The role of contradictions and counterexamples in the rejection of false sentences

The Representation of Coordinate Relations in Lexical Semantic Memory

Two experiments examined the size of the typicality effect for true items in a category verification task as a function of the type of false item used. In Experiment 1, compared to the case where false items paired unrelated concepts ("carrot-vehicle"), the typicality effect was much larger when false items paired an exemplar with a category coordinate to its proper category ("carrot-fruit"). In contrast, when false items paired coordinate concepts ("carrot-pea") or reversed the ordering of subject and predicate terms ("All vegetables are carrots"), the typicality effect did not change in size. Further, the time to verify true sentences did not increase monotonically with the semantic similarity of the two terms used in false sentences. Experiment 2 showed that the pattern of results for coordinate items reflected semantic processing, not simply task difficulty. A combined analysis examined data across multiple experiments, increasing the power of the statistical analysis. The size of the typicality effect when coordinate false items were used was again the same as when false items paired unrelated concepts. The most straightforward explanation of this pattern of results seems to be in terms of a sparse semantic network model of lexical semantic memory, in which labeled links are used to indicate the semantic relation that exists between pairs of words.

Semantic Memory Redux: An Experimental Test of Hierarchical Category Representation

Four experiments investigated the classic issue in semantic memory of whether people organize categorical information in hierarchies and use inference to retrieve information from them, as proposed by Collins & Quillian (1969). Past evidence has focused on RT to confirm sentences such as "All birds are animals" or "Canaries breathe." However, confounding variables such as familiarity and associations between the terms have led to contradictory results. Our experiments avoided such problems by teaching subjects novel materials. Experiment 1 tested an implicit hierarchical structure in the features of a set of studied objects (e.g., all brown objects were large). Experiment 2 taught subjects nested categories of artificial bugs. In Experiment 3, subjects learned a tree structure of novel category hierarchies. In all three, the results differed from the predictions of the hierarchical inference model. In Experiment 4, subjects learned a hierarchy by means of paired associates of novel category names. Here we finally found the RT signature of hierarchical inference. We conclude that it is possible to store information in a hierarchy and retrieve it via inference, but it is difficult and avoided whenever possible. The results are more consistent with feature comparison models than hierarchical models of semantic memory.

Counterexamples in sentential reasoning

How do logically naive individuals determine that an inference is invalid? In logic, there are two ways to proceed: (1) make an exhaustive search but fail to find a proof of the conclusion and (2) use the interpretation of the relevant sentences to construct a counterexample--that is, a possibility consistent with the premises but inconsistent with the conclusion. We report three experiments in which the strategies that individuals use to refute invalid inferences based on sentential connectives were examined. In Experiment 1, the participants' task was to justify their evaluations, and it showed that they used counterexamples more often than any other strategy. Experiment 2 showed that they were more likely to use counterexamples to refute invalid conclusions consistent with the premises than to refute invalid conclusions inconsistent with the premises. In Experiment 3, no reliable difference was detected in the results between participants who wrote justifications and participants who did not.

Retrieval and comparison processes in part--whole decisions

Undergraduate students were presented with word pairs (e.g., egg-yolk) and were timed as they decided whether one word named part of the thing named by the other word. In Experiment 1, "no" responses to nonpart pairs (e.g., fish-flaps) were slowed by the similarity of the stimulus part (flaps) to a part that the stimulus object did possess (fins). This suggested that decisions were made by retrieving parts of the stimulus object from memory and comparing them to the stimulus part. Whereas the parts used as stimuli in Experiment 1 were nonspecific, belonging to several different types of object (e.g., wheel), those selected for Experiment 2 were specific to a single type of object (e.g., thumb). In Experiment 2, "no" responses to nonpart pairs (e.g., foot-thumb) were slowed by similarity of the stimulus object (foot) to an object that the stimulus part (thumb) belonged to (hand). This suggested that decisions were made by retrieving the object to which the stimulus part belonged and comparing it to the stimulus object. The results support a hybrid model of part-whole decisions that includes directed retrieval of relational knowledge from memory and a comparison process.

Semantic memory: a bibliography, 1968-1975

Semantic memory research is briefly described. Then a bibliography of 105 published references in semantic memory, calendar years, 1968-1975, is presented.