Faculty Books

Developmental Dysgraphia

Developmental Dysgraphia

The ability to communicate with written language is critical for success in school and in the workplace. Unfortunately, many children suffer from developmental dysgraphia―impairment in acquiring spelling or handwriting skills―and this form of impairment has received relatively little attention from researchers and educators. This volume brings together, for the first time, theoretically grounded and methodologically rigorous research on developmental dysgraphia, presented alongside reviews of the typical development of spelling and writing skills. Leading experts on writing and dysgraphia shed light on different types of impairments that can affect the learning of spelling and writing skills, and provide insights into the typical development of these skills. The volume, which contributes both to the basic science of literacy and to the applied science of diagnosing and treating developmental dysgraphia, should interest researchers, educators, and clinicians. This book was originally published as a special issue of Cognitive Neuropsychology.


Optimality-theoretic syntax, semantics, and pragmatics: From uni- to bidirectional optimization

Optimality-theoretic syntax, semantics, and pragmatics: From uni- to bidirectional optimization

This book investigates the morphosyntactic, semantic, and pragmatic properties of language, and the interactions between them, from the perspective of Optimality Theory. It integrates optimization processes into the formal and functional study of grammar, interpreting optimization as the result of conflicting, violable ranked constraints.

Unlike previous work on the topic, this book also takes into account the question of directionality of grammar. A model of grammar in which optimization processes interact bidirectionally allows both language generation-the process of selecting the optimal form of a given meaning-and language interpretation-the process of optimal interpretation of a given form-to be taken into account. Chapters in this volume explore the consequences of both symmetric (unidirectional) and asymmetric (bidirectional) versions of Optimality Theory, investigating the syntax-semantics interface, first language acquisition, and sequential bilingual grammars.

The volume presents cutting edge research in Optimality-Theoretic syntax and semantics, as well as demonstrating how optimization processes as modelled in this formalism serve as a viable approach for linguists and scholars in related fields.

By G. Legendre. M. Putnam, H. de Swart, & E. Zaroukian.


Scene Vision: Making Sense of What We See

Scene Vision: Making Sense of What We See

For many years, researchers have studied visual recognition with objects — single, clean, clear, and isolated objects, presented to subjects at the center of the screen. In our real environment, however, objects do not appear so neatly. Our visual world is a stimulating scenery mess; fragments, colors, occlusions, motions, eye movements, context, and distraction all affect perception. In this volume, pioneering researchers address the visual cognition of scenes from neuroimaging, psychology, modeling, electrophysiology, and computer vision perspectives.

Building on past research — and accepting the challenge of applying what we have learned from the study of object recognition to the visual cognition of scenes — these leading scholars consider issues of spatial vision, context, rapid perception, emotion, attention, memory, and the neural mechanisms underlying scene representation. Taken together, their contributions offer a snapshot of our current knowledge of how we understand scenes and the visual world around us.


Understanding Cognitive Development: Approaches from Mind and Brain

Understanding Cognitive Development: Approaches from Mind and Brain

The papers in this volume examine the state of the art in key areas of developmental cognitive neuroscience, focusing on theoretically driven research on cognition and its development. The past decade has seen an increasing number of empirical papers on the relationship between brain and cognitive development. But despite the clearly burgeoning interest in this topic, there is a relative paucity of work motivated by deep theoretical questions about the nature of cognition and its development. Many papers are still in the mode of reporting brain-cognition correlations with a focus on regional activations during brain imaging – a useful approach, but one that is limited with respect to its contributions to understanding the structure of cognition and its development. The papers in this special issue of Cognitive Neuropsychology consider a number of domains and mechanisms in cognition, including language, number, space, faces, reading, memory, and attention, and represent the wealth of approaches and techniques that can be used to shed light on the nature of cognitive development in brain and mind. These include cross-species comparisons, studies of development under experiential deprivation or genetic differences, classical developmental experimentation, and imaging techniques such as NIRS and fMRI which have recently been applied to developmental questions. The combination of solid theorizing together with a broad range of approaches allows a critical but constructive look at the latest findings in the field relevant to answering enduring questions about cognition, its development, and its realization in the developing brain.


