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A description of the interpretation of language in the form of speech

Introduction

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This article has been cited by other articles in PMC. Abstract Language production processes can provide insight into how language comprehension works and language typology—why languages tend to have certain characteristics more often than others. Drawing on work in memory retrieval, motor planning, and serial order in action planning, the Production-Distribution-Comprehension PDC account links work in the fields of language production, typology, and comprehension: The claim that language form stems in large degree from producers' attempts to mitigate utterance planning difficulty is contrasted with alternative accounts in which form is driven by language use more broadly, language acquisition processes, or producers' attempts to create language forms that are easily understood by comprehenders.

In particular, they learn to predict the sequential structure of linguistic signals, based on the statistics of previously-encountered input. Thus, key aspects of comprehension behavior are tied to lexico-syntactic statistics in the language, which in turn derive from utterance planning biases promoting production of comparatively easy utterance forms over more difficult ones.

This approach contrasts with classic theories in which comprehension behaviors are attributed to innate design a description of the interpretation of language in the form of speech of the language comprehension system and associated working memory. The PDC instead links basic features of comprehension to a different source: The origins of intelligent behavior are at the core of classic debates in cognitive science concerning the contributions of innate capacities and experience in the development of thought, perception, and action.

For example, the fact that perception of motion in cardinal directions vertical, horizontal is superior to that in oblique directions has been attributed to the greater number of cells in visual cortex devoted to processing cardinal motion directions than oblique ones Rokem and Silver, 2009and this result in turn is thought to arise from visual experience: There are more motion events in the world in cardinal directions than in oblique ones Dakin et al.

Similarly, experience-based accounts of face perception hold that face recognition behavior diverges from object recognition because perceivers' visual experience with faces differs in critical ways from their experience with objects Tarr and Gauthier, 2000. While such accounts don't deny innate factors in perception, they are notable in ascribing a central role for experience in development and in adult performance.

The statistical properties of the input have a description of the interpretation of language in the form of speech similarly crucial role in some accounts of language use, including the role of linguistic experience in acquisition Hart and Risley, 1995 and in adult comprehension processes MacDonald et al.

However, the nature of the argument is critically different in vision and in language. Visual experience reflects the nature of the physical world: Vision scientists do not need to explain why gravity creates many experiences of downward motion, and no one expects face perception researchers to explain why faces have particular shapes.

In language, however, the input to the perceiver is itself the consequence of language behavior—it is the utterances produced by other language users, who have their own cognitive systems presumably shaped by their own experiences. This situation lends potential circularity to experience-based accounts of language Frazier, 1995requiring solutions for two unknowns at once: This difficult task is compounded by the fact that the psycholinguists who study language use are typically not the same people as the linguists who study the nature of language form, so that there is a gulf between linguistic theories of the nature of language and psycholinguists' accounts of the effects of experience with language patterns.

This article is a step toward bridging this divide, offering insight into both the origin of language form and also the effect of experience with these forms. The Production-Distribution-Comprehension PDC account, first sketched in MacDonald 1999 and elaborated in work described here, holds that the memory and planning demands of language production strongly affect the form of producers' utterances. Constraints imposed by the production process have two important consequences.

First, they contribute to understanding regularities in linguistic form: Second, they determine many aspects of language comprehension. The claim is not that all aspects of language form and comprehension can be traced to the computational demands of language production, but rather that production's impact in these areas is so pervasive that understanding production becomes essential to explaining why language is the way it is, and why language comprehension works the way it does.

In this article I describe the Production, Distribution, and Comprehension components of the PDC in that order, focusing particularly on lexico-syntactic phenomena.

Production Difficulty and its Amelioration reviews the memory and control demands of language production, producers' attempts to mitigate them, and the patterns of word order, sentence form, and lexical-sentence pairings that result. Findings in motor control, memory retrieval, and short term maintenance suggest that many properties of language production that affect utterance form also arise in action and motor planning more generally.

Next, the section entitled Distributional Regularities and Language Typology considers the effects of language production on language form and views the potential contributions of the PDC in the context of other accounts of why languages have some properties more than others.

Finally, Comprehension Consequences in the PDC addresses comprehension, showing that the PDC provides a different framework for thinking about sentence comprehension and offers a different explanation of some classic results.

The first step in the PDC: He argued that complex sequential actions such as speaking must be guided by a plan that is developed before execution, a view that continues to pervade research in motor behavior, including language production.

