A Time Course View of Sentence Priming Effects - Springer Link

Journal of Psycholinguistic Research, Vol. 33, No. 5, September 2004 (© 2004)

A Time Course View of Sentence Priming Effects Stephen T. Paul,1,3 and George Kellas2 Meaning activation was estimated during (standard naming) and after (delayed naming) target presentation to chart the time course of priming effects during reading comprehension. Using sentences biasing homographs toward their dominant and subordinate meanings, two experiments evaluated context effects across three naming-cue delays: immediate, baseline, baseline+600 ms all at a 0-ms interstimulus interval. When participants named a target immediately as it was presented, results converged with previous findings demonstrating initial context-sensitive meaning activation. The delayed naming conditions revealed little post-access influences for dominant contexts. Subordinate contexts, however, provided the strongest evidence of continued (or sustained) processing. It was concluded that context has immediate and automatic effects on initial meaning activation, after which, strategies are invoked for fine-tuning an interpretation of a sentence and integrating it with new information. KEY WORDS: time course; semantic priming; lexical ambiguity; comprehension.

INTRODUCTION Comprehending a written passage would seem to require context to affect all moments of the process of activating upcoming words. However, a great deal of effort has been devoted to determining the primary locus of context effects on reading performance. When responses are faster to word targets preceded by related words (primes) compared to when they are preceded by unrelated primes, such outcomes have served as evidence that context contributes to the earliest stages of word recognition, lexical access (e.g., Meyer & Schvaneveldt, 1971; Neely, 1977). However, it has been argued that, in some cases, such context effects may be the result of later occurring, or post-access, strategies based on semantic comparisons between prime and target following target identification 1

Robert Morris University. University of Kansas. 3 To whom all correspondence should be addressed: Robert Morris University, 6001 University Boulevard, Moon Township, PA 15108-1189. email: [email protected] 2

383 0090-6905/04/0900-0383/0 © 2004 Springer Science+Business Media, Inc.

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(Balota & Chumbley, 1984, 1985; Chumbley & Balota, 1984; Neely, et al., 1989; Seidenberg, 1985). Thus, the popular view that has resulted from these findings is that context effects observed early during word identification reflect access processes, while context effects that emerge later reflect post-access processes. However, although context could conceivably affect either access processes or processes following lexical access, it seems most likely that context influences processing continuously across both loci 4 (cf. Gerrig, 1986). The following debate illustrates the focus on determining the primary locus of context effects on meaning activation. According to one view, context effects are primarily the result of processes following initial meaning activation (e.g., Onifer & Swinney, 1981; Seidenberg et al., 1982). This position has been directly challenged by a continuously growing accumulation of counter evidence (e.g., Duffy et al., 1988; Kellas et al., 1991; Martin et al., 1992; Martin et al., 1999; McClelland, 1987; Paul, et al., 1992; Sharkey & Sharkey, 1992; Tabossi, et al., 1987; Van Petten & Kutas, 1987; Vu et al., 1998; Vu et al., 2000). Primarily, the conclusions that are being drawn are that context affects initial meaning activation by providing more activation to contextually appropriate information, than to contextually inappropriate information. The bulk of the research supporting this context sensitive view has utilized lexically ambiguous words in context. While debates regarding whether initial activation is always affected by a prior context may never be completely resolved, there does not seem to be any disagreement as to whether context contributes to late occurring processes. One consequence of this agreement is that the time course of meaning activation and context effects is rarely examined fully. To address this, the goal of the present research will be to track the early and late occurring influences of context on priming effects at various points during the time course of meaning activation (and presumably during comprehension). The examination of early and late processing influences should result in a more complete view of context effects than is typically observed. Additional goals of the present research will be to address two questions raised by the results of Paul et al. (1992).

4

Although we make use of the terms “access” and “post-access,” we do not wish to imply that we subscribe to a threshold model over a graded activation model (cf. Balota, 1990). Rather, we are keeping with the terms most commonly associated with the arguments and issues relevant to the present article. It would not change the spirit of the present research if one were to substitute the terms “access” and “post-access” with “early occurring” and “later occurring,” respectively.

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The first question the present research will be concerned with is the initial activation of low-salient information observed by Paul et al. (1992). To observe whether context-sensitive outcomes vary with the strength of the prime-target semantic relationship, Paul et al. utilized targets known to be related to homograph meanings as they occurred in the sentences used. The targets were normatively ranked according to how related or “salient” they were to the sentence context. It was found that responses to contextually appropriate senses of the homographs were initially facilitated relative to contextually inappropriate senses whether the context biased the ambiguous word toward its most (dominant) or least frequent (subordinate) meaning. This outcome obtained whether the strength of the prime-target relationship was one of high- or low-salience. Subsequent interstimulus interval (ISI) conditions, however, yielded different outcomes for the high- and low-salient items. For the 300 and 600 ms ISI conditions, responses suggested that contextually appropriate high-salient information remained active across the timecourse. This was not found to be the case for the low-salient conditions. By 300 ms following the sentence, responses indicated that low-salient information was no more activated than unrelated information. (It is noteworthy that a similar pattern of results was obtained by Whitney et al. (1985) who utilized sentences containing unambiguous words.) Paul et al. (1992) concluded that initial activation was broadly sensitive to context. Over time, comprehension processes serve to eliminate low-relevant information as a means of focusing the content of the text message. What remains to be determined is whether this low-salient information is simply activated by specific words in the sentence, or, if the activation of low-salient information is a consequence of sentence comprehension processes. In other words, the targets may have related to the context directly (i.e., related primarily to the homograph) or indirectly (i.e., inference information generated from comprehending the sentence as a whole). If low-salient targets represent information generated as a result of comprehending the context, then it seems reasonable to expect that activation of low-salient concepts relies more heavily on late occurring comprehension/integration processes than high-salient concepts. In fact, high-salient concepts seem the more likely candidates to be directly activated by the context (i.e., associative and/or intralexical priming). Such findings would be consistent with Dixon and Twilley (1999) who proposed that activation of homograph meanings in context is the result of an additive contribution of orthography and context. The present research, though, would elaborate on Dixon and Twilley’s proposal by revealing the nature of the information activated (i.e., low-salient, rather than highsalient) by processing the context as a whole.