Spatial Representation: From Gene to Mind

Spatial Representation: From Gene to Mind

In this book, the authors present evidence that this domain-specific specialization in cognitive function emerges early in development and is reflected in patterns of breakdown that occur under genetic defect. The authors focus on spatial representation in children and adults with Williams syndrome, a relatively rare genetic syndrome that gives rise to an unusual profile of severely impaired spatial representation together with spared language. Results from a variety of spatial domains — including object representation, motion perception, action, navigation, and spatial language — appear to display a strikingly uneven profile of sparing and deficit within spatial representations, consistent with the idea that specialization of function drives development and breakdown. These findings raise a crucial question: Can specific genes target specific aspects of cognitive structure? Looking deeper into the patterns of performance across spatial domains, the book explores the notion that understanding patterns of normal development across domains is crucial to understanding unusual development. Using insights from normal development, the authors propose a speculative hypothesis that explains the emergence of the William syndrome profile, and how complex cognitive outcomes can arise from the deletion of a small set of genes.


The Neural Bases of Language Production (Special Issue of Language and Cognitive Processes)

The Neural Bases of Language Production (Special Issue of Language and Cognitive Processes)

The papers in this special issue of Language and Cognitive Processing on the neural bases of language production illustrate two general approaches in current cognitive neuroscience. One approach focuses on investigating cognitive issues, making use of the logic of associations/dissociations or the logic of neural markers as key investigative tools. The other approach has as its primary goal identifying the cognitive and computational functions performed by specific brain areas and understanding the underlying neurobiological mechanisms. The research described in the papers of this special issue applies these approaches to the study of fundamental questions concerning sign language, multilingualism, speech motor control and the interaction between speech production, and comprehension. We discuss how, in doing so, this research sheds light on the cognitive and brain mechanisms of language production.

Language and Cognitive Processes. Volume 26, Issue 7, 2011


Case Series in Cognitive Neuropsychology (Special Issue of Cognitive Neuropsychology)

Case Series in Cognitive Neuropsychology (Special Issue of Cognitive Neuropsychology)

Schwartz and Dell (2010) advocated for a major role for case series investigations in cognitive neuropsychology. They defined the key features of this approach and presented a number of arguments and examples illustrating the benefits of case series studies and their contribution to computational cognitive neuropsychology. In the Special Issue on “Case Series in Cognitive Neuropsychology” there are six commentaries on Schwartz and Dell as well as a response to the six commentaries by Dell and Schwartz (2011 this issue). In this paper, I provide a brief summary of the key points made in Schwartz and Dell, and I review the promise and perils of case series design as revealed by the six commentaries. I conclude by placing the set of papers within a broader perspective, providing some clarification of the historical record on case series and single-case approaches, raising some cautionary notes for case series studies and situating both case series and single-case approaches within the larger context of theory development in the cognitive sciences.

Cognitive Neuropsychology. Volume 28, Issue 7, 2011.


The Harmonic Mind (Vol I)

The Harmonic Mind (Vol I)

Despite their apparently divergent accounts of higher cognition, cognitive theories based on neural computation and those employing symbolic computation can in fact strengthen one another. To substantiate this controversial claim, this landmark work develops in depth a cognitive architecture based in neural computation but supporting formally explicit higher-level symbolic descriptions, including new grammar formalisms. Detailed studies in both phonology and syntax provide arguments that these grammatical theories and their neural network realizations enable deeper explanations of early acquisition, processing difficulty, cross-linguistic typology, and the possibility of genomically encoding universal principles of grammar. Foundational questions concerning the explanatory status of symbols for central problems such as the unbounded productivity of higher cognition are also given proper treatment. The work is made accessible to scholars in different fields of cognitive science through tutorial chapters and numerous expository boxes providing background material from several disciplines. Examples common to different chapters facilitate the transition from more basic to more sophisticated treatments. Details of method, formalism, and foundation are presented in later chapters, offering a wealth of new results to specialists in psycholinguistics, language acquisition, theoretical linguistics, computational linguistics, computational neuroscience, connectionist modeling, and philosophy of mind.


