Exemplar Theory Research Articles

Multilevel Exemplar Theory

This paper presents recent research that provides an overarching model of exemplar theory capable of explaining phenomena across the phonetic and syntactic strata. The model represents a unique exemplar-based account of constituency interactions encompassing both linguistic domains. It yields simulation and experimental results in keeping with experimental findings in the literature on syllable duration variability and offers an exemplar-theoretic account of local grammaticality. In addition, it provides some insights into the nature of exemplar cloud formation and demonstrates experimentally the potential gains that can be enjoyed via the use of rich exemplar representations.

Exploring social-indexical knowledge: A long past but a short history

AbstractThis article has three main aims. First, I review what is known about encoding social-indexical information in phonetics/phonology, suggesting that it is more complex and more extensive than typically acknowledged in laboratory phonology. Secondly, I explore evidence for the development of indexical knowledge in phonological acquisition, considering indexical learning from the perspective of exemplar theory. One of the attractions of exemplar theory is its capacity to predict learning of both linguistic and social structures through the same mechanism. The tenets of exemplar theory also make a number of predictions about indexical learning: some types of indexical properties are likely to be transmitted more readily than others, as a function of the frequency and phonetic transparency with which they are manifested. The predictions appear to be borne out relatively well by the available data. I end by raising a number of implications and challenges, in particular, but not exclusively, for exemplar theory.

Dual processing and diagnostic errors

In this paper, I review evidence from two theories in psychology relevant to diagnosis and diagnostic errors. "Dual Process" theories of thinking, frequently mentioned with respect to diagnostic error, propose that categorization decisions can be made with either a fast, unconscious, contextual process called System 1 or a slow, analytical, conscious, and conceptual process, called System 2. Exemplar theories of categorization propose that many category decisions in everyday life are made by unconscious matching to a particular example in memory, and these remain available and retrievable individually. I then review studies of clinical reasoning based on these theories, and show that the two processes are equally effective; System 1, despite its reliance in idiosyncratic, individual experience, is no more prone to cognitive bias or diagnostic error than System 2. Further, I review evidence that instructions directed at encouraging the clinician to explicitly use both strategies can lead to consistent reduction in error rates.

The aquisition of sonorant voicing.

In the view of Exemplar Theory phonetic variants of words are stored by speakers in their memory as a set of exemplars organized into clusters and grow stronger or decay over time depending on language experience (Bybee, 2002). In Polish and French sonorant consonants in clusters are devoiced word finally, which does not occur in German and English because of phonotactical constraints. A study based on automatic speech alignment and voicing profile extraction from Polish, French, German, and English speech corpuses aims at defining voicing sonorant temporal structure and voicing profile acquisition. The hypothesis is that Polish and French native speakers transfer their L1 exemplars during L2 acquisition of English and German and thus devoice sonorant. After extracting voicing profiles from recordings of native Polish and French speakers speaking English and German as an L2/L3, comparison of voicing profiles of English and German native speakers will be made in order to define the exemplar transfer.

The phoneme in cognitive phonology: episodic memories of both meaningful and meaningless units?

Cognitive linguistics assumes that languages are symbolic systems that emerge through frequent usage. If we accept the fundamentally symbolic nature of language, the question arises as to whether, in addition to the meaningful units, speakers would form separate memory structures of the meaningless ones as well. For example, would the speech sounds be stored independently of the lexical entries? In the framework of exemplar theory, there are at least two different points of view as to what the basic unit of representation in exemplar-based phonologies is. For one, it is the speech sounds and for the other it is the words. Psycholinguistic studies lend support to episodic memories of words, and neuroscience evidence, also concurring with exemplar-based approaches, suggests that the phonological aspects of the mental lexicon are primarily auditory. In this paper I argue that there are exemplar memories of meaningful units only, and that forming and storing separate exemplar clouds of speech sounds per se is not only unmotivated but problematic as well.

