Theoretical implications of disordered syntactic comprehension

Language Sciences, Printed

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14, Number

112, pp. 129-153,

1992

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1992 Pergamon

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Theoretical Implications of Disordered Syntactic Comprehension1

Thomas C. Rindflesch

Jennifer E. Reeves

University of Minnesota

University of Minnesota

Michael B. Kac2 University of Minnesota

ABSTRACT We reexamine data from Caplan and Hildebrandt

1988 within the context of a different set

of background assumptions, concluding that where these can be clearly distinguished from those underlying GB theory the evidence favors a non-GB-based account. We attribute the deficits observed in the process of infinitival complement constructions to an inability on the part of the patients to access either or both of two data structures required to support our proposed parsing algorithm,

and show that on this account it is unnecessary to posit a compensatory heuristic

to account for the behavior observed. We also question some other cases where Caplan and Hildebrandt

advert to compensatory heuristics.

INTRODUCTION Caplan and Hildebrandt

(1988) present a series of detailed case studies documenting

the disordered syntactic comprehension of a group of aphasic patients and seek to interpret the observed disturbances within the framework of the theory of government and binding (Chomsky 1981). The notion ‘(phonetically) empty NP’ plays a crucial role in the interpretation, in part because of the authors’ decision to adopt the parsing model of Berwick and Weinberg (1984), and recourse to it is explicitly claimed to provide insight into the phenomena observed. In this paper, we reexamine the data within the context of a different set of background assumptions, concluding that where these can be clearly distinguished from those underlying GB the evidence

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Language Sciences, Volume 14, Number l/2 (1992)

favors a non-GB-based

account.

The issue which is raised here is a fundamental widely assumed

in contemporary

grammatical

one in the following

sense. It is

theory that the notion of a ‘syntactic

gap’ must somehow overtly enter into the formal description of constructions in which a position that can be occupied by an NP fails to be: put in psychological terms, a gap is taken to coincide with the position of the NP which is ‘mentally present’ even if not physically manifested in the speech signal (see especially Chomsky 1975: 123). It is thus commonly assumed that such positions must somehow be overtly marked in syntactic representations, an assumption characteristic not only of GB theory but also of generalized phrase structure grammar (Gazdar et al 1985) and lexical-functional grammar (Bresnan 1982).3 Disorders of syntactic processing could reasonably be expected to provide a good testing ground for this view (taken as a psychological hypothesis) given that in the theory of government and binding the various kinds of empty elements have crucial properties in common with overt ones, most particularly reflexive

and nonreflexive

pronouns.

If, for example,

we were to find difficulty

in

binding the former to their antecedents then we would expect to also find difficulties in binding NP-trace, whose properties are taken to parallel those of elements specified as [ -pronominall; similarly, difficulty in binding [ +pronominall elements would be expected to involve both overt pronouns and PRO. A related issue has to do with the notion ‘compensatory heuristic’, on which Caplan and Hildebrandt must rely given their particular background assumptions. In their view (Caplan and Hildebrandt: 281), the comprehension errors made by the patients must be a function not only of the loss of the ability to apply specific parts of the parsing algorithm but also of the substitution for the normal routines of strategies which give the correct results in at least some cases but which fail on the full range of syntactic constructions. On one level, this is a reasonable enough conclusion: if, for example, a tendency

a patient given a sentence

like It was Patrick that Nicholas saw displays

to take the first NP as the subject,

then it is natural to infer that a com-

putational routine distinct from the one normally used by speakers of English has been invoked. From this alone, however, very little follows: in particular, it does not follow that the substitute routine is ‘compensatory’ if what is meant by this term is that a language user forced to make use of such a routine has created a new processing strategy specifically in response to the impairment. Without denying that compensatory heuristics might arise in some cases, we would nonetheless suggest that there is no reason why it must automatically be concluded in a particular case that differences between abnormal and normal behavior are due to such a mechanism, since the possibility cannot be ruled out a priori that when the ability to correctly process a given type of construction is lost the observed behavior is a consequence solely of what abilities remain after the onset of the impairment without addition of anything that was not present prior to that point. All else being equal, the foregoing would seem to be

Disordered Syntactic Comprehension

the preferred

alternative

(where it is feasible) since it is more parsimonious:

anism need be posited that was not present premorbidly.4 “Further

commentary

on the notion

‘Compensatory

131

no mech-

We return to this point in

Heuristic’. ”

Three possibilities (at least) present themselves as alternative explanations to ones based on compensatory heuristics. Consider first the case where some aspect of processing is governed by a number of rules some of which apply when specific conditions are satisfied, and one of which represents the default case - that is, the case in which none of the aforementioned conditions are satisfied. We shall argue later that certain types of behavior reported by Caplan and Hildebrandt represent the loss of non-default rules in the internalized parser (more accurately, circumstances rendering these rules otiose) while the default rule remains unaffected; certain others strongly suggest Jakobsonian developmental regressiom5 in still others, there may be strategies in use part of the time even in normal processing which give results comparable to those used by aphasics. In any of the foregoing eventualities, there is no compensation in the usual sense of this term. But wherever recourse to the notion of compensation can be dispensed with, the resulting theory is simpler, ceteris pa&us, than it would be otherwise. We shall show below that this is in fact possible in several cases. Specifically, we show below that a treatment of infinitival complementation which does not advert to empty NPs obviates the need for a compensatory heuristic (whereas Caplan and Hildebrandt’s treatment, which makes crucial use of empty NPs, requires that such a heuristic be presumed to exist); we then show that in a number of other construction types, the strategies favored by aphasics are used in normal sentence processing as well, either by children or adults. The foregoing notwithstanding, the issue here is not between an approach which recognizes an independent role for syntax and one which does not: we take the interest of Caplan and Hildebrandt’s data to lie partly in the extent to which they support the view that there is a purely syntactic

component

to human linguistic

processing.

Nor

do we deny that the facts favor a syntactic framework which supports a parsing mechanism that recognizes, as ours in fact does, a principled distinction between raising and Subject control.6 Still less is it our intent to take issue with a principlesand-parameters approach to syntactic theory as opposed to some other variety - as should become apparent when we present the details of our own approach, which shares some of the characteristics of GB theory that justify affixing the ‘principlesand-parameters’ label to it. In this connection, however, we would caution that very little follows from the decision to adopt such a point of view in regard to what specific principles and parameters are to be recognized. The main question is that of whether the notion ‘empty NP’ has any role to play in regard to either.’