The Harmonic Mind (Vol II)

The Harmonic Mind (Vol II)

Despite their apparently divergent accounts of higher cognition, cognitive theories based on neural computation and those employing symbolic computation can in fact strengthen one another. To substantiate this controversial claim, this landmark work develops in depth a cognitive architecture based in neural computation but supporting formally explicit higher-level symbolic descriptions, including new grammar formalisms. Detailed studies in both phonology and syntax provide arguments that these grammatical theories and their neural network realizations enable deeper explanations of early acquisition, processing difficulty, cross-linguistic typology, and the possibility of genomically encoding universal principles of grammar. Foundational questions concerning the explanatory status of symbols for central problems such as the unbounded productivity of higher cognition are also given proper treatment. The work is made accessible to scholars in different fields of cognitive science through tutorial chapters and numerous expository boxes providing background material from several disciplines. Examples common to different chapters facilitate the transition from more basic to more sophisticated treatments. Details of method, formalism, and foundation are presented in later chapters, offering a wealth of new results to specialists in psycholinguistics, language acquisition, theoretical linguistics, computational linguistics, computational neuroscience, connectionist modeling, and philosophy of mind.


Optimality-Theoretic Syntax: Language, Speech and Communication

Optimality-Theoretic Syntax: Language, Speech and Communication

Recent work in theoretical syntax has revealed the strong explanatory power of the notions of economy, competition, and optimization. Building grammars entirely upon these elements, Optimality Theory syntax provides a theory of universal grammar with a formally precise and strongly restricted theory of universal typology: cross-linguistic variation arises exclusively from the conflict among universal principles.Beginning with a general introduction to Optimality Theory syntax, this volume provides a comprehensive overview of the state of the art, as represented by the work of the leading developers of the theory. The broad range of topics treated includes morphosyntax (case, inflection, voice, and cliticization), the syntax of reference (control, anaphora, and pronominalization), the gammar of clauses (complementizers and their absence), and grammatical and discourse effects in word order. Among the theoretical themes running throughout are the interplay between faithfulness and markedness, and various questions of typology and of
inventory.

Contributors: Peter Ackema, Judith Aissen, Eric Bakovic, Joan Bresnan, Hye-Won Choi, João Costa, Jane Grimshaw, Edward Keer, Géraldine Legendre, Gereon Müller, Ad Neeleman, Vieri Samek-Lodovici, Peter Sells, Margaret Speas, Sten Vikner, Colin Wilson, Ellen Woolford.


Visual reflections: A perceptual deficit and its implications

Visual reflections: A perceptual deficit and its implications

How much can we learn about normal visual perception and cognition from a malfunctioning visual system? Quite a lot, as Michael McCloskey makes abundantly clear in this book. McCloskey presents his work with AH, a college student who has an extraordinary deficit in visual perception. When AH looks at an object, she sees it clearly and identifies it readily; yet she is often dramatically mistaken about where the object is or how it is oriented. For example, she may reach out to grasp an object that she sees on her left, but miss it completely because it is actually on her right; or she may see an arrow pointing up when it is really pointing down. AH’s errors, together with many other clues, lead McCloskey to some very interesting conclusions about how we perceive the world. He develops theoretical claims about visual subsystems, the nature of visual location and orientation representations, attention and spatial representations, the role of the visual system in mental imagery, and the levels of the visual system implicated in awareness. Visual Reflections makes a fascinating and compelling case that we can often learn more about a process when it goes awry than when it functions flawlessly.


Information Theory in Computer Vision and Pattern Recognition

Information Theory in Computer Vision and Pattern Recognition

Information theory has proved to be effective for solving many computer vision and pattern recognition (CVPR) problems (such as image matching, clustering and segmentation, saliency detection, feature selection, optimal classifier design and many others). Nowadays, researchers are widely bringing information theory elements to the CVPR arena. Among these elements there are measures (entropy, mutual information…), principles (maximum entropy, minimax entropy…) and theories (rate distortion theory, method of types…).

This book explores and introduces the latter elements through an incremental complexity approach at the same time where CVPR problems are formulated and the most representative algorithms are presented. Interesting connections between information theory principles when applied to different problems are highlighted, seeking a comprehensive research roadmap. The result is a novel tool both for CVPR and machine learning researchers, and contributes to a cross-fertilization of both areas.

Contains a Foreword by Professor Alan Yuille


Optimality Theory: Constraint Interaction in Generative Grammar

Optimality Theory: Constraint Interaction in Generative Grammar

This book is the final version of the widely-circulated 1993 Technical Report that introduces a conception of grammar in which well-formedness is defined as optimality with respect to a ranked set of universal constraints.

  • Final version of the widely circulated 1993 Technical Report that was the seminal work in Optimality Theory, never before available in book format.
  • Serves as an excellent introduction to the principles and practice of Optimality Theory.
  • Offers proposals and analytic commentary that suggest many directions for further development for the professional.

