Accessing lexical ambiguity in different types of sentential contexts

JOURNAL

OF MEMORY

Accessing

AND

LANGUAGE

27, 324-340 (1988)

Lexical Ambiguity

in Different Types of Sentential

Contexts

PATRIZIA TABOSSI Universitci

di Bologna,

Bologna,

Italy

Access of ambiguous words was investigated in three cross-modal experiments using the same ambiguous items and the same task (lexical decision), but different types of sentential contexts and semantic relations between an ambiguity and its paired target word. The results demonstrate that in a context biasing its dominant meaning, an ambiguity can be accessed selectively or exhaustively depending upon whether the context places sufftcient constraints on the semantic features of its contextually congruent meaning. Different semantic relations between the ambiguity and the subsequent target word, namely, association and feature-denoting, did not alter this pattern of results. It is argued that the dominant meaning of an ambiguous word can be selectively activated-and the cross-modal technique reflects this activation-provided that the ambiguity occurs in a sufficiently constraining sentential COtIteXt. 0 1988 Academic Press, Inc.

Lexical ambiguity is a pervasive phenomenon in language. It is therefore not surprising that a great deal of current research in psycholinguistics is devoted to the study of how people understand ambiguous words, in particular to the study of when context becomes effective in determining their contextually appropriate interpretation. Although there is no doubt that context operates effectively in specifying the appropriate meaning of ambiguous words, many studies on lexical access suggest that context takes time to have its effect and that all the meanings of an ambiguous word are initially activated (Cairns & Kamerman, 1975; Conrad, 1974; Dooling, 1972; Foss, 1970; Foss & Jenkins, 1973; Oden & Spira, 1983; Swinney, 1979; Tanenhaus, Leiman, & Seidenberg, 1979). These studies support the hypothesis that The present research was supported by C.N.R. (Grants CT. 84.1659, CT 85.2567, and CT 86.1131). I would like to thank Curt Burgess, Corrado Cavallero, Gray Dell, Susan Gamsey, Padraig O’Seaghdha, and Mike Tanenhaus for their helpful comments and support. Requests for reprints should be sent to Patrizia Tabossi at Dipartimento di Psicologia, Viale Berti-Pichat 5, 40127, Bologna, Italy.

lexical access is an exhaustive, context-insensitive process: all meanings of a lexical ambiguity are initially accessed, regardless of their context of occurrence, and context intervenes in selecting the appropriate interpretation of the lexical item only subsequently, at a postaccess stage. While providing evidence for the context-insensitive view, this work does not take into account possible effects of dominance on lexical access. This issue was initially addressed by Hogaboam and Perfetti (1975), who asked their subjects to decide whether or not the last word in a sentence was ambiguous. The sentence, which was presented visually, biased either the dominant or the subordinate meaning of the ambiguity. The results showed that the subjects were faster at detecting a homograph when it occurred in a sentence that biased its subordinate rather than its dominant meaning. According to the authors, these findings support an ordered search model of lexical access in which the dominant meaning of an ambiguity is accessed first, regardless of context, and is then matched for congruence with context. Only when this matching fails, does the search continue and the next most frequent meaning 324

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LEXICAL

ACCESS AND SENTENTIAL

is accessed and matched for context congruency. Unfortunately, in this study reaction times measure the time required to a subject to consciously search and detect an ambiguity. But a similar task requires processes different from those used in normal language comprehension. Moreover, it is certainly a postperceptual task which is more likely to reflect postaccess phenomena rather than immediate access ones. Perhaps one of the most compelling pieces of evidence on whether context and dominance can affect lexical access comes from Onifer and Swinney (1981), who used a cross-modal priming paradigm (Swinney, Onifer, Prather, & Hirshkowitz, 1979). They had their subjects listen to sentences such as: (1) The housewife’s face literally lit up as the plumber extracted her lost wedding ring from the sink. (2) The office walls were so thin that they could hear the ring of their neighbor’s phone whenever a call came in. Sentence 1 biases the dominant meaning of ring, whereas sentence 2 biases its subordinate meaning. The visual words, which were presented precisely at the offset of ring, were related to one of the meanings of the ambiguity or were unrelated control words (FINGER-TALENT; BELLWHIP). The results showed that sentences 1 and 2 facilitated lexical decision on FINGER and BELL, which were both faster than their controls, whereas no effects of either context or dominance were found. Thus, according to Onifer and Swinney (1981), neither dominance nor context affects the initial activation of the meaning of a word, whose access is an autonomous subprocess of the process of language comprehension. Though widely accepted, this view has not gone unchallenged, and indeed several studies have failed to support it (Glucksberg, Kreutz, & Rho, 1986; Schvaneveldt, Meyer, & Becker, 1976; Swinney & Hakes,

CONTEXT

325

1976). Simpson (1981), for example, used a cross-modal, lexical decision paradigm to investigate the effects of dominance and different types of context on the resolution of lexical ambiguity. He found that when an ambiguous word (e.g., COUNT) with a dominant and a subordinate meaning (i.e., related to numbers and nobility, respectively) occurred in a neutral context (e.g., “He had trouble keeping track of the count”), the dominant meaning was accessed first. However, when the sentence weakly biased one meaning, access was selective if the sentence biased the dominant meaning (e.g., “The musician kept losing track of the count”), but was exhaustive otherwise (e.g., “The king kept losing track of the count”). Finally, if the ambiguity occurred in a context that strongly biased one of its meanings (e.g., “The dog wasn’t included in the final count,” or “The vampire was disguised as a handsome count”), only that meaning was accessed. Simpson’s findings seem to support a model of lexical access, where both dominance and context type have an effect. His results, however, were obtained using a cross-modal priming paradigm, in which the visual target word occurred 120 ms after the offset of the ambiguity. Unfortunately, this delay might be sufftciently long to allow the lexical decision to reflect postaccess rather than initial access effects, thus accounting for the results without calling the context-insensitive hypothesis into question. Effects of dominance and strength of context have also been addressed by Carpenter and Daneman (1981). In an eye-fixation study, their subjects read aloud passages containing nonhomophonic homographs (e.g., BASS) in four different contexts, as illustrated in the following examples: (1) Context primes music note: target is music note: Tomorrow was the annual one-day rock

