans when “Europe” (including Poles), but not when “West-Europe” (excluding Poles), was the superordinate category. In Experiment 2 (N=63), female single parents’ attitudes about the competence of single parents to raise children depended on the in-group’s relative prototypicality for “single parents” (including fathers), but not on their relative similarity to “mothers” (excluding fathers). Both experiments showed that inclusion in a superordinate category had a more negative influence on attitudes towards the out-group when relative in-group prototypicality is high rather than low.