By Alan Prince and Paul Smolensky


Dysgraphia: Cognitive Processes, Remediation, and Neural Substrates: A Special Issue of Aphasiology

Dysgraphia: Cognitive Processes, Remediation, and Neural Substrates: A Special Issue of Aphasiology

Written language permeates virtually every aspect of modern society and literacy plays a central role in determining the economic and personal success of the individual. However, while the importance of written language comprehension (reading) is generally acknowledged, the significance of written language expression (spelling) is often overlooked. As a result, there has been relatively little research directed at understanding the cognitive and neural bases of written language production. Equally surprising is that the treatment of written language deficits is largely neglected in the training of clinical aphasiologists and speech and language pathologists. This is particularly problematic given the evidence that written language skills may be amenable to treatment even when spoken language deficits are not. Thus the successful treatment of acquired dsygraphia may provide a means of communication for individuals who otherwise may be severely limited in their communication abilities. This volume seeks to provide an overview of the state-of-the-field by bringing together a collection of research papers concerning the treatment of written language deficits in individuals with acquired dysgraphia, along with investigations of the cognitive processes and neural substrates of written language production. In addition, the inclusion, within this volume, of papers investigating the cognitive processing and neural substrates of non-alphabetic written language codes such as Chinese and Japanese, provides an impetus to consider the ways in which the cognitive processes and neural substrates responsible for written language processing may be similar or different across languages and language codes. The broadening of the domain of investigation in this manner can only lead to a deeper understanding of written language processing, its neural bases and the methods that can be successfully used in facilitating its recovery.


Perception, Cognition, and Language: Essays in Honor of Henry and Lila Gleitman

Perception, Cognition, and Language: Essays in Honor of Henry and Lila Gleitman

These original empirical research essays in the psychology of perception, cognition, and language were written in honor of Henry and Lila Gleitman, two of the most prominent psychologists of our time. The essays range across fields foundational to cognitive science, including perception, attention, memory, and language, using formal, experimental, and neuroscientific approaches to issues of representation and learning. An introduction provides a historical perspective on the development of the field from the 1960s onward. The contributors have all been colleagues and students of the Gleitmans, and the collection celebrates their influence on the field of cognitive science.


Handbook of Cognitive Neuropsychology: What Deficits Reveal About the Human Mind

Handbook of Cognitive Neuropsychology: What Deficits Reveal About the Human Mind

This volume reviews the full range of cognitive domains that have benefited from the study of deficits. Chapters covered include language, memory, object recognition, action, attention, consciousness and temporal cognition.


Learnability in Optimality Theory

Learnability in Optimality Theory

Highlighting the close relationship between linguistic explanation and learnability, Bruce Tesar and Paul Smolensky examine the implications of Optimality Theory (OT) for language learnability. They show how the core principles of OT lead to the learning principle of constraint demotion, the basis for a family of algorithms that infer constraint rankings from linguistic forms.

Of primary concern to the authors are the ambiguity of the data received by the learner and the resulting interdependence of the core grammar and the structural analysis of overt linguistic forms. The authors argue that iterative approaches to interdependencies, inspired by work in statistical learning theory, can be successfully adapted to address the interdependencies of language learning. Both OT and Constraint Demotion play critical roles in their adaptation. The authors support their findings both formally and through simulations. They also illustrate how their approach could be extended to other language learning issues, including subset relations and the learning of phonological underlying forms.

By Bruce Tesar and Paul Smolensky


Mathematical Perspectives on Neural Networks

Mathematical Perspectives on Neural Networks

Recent years have seen an explosion of new mathematical results on learning and processing in neural networks. This body of results rests on a breadth of mathematical background which even few specialists possess. In a format intermediate between a textbook and a collection of research articles, this book has been assembled to present a sample of these results, and to fill in the necessary background, in such areas as computability theory, computational complexity theory, the theory of analog computation, stochastic processes, dynamical systems, control theory, time-series analysis, Bayesian analysis, regularization theory, information theory, computational learning theory, and mathematical statistics.

