John Macnamara

Linguistic independence of bilinguals: The input switch

The paper reports on four experiments which deal with a bilinguals capacity to interpret linguistically mixed passages. The first required Ss to read continuous passages. The second and third required Ss to judge the truth or falsehood of written sentences. The fourth required them to judge the truth or falsehood of spoken sentences. The main conclusions were that switching languages in input takes an observable amount of time, that the input language switch is automatic, that the input and output switches operate sequentially and independently, and that bilinguals do not usually translate from their weaker to their stronger language.

Projective invariance and picture perception.

Four experiments test the assumption that, in the visual perception of pictures, observers have reliable and direct access to the equivalence of shapes in projective geometry. The assumption is that perception of projective equivalence is the basis of shape constancy (‘the projective thesis’). Observers matched or reproduced abstract planar shapes under conditions of rotation in the picture plane, and pictured rotation in depth. Departure from projective equivalence was assessed in each study by measuring the planar analogue of cross ratio. Projective equivalence was not found to be perceived uniformly where Euclidean equivalence was not judged uniformly, either in recognition tasks or in production tasks. When the projective thesis is put to a suitably general test, confidence in the thesis is undermined.

Proper names and how they are learned.

Proper names function in our conceptual lives as means for denoting individuals in kinds. Kinds are denoted by common names, more precisely count nouns, and so there are important interrelations between proper names and common nouns. All of this shows up in the way we interpret proper names and employ them in everyday inferences. For example, an airline may count three passengers in relation to a single person Jane, if Jane takes three trips with the airline. Each of the three passengers is Jane, but there is only one Jane. To handle such operations we propose a theory of proper names as part of the theory of kinds. This enables us to specify certain resources (some of them unlearned) that are necessary for the learning of proper names and also a theory of how they are learned. We review the experimental literature on the learning of proper names from the standpoint of the theory. We do not extend the theory to cover recognition or recall.

Actions, laws, and scientific psychology

Abstract The paper argues that it is impossible to discover causal laws that cover human actions. This is not due to a general scepticism about laws in science but is the result of features peculiar to the explanation of actions. These features do not, we argue, preclude the scientific exploration and explanation of actions. The idea that they do is based on an outmoded view of scientific explanation. We illustrate our case with some relevant lines of experimental literature. In conclusion we touch on the relevance of our work to contemporary psychological attitudes to the issue of free will.

Resolving apparent contradictions: adults' and preschoolers' ability to cope with non-classical negation

If the logic of natural language negation were classical – a simple matter of true and false – then it would be a disaster to answer a question like Is this essay good? with Yes and no . The overwhelming majority of adults ( N = 40) asked to resolve this apparent contradiction were found to do so by appealing to the structure of the essay (e.g. Its thesis was good but its argument was not ). Three-year-olds ( N = 24), when suitably prepared, also appealed to object structure to resolve a similar apparent contradiction. These results are discussed in relation to a non-classical logical model that can handle object structure.

Functoriality and grammatical role in syllogisms

We specify two problems in syllogistic: the lack of functoriality of predicates (although a thief is a person, a good thief may not be a good person) and the change of grammatical role of the middle term, from subject to predicate, in some syllogisms. The standard semantics, the class interpretation, by-passes these difficulties but, we argue, in a manner that is at odds with logical intuition. We propose a semantics that is category theoretic to handle these difficulties. With this semantics we specify when syllogisms are valid and we set limits to the class interpretation. To perform this task we show how to construct the categorical notion of an entity in a system of kinds. We devote two brief sections to an argument that our approach is very much in the spirit of Aristotle.

First and Second Language Learning: Same or Different?

The thesis of the following paper is that the process of learning a second language, if it produces successful results, is the same as that of learning a first language. The paper reviews various objections that have been raised against this thesis, and it discusses the considerable body of research which explores it. It examines the appropriateness of the research data for throwing light on the validity of the thesis. It concludes with some practical guidelines for language teachers drawn from observations of babies learning their mother tongue.

Models for Non-Boolean Negations in Natural Languages Based on Aspect Analysis

Since antiquity two different negations in natural languages have been noted: predicate negation (‘not honest’) and predicate term negation (‘dishonest’). Aristotle tried to formalize them in his system of oppositions, distinguishing between affirmation and negation (‘honest’ and ‘not honest’) and contraries (‘honest’ and ‘dishonest’). The Stoics replaced Aristotle’s logic of terms by their logic of propositions. Although they considered three types of negation, none of them corresponded to Aristotle’s predicate term negation. Frege and modern logic have followed the Stoics in either identifying predicate term negation with predicate negation or in casting predicate term negation out of logic into the realm of pragmatics. Although an extensive literature has arisen on these issues, we have not found mathematical models. We propose category-theoretic models with two distinct negation operations, neither of them in general Boolean. We study combinations of the two (‘not dishonest’) and sentential counterparts of each. We touch briefly on quantifiers and modalities. The models are based on an analysis of aspects. For instance, to give an overall, global judgement of John’s honesty we must agree on what aspects of John are relevant for that judgement: John qua person (global aspect), John qua social being (social aspect), John qua family man, John qua professional man, etc. We conceptualize this ‘Aristotelian’ analysis by means of a category of ‘aspects’. A model (for the negations) is obtained from the category of presheaves on this category. Although neither of the negations is Boolean, predicate negation turns out to be Boolean at the ‘global’ aspect (the aspect of the overall judgement) which may help to explain the persistent belief that logic is naturally Boolean.

A Category-Theoretic Approach to Aristotle’s Term Logic, with Special Reference to Syllogisms

When Aristotle invented logic, what he invented was a logic of terms. The Stoics replaced Aristotle’s term variables with propositional ones, and with that propositional logic was born (see [16]). For a long time term logic and propositional logic existed together. For example, William of Ockham [21] devoted the first part of his Summa logicae to terms and the second part to propositions. Perhaps it was Kant who was responsible for the emphasis on propositional logic at the expense of term logic. For where Aristotle had categories of objects and attributes, closely related to the grammatical categories of terms that normally denote them, Kant had categories of concepts. Kant, however, derives categories of concepts from categories of judgments; that is, from categories of propositions. With the move to categories of judgments, term logic in anything like Aristotle’s sense drops from view. In this Frege follows Kant and so does what is now called “classical logic”. (These remarks were inspired by a comment of F. W. Lawvere.)

But What is Belief Itself

Owen Egan has given us a masterly survey of the psychological literature on belief. He leads us into alleys that we might not have anticipated visiting, such as the status of basic logical laws. He considers the possibility that such laws can profitably be regarded as master beliefs that guide the formation of lower-order beliefs. Everywhere there are interesting comments on research techniques and designs, on the interpretation of findings, and on the basic conceptualization of what belief is that inspires data gathering and interpretation.