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Language Sciences, Volume 14, Number 112 (1992)

THE SYNTACTIC

FRAMEWORK

The approach to syntactic analysis to be assumed is a descendant

of the ‘corepresen-

tational’ model developed in Kac 1978 (see also Kac 1980 and 1985; Ryan 1983; and Rindflesch 1990) which, as in Kac 1985, we refer to as ‘framework F’. Some differences of terminology and emphasis aside it shares many individual characteristics with other theories of syntax, though the particular constellation of features is distinctive. Our description of it will be rather informal, in the interest of making the underlying ideas reasonably accessible. It is neither possible nor appropriate to seek to make the full case for the framework here, and we shall accordingly focus on those characteristics of it most directly relevant to the topic of this paper. A rigorous formalization in computational terms of many of the essential ideas can be found in Olawsky 1990. The grammatical structure of a sentence is taken to have two modes of representation, termed Categorial and Relational. The former delineates the meaningful expressions of which the sentence is constituted and assigns each to a syntactic category while the latter identifies relations between expressions, such as grammatical relations. This distinction may be thought of in the present context as parallel in essential respects to the one in LFG between c- and f-structure; and needless to say, the idea of direct reference to grammatical relations is shared with Relational Grammar. The pairing of a categorial and relational representation for a sentence is termed a Corepresentation. The categorial representation takes the form of an unordered labelled bracketing; an expression is accordingly completely determined by its subexpressions (if any); considerations pertaining to the manner in which the parts of an expression are deployed in a specific sentence or construction are thus irrelevant at this level. Similarly, the relational representation takes the form of a set of statements each of which asserts that some expression bears a specified relation to another (e.g. that in Patrick saw Nicholas, Patrick bears the relation Subject to saw). A crucial distinction is made between statements whose effect is to constrain the manner in which expressions are manifested in actual sentences and ones which pertain to the well-formedness of expressions regardless of how they are manifested. For example, French attributive adjectives must be distinguished as to whether they occur pre- or postnominally, and statements must thus appear in a grammar of French indicating which ones occur where. On the other hand, it is true of every attributive adjective in French, regardless of position relative to the modified noun, that the adjective must agree in number and gender with the modified noun - a paradigmatic manifestation-independent constraint on the well-formedness of attributive constructions. A grammar on this model is taken to consist of a set of constraints on the wellformedness of string-corepresentation pairings. Using terminology due to Olawsky (1990), the approach is Interdictive rather than Approbatory in that anything is

Disordered Syntactic Comprehension

allowed that is not explicitly detail, the approach A predication

ruled out. 8 Thus, despite differences

is in an obvious

and significant

(category label Pr) is an expression

133

at a finer level of

respect very like GB in spirit.

consisting

of a predicate (category

label P) and all arguments of that predicate. By A we denote the class of expressions which can serve as arguments of predicates, predications among them; an A which is not a predication, such as an NP, is a term (category label T). By P we denote the union of the class of predicates and the class of prepositions. An A which is identified as standing in an A-to-P relation to a P is said to be relationally analyzed. We take the arguments of a P to be just those As standing in A-to-P relations to it. We distinguish three A-to-P relations, which we designate by the traditional terms subject, (direct) object and indirect object, though we depart from traditional practice in reserving these terms for ‘logical’ rather than ‘surface’ grammatical relations. So, for example, in 7?re cur was washed by Patrick, we label Patrick as Subject of the verb and rhe cur as Object, just as we would do in the corresponding active - done in part to assume that generalizations motivating the notion of ‘initial 1’ in the terminology is necessary

of Relational Grammar can be properly handled.9 At the same time, it to also accommodate certain generalizations which cannot be formulated

in terms of these relations as we have defined them. Following Rindflesch 1990 we do this by means of a notion that is, to our knowledge, unique to this theory, namely that of what we term associates of a predicate. To explicate this notion, we consider first the active-passive relationship. In an active sentence, the Subject (in our sense) controls the agreement of the verb whereas in a passive, some non-Subject must act as the controller. We term the agreement-controlling element the essential associate of the verb; all other associates are contingent. i” The essential associate thus corresponds roughly to the ‘Surface Subject’ of classical transformational grammar (or ‘final 1’ in RG);” this analogy must be taken with a grain of salt, however, since we shall see directly that an essential

associate need not be an argument

verb with which it is affiliated.

Consider

in particular

in any relation of the

a sentence

like

(1) Patrick seems to be praying. Since Patrick in this sentence controls person and number

on seem in (l), Patrick

is the essential associate of seem in this sentence. However, we postulate that it is not an argument of seem, that is, bears no A-to-P relation to it. (We defer discussion of the Subject of seem.) It will be readily noted that associatehood without argumenthood is symptomatic of Ts which, in other frameworks, have undergone ‘raising’. Note also that this way of handling verbs of the seem type comports closely with the GB conception of such verbs as non-&role assigners. i* Predications are subject to a set of (putatively) universal constraints on wellformedness referred to as metaconditions. Two that are of special relevance here

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Language Sciences,Volume 14, Number 112 (1992)

are the Laws of Correspondence Law of Correspondence Every nonvocative

and Association,

as follows:

(Kac 1978: 32) T in a sentence

must bear an A-to-P relation to some P in that

sentence. I3 Law of Association (Kac 1978: 33) Every predicate in a sentence must have an argument Although a relational

the picture is still incomplete, analysis

is determined

in the relation

we can now illustrate

using the principles

Subject.i4

in more detail how

just presented.