ACQUIRED EQUIVALENCE CHANGES STIMULUS REPRESENTATIONS

Acquired equivalence is a paradigm in which generalization is increased between two superficially dissimilar stimuli (or antecedents) that have previously been associated with similar outcomes (or consequents). Several possible mechanisms have been proposed, including changes in stimulus representations, either in the form of added associations or a change of feature salience. A different way of conceptualizing acquired equivalence is in terms of strategic inference: Confronted with a choice on which it has no evidence, the organism may infer from its history of reinforcement what the best option is, and that inference is observed as acquired equivalence. To test this account, we combined an incremental learning task with an episodic memory test. Drawings of faces were made equivalent through acquired equivalence training, and then paired with words in a list learning paradigm. When participants were asked to recognize specific face-word pairings, they confused faces more often when they had been made equivalent. This suggests that prior acquired equivalence training does influence how memories are coded. We also tested whether this change in coding reflected acquisition of new associations, as suggested by the associative mediation account, or whether stimuli become more similar through a reweighting of stimulus features, as assumed by some categorization theories. Results supported the associative mediation view. We discuss similarities between this view and exemplar theories of categorization performance.

Forensic Phonetics

AbstractAn overview of forensic phonetics is presented, focusing on speaker identification as its core task. Speaker profiling/speaker classification is applied when the offender has been recorded, but no suspect has been found. Auditory speaker identification by victims and witnesses becomes relevant when no speech recording of the offender is available. It can take the form of familiar‐speaker identification or unfamiliar‐speaker identification, and in the latter case a voice line‐up/voice parade can be carried out. When recordings of both the offender and a suspect are available, a voice comparison is done by an expert in forensic speech analysis. Current issues and domains in voice comparison analysis include the Bayesian approach to forensic reasoning and the Likelihood Ratio, the use of formant frequency measurements, non‐analytic perception and Exemplar Theory, forensic automatic speaker identification, and the interaction between different methods.

Generalization and similarity in exemplar models of categorization: Insights from machine learning

Exemplar theories of categorization depend on similarity for explaining subjects' ability to generalize to new stimuli. A major criticism of exemplar theories concerns their lack of abstraction mechanisms and thus, seemingly, of generalization ability. Here, we use insights from machine learning to demonstrate that exemplar models can actually generalize very well. Kernel methods in machine learning are akin to exemplar models and are very successful in real-world applications. Their generalization performance depends crucially on the chosen similarity measure. Although similarity plays an important role in describing generalization behavior, it is not the only factor that controls generalization performance. In machine learning, kernel methods are often combined with regularization techniques in order to ensure good generalization. These same techniques are easily incorporated in exemplar models. We show that the generalized context model (Nosofsky, 1986) and ALCOVE (Kruschke, 1992) are closely related to a statistical model called kernel logistic regression. We argue that generalization is central to the enterprise of understanding categorization behavior, and we suggest some ways in which insights from machine learning can offer guidance.

The Need for International Nursing Diagnosis Research and a Theoretical Framework

To describe the need for nursing diagnosis research and a theoretical framework for such research. A linguistics theory served as the foundation for the theoretical framework. Reasons for additional nursing diagnosis research are: (a) file names are needed for implementation of electronic health records, (b) international consensus is needed for an international classification, and (c) continuous changes occur in clinical practice. A theoretical framework used by the author is explained. Theoretical frameworks provide support for nursing diagnosis research. Linguistics theory served as an appropriate exemplar theory to support nursing research. Additional nursing diagnosis studies based upon a theoretical framework are needed and linguistics theory can provide an appropriate structure for this research.

Prototype abstraction by monkeys (Macaca mulatta).

The authors analyze the shape categorization of rhesus monkeys (Macaca mulatta) and the role of prototype- and exemplar-based comparison processes in monkeys' category learning. Prototype and exemplar theories make contrasting predictions regarding performance on the Posner-Homa dot-distortion categorization task. Prototype theory--which presumes that participants refer to-be-categorized items to a representation near the category's center (the prototype)--predicts steep typicality gradients and large prototype-enhancement effects. Exemplar theory--which presumes that participants refer to-be-categorized items to memorized training exemplars-predicts flat typicality gradients and small prototype-enhancement effects. Across many categorization tasks that, for the first time, assayed monkeys' dot-distortion categorization, monkeys showed steep typicality gradients and large prototype-enhancement effects. These results suggest that monkeys--like humans--refer to-be-categorized items to a prototype-like representation near the category's center rather than to a set of memorized training exemplars.

A sociolinguistic perspective on sociophonetic research

The four papers in this issue of the journal are jointly focused on two distinct themes: sociophonetics—the study of speakers and listeners’ sensitivity to the social context in which language is produced and perceived—and exemplar theory, as a way of explaining this behavior. In these comments, I will try to relate the findings in the first area to the field of sociolinguistics, and then relate the discussion of exemplar theory to recent studies of change in progress.

