Concepts as Representations for Essences: Evidence from Use of Generics

Concepts as Representations for Essences: Evidence from Use of Generics Iris Oved 1 (irisoved@gmail.com) Pierina Cheung 2 (mpcheung@uwaterloo.ca) Department of Psychology, University of California, San Diego 9500 Gilman Drive, San Diego, CA 92093, USA Department of Psychology, University of Waterloo 200 University Avenue W. , Waterloo, Ontario, N2L 3G1, Canada Abstract experiments on the conditions for use of generic sentences that support the essentialist approach over the descriptivist approach. This paper compares descriptivist approaches for concept acquisition with essentialist approaches by exploring the conditions under which people use generic sentences (sentences such as ‘Apples are round’ which contrast with sentences about particulars like ‘All/most of the apples are round’). It fleshes out the essentialist approach in terms of the Baptism theory of concept acquisition (Oved, 2009; 2014), which is made precise with an implementation in which concepts are values of latent variables in a Bayesian network, posited as explanations for observed patterns in objects’ perceptible properties (Oved & Fasel, 2011). Two experiments measuring the use of generics are described and used as support for this essentialist approach over descriptivist approaches. Keywords: Concepts; Concept-Acquisition; Explanation; Bayesian Networks; Generics. David Barner 1 (barner@ucsd.edu) Baptizing Concepts for Hypothesized Kinds Essences; Introduction When we hear, “these are kiwanos”, while being shown a set of objects each displaying a novel combination of yellowness, spikiness, and ovalness, how do these regularities factor into our hypotheses of what ‘kiwano’ means? One possibility is that we acquire a new concept, KIWANO, by conjoining the representations YELLOW, SPIKEY, and OVAL such that the observed regularities are directly encoded as part of the meaning of the concept. Perhaps over time, and over multiple learning instances, criterial information is differentiated from noise, and we come to represent KIWANO as a set of probability distributions over the most typical features. Variants of this descriptivist approach include classical definition theories (Locke, 1690; Hume, 1748), prototype theories (Rosch, 1978; Barsalou, 1987, 1999; Prinz 2002), and exemplar theories (Smith & Medin 1981). Another possibility, however, is that observed regularities are not themselves constitutive of meanings, but instead serve only as the basis for positing hidden/latent properties to explain the regularities. On such essentialist accounts, the learned concept KIWANO may be simple in representational structure (Gelman, 2003; Keil, 1989; Carey, 1985). The present paper articulates a favored version of the essentialist approach (Oved, 2009; 2014; Oved & Fasel 2011), an account in the spirit of Bayesian cognitive science (following Griffiths, Kemp, & Tenenbaum, 2008; Xu & Tenenbaum, 2007; Gopnik & Tenenbaum, 2007; Kemp, Perfors, & Tenenbaum, 2007). The paper then describes two Descriptivist accounts of concepts are largely motivated by the idea that many of our concepts are acquired as the result of observed associations, and the most straight-forward way to acquire them is to compose them directly from perceptual representations. Nativists since Plato have insisted, however, that many of our concepts cannot be composed from (even probability distributions over) perceptual representations (for arguments see Fodor, 1975, 1981, 1998, 2008). The Baptism view of concept acquisition is motivated by Fodor’s Challenge – the challenge of showing how a representationally simple concept can be learned from observed associations, genuinely learned in the sense of hypothesis formation and testing (Oved, 2009; 2014). The view is inspired by Kripke's (1972) baptism view on the analogous question of how proper names in natural languages come to have their meanings, treating the concept-acquisition question as the question of how mental names for properties/kinds come to have their meanings. Kripke's maneuver for the meanings of proper names was to use a reference-fixing description that involves deictic representations, or pointers – e.g., ‘this baby in my arms now’, to avoid identifying proper names with descriptions. A similar approach is used in the Baptism account for concepts, where the reference-fixing description, e.g., for the concept APPLE, might be, ‘the latent/unobservable property that these objects have that explains this similarity (in redness, roundness, sweetness, etc.)’. Notice that the description appeals to deep/hidden/latent properties, which is what makes the account a species of psychological essentialism. As long as this description manages to uniquely pick out the property of appleness, it can serve as a step in acquiring a simple mental term for appleness. 1 To see that the Baptism process answers Fodor’s challenge of showing how a representationally simple Note that a different description could have been used, say, using taste and touch information, perhaps by a blind child, so long as it too manages to pick out appleness. See (Oved, 2009; 2014) for details on how to deal with what philosophers have called the qua-problem (Devitt & Sterelny, 1999). Roughly, different sets of similarities are explained by appleness than by fruitness, edibleness, organicness, McIntoshness, etc.