326

PATRIZIA

concert and musicians would invade the place. Some of the best buss guitarists in the country would come to this spot. (2) Context primes fish; target is music note: Tomorrow was the one-day fishing contest and the fishermen would invade the place. Some of the best bass guitarists in the country would come to this spot. (3) Context primes fish; target is fish: Tomorrow was the annual one-day fishing contest and the fishermen would invade the place. Some of the best buss catchers in the country would come to this spot. (4) Context primes music note; target is fish: Tomorrow was the annual one-day rock concert and musicians would invade the place. Some of the best bass catchers in the country would come to this spot.

TABOSSI

naming study by Seidenberg, Tanenhaus, Leiman, and Bienkowski (1982). Their subjects listened to sentences containing an ambiguity, whose meanings either were both nouns (e.g., STRAW) or were a noun and a verb (e.g., TIRE). The sentences were also of two types: priming and nonpriming. The former contained a word strongly semantically related or associated to one meaning of the ambiguity; the latter biased the ambiguity either syntactically or by means of some kind of pragmatic information. Seidenberg et al. (1982) found that with noun-noun ambiguities, naming a word is faster after the appropriate priming context (e.g., “The farmer bought the straw,” HAY) than after an inappropriate one (e.g., “The farmer bought the straw,” SIP). This difference did not hold, however, either with noun-verb ambiguities or with nonpriming contexts. According to the authors, these results suggest that the structure of the ambiguous The relative frequency of one interpretaitems (i.e., noun-noun, noun-verb) and tion of a homograph over the other varied the organization of the semantic informafrom very balanced (e.g., BASS) to very different (e.g., BUFFET). The strength of tion in the lexicon (i.e., semantic relatedthe priming context also varied from neu- ness or association among words) have an effect on access. There is no evidence that tral to very strongly biasing. The results top-down information provided by a prior showed that eye fixation was shorter on sentential context can also influence the homographs which occurred in strong coninitial activation of the meaning(s) of an texts than on homographs which occurred ambiguity. Hence, insofar as it shows intrain weaker ones. Moreover, eye fixation lexical, but not sentential effects of conwas shorter when the homographs were text, the work of Seidenberg et al. (1982) pronounced according to the dominant indoes not challenge the context-insensitive terpretation than according to the suborditheory of lexical access, but rather supnate one. ports it. While these findings corroborate While the research discussed above has Simpson (1981), providing evidence for failed to show convincingly that either both context and dominance effects, they dominance or sentential context can affect give no hint as to what information about a lexical access, a recent cross-modal, lexhomograph has been initially activated. In ical decision study appears to provide evifact, as the authors point out, eye fixation dence for both effects. In Tabossi, Cotimes cannot discriminate among the various processes engaged in reading a lombo, and Job (1987), the subjects listened to a sentence that biased either the domiword -encoding, retrieving, and integranant or the subordinate meaning of an amtion processes. Hence, they are not adebiguity occurring in the sentence, as in the quate to the investigation of issues related following example: to lexical access. More to the point is a cross-modal, (1) The violent hurricane did not damage

LEXICAL

ACCESS AND SENTENTIAL

the ships which were in the port, one of the best equipped along the coast. (2) Deceived by the identical color, the host took a bottle of barolo, instead of port, and offered it to his guests. The sentential contexts were constructed in such a way as to make salient a very characteristic feature of either the dominant or the subordinate meaning of the ambiguous word (i.e., SAFE and RED, respectively).’ At the offset of the ambiguous word, the subjects were presented with a visual word which either denoted one of the features primed by the sentences or was an unrelated control (e.g., SAFE, RED, SHORT). It was found that after the subjects listened to a sentence biasing the dominant meaning of an ambiguous word, they were faster at deciding that the target related to that meaning was a word than at deciding that either the target related to the subordinate meaning or the unrelated target were words. Decision times on the latter two words did not differ significantly from each other. However, after listening to a sentence biasing the subordinate meaning of the ambiguous word, decision times to targets related to either of its meanings did not differ from each other and were both reliably faster than decision time to the unrelated target. Tabossi et al. (1987) argued that the difference between their results and those of Onifer and Swinney (1981) are likely to be due to differences in the materials em-

’ This example is somewhat misleading, since looking at sentence 1 one might be tempted to conclude that materials in Tabossi et al. (1987) are not really different from those in Seidenberg et al. (1982). However, this is the only sentence in Tabossi et al. (1987) where a word in the context (ship) is strongly semantically related or associated to the ambiguity @orf) (see Appendices 1 and 2). In spite of this, the example was kept for the convenience of the English readers, since porr is the only word in the study which maintains its ambiguity in English. In fact, Tabossi et al. (1987) was conducted with Italian subjects and Italian materials.