Modeling unidimensional categorization in monkeys

The categorization performance of monkeys on a unidimensional perceptual categorization task was examined with reference to decision bound and exemplar theories of categorization. Three rhesus monkeys were presented with stimuli varying along a single dimension, the displacement of a target light from a fixation point. Left or right saccade responses were probabilistically reinforced according to one of three functions, two of which were nonmonotonic at one end of the stimulus space. The monkeys all showed a monotonic increase in response probability as a function of target light displacement in this region, consistent with decision bound theory. Fits of a single-boundary model (GRT, Ashby & Gott, 1988) and two exemplar models--one using a probabilistic response function (GCM; Nosofsky, 1986), the other using a deterministic response function (DEM; Ashby & Maddox, 1993)--revealed overall support for the decision bound model. The results suggest that monkeys used a perceptual decision boundary to perform the task.

Spoken syntax: The phonetics of giving a hand in New Zealand English

This article considers the exemplar theories which are independently developing in phonetics and in syntax, and argues that they jointly make some predictions that neither does alone. One of these predictions is explored in the context of two sound changes which occurred in the history of New Zealand English. We show that both of these phonetic changes were affected by phrase-level factors. The raising of /æ/ was more advanced in the word hand when it referred to a limb, than when used in phrases such as give a hand or lend a hand . And the centralization of the / i / vowel was more advanced in utterances of give involving abstract themes ( give a chance ), than when it had a meaning of transfer of possession ( give a pen ). We argue that existence of such effects lends support both to the idea (from syntactic exemplar theory) that phrases are stored, and the idea (from phonetic exemplar theory) that lexical representations are phonetically detailed.

Wanted: A new psychology of exemplars.

Present-day exemplar theory faces difficult challenges, and important questions have arisen about the kinds of exemplar effects and processes that are empirically supported, and about the kind of exemplar theory that could still be constructive. One question concerns whether exemplar generalization in memory and categorization is broad and collective--extending to many related exemplars stored in memory--or whether it is focused and singular--extending only to highly similar (nearly identical) exemplars. The present article considers this continuum from broad to narrow generalization. I demonstrate that in prominent memory and category tasks--tasks in which exemplar theory predicts broad generalization--generalization is in psychological reality very tightly focused. These demonstrations could ground a new, productive exemplar theory that is true to psychological process as humans conduct themselves in memory and category tasks. This new psychology may actually reprise the traditional exemplar theory that predated our sophisticated, mathematical exemplar models.

Do chickens (Gallus gallus f. domestica) decompose visual figures?

To investigate whether learning to discriminate between visual compound stimuli depends on decomposing them into constituting features, hens were first trained to discriminate four features (red, green, horizontal, vertical) from two dimensions (colour, line orientation). After acquisition, hens were trained with compound stimuli made up from these dimensions in two ways: a separable (line on a coloured background) stimulus and an integral one (coloured line). This compound training included a reversal of reinforcement of only one of the two dimensions (half-reversal). After having achieved the compound stimulus discrimination, a second dimensional training identical to the first was performed. Finally, in the second compound training the other dimension was reversed. Two major results were found: (1) an interaction between the dimension reversed and the type of compound stimulus: in compound training with colour reversal, separable compound stimuli were discriminated worse than integral compounds and vice versa in compound training with line orientation reversed. (2) Performance in the second compound training was worse than in the first one. The first result points to a similar mode of processing for separable and integral compounds, whereas the second result shows that the whole stimulus is psychologically superior to its constituting features. Experiment 2 repeated experiment 1 using line orientation stimuli of reversed line and background brightness. Nevertheless, the results were similar to experiment 1. Results are discussed in the framework of a configural exemplar theory of discrimination that assumes the representation of the whole stimulus situation combined with transfer based on a measure of overall similarity.

The Simplicity Principle in Human Concept Learning

How do we learn concepts and categories from examples? Part of the answer might be that we induce the simplest category consistent with a given set of example objects. This seemingly obvious idea, akin to simplicity principles in many fields, plays surprisingly little role in contemporary theories of concept learning, which are mostly based on the storage of exemplars, and avoid summarization or overt abstraction of any kind. This article reviews some evidence that complexity minimization does indeed play a central role in human concept learning. The chief finding is that subjects' ability to learn concepts depends heavily on the concepts' intrinsic complexity; more complex concepts are more difficult to learn. This pervasive effect suggests, contrary to exemplar theories, that concept learning critically involves the extraction of a simplified or abstracted generalization from examples.

Phonetic diversity, statistical learning, and acquisition of phonology.