Consider

first

(2) Bill wants to go. By Correspondence, Bill must be assigned at least one relational role, and by Association both want and go must have Subjects. One way to satisfy these requirements (in fact, the only way, though other elements of the grammar must come into play which we ignore here) is to analyze Bill as the Subject of both verbs. Note that this eliminates any necessity for a phonetically empty element to fill the Subject role for go. More generally, the familiar notion of ‘control’ is replaced in this approach by the notion of ‘argument sharing’ by distinct predicates. This notion bears an obvious kinship to that of multiattachment in Relational Grammar. (See also Postal and Perlmutter 1978 for an analysis of English to- contraction which employs argument sharing in almost exactly our sense.) For convenience, however, we shall continue to use the terms ‘raising verb’ and ‘control verb’ to refer to verbs of the seem and want types respectively. (3) Bill seems to Pete to go. Recall Law of predicate The only

that Bill, while the essential association of seem, is not its Subject.i5 But the Correspondence requires that Bill be analyzed as an argument of some in the sentence, and the Law of Association requires that go have a subject. way to satisfy both requirements simultaneously is to take Bill as the Subject

of go. (Note in particular that so analyzing Pete would satisfy the latter but not the former.) We thus have a case here of associate sharing that does not involve argument sharing; furthermore, the fact that it is Bill rather than Pete that is shared with go follows automatically from the Law of Correspondence given the characterization of Bill as a non-argument of seem.i6 To summarize, a P has both arguments and associates and while it is possible for an associate of a given P to also be an argument thereof, it is not necessary. In particular, ‘raising’ constructions are, in our terms, exactly those in which an associate

Disordered Syntactic Comprehension

of a P fails to also be an argument in terms of associatehood a given A may function

-

of that P. Certain generalizations

e.g. that essential

as an argument

associates

135

are formulated

control agreement.

Just as

of more than one P, as does Bill in (2), an

A may function as an associate of more than one P - as Bill does in (3). In the latter sentence, Bill is an (essential) associate of both verbs, but an argument only of go. It will be helpful later on to have all relevant lexical information for a number of English complement-taking verbs. We here select from the more comprehensive treatment in Rindflesch 1990, Chapter 6, limiting our attention to properties of superordinate verbs in infinitival complement constructions. The relevant parameters in the present context are: whether a P is associate-sharing; whether, in the event a P shares an associate, it is required that the associate in question be the essential associate; whether a shared associate of an associate-sharing P is also an argument thereof; and the relational role of a shared argument. In Table 1 below, we give the values for these parameters for five verbs: insist, want, seem, promise, persuade and believe. In the first two columns, + indicates that sharing is obligatory and - that it is prohibited, while a 0 indicates that sharing is permitted but not required. In the final column, the blank cells indicate that the parameter is not relevant to the associated verb (since seem and believe are classified as non-argument-sharing).

1 Lexical Properties of Selected Infinitival Complement-Taking Verbs TABLE

Associate sharing

Shares essential

Shared associate

Relational role of shared

associate

an arg.?

argument

yes no

Subject

yes

Subject Object

insist” want seem promise persuade believe

The following

yes no

additional

items of information

are also helpful.

Seem differs from

the other verbs in that if it occurs with a complement, the complement is its Subject, whereas all the others prohibit predicational Subjects; want allows its Object to be predicational whereas seem does not; finally, both promise and persuade allow two Objects, one of category T and one of category Pr. When we identify the shared associate of persuade as an Object, the intent is to require that this be the nonpredicational one. In the paradigm

136 (4)

Language Sciences, Volume 14, Number l/2 (1992) a.

John persuaded

Pete to go.

b. John wants Pete to go. c.

John believes

Pere is both a contingent an associate

Pete to be praying. associate and an Object of persuade

nor an argument

(5) Pete is believed

of want or believe in (4b-c).

in (4a), but is neither However,

in

by John to be praying.

Pere controls the agreement in the main clause and thus is the essential associate of believe. Since Pete is not an argument of believe, (5) is parallel to (3) in the important respect that in both cases the essential associate of the main verb fails to be an argument of it. The only difference between seem and believe in this respect is that seem must share a nonpredicational associate whereas believe need not (as in (4~)) thought it is not prohibited from doing so (as in (5)). One further property of seem that is relevant in this context is that the this verb may occur as either the essential associate (as in e.g. Thut John seems unlikely, the Subject-cum-essential associate in boldface) or as a one (e.g. John seems to be praying, the Subject-cum-contingent associate

Subject of is praying contingent of seem in

boldface and the essential associate underscored); in the latter case, the essential associate of the complement verb also serves as the essential associate of seem. PROCESSING

OF INFINITIVAL

COMPLEMENT

CONSTRUCTIONS

Normal Processing We now sketch the outlines of a parsing algorithm which handles the properties of infinitival complement constructions discussed above. The algorithm must be supported by two data structures: the first, termed the Must-Share Stack, holds the essential associate of any ‘raising’ verb while the second, termed the Might-Share Stack, holds the essential associate of ‘control’ verbs.i8. As will become apparent in due course, the circumstances under which the Must-Share and the Might-Share Stacks are invoked coincide exactly with whether a shared associate of the main verb in a complement construction is also an argument of that verb. In the Must-Share case (as noted in “The Syntactic Framework”) the Law of Correspondence requires that an associate of a complement-taking verb which is not an argument thereof be shared with some other verb in the sentence - whence the provision of the Must-Share Stack in the processing model. The provision of a separate Might-Share Stack, on the other hand, is necessitated by the behavior of verbs like wunr. We will produce examples shortly showing how the parser’s behavior when it has at least the option to use a

Disordered Syntactic Comprehension

137

stored T in identifying the essential associate of the complement verb depends on whether or not this stored T is an argument of the main predicate, and assuring that the parser can make this distinction by providing separate stacks. The relevant part of the algorithm itself can now be specified as follows:i9 I.

To find the essential associate for any verb: (i) If the verb is finite, go to (iv).2o (ii) If the Must-Share Stack is nonempty, choose the top of this stack. (iii) If the first T to the left of the verb is already relationally analyzed, choose the top of the Might-Share Stack if it is nonempty. (iv) Otherwise, choose the nearest T to the left of the verb.21

II. To find the nonpredicational contingent associate of any verb whose subcategorization allows such an associate: (v) Choose the first T to the right of the verb. III. Upon encountering a verb capable of taking an infinitival complement: (vi) If the essential associate of the verb is not an argument thereof, push the essential associate onto the Must-Share Stack. (vii)If the essential associate of the verb is an argument thereof, push the essential associate onto the Might-Share Stack (subcategorization permitting). We assume that verbs are considered in left-to-right order and that a complete iteration is made through all relevant parts of the module as each verb is considered. The following examples illustrate: (6) Bill wants to go. At the beginning of the parse, only (iv) is applicable since wants is finite; Bill is thus the essential associate of want (and is in turn analyzed as its Subject given the lexical features for this verb and that fact that it is active). Given that there is no T to the right of want, and that want may but need not have a T as a contingent associate, rule (v) is similarly inapplicable. Rule (vi) is inapplicable with want, so rule (vii) applies to place Bill in the Might-Share Stack. We then move on to go and iterate. Since the Must-Share Stack is still empty, (i) is inapplicable. Note, however, that Bill is relationally analyzed at this point (as the Subject of want) and the Might-Share Stack is nonempty, and hence that (iii) is applicable. Consequently, Bill is taken off the Might-Share Stack and assigned to go as its essential associate. (7) Bill wants Pete to go.