CONTEXT

327

ployed in the two studies. In Onifer and Swinney (1981), the context biased one meaning of an ambiguity in a number of different ways, but primed no particular aspect of that meaning, whereas in Tabossi et al. (1987), contexts primed features that could establish constraints on the information provided the upcoming ambiguous word. Also, the relation between the ambiguous and the related target words differed in the two studies. In Tabossi et al. (1987) the target words denoted very characteristic aspects of either meaning of the ambiguity and were not highly associated to it. In Onifer and Swinney (1981), the related visual words were either synonyms or associates to either meaning of the ambiguous item. But these targets might be more sensitive to intra-lexical relations of the ambiguities than to their contextual interpretation (Barclay, Bransford, Franks, McCarrell, & Nitsch, 1974). Therefore, they may not be adequate to reflect possible effects of context on the access of the ambiguity. Tabossi et al. (1987) did not decide which of the two factors was responsible for the discrepancy between their results and those of Onifer and Swinney (1981). and indeed their data do not resolve the issue. However, the implications in the two cases are rather different. Suppose, first, that it is the nature of the context that explains the different results in the two studies. This would suggest that research on lexical access ought to reconsider the widely accepted view that seems to assume that either context affects lexical access or it does not, and to focus on defining the nature of context far more than it has done so far. Alternatively, imagine that the discrepant results are due to the semantic relation holding between ambiguous and target words. On the one hand, this result would provide further evidence that semantic features are context-sensitive aspects of meaning (Barclay et al., 1974; Tabossi, 1988). On the other hand, it would call for a more careful use of the target

pATRlZIATABOSS1

328

words employed in cross-modal studies and a better comprehension of the different processes they may reflect. The exploration of these alteratives is the main objective of the present study. The first and most obvious point that needs to be clarified is whether the nature of context and/or the type of link between an ambiguous word and a related visual target word affect the results that can be obtained in investigating lexical access with the crossmodal priming paradigm. If either or both these factors are effective, one would expect that the same ambiguous words that in Tabossi et al. (1987) primed only the target words related to their dominant, contextually congruent meanings should prime target words related to both their dominant and their subordinate, contextually incongruent meanings under the following conditions. First, the ambiguous words occur in sentential contexts that bias their dominant meaning, but prime no specific feature of it (e.g., “The man had to be at five o’clock at the port for a very important meeting”).* Second, the related visual words are associates to one meaning of the ambiguous item, but do not denote any feature of it (e.g., SEA: dominant, contextually congruent; LIQUEUR: subordinate, contextually incongruent; HAND: unrelated control). In order to test this hypothesis Experiment 1 was concluded. EXPERIMENT

1

Method Subjects. The subjects were 28 undergraduate volunteers from the University of Bologna (18 women and 10 men). Four subjects, who failed to meet the require-

* All experiments were conducted with Italian subjects and Italian materials, which are listed in Appendix 1. The corresponding English translations are presented in Appendix 2. English translations have been used in the text.

ments of a recognition test (see below), were eliminated and their data were not analyzed . Materials, apparatus, and design. Nine ambiguous words, with a dominant and a subordinate meaning, were employed in this experiment. These words, which were the same as those in Tabossi et al. (1987), had the following characteristics: both of their meanings were familiar to 12 judges who were asked and one of their meanings was clearly dominant over the other (83% of agreement among the judges). For each ambiguity, a sentence biasing its dominant meaning was constructed so that this meaning was far more plausible than the other, but no priming mechanism similar to that used in Tabossi et al. (1987) and in Experiment 3 (see below) was employed. To make sure that the sentences did bias the intended meaning of the ambiguities, but did not make salient any specific feature of either meaning, 10 Italian speakers were requested to give, for each sentence, two judgments: (I) What was the meaning of the ambiguous word in that sentence? (2) Was there any particular feature of the meaning of the ambiguity that the sentence made them think of? All the judges agreed that the sentences biased the intended meanings of the ambiguities. Also, there was 91% agreement that no specific feature of those meanings was particularly relevant in the contexts. When features of the dominant meaning of an ambiguity were produced (8% of the time), they were very general, classification-type features (e.g., “A port is a place”). In no case was any of the features used in Tabossi et al. (1987) mentioned. Ten new judges were used in order to select the associate words to be used as visual targets in the experiment. Each judge was presented with the nine ambiguous words in a random order, and for each of them he/she was requested to produce the

LEXICAL

ACCESS AND SENTENTIAL

first associates that came to mind. Because the first answers were always words associated to the dominant meanings of the ambiguities, the judge was then asked to produce other words associated to the subordinate meanings of the ambiguities. Based on the judges’ responses, 18 associate words (two for each ambiguity) were selected by the following criteria: (a) They had been produced by at least seven of the judges. (b) They denoted no feautures of either meaning of the ambiguities. There was no overlap between the present set of target words and the words used in Tabossi et al. (1987) or in Experiment 2 below. In addition to the 18 associate words, 9 new words were selected for use as controls. These were not related to either meaning of the ambiguities. To make sure that lexical decisions to the 27 selected words presented in isolation were comparable, they were included in a list of 118 words and 118 legal nonwords. The list was presented to 21 subjects who were asked to perform a lexical decision task on each item of the list. The results of this preexperiment showed that the words associated to the dominant meaning of the ambiguous items, the words associated to their subordinate meaning, and the control words did not differ significantly from one another. Their mean reaction times were 499, 500, and 501 ms, respectively. In addition to the experimental materials (see Appendices 1 and 2), filler materials (11 sentences paired with word targets and 20 sentences paired with nonword targets) were also used. One list of sentences containing the 9 test sentences and the 31 filler sentences in a random order was constructed. The list was recorded by a male speaker on one channel of a tape recorder. There was a 5-s delay between sentences. An impulse of 1000 Hz was placed automatically on the other channel of the tape, precisely at the offset of one word in each sentence (0-ms

CONTEXT

329

delay).3 In the case of the experimental sentences, the impulse, inaudible to the subjects, was at the end of the ambiguous word. In the case of the filler sentences, it occurred at the offset of a word chosen in such a way as to cover a wide range of positions within the sentences (i.e., early, middle, end). The impulse caused a visual word to be projected on the screen of an Apple microcomputer for 1500 ms. It also started a digital timer which stopped when the subjects pressed the space bar or reset automatically after 5 s. Three sets of 40 visual targets (9 test words, 11 filler words, and 20 filler nonwords) were also constructed to be paired with the list of sentences. They were the same, except that in one set the target word paired with an ambiguity was associated to its dominant meaning, in another set it was associated to its subordinate meaning, and in the third set it was an unrelated target word. Within each set there were three trials in each experimental condition, yielding a total of nine test trials. Each set, paired with the list of sentences, was randomly assigned to an equal number of subjects, who acted as their own controls. The relation between the experimental target words and their ambiguous primes (congruent, incongruent, control) was the only factor in the experiment. Procedure. The subjects were tested individually. They sat in a sound-attenuated booth in front of an Apple computer connected to a stereo tape recorder. They were instructed to perform a lexical decision task on items that would appear on the screen in front of them, while listening to a list of sentences. They had to press the space bar of the Apple keyboard with their dominant hand if the string was an actual word, and do nothing otherwise (go-no go technique). After eight practice trials, 3 Pulses were placed automatically by using a program developed at the lstituto di Elettronica ed Elettrotecnica dell’ Universita’ di Padova using a Nova computer.

