Attention and Effort

http://matt.colorado.edu/teaching/categories/rm75.pdf

Family Resemblances: Studies in the Internal Structure of Categories

Cognitive Representations of Semantic Categories.

Since the publication of Oldfield's (1966) seminal article, “Things, Words and the Brain,” a great deal of attention has been devoted to the structural organization of words in the mental lexicon. Most of this research, however, has focused on the structure of higher level aspects of lexical representations, namely the semantic and conceptual organization of lexical items in memory (e.g., Miller & Johnson-Laird, 1976; Smith, 1978). As a consequence, little attention has been directed to the structural organization of the representations of sensory and perceptual information used to gain access to these higher level sources of information. The goal of the present investigation was to explore in detail this structure and its implications for perception of spoken words by normal and hearing-impaired listeners.

In the present set of studies, structure will be defined specifically in terms of similarity relations among the sound patterns of words. Similarity will serve as the primary means by which the organization of acoustic-phonetic representations in memory will be investigated. We assume that similarity relations among the sound patterns of spoken words represent one of the earliest stages at which the structural organization of the lexicon comes into play. The precise aim of the present investigation was to gain a detailed understanding of the lower level relations between stimulus input, activation of phonetic representations, and, subsequently, recognition of spoken words.

The identification of structure with similarity relations among sound patterns of words raises the difficult problem of defining similarity. Similarity, although crucial to the present investigation, is an ill-defined concept in research on speech perception and spoken word recognition, and one that deserves considerably more work in these areas of research (see Mermelstein, Reference Note 7). However, similarity can be approximated by both computational and behavioral predictors of confusion, the approach taken here. Thus, similarity will be defined in terms of a specific computational metric for predicting confusions among phonetic patterns as well as a behavioral, or operational, metric based on the results of a series of perceptual experiments.

Having defined structure as the similarity relations among the sound patterns of words, the question arises: Should the structural organization of representations in memory have consequences for spoken word recognition? Consider a content-addressable memory system in which there is no noise either in the signal or the listener (Kohonan, 1980). In such a system, encoding the acoustic-phonetic information in the stimulus word is tantamount to locating the word in memory. In this case, the structural organization of acoustic-phonetic representations in memory would have no consequences for word identification. Instead, the task of spoken word recognition would be identical to phonetic perception, and one need only study phonetic perception to understand how words are recognized. (By phonetic perception we are referring to the perception of individual segments such as consonants and vowels.)

It is undeniable that phonetic perception is important in spoken word recognition. It is not undeniable, however, that the human word recognition system operates as a noiseless content-addressable system or that the acoustic-phonetic signal itself is devoid of noise. To begin, the signal is very often less than ideal for the purposes of the listener. Words are typically perceived against a background of considerable ambient noise, reverberation, and the voices of other talkers. In addition, coarticulatory effects and segmental reductions and deletions substantially restructure the phonetic information in a myriad of ways (Luce & Pisoni, 1987). Although such effects may indeed be useful to the listener (Church, Reference Note 3; Elman & McClelland, 1986), they also undoubtedly produce considerable ambiguities in the speech signal, making a strictly content-addressable word recognition system based on phonetic encoding unrealistic. In short, both the noise inherent in the signal as well as the noise against which the signal is perceived make it unlikely that word recognition is accomplished by direct access, based solely on phonetic encoding, to acoustic-phonetic representations in memory.

Not only is the speech signal noisy, so too is the recognition system of the listener. Although the human is clearly well adapted for the perception of spoken language, the system by which language is perceived is by no means a perfect one. In normal listeners, encoding, attentional, and memory demands frequently result in the distortion, degradation, or loss of important acoustic-phonetic information. The data on misperceptions alone attest to the fact that spoken word recognition is less than perfect (Bond & Garnes, 1980). In hearing-impaired listeners, the problems faced by normal listeners are exacerbated by impoverished input representations. Thus, again, a strictly content-addressable system does not suffice as a model of human spoken word recognition.