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Language Sciences, Volume 14, Number l/2 (1992)

On the first iteration, the parse proceeds exactly as it did before except that there is a T intervening between the two verbs. 22 On the second iteration, although the Might-Share

Stack is nonempty,

ally unanalyzed

the first T to the left of to go is to this point relation-

(recall from “The Syntactic Framework”

that Pete is not an argument

of wunt and hence is not relationally analyzed at the point go is encountered). Rule (iii) is therefore inapplicable and rule (iv) applies instead to identify Pete as essential associate of go. (8) Bill seems to Pete to go. On the first iteration,

Bill goes into the Must-Share

a contingent associate of seem. On the second iteration, Share Stack is occupied. (9) Bill promised On the first iteration,

Stack and Pete is analyzed

as

(ii) applies since the Must-

Pete to go. Bill and Pete are analyzed

respectively

as essential

associate

(and Subject) and contingent associate (and Object) of promise, and Bill goes into the Might-Share Stack. On the second iteration, since Pere is already relationally analyzed and the Might-Share Stack is nonempty, rule (iii) applies and Bill is assigned to go as essential associate. (10)

Bill persuaded

Pete to go.

Since Bill and Pete are both arguments

of persuade but persuade cannot share its

Subject with the verb of its complement, both stacks are empty at the end of the first iteration; on the second, neither (ii) nor (iii) is applicable (although Pete is relationally analyzed,

as Object of persuade, the Might-Share

Stack is empty) so (iv) applies to

assign Pete to go as Subject. Recall that the distinction between the two stacks is intended to reflect the difference in the way in which framework F treats raising vs control verbs. For example, in (11)

Bill seems to Pete to be praying.

Bill is not an argument of seems and consequently there is no way to satisfy the Law of Correspondence except by an analysis in which seem shares Bill with be praying. This is reflected in parsing by the placement of Bill in the Must-Share Stack on the first iteration. Compare now (12)

a. Bill wants Pete to go. b. Bill wants to go.

Disordered Syntax

Com~e~~ion

139

In the processing of both sentences, Bill is pushed onto the Might-Share Stack on the first iteration; the contents of the stack are employed, however, only in (12b). At the end of the first iteration, Pete in (12a) is still relationally unanalyzed so rule (iii) is inapplicable; at the same point in the parse of (12b), rule (iii) is satisfied since Bill is analyzed as Subject of want. The two examples are thus parsed in such a way that the Law of Correspondence (the requirement that every T be relationally analyzed) will be satisfied in (12a) only if Pere is taken as an argument of go given that this T is not an argument of wunr) while in (12b) the Law of Association (the requirement that every P should have a Subject) will be satisfied only if there is argument sharing. For contrast, consider a sentence like (13) Bill promised Pete that John would go. As in (9), Bill is placed in the Might-Share Stack on the first iteration. However, since the complement has a finite verb (woman the algorithm simply skips over (ii-iii) altogether. If we assume that the parser does not have access to following material at the time it encounters promise, it must be prepared for the eventuality that the Subject of promise will be shared with the complement verb; but this eventuality will arise only if the latter is in a nonfinite form. (Hence the designation ‘Might-Share’ for the associated memory location.) It is also worth taking a moment to describe how the algorithm treats the sentences (14) a. It seemed to Bill to be getting smaller. b. It seemed to Bill that Pete was getting smaller. In (14a), it is an ordinary referential pronoun while in (14b) it is the ‘expletive’ it associated with extraposition; correspondingly, only (14a) is a ‘raising’ construction. This difference is reflected in the operation of the parser by virtue of the fact that while, in either case, if goes into the Must-Share Stack, it is analyzed as an associate of the complement verb (actually, in this case, the auxiliary-verb complex) only in the first. To summarize: the ‘raising’ construction, in our terms, is one in which the essential associate of the main verb must be shared with the complement verb; the ‘control’ construction is one in which such sharing of the essential associate of the main verb can occur (as in Bill wants to go but need not (as in Bill wants Pete to go). Verbs like seem are lexically marked as able to enter into the former but not the latter, while verbs like want and promise are marked in the opposite fashion. Depending on which type of verb occurs, the essential associate goes into one or the other of two memory locations, thus assuring that when the complement verb is encountered the parser ‘remembers’ what kind of main verb it was dealing with.

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Language Sciences, Volume 14, Number 112 (1992)

Suppose disturbances

that it assumed,

as it indeed

of comprehension

during parsing.

is by Caplan

are due to impairment

and Hildebrandt, of the workspace

Note that in our model, insofar as it applies to infinitival

that some employed complement

constructions, there are three imaginable forms of such an impairment: one affecting the Must-Share Stack, one affecting the Might-Share Stack, and one affecting both. This would lead us to make the following predictions: that there should be patients who experience difficulty with raising but not control; that there should be ones who experience difficulty with control but not raising; and that there should be patients who experience

difficulty

and Hildebrandt’s Impaired

with both constructions.

This prediction

is borne out in Caplan

data, as we see in the next section.

Processing

The first group of cases we will consider

includes

two especially

interesting

ones,

namely patients JV and GG, who had little difficulty on most of the constructions considered by Caplan and Hildebrandt but could not reliably process sentences such as Patrick seems to Joe to be praying, and/or Patrick promised Joe to wash. In both kinds of sentences, the failure consisted in taking Joe rather than Patrick as the Subject of the complement verb. In addition, two more severely impaired patients (KG and GS) had difficulties with these structures. The data are shown in Tables 2 and 3 below .23

TABLE 2 on Patrick seems to Joe to be praying24

Performance

lV* 2v Other

JV

GG

KG

GS

25 75 0

0 100 0

33 58 8

92 8 0

Performance

1v* 2v

TABLE 3 on Patrick promised Joe to wash

JV

GG

KG

GS

100 0

17 83

75 25

50 50

Disordered Syntactic Comprehension

These cases present certain difficulties it is problematical

for Caplan and Hildebrandt.

within their framework

GG. If JV is considered

to reconcile

to have difficulty

binding

141

For example,

the patterns shown by JV and

across an SIboundary,

then PRO

must be presumed bound not in the syntax but in the propositional list. If this is so, however, then GG is anomalous since he has difficulty with both types of structures; another possibility that must be considered then, is that PRO is coindexed in the syntax and that JV’s impairment consists in difficulty in transmitting a O-role while GG’s impairment consists in difficulty in coindexing NP-trace and PRO across an S’ boundary.