In learning to perceive and produce speech, children master complex language-specific patterns. Daunting language-specific variation is found both in the segmental domain and in the domain of prosody and intonation. This article reviews the challenges posed by results in phonetic typology and sociolinguistics for the theory of language acquisition. It argues that categories are initiated bottom-up from statistical modes in use of the phonetic space, and sketches how exemplar theory can be used to model the updating of categories once they are initiated. It also argues that bottom-up initiation of categories is successful thanks to the perception-production loop operating in the speech community. The behavior of this loop means that the superficial statistical properties of speech available to the infant indirectly reflect the contrastiveness and discriminability of categories in the adult grammar. The article also argues that the developing system is refined using internal feedback from type statistics over the lexicon, once the lexicon is well-developed. The application of type statistics to a system initiated with surface statistics does not cause a fundamental reorganization of the system. Instead, it exploits confluences across levels of representation which characterize human language and make bootstrapping possible.

Furnishing the mind: concepts and their perceptual basis

Western philosophy has long been divided between empiricists, who argue that human understanding has its basis in experience, and rationalists, who argue that reason is the source of knowledge. A central issue in the debate is the nature of concepts, the internal representations we use to think about the world. The traditional empiricist thesis that concepts are built up from sensory input has fallen out of favor. Mainstream cognitive science tends to echo the rationalist tradition, with its emphasis on innateness. In Furnishing the Mind, Jesse Prinz attempts to swing the pendulum back toward empiricism. Prinz provides a critical survey of leading theories of concepts, including imagism, definitionism, prototype theory, exemplar theory, the theory theory, and informational atomism. He sets forth a new defense of concept empiricism that draws on philosophy, neuroscience, and psychology and introduces a new version of concept empiricism called proxytype theory. He also provides accounts of abstract concepts, intentionality, narrow content, and concept combination. In an extended discussion of innateness, he covers Noam Chomsky's arguments for the innateness of grammar, developmental psychologists' arguments for innate cognitive domains, and Jerry Fodor's argument for radical concept nativism.

Exemplar theory's predicted typicality gradient can be tested and disconfirmed.

One of exemplar theory's central predictions concerns the shape of typicality gradients. The typicality gradient it predicts is a consequence of its exemplar-based comparisons and appears no matter how the theory is evaluated. However, this predicted typicality gradient does not fit the empirical typicality gradients obtained in an influential version of the dot-distortion category task, and this is true even when the exemplar model is made more flexible and mathematically powerful. Thus, exemplar theory is disconfirmed in this domain of categorization. In contrast, prototype theories are consistent with the empirically obtained typicality gradients.

How to Blunt the Sword of Compositionality

Concepts—the elementary building-blocks of thought—have long been a focusof research in psychology, and it shows. A naturalistically minded philosopherwho goes shopping for a theory of concepts finds herself faced with a fairlydizzying array of options, including definition theories, prototype theories,exemplar theories, theory theories, and an assortment of hybrids. It is with somesense of relief, perhaps, that she learns of a device—what I shall call, follow-ing Fodor 1998a, the “sword of compositionality”—with which to cut downthe space of possibilities. In particular, the sword is supposed to greatly sim-plify the selection task by eliminating in one fell swoop the largest and mostinfluential class of theories currently on the market. The aim of this paper isto test the credibility of this rather bold supposition.To get a sense of what’s at stake here requires a quick survey of the theoret-ical terrain. Most contemporary thinking about concepts is informed by thelexical semantics tradition, which approaches the study of concepts via the nat-ural language expressions that encode them. Of special importance to this studyare lexical concepts, that is, concepts encoded by monomorphemic words like‘cat’ or ‘bachelor’. Non-lexical concepts—concepts encoded either by polymor-phemic words ~‘housebroken’, ‘unmarried’! or by phrases ~‘cat fur’, ‘bachelorparty’!—are understood to be built up somehow from lexical ones, and henceare explanatorily posterior to them.Theories of concepts in the lexical semantics tradition can be sorted usinga binary decision tree with three branches. First there is the question of atom-ism. Atomists say that lexical concepts are by and large semantically primi-tive or unstructured, in that they have the content they do independently oftheir relations to particular other concepts ~Fodor 1998a!. Anatomists deny this,opting instead for the idea that concepts generally exhibit semantic structureof some sort. Second there is the question of classicalism. Classical anatomisttheories dictate that the kind of structure possessed by concepts is definitional