The construction of motor plans is a cognitively demanding activity; developing the utterance plan can be more demanding than speaking itself Kemper et al. The significant computational difficulty of constructing and maintaining an utterance plan is a key component of the PDC, and so we consider these planning operations in some detail. Development and care of the utterance plan Language planning shares features of both high-level non-linguistic action planning and more fine grained motor control.

In high-level action plans, some elements have only loosely constrained sequences. In making coffee, an example extensively discussed in research on action planning and control Cooper and Shallice, 2000 ; Botvinick and Plaut, 2004the coffee, cream, and sugar can go into the cup in any order.

Similarly, in some though by no means all aspects of language planning, some elements may be ordered in several ways, as in Jane bought a hammer and some batteries at the hardware store, vs. At the hardware store, Jane bought some batteries and a hammer. Thus language producers have word order options in some cases but not others, and when there are options, producers must very rapidly settle on one form and inhibit others from interfering, so as not to make speech error blends of alternative forms such as some hammer and a batteries.

Definitions of language

This behavior is an example of a winner-take-all process, and winner-take-all neural mechanisms form an important part of accounts and computational models of both language production Hartley and Houghton, 1996 ; Dell et al.

This winner-take-all property of language production is critical in accounts of how producers activate the correct serial order of elements in articulation Hartley and Houghton, 1996and it provides our first example of how properties of motor planning affect distributional patterns in the language, in that this property affects the incidence of speech errors.

The developing utterance plan must be maintained in an executable state as it is being developed. Indeed, verbal working memory studies offer important insights into some of the memory demands of language production.

In both serial recall tasks in which unrelated words are recalled in the same order they were presented and language production tasks such as describing pictureselements in the utterance plan tend to interfere with one another, affecting the fluency of speech. For example, phonological overlap among elements in the utterance plan increases the difficulty in both production and memory tasks Acheson and MacDonald, 2009and semantic overlap between words increases errors in language production Smith and Wheeldon, 2004 and memory tasks Tse et al.

Conversely, production of the correct serial order of elements is improved by increased linguistic frequency or coarticulatory experience, both for memory tasks Woodward et al. Thus, production planning has inherent working memory demands, with consequent interference and other pitfalls well known to memory researchers. Because planning precedes execution, a key question in language production concerns the degree of advance planning before execution begins.

Language production is said to be incremental, meaning that partial planning, execution, and subsequent planning are interleaved.

The scope of advance planning varies in different circumstances and is at least partially under the producer's strategic control Ferreira and Swets, 2002. Again, production behavior is shaped by learned implicit strategies that maximize fluency, as the scope of planning strikes a balance between competing demands.

On the one hand, initiating execution before much planning is complete allows producers to begin speaking earlier, avoiding long pauses and retaining the floor in a conversation. Early execution also avoids the memory burden of maintaining and executing a large plan, as more complex plans require more time to initiate execution, both in speech Ferreira, 1991 and in non-linguistic motor behaviors Rosenbaum et al.

How language production shapes language form and comprehension

However, interleaving planning and execution has the occasional negative consequence of the producer finishing the executable portion of the plan before the next portion is ready.

Beyond juggling planning and executing, language producers must also keep track of where they are in the plan as it is being executed.

Tracking the state of progress through the plan is critical for avoiding repetitions, omissions and other sequencing errors, but it comes at a cost, in that tracking plan progress itself carries substantial additional attention or maintenance burdens Botvinick and Plaut, 2004. At the same time, the memory for what has been uttered cannot remain too strong, because recently-executed actions can interfere with upcoming ones, leading to perseverations and other errors Tydgat et al.

An efficient allocation of attention to past, present, and future is learned over time: Fluent adult speech reflects a bias toward the future, with comparatively more anticipation errors elements of the upcoming plan incorrectly influencing the current execution than perseverations of previously-uttered elements Dell et al.

By contrast, young children, who are less experienced speakers, produce more errors overall and a relatively higher proportion of perseverations Stemberger, 1989. The impact of these phenomena is threefold. First, they illuminate the demands of language planning, which include developing the plan, maintaining it, monitoring the state of execution, and shifting attentional focus as the plan is executed over time.

Second, they illustrate how speakers learn implicit strategies to mitigate production difficulty, in this case learning to allocate more attention to the upcoming plan as they become more fluent, and learning to favor early execution and incremental planning, with delaying tactics and additional damage control if the plan runs out.

And third, production-related learning affects the distribution of utterance a description of the interpretation of language in the form of speech that people produce, in this case the rate and distribution of speech errors and pauses in utterances.