However,

as shown in Table 4, this does not put an end to the matter since

none of the patients in this group has difficulty binding PRO across such a boundary when the controller is an Object rather than a Subject. TABLE

4

Performance on Patrick persuaded Joe to wash

2v* 1v

JV

GG

KG

GS

100 0

100 0

100 0

92 8

Note that there are two problems here. First, there is no explanation of why patients consistently treat seem and promise on the model ? persuade and not the other way around.25 More seriously, if all that were involved were the loss of the ability to bind a PRO or an NP-trace across an Sboundary, then we would expect some sort of difficulty with the persuade class of verbs as well as the promise and seem type. To resolve this anomaly, Caplan and Hildebrandt must postulate a compensatory heuristic, one which says in effect to take the first NP to the immediate left of the subordinate verb as the essential associate regardless of the properties of the superordinate verb. Further complications arise from that fact that there is a patient (GS) who has difficulty

with Subject control but not raising.

The problem here is in reconciling

GS

with GG under the assumption that PRO is coindexed in the syntax, since if PRO and NP-trace are both bound in the syntax then GS is unaccounted for whereas GG’s behavior is unexplained if PRO is taken to be bound in the propositional list. Note further that if we return to the view that PRO is coindexed in the propositional list, then the difficulty reemerges of reconciling GG and JV. It is therefore necessary for Caplan and Hildebrandt to claim that GS suffers from an impairment which is of a different type from those seen in the other patients under discussion, involving difficulty in initiating a gap-hunting procedure. Without going into further detail, we think it fair to suggest that interpretation of the behavior of the patients in this group within Caplan and Hildebrandt’s conceptual framework is less than entirely straightforward

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Language Sciences, Volume 14, Number 112 (1992)

and that recourse The conception described

to empty NP’s does not obviously of syntactic

in the preceding

processing

confer any special advantage.

of in~nitiva~

section suggest an alternative,

~ompiement

const~ctions

namely that the crucial char-

acteristic with respect to comprehending sentences containing infinitival complements which distinguishes aphasic patients exhibiting the disorders under discussion from nonaphasics is that the aphasics suffer impairment affecting access to one or both of the memory facilities needed to support our proposed algorithm for processing in~nitival complements. Thus in our analysis, patients such as JV who have difficulty with raising

but not with Subject control

suffer an impairment

affecting

the Must-

Share Stack not the Might-Share Stack. Those with the opposite problem such as GS, have an impairment affecting the Might-Shark Stack but not the Must-Share Stack, while those who experience problems with both constructions have both stacks impaired. The difficulties experienced by the patients in this group with infinitival complements can all be accounted for by the supposition that when the time comes to retrieve stored items from the Must- or Might-Share Stack, this structure is empty. This means that only (iv), the default rule, will ever be involved in the parsing sentences with control or raising verbs. But since, on our account, neither stack is needed for identifying the arguments of infinitival complements of persuade-type verbs, impairments affecting one or both these structures have no effect on patients’ ability to deal with Object control. Notice as well that given the impairment-ofworkspace hypothesis, which we share with Caplan and Hildebrandt, the model proposed in the section “Normal Processing” and independently motivated as the basis for an account of normal processing predicts the observed pattern. The model assumed by Caplan and Hildebrandt preting what has occurred,

provides them with a variety of post facto ways of interbut does not seem to have the same predictive force.

It is unclear what precisely causes the Must- or Might-Share an attempt is made to retrieve its contents, themselves

for consideration

but two possibilities

Stack to be empty when that naturally

present

are first, that the ability is lost to insert items into these

memory locations; and second, that the contents of the two structures are subject to abnormally rapid decay, making it impossible to hold an item in memory long enough to have it available for retrieval at the appropriate point. (Note that one could occur in some cases and the other in others.) Fu~ermore, the inde~ndence of the stacks naturally allows the possibility that although both stacks may be impaired, one may be affected more severely than the other. Such may be the case with KG, who experiences difficulty with both raising and control but to differing degrees. One possible objection to the foregoing is that while it accounts in uniform fashion for behavior on infinitival complements, it does not generalize beyond such constructions. By way of response, we would first point out that although Caplan and Hildebrandt provide a comprehensive account of the data, it is not especially elegant. They fail for a number of patients to provide, in each individual case, a uniform

Disordered Syntactic Comprehension

analysis

which accounts

for that patient’s

difficulties

with all the construction

143

types

considered. (For example GS’s performance on subject control sentences is attributed, in Caplan and Hildebrandt’s analysis, to difficulty in initiating gap-hunting procedures. However, his performance on relative clauses is also impaired, but is assumed to be due to some other deficit.) They also fail to provide an analysis for each structure type valid across patients, whereas we are at least able to present a simple and coherent picture for all the patients in this group with regard to a class of structures on which all have difficulty regardless of other differences (which are considerable). Further, in the individual cases, we do not encounter any of the uncertainties which prove so troublesome for Caplan and Hildebrandt. More positively, we would submit for consideration the proposal that grammars and parsers may be modularized in a way which parallels traditionally recognized divisions among construction types - at the very least that there are rules specific to infinitival complementation. The thrust of GB theory is very much antithetical to such a view, which is nonetheless rendered plausible by the fact that infinitival complement constructions appear to be distinctive in involving restrictions on sharing tied to lexical properties of specific verbs. (For example, though there can be sharing in coordinate structures, as in John run and jumped, lexical properties of the verbs involved do not come into play in the same way as in infinitival complementation.) One part of our algorithm, namely Part III, pertains exclusively to verbs which may enter into infinitival complement constructions while rules (ii-iii) of Part I pertain exclusively to verbs in infinitive form, so that the overall approach embodies exactly the sort of modularization that we have just suggested. Some support for this view comes from the cases of GG and AB in that, in different ways, they suggest that infinitival complement constructions difficulties involve only

do indeed have a special status in processing. Patient GG’s such constructions. AB adheres to a rigid first-NP-asessential-associate strategy in the processing of some sentences, but not all: specifically, in all sentences containing relative clauses he takes the initial NP of the sentence as the essential associate of both verbs but he responds correctly to the simplest subject control cases (i.e. those not involving reflexive anaphors or pronominals) only 33% of the time -

indicating

that he does not use this strategy frequently

(if at all) in such

cases.