Mathematical models of neural networks display an amazing richness and diversity. Neural networks can be formally modeled as computational systems, as physical or dynamical systems, and as statistical analyzers. Within each of these three broad perspectives, there are a number of particular approaches. For each of 16 particular mathematical perspectives on neural networks, the contributing authors provide introductions to the background mathematics, and address questions such as:

  • Exactly what mathematical systems are used to model neural networks from the given perspective?
  • What formal questions about neural networks can then be addressed?
  • What are typical results that can be obtained? and
  • What are the outstanding open problems?

A distinctive feature of this volume is that for each perspective presented in one of the contributed chapters, the first editor has provided a moderately detailed summary of the formal results and the requisite mathematical concepts. These summaries are presented in four chapters that tie together the 16 contributed chapters: three develop a coherent view of the three general perspectives — computational, dynamical, and statistical; the other assembles these three perspectives into a unified overview of the neural networks field.

Edited by P. Smolensky, M. Mozer, & D.E. Rumelhart


Principles of English Stress

Principles of English Stress

In this provocative work, Luigi Burzio argues that many common assumptions within stress theory, and phonological theory more generally, are in fact rather arbitrary. He proposes radical departures from recent tradition. In Part I he analyzes stress in the underived English lexicon, arguing that the basic accentual groups or “feet” are not monosyllabic or bisyllabic, as often assumed, but rather bisyllabic or trisyllabic. This analysis brings significant simplifications to other recent theorizing, including the elimination of standard extrametrically and all rules destressing. In Part II Professor Burzio deals with morphologically complex words, and argues that various phenomena of stress preservation, including the apparent stress “neutrality” of a class of affixes, are all predictable reflexes of a single principle of Metrical Consistency. In addition to a superior account of stress, the proposed metrical theory yields a unitary account of a wide spectrum of vowel-length alternations, in an overall conception of phonology which is modular, like that of contemporary syntax. The book makes a major theoretical contribution to the analysis of English word stress and to phonological theory.


The Acquisition of the Lexicon

The Acquisition of the Lexicon

Between the ages of eighteen months and six years, children acquire about eight words each day without specific instruction or correction, simply through the course of natural conversational interactions. This book brings together investigations from a variety of disciplinary backgrounds (with an emphasis on linguistics, psycholinguistics, and computer science) to examine how young children acquire the vocabulary of their native tongue with such rapidity, and with virtually no errors along the way. The chapters discuss a number of issues relating to the child’s mental representation of objects and events on the one hand, and of the linguistic input on the other; and the learning procedures that can accept such data to build, store, and manipulate the vocabulary of 100,000 words or so that constitute the adult state. Taken together, these essays provide a state-of-the art analysis of one of the most remarkable cognitive achievements of the human infant.


Proceedings of the Connectionist Models Summer School 1993

Proceedings of the Connectionist Models Summer School 1993

The result of the 1993 Connectionist Models Summer School, the papers in this volume exemplify the tremendous breadth and depth of research underway in the field of neural networks. Although the slant of the summer school has always leaned toward cognitive science and artificial intelligence, the diverse scientific backgrounds and research interests of accepted students and invited faculty reflect the broad spectrum of areas contributing to neural networks, including artificial intelligence, cognitive science, computer science, engineering, mathematics, neuroscience, and physics. Providing an accurate picture of the state of the art in this fast-moving field, the proceedings of this intense two-week program of lectures, workshops, and informal discussions contains timely and high-quality work by the best and the brightest in the neural networks field.

Edited by M.C. Mozer, P. Smolensky, D. Touretzky, J. Elman, & A. Weigend.


Il Connessionismo: Tra Simboli e Neuroni

Il Connessionismo: Tra Simboli e Neuroni

The Italian player who wants to know an authoritative perspective on the possible relationships between cognitive science and connectionism now has the excellent opportunity to do so with this volume. It is actually an Italian translation of a long article, published in 1988 in the authoritative of cognitive science journal “Behavioral and Brain Sciences”. According to the custom of the magazine, the article is followed by several speeches of researchers trained in different directions and different skills, with the author’s final reply.

The introduction of Marcello Frixione also reconstructs clearly and politically effective the premise of the dispute on cognitive science and functionalism. Smolensky presents in this paper a version of connectionism. He contrasts the “symbolic” models of classic cognitive science the “subsymbolic” models of connectionism, and proposes to do in the first high-level approximations of cognitive processes, which find their perspicuous and detailed description only the lower level (subsymbolic). In short, the symbolic models are placed at a level of abstraction or idealization greater than Connectionist, which are closest to the neurological level Smolensky. The conclusions of the analysis does not lead to interpret connectionism shared by others, that the low-level theories are intended to replace those of high level. On the contrary, “the purpose of subsymbolic research should not be to replace the symbolic cognitive science, but rather to explain the strengths and weaknesses of the existing symbolic theory.”