The intersection of these last two points—that the computational demands of language production can be mitigated, but with consequences for utterance form—will reappear below as a force in the distribution of syntactic forms in languages. Minimizing difficulty during production Incremental production—the interleaving of plan and execution—works only if new plan segments can be developed at a rate that keeps up with execution.

New plan development in turn relies on retrieval from long term memory, and when this retrieval fails or requires extra time, production is delayed or derailed.

We next review three memory-related production biases that have substantial consequences for lexico-syntactic distributions in utterance form. This fact has enormous influence on language form, because easily retrieved words and phrases tend to appear both earlier in utterances and at more prominent syntactic positions e. An Easy First bias in incremental production allows execution of utterances to begin early, starting with easily planned elements, leaving more time for planning of more difficult ones.

There are enough different forces affecting ease of planning that the claims can seem circular: Easy entities are easy because they appear earlier in the utterance. However, the essential claim—that utterance planning difficulty affects speakers' choices of word order and sentence structure—gains external validity in several ways.

Second, other action and motor planning processes show these same Easy First tendencies. MacNeilage and Davis 2000 argued that the distributional regularities of consonant and vowels in infants' babbling and early words reflect infants' tendencies to order segments more easily articulated within the infant vocal tract before more difficult ones.

Similarly, research in navigation shows an Easy First action ordering preference: Similarly, when humans are describing routes through a network, they also tend to begin by describing the simplest one first Levelt, 1982. Third, Easy First biases in serial ordering inherently follow from computational models of action planning, in which alternative sub-plans compete for entrance into an action plan, via selection mechanisms in sequence planning e. Thus, the Easy First bias in language production is not a stipulative principle or language-specific phenomenon; instead it follows naturally from attested aspects of motor and action planning—that a plan precedes its execution, that planning is incremental, that the plan is hierarchical with subplans that must be ordered in some way, that plan development entails retrieval from long term memory, and that this retrieval varies in speed and accuracy.

These results suggest that the way that utterance planning unfolds over time has a substantial impact on the word orders and sentence structures that language users produce. The boy was startled by the noise and the English dative alternation give Mary a book vs. Thus, in contrast to Jackendoff's 2002 suggestion that syntactic flexibilities are vestiges of ancient protolanguage, before syntactic constraints became more rigid, the PDC holds that word order flexibility has real value to language producers and emerges from action planning mechanisms that maximize fluency.

Production also accommodates constraints on permissible word orders in a language. A second significant influence on utterance form also favors easy, more practiced plans, but in this case, what is easy is the abstract sentence plan itself rather than the word or phrase elements sub-plans within it. Producers have a conspicuous tendency to reuse recently executed utterance plans, so that the likelihood that a speaker utters a passive sentence, for example, increases if that speaker has recently heard, read, or uttered another passive sentence Weiner and Labov, 1983 ; Ferreira and Bock, 2006.

This tendency toward Plan Reuse also called structural persistence or syntactic priming persists over time and over other intervening utterances.

The effect is argued to be not or not only the temporary activation of recent plans but rather a manifestation of long-term implicit learning of syntactic structure cf. On this view, language users are continually learning from their and others' language use; with every utterance, a syntactic plan becomes more likely to be used in the future.

Thus, while the phenomenon is often described as one of short-term repetition, its learning basis links it to retrieval from long term memory—whereas Easy First refers to the effect of retrieval of individual words on word order, Plan Reuse effectively refers to the retrieval of the sentence structure itself.

The two constraints jointly exert their influence on utterance form: Even in languages with very free word order, allegiance to favored structures Plan Reuse combines with Easy First in shaping utterance forms Christianson and Ferreira, 2005. The reuse of at least partially lexically-independent abstract plans is in some ways consistent with an autonomous syntactic representation independent of semantics Chomsky, 1957although the notion of adapting a prior syntactic plan to a new utterance, and the notion of sentences, phrases, and words as plans and sub-plans, are less consistent with the contrast in generative linguistics between a stored lexicon vs.

Moreover, the reuse of abstract plans is not unique to language, as Plan Reuse appears in many non-syntactic and non-linguistic domains.

Its effects are evident in recall from long term memory, in which people have a tendency to recall elements in the serial order in which they have frequently occurred in past experience Miller and Selfridge, 1950.

There is also increasing evidence for structured non-linguistic stimuli such as action sequences affecting subsequent production of certain sentence structures, suggesting that the re-use phenomena are not inherently linguistic Allen et al.

More broadly, similar Plan Reuse appears in many non-linguistic motor behaviors in humans and animals and is attributed to implicit motor learning.