The ability to evaluate arguments is a fundamental skill essential for social interaction and human decision-making (cf. Larson, Britt, and Kurby, 2009), and children are expected to learn the evaluative skill in high school (National Science Standards, 1996). However, many high school students lack these evaluative skills (National Science Board, 2006). In fact, a recent study has found that about 35% of college students have difficulty evaluating simple arguments like "vaccinations should be required for all children because inoculations contain dead or weekend organisms" (Britt, Kurby, Dandotkar, & Wolfe, 2008). This dissertation examined whether students' difficulty in evaluating arguments is due to their over dependence on the semantic, more than the logical, relatedness between the claims (e.g., vaccinations should be required for all children) and reasons (e.g., because inoculations contain dead or weekend organisms) of arguments. Semantic relatedness refers to overlap of words or concepts constituting claims and reasons while a logical relatedness refers to a support relationship of claims and reasons of arguments.;Two experiments examined the effect of semantic and logical relatedness between arguments' claims and reasons on skilled and less-skilled reasoners' evaluations of arguments under two different evaluative tasks. The semantic (high/low) and logical (high/low) relatedness between claims and reasons was manipulated across two experiments. Participants in Experiment 1 made quality judgments (acceptable/flawed) while the participants in Experiment 2 made agreement judgments (1=Strongly Agree; 5=Strongly Disagree). Participants read reason-claim ordered arguments one-at-a-time and made evaluative judgments and later recalled the arguments. Participants' reasoning skill was determined by their performance on the verbal reasoning section of the Law School Admissions Test (LSAT). Participants' evaluative judgments, judgment time and accuracy in predicate recall were measured. Predicates are the main verbs (e.g., should be required) of the argument claims.;Experiment 1 found that both semantic and logical relationships influenced quality judgments. As expected, high logical arguments were accepted more often than low logical arguments. Although high semantic arguments were accepted more often than low semantic ones, this effect was found only for high logical arguments. These results suggest that semantic relationship increases the acceptance of high logical, but not low logical arguments. Processing of arguments, however, was only influenced by semantics. High semantic arguments were evaluated faster than low semantic ones. There was no predicted skill difference in the effect of semantic relatedness. However, skilled reasoners' quality judgments were more affected by logical relatedness than less-skilled reasoners. As expected, skilled reasoners recalled predicates more than less-skilled reasoners.;Experiment 2 found that logical relatedness alone influenced agreement judgments. Overall, high logical arguments were agreed with more often than low logical ones. Processing of arguments was influenced both by semantic and logical relatedness. As predicted, skilled reasoners recalled predicates more than less-skilled reasoners. These results suggest that semantic relatedness does not account for students' difficulty in evaluating arguments. However, these study findings show that students' difficulty is related to their difficulty in precisely representing the predicates of argument claims. Additionally, post hoc analyses suggest that less-skilled reasoners are biased to incorrectly accept the low logical arguments that are consistent with their attitudes, suggesting students' difficulty is likely related to their attitude consistency bias. Theoretical and educational implications of the findings are discussed.
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