330

PATRIZIA

the list of sentences paired with one of the three sets of visual words was presented to each subject. Reaction times for lexical decisions were collected. The subjects were warned in the instructions that they should pay attention to the sentences, because at the end of the experimental session they would be asked questions about the sentences. Immediately after the end of the sequence, the subjects were given 20 sentences, each printed on a card. Half of the sentences had been presented in the experiment and half were new. The new ones were close derivations of sentences that the subjects had heard. Subjects who failed to correctly recognize 65% of the sentences (hits and correct rejections) were excluded from subsequent statistical analyses. Among the subjects who reached the criterion, the mean level of correct recognitions was 76%. The entire session lasted about 25 min.

TABOSSI

the analysis by items (F,(2,16) = 4.438, p < .05).

Planned nonorthogonal comparisons showed that the contextually congruent (dominant) and contextually incongruent (subordinate) visual words were both faster than the unrelated control words and did not reliably differ from each other (Congruent vs Control: F(2,46) = 10.516, p < ,001; Incongruent vs Control: F(2,46) = 7.137, p < 0.005; Congruent vs Incongruent: F(2,46) = .32, ns). These findings support the hypothesis that whether or not context may be shown to affect lexical access in cross-modal priming paradigm experiments depends crucially on the type of materials employed in those studies. In fact, if considered in isolation, the present findings support the currently accepted view that lexical access is context-insensitive. In particular, they suggest that both meanings of an ambiguity are initially activated, even if the ambiguity Results and Discussion occurs in a sentential context that biases its The mean percentage of errors was 1.38. dominant meaning. However, these results In order to reduce variability, data points were obtained using the same ambiguous two standard deviations above and below items and the same procedure as in Tabossi each subject’s mean reaction times (3.27% et al. (1987), where context effects were of all data) were excluded from subsequent observed. Indeed, the only differences beanalyses. The mean reaction times and tween the two studies are in the manner in standard deviations of correct responses in which contexts biased the dominant the three experimental conditions are re- meanings of the ambiguities and in the naported in Table 1. The results showed a reli- ture of the semantic links between the amable main effect both in the analysis by biguous items and the related visual words. subjects (F,(2,46) = 5.994, p < .Ol) and in One or both of these factors must therefore

TABLE 1 MEANREA~TIONTIMES (ms) ANDSTANDARDDEVIATIONSFORLEXICALDECISIONTOTARGETWORDSINTHE THREEEXPERIMENTALCONDITIONS(CONTEXTUALLYCONGRUENT,CONTEXTUALLYINCONGRUENT,AND UNRELATEDCONTROL)INEXPERIMENTS~,~, ANDY Experimental

condition

Experiment

Congruent

Incongruent

Control

Nonconstraining context; associate visual words (Expt 1) Nonconstraining context; feature denoting visual words (Expt 2) Constraining context; associate visual words (Expt 3)

592 63.26 60.5 68.63 643 81.41

600 73.24 619 73.29 688 102.39

634 77.32 648 85.49 682 92.10

LEXICALACCESSANDSENTENTIALCONTEXT

be responsible for the different findings. But while clearly establishing this point, the present results do not allow discrimination between the two factors. To this purpose, Experiment 2 was devised. EXPERIMENT 2

In this experiment, the subjects listened to a sentence that biased the dominant meaning of an ambiguous word occurring in it, but primed no specific aspect of it, as in Experiment 1. Precisely at the offset of the ambiguity, however, they were presented with a visual word which either denoted a very characteristic feature of one meaning of the ambiguity or was a control, as in Tabossi et al. (1987). The following example illustrates the experimental conditions: The man had to be at five o’clock at the for a very important meeting. SAFE Dominant, contextually congruent . RED Subordinate, contextually incongruent. SHORT Unrelated control.

port

If what is crucial in order to detect context effects on access in cross-modal studies is the kind of semantic relation between one meaning of an ambiguity and a related visual word, then SAFE should be faster than both RED and SHORT, as in Tabossi et al. (1987). If, however, it is the nature of the sentential context, or the conjunction of the nature of the context with the nature of the target, that determines the different patterns of results, then in the present experiment one should expect both SAFE and RED to be faster than SHORT, as in Experiment 1. Method Subjects. Thirty undergraduates (20 women and 10 men) at the University of Bologna volunteered for the experiment. Six of them failed to reach the criterion in the recognition test (see above), and their data were excluded from all the analyses.