The alternative to a noiseless content-addressable system is one in which the stimulus input activates a number of similar acoustic-phonetic representations or candidates in memory, among which the system must choose (Marslen-Wilson, 1989; Marslen-Wilson & Welsh, 1978; Triesman, 1978a, b). In this system, a considerable amount of processing activity involves discriminating among the lexical items activated in memory. Indeed, many current models of word recognition subscribe to the view that word recognition is to a great degree a process of discriminating among competing lexical items (Forster, 1979; Luce, Pisoni, & Goldinger, 1990; Marslen-Wilson, 1989; Marslen-Wilson & Welsh, 1978; McClelland & Rumelhart, 1981; McQueen, Cutler, Briscoe, & Norris, 1995; Morton, 1979; Norris, 1994).

Given that one of the primary tasks of the word recognition system involves discrimination among lexical items, the study of the structural organization of words in memory takes on considerable importance, especially if structural relations can be shown to influence the ease or difficulty of lexical discrimination, and, subsequently, word recognition and lexical access. By the same token, under the assumption that word recognition involves discrimination and selection among competing lexical items, variations in the ease or difficulty of discriminating among items in memory can enlighten us as to the structural organization of the sound patterns of words. In short, lexical discrimination and structure are so inextricably tied together that the study of one leads to a further understanding of the other.

Assuming, then, that structural relations among words should influence spoken word recognition via the process of discrimination, it is important to determine that structural differences among words actually exist. Previous research by Landauer and Streeter (1973) has demonstrated that words vary substantially not only in the number of words to which they are similar, but also in the frequencies of these similar words. These findings suggest that both structural and frequency relations among words may mediate lexical discrimination. Investigation of the behavioral effects of these relations should help us to understand further not only the process of lexical discrimination, but also the organization of the sound patterns of spoken words in memory.

The issue of word frequency takes on an important role in the investigation of the structural organization of the sound patterns of words. Numerous studies over the years (Howes, 1954, 1957; Newbigging, 1961; Savin, 1963; Soloman & Postman, 1952) have demonstrated that the ease with which spoken words are recognized is monotonically related to experienced frequency, as measured by some objective count of words in the language. However, little work has been devoted to detailing the interaction of word frequency and structural relations among words (see, however, Triesman, 1978a, b). If word frequency influences the perceptibility of the stimulus word, it should also influence the degree of activation of similar words in memory. Frequency is important, then, in further specifying the relative competition among activated items that are to be discriminated among.

The goal of the present investigation was, therefore, to examine the effects of the number and nature of words activated in memory on auditory word recognition. Throughout the ensuing discussion, the term similarity neighborhood will be employed. A similarity neighborhood is defined here as a collection of words that are phonetically similar to a given stimulus word. (The term stimulus word will be used to refer to the word for which a neighborhood is computed.) Similarity neighborhood structure refers to two factors: 1) the number and degree of confusability of words in the neighborhood, and 2) the frequencies of the neighbors. This first factor will be referred to as neighborhood density or neighborhood confusability; the second factor will be called neighborhood frequency. In addition to neighborhood structure, the frequency of the stimulus word itself will be of interest.

/pdf/recognizing-spoken-words-the-neighborhood-activation-model-2f14utsyjc.pdf

Recognizing Spoken Words: The Neighborhood Activation Model

People construct ad hoc categories to achieve goals. For example, constructing the category of “things to sell at a garage sale” can be instrumental to achieving the goal of selling unwanted possessions. These categories differ from common categories (e.g., “fruit,” “furniture”) in that ad hoc categories violate the correlational structure of the environment and are not well established in memory. Regarding the latter property, the category concepts, concept-to-instance associations, and instance-to-concept associations structuring ad hoc categories are shown to be much less established in memory than those of common categories. Regardless of these differences, however, ad hoc categories possess graded structures (i.e., typicality gradients) as salient as those structuring common categories. This appears to be the result of a similarity comparison process that imposes graded structure on any category regardless of type.

https://link.springer.com/content/pdf/10.3758/BF03196968.pdf

Ad hoc categories

The relationship between two indices of the internal structure of natural-language categories, goodness-of-example (as measured by subjects’ ratings), and item dominance (as assessed by category-norm data) was assessed by correlational analysis. For all eight categories examined, the two variables are significantly positively correlated. Item dominance also bears some positive relationship to word frequency, while goodness-of-example does not.

Jack Catlin

Papers

Relationships among goodness-of-example, category norms, and word frequency

On the word-frequency effect.

Development of the Structure of Color Categories.

Verifying Affirmative and Negative Sentences.

Monaural right-ear advantage in a target-identification task.