(If he did, he would get consistently correct results on sentences like Bill promised Pete to shave.) The view that there are no construction-specific rules (or parsing strategies would lead us to expect that such a pattern would be impossible quite wrongly, as it turns out. SOME

FURTHER

DIFFICULTIES

We would also point out that there are problems of another kind confronting based analysis. We find impairments characterized by all of the following:

a GB-

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Language Sciences, Volume 14, Number 112 (1992)

(i) inability (ii) inability

to correctly

analyze

reflexive

anaphors

NP-trace,

and NP-trace;

to correctly

analyze

but no impairment

relative

to correctly to correctly

analyze overt pronominals and PRO; analyze PRO, but no impairment relative

to overt

reflexives; (iii) inability (iv) inability

to overt pro-

nominals. The GB analysis in concert with the Berwick-Weinberg parser would lead us to expect to find patients exhibiting (i) but not (iv), as well as patients exhibiting (iii) but not (ii). Such dissociations would be expected since separate conditions of the Binding Theory apply to NP-trace and PRO, these being respectively the conditions for anaphors and pronominals. However, no such patients are found in Caplan and Hildebrandt’s ~pulation. Rather, the following patterns are among those found: (v) inability to correctly bind reflexive anaphors and impairment in binding of all empty categories, without impairment of the ability to bind pronominals (patient AB); (vi) inability to correctly bind overt pronominals and impairment in binding all empty categories, without impairment of the ability to bind reflexive anaphors (patient CV); (vii) inability

to correctly

RL). This pattern

is consistent

bind WH-trace

and, possibly,

with the hypothesis

NP-trace

(patients

SP and

that empty NPs are problematical

regardless of their specification for [pronominal] and thus that the ability to bind such NPs is independent of the ability to bind overt anaphors and pronouns. But the absence of the predicted patterns means that there is no support in the data for the strategy, central to GB theory, of seeking to generalize the constraints on control and raising with constraints on the coindexation of overt elements. An issue which must nonetheless be addressed has to do with the fact that Caplan and Hildebrandt (13)

report a difference

a. John promised b. John promised

in ease of processing

between

sentences

like

Bill that he would shave. Bill to shave.

the latter being more difficult than the former. This result is claimed to be precisely what would be expected given the Berwjck-Weinberg parser since there is an additional computational step in the processing of (13b) consisting of the creation of the empty complement Subject. But if this interpretation were correct then it would be expected that all control structures would impose such a burden, not just those involving Subject control. We would thus expect that Object control should pose similar difficulties, which it does not. It should be noted that one prediction of the GB analysis is borne out in Caplan and Hildebrandt’s data, namely that no patients should show impairment in the handiing

Disordered Syntactic Comprehension

of overt pronominals corresponding

and anaphors

empty categories.

such an analysis

while experiencing

no difficulty

In the light of the foregoing

14s

with the putative

discussion,

would appear to create at least as many difficulties

however,

as it solves,

engendering a measure of scepticism as to its viability over the long term. As a tentative first step toward developing an alternative, we advance the admittedly speculative suggestion that the Might-Share Stack (which is involved in the processing of (13b) but not (13a)) is more fragile than is the mechanism (whatever it might be) which is involved in processing the coreference of pronouns. If the more robust mechanism for processing pronominal coreference is impaired, the more sensitive mechanisms of the Might-Share Stack is also impaired, but the reverse is not true. The more delicate Might-Share Stack may be impaired, while the more resilient mechanism for processing pronominal coreference remains intact. FURTHER COMMENTARY HEURISTIC’

ON THE NOTION

A key feature of our proposal regarding

infinitival

‘COMPENSATORY

complements

is that it does not,

in contradistinction to Caplan and Hildebrandt’s, require recourse to a compensatory heuristic. Rather, we attribute the observed behavior to an impairment the workspace supporting the relevant part of the parsing algorithm which has the consequence that certain rules in the parser are rendered otiose even though they remain intact; the question then naturally arises as to whether it is necessary to postulate compensatory heuristics in the processing of other types of constructions. The weight of the evidence might, primfacie,

appear to favor an affirmative

answer. For example, those patients

who fail to distinguish active and passive appear to be applying a heuristic calling for consistent assignment of the relation Logical Subject to the essential associate of the verb, while patients who experience difficulties with e.g. object-extracted clefts appear to be applying

a heuristic

calling

for consistently

treating

the first NP of a

sentence or clause as the essential associate of the verb of the sentence or clause. In the first case, however, it is not clear that there is any need to talk in terms of heuristics since the possibility is open of attributing the behavior to an impairment which amounts to inability to recognize the significance of the trappings of the passive construction. In regard to the second case, we find it significant that Bates et al. (1984) report that 4- and (to a lesser extent) 5-year old English speakers show a definite tendency to take the first N in an NNV sentence as the essential associate of the verb when either could (on grounds of animacy) be so construed without violation of pragmatic plausibility considerations. This in turn casts doubt on the idea that the strategy employed by the adult aphasics has arisen as part of a compensatory mechanism triggered by the onset of the disorder; rather, we would appear to be looking at a clear case of developmental regression. We here reiterate our comment

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Language Sciences, Volume 14, Number l/2 (1992)

in note 5, to the effect that the developmental in good standing; young children,

but the similarities

regression

hypothesis

is not currently

that we have just noted between

if not merely coincidental,

aphasics

and

are quite striking.