331

Materials, apparatus, and design. The critical sentences and the filler materials were the same as those in Experiment 1, and the critical targets were the same as those in Tabossi et al. (1987). They were unrelated controls or denoted very characteristic features of one meaning of the ambiguities (see Appendices 1 and 2). These features were collected by asking 12 judges to characterize both meanings of each ambiguity. On the basis of their responses, two words -one labeling an aspect relative to the dominant meaning and one labeling an aspect relative to the subordinate meaningwere selected. In order to make sure that the selected aspects were both central to the meanings of the ambiguities. only features produced by at least nine judges were considered. For a more detailed description of how the ambiguous items and their features have been collected, see Tabossi et al. (1987). In addition to the 18 feature-denoting visual words, 9 unrelated controls were also selected. A preexperiment like that described in Experiment 1 was run on these items. The results showed that 9 words related to the dominant meanings of the ambiguities, 9 words related to their subordinate meanings, and 9 unrelated controls did not differ significantly. Their mean reaction times were 528, 525, and 528, respectively. Apparatus and design were the same as those in Experiment 1. Procedure. This was the same as that in Experiment 1. Correct identifications in the recognition test, among the 24 subjects who met the criterion, was 68%. Results

The mean percentage of errors was 2.4. In order to reduce variability, data two standard deviations above and below each subject’s mean reaction times were discarded (4.6% of all data). The mean reaction times and standard deviations of correct responses in the three experimental conditions are reported in Table 1. The main effect was reliable in the anal-

332

PATRIZIA

ysis by subjects (F,(2,46) = 4.667, p < .025) as well as in the analysis by items (F,(2,16) = 3.73, p < .05). Planned nonorthogonal comparisons showed that the subjects were faster at deciding that a string was a word when it was semantically related to either meaning of the ambiguous word than when it was a control (Congruent vs Control: F(1,46) = 9.13, p < .OOS; Incongruent vs Control: F(1,46) = 4.15, p < .05). Lexical decision on a visual word related to the contextually congruent (dominant) meaning of an ambiguity did not differ significantly from a lexical decision on a visual word related to the contextually incongruent (subordinate) meaning of the same ambiguous item (Congruent vs Jncongruent: F(1,46) = 0.968, ns). Discussion

The present findings replicate those of Experiment 1. In both cases there is no suggestion that context can affect lexical access. Evidence in support of this view was obtained by looking at how effectively an ambiguity primed either words associated to one of its meanings (Experiment 1) or words denoting features of one of its meanings (Experiment 2). Clearly, both types of words are comparable in their sensitivity to the semantic activation of the ambiguity. Therefore, the discrepancy between Onifer and Swinney (1981) and Experiments 1 and 2 on one hand and Tabossi et al. (1987) on the other hand cannot depend upon the different types of target visual words used in the studies. Since the only other dimension along which the experiments differ is the nature of the sentential contexts, the obvious hypothesis is that this is the critical factor in determining lexical access; that is, cross-modal studies can show or fail to show sentential context effects on lexical access depending on whether context is sufficiently constraining. Before drawing this conclusion, however, some caution is in order. It is still possible that the context effects observed in

TABOSSI

Tabossi et al. (1987) can only be obtained when appropriately constraining contexts are used in conjunction with targets that, like the feature-denoting targets, are particularly sensitive to the contextual interpretation of an ambiguous word. This is not to say that the selective results in Tabossi et al. (1987) are an artifact produced by some word in the dominant biasing context (e.g., damage) directly priming the contextually related target word (e.g., SAFE). In this case, the findings would still be compatible with the context-insensitive theory of lexical access. But if such an effect had occurred, and lexical access of the ambiguity had not been affected by prior context, the target related to the subordinate, contextually incongruent meaning (e.g., RED) ought to be not only slower than the contextually congruent target (e.g., SAFE), but also faster than the unrelated target (e.g., HAND), a difference that was not found. However, showing context effects with the same sentences as in Tabossi et al. (1987), but with visual words holding a semantic association to the ambiguities rather than a feature-denoting relation would be useful in several respects. First, the hypothesis that only particular combinations of sentential contexts and visual targets give rise to the pattern of results observed in Tabossi et al. (1987) would be ruled out. Second, associates to either meaning of an ambiguity, frequently used as visual targets in cross-modal studies, would be shown to be sensitive to possible effects of context on lexical access. Third, the existing evidence of genuine effectiveness of featurepriming contexts on lexical access would be strengthened. Accordingly, Experiment 3 was devised. In this experiment, the associated targets of Experiment 1 were paired with the constraining contexts of Tabossi et al. (1987). EXPERIMENT

3

The subjects listened to a sentence that biased the dominant meaning of an ambig-

LEXICAL

ACCESS AND SENTENTIAL

uous word by making salient a characteristic feature of that meaning. At the offset of the ambiguity they were visually presented with a word on which they had to perform a lexical decision task. The word was associated to the dominant, contextually congruent meaning of the ambiguity or was associated to the subordinate, contextually incongruent meaning of it or was an unrelated control. The following example illustrates the three conditions: The violent hurricane did not damage the ships which were in the port, one of the best equipped along the coast. SEA Dominant, contextually congruent . LIQUEUR Subordinate, contextually incongruent. HAND Unrelated control. If an appropriate context can affect lexical access, at least when it biases the dominant meaning of an ambiguity, and the effect can be detected regardless of the nature of the link between the ambiguity and its related visual words, then, unlike Experiment 2, SEA should be primed relative to LIQUEUR and HAND, which should not differ from each other. Method

Subjects. Thirty-one undergraduates (13 women and 18 men) volunteered for the experiment. Seven of the subjects failed to reach the 65% correct identifications in the recognition test. Their data were therefore excluded from the analyses. Materials, apparatus, and design. The ambiguous words as well as the visual target words paired with them were the same as those in Experiment 1, The experimental sentences, which were the same as those in Tabossi et al. (1987), were obtained as follows. For each of the nine ambiguous words, a sentence was constructed so as to render a central aspect of its dominant meaning particularly salient. This aspect was the same as the one denoted by the visual word related to the dominant meaning

CONTEXT

333

of the ambiguity in Experiment 2 and in Tabossi et al. (1987). In order to assess the adequacy of these sentences, six judges were requested to indicate what aspect of the meaning of the ambiguous word each sentence made them think of. Eight of the sentences reached 75% agreement on the intended aspect; the ninth sentence, on which the judges disagreed, was modified to match the criterion (see Appendices 1 and 2). Finally, the filler materials were the same as those in Experiments I and 2. Apparatus and design were also the same. Procedures. It was the same as that in Experiments 1 and 2. Among the subjects who met the criterion in the recognition test, the mean number the correct responses was 71%. Results and Discussion