In this essay Smolensky also offers a first response to ‘ now famous critique of connectionism move by the staunchest supporters of functionalism and symbolic level, Jerry Fodor and Zenon Pylyshyn. They argued that connectionist models are inadequate models of cognition, because they can not reproduce some central features, easily captured instead by symbolic models, such as the ability of the mind to grasp the structural relationships between symbols, for example, the all-share (in Therein lies the so-called “compositionality” of the mind). According to Smolensky, the criticism of Fodor and Pylyshyn just apply to some versions of connectionism. This criticism has nevertheless raised a number of objections and counter-objections (even in subsequent interventions of the same Smolensky) that have invaded and continue to invade the magazines: the problem seems still far from being clarified satisfactorily. As yet not clarified, warns Frixione, is generally that of relations between symbolic models and connectionist models of cognition.


Active Vision

Active Vision

Active Vision explores important themes emerging from the active vision paradigm, which has only recently become an established area of machine vision. In four parts the contributions look in turn at tracking, control of vision heads, geometric and task planning, and architectures and applications, presenting research that marks a turning point for both the tasks and the processes of computer vision.The eighteen chapters in Active Vision draw on traditional work in computer vision over the last two decades, particularly in the use of concepts of geometrical modeling and optical flow; however, they also concentrate on relatively new areas such as control theory, recursive statistical filtering, and dynamical modeling.Active Vision documents a change in emphasis, one that is based on the premise that an observer (human or computer) may be able to understand a visual environment more effectively and efficiently if the sensor interacts with that environment, moving through and around it, culling information selectively, and analyzing visual sensory data purposefully in order to answer specific queries posed by the observer. This method is in marked contrast to the more conventional, passive approach to computer vision where the camera is supposed to take in the whole scene, attempting to make sense of all that it sees.


Data Fusion for Sensory Information Processing Systems

Data Fusion for Sensory Information Processing Systems

The science associated with the development of artificial sensory systems is occupied primarily with determining how information about the world can be extracted from sensory data. For example, computational vision is, for the most part, concerned with the de­velopment of algorithms for distilling information about the world and recognition of various objects in the environment (e. g. localization) from visual images (e. g. photographs or video frames). There are often a multitude of ways in which a specific piece of information about the world can be obtained from sensory data. A subarea of research into sensory systems has arisen which is concerned with methods for combining these various information sources. This field is known as data fusion, or sensor fusion. The literature on data fusion is extensive, indicating the intense interest in this topic, but is quite chaotic. There are no accepted approaches, save for a few special cases, and many of the best methods are ad hoc. This book represents our attempt at providing a mathematical foundation upon which data fusion algorithms can be constructed and analyzed. The methodology that we present in this text is motivated by a strong belief in the importance of constraints in sensory information processing systems. In our view, data fusion is best understood as the embedding of multiple constraints on the solution to a sensory information processing problem into the solution process.

From the The Springer International Series in Engineering and Computer Science.


Italian Syntax: A Government-Binding Approach

Italian Syntax: A Government-Binding Approach

In the course of our everyday lives, we generally take our knowledge of language for granted. Occasionally, we may become aware of its great practical importance, but we rarely pay any attention to the formal properties that language has. Yet these properties are remarkably complex. So complex that the question immediately arises as to how we could know so much. The facts that will be considered in this book should serve well to illustrate this point. We will see for example that verbs like arrivare ‘arrive’ and others like telefonare ‘telephone’, which are superficially similar, actually differ in a large number of respects, some fairly well known, others not. Why should there be such differencces. we may ask. And why should it be that if a verb behaves like arrivare and unlike tetefonare in one respect. it will do so in all others consistently, and how could everyone know it? To take another case, Italian has two series of pronouns: stressed and unstressed. Thus, for example, alongside of reflexive se stesso ‘himself which is the stressed form. one finds si which is unstressed but otherwise synonymous. Yet we will see that the differences between the two could not simply be stress versus lack of stress, as their behavior is radically different under a variety of syntactic conditions.