A different test of our claim that aphasics can make existence at the time of the onset of the disorder can be for performance on sentences containing relative clauses work on relative clause comprehension by children and The methodology of these studies is different in certain

use of strategies already in made by comparing the data with the results of Sheldon’s adults (1974a, b and 1975). respects from that used by

Caplan and Hildebrandt, which makes the following somewhat nonetheless that the similarities that we shall note are sufficiently

speculative; we think suggestive to warrant

closer investigation. Sheldon compares performance on sentences of four types also considered by Caplan and Hildebrandt: those in which a Subject relative (e.g. the dog rhar bit rhe car) appears in Subject and in Object position in the main clause; and those in which an Object relative (e.g. the car that the dog bit) appears in each of these positions in the main clause. This leads to a four-way classification of sentences hereinafter designated SS, SO, OS, 00 (where the initial letter of the abbreviation refers to the function of the entire construction in the main clause and the second to the function of the head noun within the construction). Following Sheldon’s terminology, we say that the SS and 00 types involve parallel function and that the SO and OS types involve nonparallel function. Sheldon’s results are reproduced below: TABLE Performance

I

II III Freq. mean

(From Sheldon

by Normal

Children

5 on Relative

Clause Types

ss

so

OS

00

1.0 1.45

0.18 0.73

0.54 0.91

1.36 1.64

2.27 1.58 > 50%

0.64 0.52 < 25%

1.17 0.88 > 25%

1.55 1.52 > 50%

1971a.)26

For comparison, we tabulate in similar fashion the performance on each of the four types of the patients in Caplan and Hildebrandt’s population, omitting those whose performance did not differ from that of normal adults. It will be observed that essentially the same pattern is found in both populations in regard to the SX cases: all patients do noticeably worse on SO than on SS. At the same time, we do not see a clear replication for the aphasics of the pattern observed in

Disordered Syntactic Comprehension

TABLE Performance

SP RL AB

regard to OS vs 00:

6

by Aphasics on Relative Clause Types

ss

so

OS

00

50%

20% 20% 17%

54.5% 70%

77.7% 80% 0% 17%

50% 75% 17% 83% 83%

cv KG GS

147

0% 92% 83% 58%

0% 25% 25%

Sheldon’s data show, in general,

lel function as compared to nonparallel

58% 50%

superior performance

on paral-

function cases whereas half of the aphasics do

at least somewhat better (and CV performs vastly better) on the nonparallel function OS type than on the parallel function 00 type. At least a partial resolution of this anomaly can be obtained by looking at individuals from Sheldon’s study (Table 5 giving only group means). We find in doing so (Sheldon 1974b: 53ff.) that although the pattern is not common, there are children in Sheldon’s population who did better on the OS than on the 00 structures: Sl 1 from Group I and S3 and S5 from Group III. Further, a pattern not unlike that shown by GS (whose percentages on the OS and 00 types are almost identical) also manifests itself in a few cases: S7 and S9 in Group I, S 1, S8 and S 11 in Group II and S2 in Group III. Finally, there are children in Sheldon’s population who, like AB, never correctly interpret either the 00 or the OS type (SlO from Group I, Sl, S4, S7 and SlO from Group II and S7-11 from Group III). It is thus possible,

in at least some of the anomalous

cases, that developmental

regression has occurred. There is, however, another possibility to be considered, namely that there is a strategy which, while overridden most of the time, is nonetheless used at least occasionally

even by normal

adults.

This is suggested

by the results

reported in Sheldon 1975, which show normal adults doing better on the OS type than on any of the others. We conclude from these data that there are ways of accounting for the observed behavior on relative clauses which do not require any auxiliary assumptions regarding heuristics: in all cases, performance is consistent either with attested patterns in young children or adults, suggesting that the strategies used by the aphasics are not developed ex niholo.27 Does this mean that compensatory heuristics are never used by aphasics? We stop short of answering this question in the affirmative. Nonetheless, there is a danger in over-reliance on this notion. First, it is unparsimonious: it seems preferable on the face of it to attribute as much as possible in the patterns of disordered comprehension to characteristics of the mechanism that do not have to be posited ad

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Language Sciences, Volume 14, Number l/2 (1992)

hoc for disordered processing but have a role in normal processing as well. Second, it invites misuse. Consider, for example, the fact that Caplan and Hildebrandt attribute some disturbances

of the ability to handle infinitival

complements

to inability

to bind

across an Sboundary. This interpretation would appear to be contradicted by the fact that Object control is unproblematical for patients to whom this inability is attributed. To posit a compensatory heuristic to rescue the interpretation should, we think, arouse some suspicion. It would appear preferable to build in a methodological bias against recourse to compensatory heuristics and in favor of a search for interpretations of observed behavior that make use of independently motivated principles. Our case would perhaps be overstated selves in a number SUMMARY

but for the fact that such interpretations

do suggest them-

of instances.

AND CONCLUSION

We have argued two interrelated

points regarding

the theoretical

interpretation

of

the behavior of patients in Caplan and Hildebrandt’s population. The first is that disorders in the comprehension of infinitival complement constructions are better accounted for via a parsing model deriving from a syntactic theory in which empty NPs play no role. The second is that there is reason to view the notion ‘compensatory heuristic’ with some suspicion - at the very least, it appears to be possible to rely on it to a lesser degree than Caplan and Hildebrandt suggest. In a previous section we showed that no such heuristic need be posited on our analysis in order to account for the observed dissociation between Subject and Object control, whereas Caplan and Hildebrandt are forced by their account (which makes crucial use of the notion of binding of PRO) to postulate such a heuristic; and in “Some Further Difficulties”, we showed that strategies

used by aphasics

in processing

relative

clauses

are also

attested in normal comprehension by children and adults, suggesting that compensatory mechanisms are not involved in these cases either. Even if compensatory heuristics cannot be eliminated entirely (see again note 27), matters are considerably simplified

by avoiding

them where possible.

A subsidiary claim is that the view that there are no construction-specific grammatical rules and parsing routines may be incorrect. There are properties of infinitival complement constructions which appear to be unique to this class and there is also some evidence from disordered comprehension that strategies employed in one construction type (such as relative clauses) do not carry over into others - as seen most particularly in the case of AB, whose ‘first NP as Subject’ strategy in processing relative clauses does not help him with Subject control in infinitival complements. GB theory gives no reason to expect such results and some reason not to, whereas they are unsurprising given our framework. We will conclude with a remark concerning modularity. We would point out first

Disordered Syntactic Comprehension

that it is one thing to subscribe in the language

149

to the view that there is a degree of modularization

faculty, quite another to specify exactly what the modules consist of.

There is no reason a priori to not entertain at least as a working hypothesis that the notion ‘grammatical construction’ holds an important key to the delineation of the modules comprising the language faculty. We would also point out, without taking a dogmatic stand on the issue, that there is a challenge here to a non-modularist point of view in that it is not obvious in what other cognitive domains one might find analogues to the Must- and Might-Share Stacks, on which our treatment crucially depends. NOTES 1.

2.