The mean percentage of errors was 1.5. In order to reduce variability, data points two standard deviations above and below the mean reaction times of each subject (4.3% of all responses) were excluded from the analyses. The mean reaction times and standard deviations for correct responses in the three experimental conditions are presented in Table 1. The results showed a significant main effect both in the analysis by subjects (F,(2,46) = 5,267, p < .Ol) and in the analysis by materials (F,(2,16) = 4.190, p < .05). Nonorthogonal planned comparisons showed that lexical decision on the visual word associated to the dominant, contextually congruent meaning of the ambiguity was significantly faster than lexical decision on both the visual word associated to its subordinate, contextually incongruent meaning and the control word (Congruent vs Incongruent: F(1,46) = 9.037, p < .005; Congruent vs Control: F(1,46) = 6.813, p < .025; Incongruent vs Control: F(1,46 = 0.157, ns). These findings support the view that, at least when the bias is toward the dominant meaning of an ambiguity, effects of context on lexical access can be detected independently of the nature of the semantic links

334

PATRIZIATABOSSI

between the meanings of the ambiguity and the related visual words employed in the cross-modal paradigm, provided that the context is a sufficiently constraining one. Thus, Experiment 3 replicates and extends Tabossi et al. (1987). As for that study, one might claim that individual words in the sentential contexts (e.g., ships) or the discourse models of the whole sentential frame constructed by the subjects during comprehension primed the contextually related visual word (e.g., SEA) (Foss, 1982). But, again, on that interpretation, LIQUEUR should be slower than SEA, and yet faster than HAND. No evidence that this was the case was obtained. Indeed, effects of context on lexical access seem the simplest explanation of the present results. GENERALDISCUSSION

Experiment 1 showed that when a sentence biases the dominant meaning of an ambiguity without imposing strong constraints on its semantic features, lexical decision on a target word associated to that meaning and lexical decision on a word associated to the subordinate, contextually incongruent meaning of the ambiguity were both faster than lexical decision on an unrelated control word. Latencies in the two experimental conditions did not reliably differ. Experiment 2 yielded the same results with target words that, instead of being associated to the meanings of the ambiguous word, denoted very characteristic features of them. Finally, Experiment 3 showed that when a sentence biases the dominant meaning of an ambiguity by making salient a characteristic feature of it, lexical decision on a visual word associated to that meaning is faster than lexical decision either on a word associated to the subordinate, contextually irrelevant meaning of the ambiguity or on a control. Moreover, the latter two conditions did not differ significantly from each other.

It is difftcult to see how these findings, which are consistent with Simpson (1981), could be explained on the basis of the methodological arguments often put forward in the current debate on lexical access. These arguments usually rest either on the delay between an ambiguity and the subsequent target word (in the cross-modal paradigm prime and target, respectively) or on the length of these words, particularly the ambiguities. It is well-known, in fact, that selective postaccess processes become effective very early (Seidenberg et al., 1982), and either an interval between prime and target or the time intervening between one’s recognition of a spoken word (especially if long) and its physical ending (Marslen-Wilson & Tyler, 1980) could be sufficiently long to allow postaccess phenomena to establish themselves. Alternatively, too short an asynchrony between the onsets of the prime and the target could produce backward priming (Kiger & Glass, 1983), thus preventing selective effects of access from being obtained in ordinary cross-modal studies. A further argument often considered is the reliability of the lexical decision in investigating lexical access. In fact, unlike other tasks, such as naming, lexical decision appears to be sensitive to postaccess phenomena (Larch, Balota, & Stamm, 1986; Lupker, 1984; Seidenberg, Waters, Sanders, & Langer, 1984). In the present study, however, different patterns of results were collected using exactly the same task on the same set of ambiguous and target words. Hence, none of these elements can be responsible for the observed differences. Two points are established by these results. First, one hypothesis of this study was that target words that are likely to reflect the intra-lexical relations of an ambiguity might prevent possible context effects from being detected in cross-modal priming paradigm studies. This hypothesis was not supported. In fact, Experiment 3 showed that context effects can be obtained even

LEXICAL

ACCESS

AND

with associated targets that strongly reflect the intra-lexical relations of an ambiguous item. Indeed, the nature of the relation between an ambiguity and the related targets does not seem to affect the experimental outcomes. Second, contrary to what is currently claimed, the results support the view that initial access of an ambiguous word can be influenced by prior context, corroborating and extending Tabossi et al. (1987). Taken together, these studies suggest that both dominance and context may have an effect on lexical access. In particular, when an ambiguity occurs in a context which, although biasing, is not sufficiently constraining, both meanings of the ambiguity are accessed. Likewise, both meanings are accessed when context is constraining, but is directed to the subordinate meaning of the ambiguity. However, when contexts impose constraints on the dominant meaning of an ambiguous word, and both dominance and context converge on the same semantic information, the subordinate, contextually incongruent meaning of the ambiguous item need not be accessed. In the current debate between those who conceive the cognitive system as mainly modular (Fodor, 1983; Forster, 1979) and those who see it as highly interactive (Rumelhart, McClelland, & the PDP Research Group, 1986), the present study fails to support the former view. In the war between these two conceptions, whether or not genuine contextual top-down effects can occur in lexical processing has become one of the major battle lines, and researchers supporting either model have almost invariably tried to account for the discrepancies existing in the literature on ambiguity on the basis of methodological differences (Fodor, 1983; Glucksberg et al., 1986; for a critique of the latter paper, see Burgess, Seidenberg, & Tanenhaus, 1986). These differences are of the greatest importance in order to interpret correctly the various findings and to compare them fruitfully. But focusing almost exclusively on

