Biomedical subjects

V Girotto

Publications and source records attributed to V Girotto.

7 recordsLinked to original sources

PubMed1999

Naive probability: a mental model theory of extensional reasoning.

This article outlines a theory of naive probability. According to the theory, individuals who are unfamiliar with the probability calculus can infer the probabilities of events in an extensional way: They construct mental models of what is true in the various possibilities. Each model represents an equiprobable alternative unless individuals have beliefs to the contrary, in which case some models will have higher probabilities than others. The probability of an event depends on the proportion of models in which it occurs. The theory predicts several phenomena of reasoning about absolute probabilities, including typical biases. It correctly predicts certain cognitive illusions in inferences about relative probabilities. It accommodates reasoning based on numerical premises, and it explains how naive reasoners can infer posterior probabilities without relying on Bayes's theorem. Finally, it dispels some common misconceptions of probabilistic reasoning.

Cognition↗

PubMed1997

The effect of premise order in conditional reasoning: a test of the mental model theory.

The difference in difficulty between modus ponens (if p then q; p; therefore q) and modus tollens (if p then q; not-q; therefore not-p) arguments has been traditionally explained by assuming that the mind contains a rule for modus ponens, but not for modus tollens. According to the mental model theory, modus tollens is a more difficult deduction than modus ponens because people do not represent the case not-q in their initial model of the conditional. On the basis of this theory, we predicted that conditions in which reasoners are forced to represent the not-q case should improve correct performance on modus tollens. In particular, we predicted that the presentation of the minor premise (not-q) as the initial premise should produce facilitation. Experiment 1 showed that this is the case: whereas the inversion of the premise order did not affect modus ponens, it produced a significant increase of valid conclusions for modus tollens. Experiment 2 showed that this facilitation does not depend on the negative form (contrary vs. contradictory) of the minor premise. Experiments 3 and 4 (and/or some of their replications) demonstrated that facilitation also occurs when participants are asked to find the cases compatible with not-q or to evaluate a p conclusion. No premise order effect was found for sentences which make explicit the not-q case right from the start, i.e. p only if q conditionals and biconditionals (Experiments 5 and 6). Finally, Experiments 7 and 8 showed that the conditional fallacies are not significantly affected by the premise order.

Adolescent↗

PubMed1995

Relevance theory explains the selection task.

We propose a general and predictive explanation of the Wason Selection Task (where subjects are asked to select evidence for testing a conditional "rule"). Our explanation is based on a reanalysis of the task, and on Relevance Theory. We argue that subjects' selections in all true versions of the Selection Task result from the following procedure. Subjects infer from the rule directly testable consequences. They infer them in their order of accessibility, and stop when the resulting interpretation of the rule meets their expectations of relevance. Subjects then select the cards that may test the consequences they have inferred from the rule. Order of accessibility of consequences and expectations of relevance vary with rule and context, and so, therefore, does subjects' performance. By devising appropriate rule-context pairs, we predict that correct performance can be elicited in any conceptual domain. We corroborate this prediction with four experiments. We argue that past results properly reanalyzed confirm our account. We discuss the relevance of the Selection Task to the study of reasoning.

Choice Behavior↗

PubMed1991

Children's communicative abilities revisited: verbal versus perceptual disambiguating strategies in referential communication.

The way seven- and nine-year-old French children and adults interpret ambiguous object descriptions was studied in four experiments. All four experiments followed the same basic procedure and consisted of two phases. During the training phase, plastic blocks varying in shape, colour and size were associated with fruit names. Some objects were always given just one label, the generic term, whereas others could be given either the generic or the specific label. For example, large circles were referred to as 'pommes' ('apples'), and large blue circles as 'reinettes' (a kind of apple). Still others were given no name at all. During the test phase of the experiment, subjects were presented with referentially ambiguous messages and asked to point to a given object (Experiments 1, 2 and 3) or to draw an object (Experiment 4). The messages consisted of either a generic term preceded by an article (e.g. '(la pomme'-'the apple') or a verbal description based on a colour adjective (e.g. 'le bleu'-'the blue one'). When presented with the generic term, older children and adults persistently chose the object for which no specific term had been given during the training phase. When presented with an adjective description, they chose the referent for which no fruit name had been given during the training phase. Younger children's choices depended on whether the article preceding the description was definite or indefinite. These results are consistent with the Gricean approach to referential communication proposed by Jackson & Jacobs (1982) and with an extended version of the principle of contrast proposed by Clark (1987, 1988).

Child↗

PubMed1989

Mental representation and hypothetico-deductive reasoning: the case of the THOG problem.

This article reports three experiments that deal with the source of the difficulty of Wason's (1977) THOG problem. The solution of this problem demands both the postulation of hypotheses and a combinatorial analysis of their consequences. Experiment 1 showed that the generation of the hypotheses is not in itself sufficient to solve the problem. Experiment 2 showed that a version presenting a plausible context for separating the level of data from that of hypotheses produced a better performance than both the original abstract version and a thematic version lacking the plausible context separating the levels. Experiment 3 gave evidence that this context can produce facilitation even with the geometric material of the classic version. This experiment also showed that a pictorial presentation of data and a verbal presentation of hypotheses affect performance negatively. The results demonstrate the role of problem representation in problem solving, and, in particular, the role of homogeneity in representing data and hypotheses in hypothetico-deductive reasoning.

Adult↗

PubMed1983

[A case report of prolonged hemolytic anemia in an infant due to a partial exchange transfusion].

An infant at the age of one month was admitted to hospital due to anaemia and icterus. Premature delivery was induced because of Rh immunisation. Newborn's grave condition permitted only one "blood volume" exchange transfusion and as a consequence prolonged haemolytic anaemia occurred. At the age of one month anti Rh-D antibody persisted in the infant circulation with the titre 1:16 in an indirect antiglobulin method.

Anemia, Hemolytic↗

PubMedDate not supplied

Focussing in reasoning and decision making.

Our principal hypothesis is that reasoning and decision making are alike in that they both depend on the construction of mental models, and so they should both give rise to similar phenomena. In this paper, we consider one such phenomenon, which we refer to as "focussing": individuals are likely to restrict their thoughts to what is explicitly represented in their models. We show that focussing occurs in four domains. First, individuals fail to draw inferences in the modus tollens form: if p then q, not-q, therefore not-p, because they focus on their initial models of the conditional, which make explicit only the case where the antecedent (p) and consequent (q) occur. Second, in Wason's selection task, they similarly tend to select only those cards that are explicitly represented in their initial models of the conditional rule. Third, their requests for information in order to enable them to make a decision about whether or not to carry out a certain action are focussed on the action to the exclusion of alternatives to it. In each of these cases, we show how the focussing bias can be reduced by certain experimental manipulations. Finally, in counterfactual reasoning, focussing underlies individuals' attempts to imagine an alternative scenario that avoids an unfortunate ending to a story.

Adolescent↗