Earlier versions of this paper were presented at the 1989 Annual Meeting of the Linguistic Society of America and to the colloquium of the Program in Language and Cognition at Northwestern University. We would like to thank Joseph Stemberger for directing us to some of the relevant psychological literature. Rindflesch is presently affiliated with the National Library of Medicine and

3. 4.

Reeves with the National Institute of Education. See, however, Kaplan and Zaenen 1986 (also Sells 1985: 179ff). We will in fact advance an even stronger methodological suggestion, recourse move.

5.

to compensatory

should

state stage of language

later in the paper. Caplan and Hildebrandt’s

criticism

acquisition,

Strictly speaking, Classical

is accordingly

the data under consideration

trace, and are neutral 8.

but a fallback

a claim that we shall document

of Lexical-Functional

dently does not support such a distinction, 7.

never be anything

We recognize that enthusiasm for developmental regression has waned among aphasiologists. There do, however, appear to be circumstances where it is difficult to ignore the similarities between aphasic behavior and that of children in a pre-steady

6.

heuristics

namely that

Grammar,

which evi-

entirely apt in our view.

here bear only on PRO and NP-

with regard to pro and WH-trace.

phrase structure

grammar,

by contrast,

is approbatory

in that nothing

is allowed that is not explicitly sanctioned by rule. Mixed cases also exist, such as GPSG, in which some rules (such as the ID-rules) are approbatory and others (such as feature co-occurrence restrictions) interdictive. GB appears largely interdictive. 9. See especially Perlmutter 1982. 10. Our discussion here is confined to English; in languages where the verb agrees simultaneously with more than one argument, essential associatehood will have to be defined in a more complex way. The possibility is also open of there being

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Language Sciences, Volume 14, Number l/2 (1992)

languages

to which the notion is not relevant.

11. It is a further nominative

property

of essential

associates

(in English)

that they occur in

case.

12. Limitations of space prevent a complete exposition of the notion of associatehood and the relevant rules; these are developed in detail in Rindflesch 1990. See also the discussion of lexical properties of complement-taking verbs below. 13. Compare the &Criterion of GB. 14. Compare the Extended Projection Principle. 15. The subject of seem in this example is Bill . . . to go; see Table 1. 16. This discussion does not address the question of how it is determined that Pete is the contingent associate. There is an English-specific principle to the effect that the default position for contingent associates of predicates is to the right, If Pete is taken as the contingent

associate

of seem, then it must be a non-Subject

(this

role being reserved, in a nonpassive sentence for the essential associate); by Association there must be a Subject, however, and by Correspondence Bill must be relationally analyzed, both requirements being satisfied by taking Bill to be the Subject of seem. Finally, since Subjects are essential associates of nonpassive predicates, it follows as well that Bill is the essential associate of seem. 17. The properties that we give here are associated with this verb when it occurs in ‘unextended’ form, that is, without a supporting preposition. In e.g. John insisted on going, the essential associate (and Subject) of the main predicate is shared; however, compare *John insisted going/to go. 18. We assume the two structures to have the form of stacks because of sentences like John seems to the girl who appears to Bill to be praying to be washing, which would -

under normal assumptions

the Must-Share girl) is analyzed

-

require that both John and the girl be in

facility until the point at which the most recently stored item (the as the Subject of be praying,

at which point it can be taken off

the stack exposing John for later use. (An analogous argument for the MightShare Stack can be made using a sentence like John promised the girl who wants to pray to wash.) 19. We have deliberately ignored many details here which would have to be taken into account in a complete specification of the algorithm but which are not of direct relevance here. We also omit the rules (which are entirely straightforward) for assigning relational roles to associates acting as arguments. Finally, we note that this formulation does not rule out ill-formed input in all cases. 20. We oversimplify here; in a tripredicational sentence like It seems that Bill wants to go, it would wrongly be taken as essential associate of go. However, only bipredicational structures are under consideration here. 21. Strictly speaking, this is the default rule only in cases where essential associates occur in their canonical positions - as compared e.g. to Who did Patrickpersuade

Disordered Syntactic Comprehension

to go?, in which who rather than Patrick is the essential Caplan and Hildebrandt processing

associate of go. Since

do not treat such cases in their discussion

of sentences with infinitival

complementation,

151

of impaired

we restrict our attention

to sentences of the type with which they do deal. 22. Rule (v) is presumed not to apply since, given the treatment in Rindflesch 1990, want is subcategorized as not taking nonpredicational contingent associates in infinitival constructions. 23. The first column in each table indicates the patient’s analysis. ‘V’ refers to the subordinate verb, while the numbers refer sequentially to the NPs in the sentence. The number preceding ‘V’ indicates the subject of that verb, the one following, the object. ‘2V’ thus means that the patient interpreted the second NP as the subject of the subordinate verb. Asterisks mark correct analyses. 24. A GB analysis predicts that passivized Sdeletion and raising should pattern similarly in disordered processing; that is, if there is a deficit in one of the structures then there should be a deficit in the other - a prediction which is in fact borne out in the data. Note that the same prediction is made by our analysis because in both these structures, the essential associate of the superordinate P is shared with the subordinate but is not analyzed as an argument of the superordinate. 25. There is a patient, namely CV, who on sentences like Patrick asked Joe himself, takes Patrick as the Subject of pinch and the antecedent of However, she correctly identifies the Subject in Patrick persuaded Joe 83% of the time (taken by Caplan and Hildebrandt to be within normal suggesting that what is involved in the other case has specifically to something other than control.

to pinch himself. to wash limits), do with

26. Roman numerals denote age groups. I = 3.8-4.3 years; II = 4.6-4.11; III = 5.0-5.5. There were 33 subjects in all, 11 in each age group. Each cell shows the mean number of correct answers (of 3) for the entire age group; at the bottom of each column is an indication (added by the authors) of the percentage of correct answers represented by the mean for the entire column. For example all age groups taken together scored above 50% on the SS type but less than 25% on the SO type. 27. This should nonetheless not be taken to imply that aphasics do not on occasion devise makeshift strategies. For example, Caplan and Hildebrandt note in connection with patient CV (p. 233) that she appears to have adopted the expedient of always taking the word friend as a Logical Subject in all sentences containing it. They suggest, however, that this is due to the fact that friend does indeed turn out to be the correct answer for a majority of the test items.

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Language Sciences, Volume 14, Number l/2 (1992)

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