SENTENTIAL

CONTEXT

335

them has had the unfortunate consequence that very little attention has been paid to what extent and under what circumstances the different subsystems involved in language comprehension operate as modules or interact with one another. Tanenhaus, Dell, and Carlson (1987)) however, have recently suggested that complete modularity and complete interaction in lexical processing can be best viewed as the two extremes along a continuum in which topdown, contextual information can act on the resolution of an ambiguity in a number of different ways. Context, for example, could send early feedback to the lexical system so that the subordinate, incongruous meaning of the ambiguity, although receiving some activation from the perceptual processing of the ambiguous word, would not reach an hypothetical access threshold. Alternatively, if the dominant meaning of an ambiguity has already received activation by the prior context, as soon as the word is actually presented. its primed meaning will become available, whereas its subordinate meaning will be inhibited. The present data do not distinguish between these alternatives. What they do show, however, is that accessing the meaning of an ambiguous word can be affected by a prior context, even when no words strongly semantically related or associated to the ambiguity occur in the sentence. But in order for such effects to take place, not all biasing sentences will be adequate. Prior context, in fact, must constrain the semantic information in the incoming ambiguity. As this study suggests, one way in which a sentential frame can impose such constraints is by priming semantic features of the upcoming word. Admittedly, semantic features are rather elusive notions and they are not easy to define. Nevertheless, similar notions have been extensively used in lexical semantics research (Barsalou, 1982; Whitney, McKay, Kellas, & Emerson, 1985); and the relative importance of different pieces of

336

PATRIZIA

information in characterizing a word meaning can be established empirically without committing oneself to any specific theory of how the lexicon is mentally represented. Likewise, the effectiveness of a sentential frame in priming a semantic feature of a subsequent word can be easily assessed empirically and so can the difference between this type of context and other biasing contexts, such as syntactic, pragmatic, lexical, and expectancy contexts. While syntactic and pragmatic contexts do not seem to affect lexical access, and intralexical mechanisms appear capable of doing so (Schvaneveldt, et al., 1976; Seidenberg et al., 1982), it is not clear to what extent rendering an ambiguous word highly predictable would affect its disambiguation. In fact, it is well-known that predictability can influence the identification of a word (Blank & Foss, 1978; Schwanenflugel & Shoben, 1985), but, although extensively used, this mechanism has never been systematically investigated in lexical ambiguity research (But see Van Petten & Kutas, 1987). In any case, whether or not it is effective, predictability differs from the feature-priming mechanism, where context points to semantic information that should be provided by a subsequent word in order for the sentence to make sense, but makes no word very predictable. In the present study, for example, predictability of the upcoming ambiguous item does not discriminate between the constraining and nonconstraining context, as has been assessedin a simple test. The whole set of experimental sentences used in the study were read up to the ambiguity, in a random order, to 10 judges, who were requested to complete the sentences. The results showed that neither set of materials made the ambiguous items very predictable (the mean number of items correctly predicted was 1.25). Moreover, the two sets hardly differed from each other: the mean number of correct predictions was 1.5 in the constraining set and 1 in the nonconstraining set.

TABOSSI

It should be noted that feature priming has a great advantage over predictability as a possible mechanism for using prior sentential information on lexical processing. In fact, as Marslen-Wilson and Tyler (1980) point out, words are hardly ever fully predictable, so that either predictability is not extensively used during comprehension or it leads to many errors from which the language system must then recover. By contrast, using the semantic constraints provided by prior context is a rather safe and usually cost-free mechanism, which can be used even in understanding figurative speech (Ortony, 1979). Indeed, the usefulness of the featurepriming mechanism has been pointed out in relation to a number of different tasks related to lexical processing. It is an established fact, for instance, that context can affect the way in which an unambiguous word gets interpreted, rendering some aspects of its meaning more salient than others (Barclay et al., 1974), and there is also evidence that these effects reflect the way in which the word is accessed, rather than later interpretative processes (Tabossi, 1988). Moreover, a feature-priming mechanism has been proposed by Schwanenflugel and Shoben (1985) in order to explain different facilitation effects produced by high- and low-constraining contexts on the recognition of expected and unexpected words. While weak, but broad effects of facilitation were produced by low-constraining sentences, only the recognition of expected words was facilitated by highly constraining sentences. When frequently completed by expected lexical items, these sentences actually inhibited unexpected words. According to the authors, high- and low-constraining sentences differentially affect the number of features that can be produced and used by the subjects as clues about a to-be-recognized word. In conclusion, the present findings strongly suggest that the way in which the resolution of lexical ambiguity has been in-

LEXICAL

ACCESS

AND

vestigated in recent years, mostly trying to find evidence for or against a modular view of the language comprehension system, may be misleading. In fact, depending upon what information is made available by a prior sentential context, results supporting either the modular or the interactive view can be obtained. The ways in which individual word meanings are integrated during real time discourse processing are as yet very poorly understood. Consequently, the investigation of how different sentential contexts affect lexical processing is hard to pursue. However, without better comprehension of this issue it is unlikely that the resolution of lexical ambiguity in context, and lexical processing in general, will be clarified. In fact, there may be many different ways in which a sentential context can influence lexical comprehension in discourse, and imposing constraints on the semantic information in a subsequent word is likely to be only one of such mechanisms. APPENDIX

1

Original Materials Employed in Experiments I, 2, and 3

For each of the nine ambiguous words used throughout the experiments the sentence biasing, but not priming its dominant meaning (B) and the sentence priming a central feature of it (P) are listed along with the associate targets and their unrelated controls (a), and the feature-denoting targets and their unrelated controls (f). Sentences (P) and target words (f) were the same as in Tabossi et al. (1987). In the present study, the following combinations were used: Sentence (B) + target word (a) (Experiment 1); sentence (B) + target word (f) (Experiment 2); sentence (P) + visual word (a) (Experiment 3). 1. (B) Durante una passeggiata, il ragazzo notb sugli alberi molte gemme bench6 la stagione fosse inoltrata. 1. (P) In primavera bastb un vento leggero tra i rami dell’albero a sciupare la prima giovane gemma, appena sbocciata.

SENTENTIAL

337

CONTEXT

(a) FIORE (f) TENERA

DIAMANTE PREZIOSA

SEDIA ORDINE

2. (B) Nel negozio di articoli da regale, dopo aver guardato vat-i oggetti, la signora vide una bella coppa, the decise di comprare . 2. (P) Nella famosa bottega in Boemia, l’artigiano osservo con soddisfazione la trasparenza e la brillantezza della fragile coppa, appena finita. (a) SPUMANTE (f) CRISTALLO

SALAME GRASSA

LIBRO SANTO

3. (B) Alla lexione di geografia l’insegnante parlo de1 polo, dimenticandosi di interrogare . 3. (P) Gli esploratori rischiarono di morire per le terribili condizioni climatiche in una spedizione al polo, lunga e difficile. (a) ORSO (f) FREDDO

GIOCO CAVALLO

FIUME TAVOLO

4. (B) La piazza era il luogo abituale dove si teneva lafiera, una volta al mese. 4. (P) Alla festa de1 patron0 de1 paese, diversi bambini si persero fra la gente the affollava la fiera, nonostante la sorveglianza dei genitori. (a) MERCATO (f) CONFUSIONE

LEONE FEROCE

FERRO PROFONDO

5. (B) L’uomo doveva travarsi alle cinque in punt0 al port0 per un appuntamento molto importante. 5. (P) La violenza dell’uragano non danneggib le navi the si trovavano dentro al porto, uno dei pib attrezzati della costa. (a) MARE (0

SICURO

LIQUORE ROSS0

MAN0 BREVE

6. (B) Nel paesaggio piatto l’auomobilista scorse uno stagno, unico element0 di interesse della zona. 6. (P) L’acqua della baia era cost calma the sembrava di trovarsi in uno stagno, anziche al mare. (a) RANA (0 FERMO

PIOMBO MORBID0

7. (B) Alcuni specialisti

MARMO PAGINA

furono chiamati

338

PATRIZIA

TABOSSI

per togliere la mina, rimasta nascosta per parency and the brilliance of the fragile bowl, just finished. molti anni. 7. (P) L’inizio dei lavori di scavo fu seg(a)CHAMPAGNE SALAMI BOOK nalato dal fragore di una mina, messa dai (f) CRYSTAL FAT SAINT tecnici dell’impresa. 3. Polo: pole (d); polo (s) (a) BOMBA PUNTA DUBBIO (b) At the geography class, the teacher (fl ESPLOSIONE GOMMA MARTELLO spoke about the pole, forgetting to give an 8. (B) La zona si prestava alla coltura examination. della vite, oltreche dell’ulivo. (P) The explorers almost died for the ter8. (P) La maestra parlo agli scolari dei rible climate conditions in an expedition to frutti di diverse piante, tra cui il frutto della the pole, which was long and difficult. vite, quell0 de1pero ed altri. (a) BEAR GAME RIVER (a) VINO Q UVA

CHIODO METALLO

(f) COLD

PERLA ZIA

9. (B) I1 bimbo capriccioso si rifiutb di mangiare il riso, facendo disperare la madre . 9. (P) Sul tavolo scuro risaltava il colore de1riso, tirato fuori dal pacco. (a) PASTA (f) BIANCO

SCHERZO ALLEGRO

SCARPA CARTE

APPENDIX

2

HORSE

TABLE

4. Fiera: fair (d); wild beast (s) (B) The square was the usual place where the fair was held, once a month. (P) At the feast of the patron saint in the village, many children got lost among the people who crowded thefair, in spite of the parents’ attention. (a) MARKET (f) CONFUSION

LION FIERCE

IRON DEEP

5. Porto: port harbor (d); port wine (s) (B) The man had to be at five o’clock at the port for a very important meeting. In order to keep the translation as close (P) The violent hurricane did not as possible to the original version, the sen- damage the ships which were in the port, tences are often unnatural. The dominant one of the best equipped along the coast. (d) and subordinate (s) meaning of each (a) SEA LIQUEUR HAND ambiguity are also given. English Translation of the Original Materials

(f) SAFE

1. Gemma: bud (d); gem (s) (B) During the walk, the boy noticed on the trees many buds, although it was already late in the season. (P) In the spring, a light wind among the branches of the tree was sufficient to damage the first, young bud, just opened. (a) FLOWER (f) DELICATE

DIAMOND PRECIOUS

CHAIR ORDER

(a) Coppa: bowl (d); a type of salami (s) (B) In the gift shop, after looking at different objects, the lady saw a beautiful bowl, which she decided to buy. (P) In the well-known shop in Bohemia, the artisan observed with pride the trans-

RED

SHORT

6. Stagno: pond (d); tin (s) (B) In the flat landscape, the driver saw a pond, the only element of interest in the area. (P) The water in the bay was so calm that it seemed to be in a pond, rather than in the sea. (a) FROG (f) STILL

LEAD SOFT

MARBLE PAGE

7. Mina: mine (d); graphite (s) (B) Some experts were called to remove the mine, remained hidden for many years. (P) The beginning of the works of digging was signaled by the loud noise of a

LEXICAL

mine,

ACCESS AND SENTENTIAL

placed by the technicians of the com-

pany. SHARP END RUBBER

(a) BOMB (f) EXPLOSION

DOUBT HAMMER

8. Vite: grapevine (d); screw (s) (B) The region was good for growing grapevine, as well as olive trees. (P) The teacher spoke to her pupils about the fruits of several plants, among which the fruit of grapevine, that of pear tree, and others. (a) WINE (f) GRAPES

NAIL METAL

PEARL AUNT

9. Riso: rice (d); laugh (s) (B) The naughty boy refused to eat the rice, making his mother angry. (P) On the dark table, stood out the color of the rice, taken out from the package. (a) MACARONI 0 WI-mE

JOKE CHEERFUL

SHOE CARDS

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