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The second question to be addressed concerns the nature of the reduction in facilitation for low-salient information over the time course (e.g., suppression below baseline or decay to baseline). Paul et al. (1992) interpreted their outcome as evidence that context is processed over time so as to emphasize salient aspects of meaning by either actively deemphasizing less salient aspects or allowing activation to decay to original baseline levels. What remains unclear is whether this process begins with competition from more highly activated concepts or results from later comprehension processes serving to make inappropriate information less available. Ideally, the strongest case for an active suppression mechanism would be if responses reflected activation levels below baseline. Nonetheless, it will be informative to determine the extent to which lowsalient information is reduced relative to baseline (cf. Simpson & Kellas, 1989). The task we have selected for examining both the early occurring effects of a context on accessing a word’s meaning, as well as later integration processes, is the delayed naming task (Balota et al., 1989; Dallas & Merikle, 1976). In standard naming tasks, a word is presented that subjects must pronounce as quickly and as accurately as possible. By enforcing a delay between target onset and the subject’s naming response, late occurring influences on target naming may be observed (hence, “delayed” naming). If sufficient time elapses between target presentation and a cue to respond, then presumably most, if not all, meaning access and identification processes will be completed. Any subsequent influence of a semantic prime on performance can be attributed to late occurring processes (e.g., semantic matching, integration with the context, etc.).

EXPERIMENT 1 In the present study naming delay was manipulated to evaluate possible post-access contributions to performance during text processing. The naming delay manipulation included three critical moments based in part around issues raised by McRae et al. (1990). McRae et al. reasoned that, if the purpose of delaying subjects’ responses is to assess potential postaccess influences on performance, then the intervals used should be relative to the time needed by each individual subject to complete all earlier processes (e.g., encoding, access, construction of an articulatory-motor program, initiation of a verbal motor response). Naming delays which equal or exceed subjects’ normal naming intervals will most likely allow for the completion of processes up to the execution of the articulatory-motor


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program.5 Influences observed beyond the normal naming interval, then, must reflect processes following the completion of these earlier stages. In the present research, it is expected that by adjusting the naming delay relative to the estimated time necessary for subjects to complete initial processing, a cleaner estimate should be obtained of additional post-access influences on comprehension (i.e., beyond response preparation/initiation). The first naming delay occurred simultaneously with the target to be named, and so always preceded the estimate of each subject’s normal naming interval. Responses made under this condition should be sensitive to early influences of context, and were expected to replicate previous outcomes (e.g., Kellas et al., 1991; Paul et al., 1992). In other words, the target, having occurred immediately following the contextually constrained homograph, should be primed to the extent that it was preactivated by the context. In these previous studies, when context served to primarily activate information consistent with the sentence, responses to contextually appropriate targets were faster than responses to contextually inappropriate targets. The remaining naming delays used were the normal naming interval (i.e., subjects’ estimated baseline naming times), and this interval plus 600 ms. In these conditions, the cue to respond should occur after most of the earlier processes have been completed. Differences in response time as a function of target appropriateness should be due to post-access (late occurring) contributions. The contributions are assumed to be those necessary to facilitate sentence comprehension and/or maintenance of the message level representation (cf. Forster, 1981). Such processes might include integrating target with context (i.e., semantic matching strategies), or inhibiting the target to prevent it from inappropriately modifying the semantic representation of the sentence (Gernsbacher, 1990). In either case, the process is likely to depend on the explicit semantic relationship that exists (or does not exist) between the priming sentence and target. If constructing a useful semantic representation of a text involves actively sustaining activation to high-salient information and/or preventing low-salient information from becoming integrated, context effects should be observed at all naming delays. This is because such processes would extend beyond those necessary for simply preparing to respond to a target. On the other hand, to the extent that the contributions from context occur during initial processing, then context effects (if any) should 5

Note that estimates of participants’ normal naming intervals also include a portion of an articulation sequence. In order to obtain a baseline naming estimate, participants must execute an articulatory motor program to trigger a voice relay. Normal naming intervals, then, reflect somewhat more than the minimum time necessary to prepare a naming response.

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attenuate across the naming delay conditions as they are gradually completed prior to the required response. As discussed already, the immediate naming delay condition approximates that used by Paul et al. (1992) and so is expected to produce similar outcomes in the present experiment (i.e., reduced priming only for low-salient targets). In addition to naming delay, Experiment 1 will include the manipulation of target dominance, and target salience. That is, although all sentence primes will be constructed so as to semantically constrain the dominant (most frequent) meaning of the sentence-final ambiguous word, targets will be used that are related to both the dominant (contextually appropriate) and subordinate (contextually inappropriate) interpretation of the homograph. This manipulation will allow us to evaluate the extent to which the contextually inappropriate (subordinate) sense of the homograph is activated early as well as later during processing. The manipulation of target salience (high vs. low salient), on the other hand, will allow us to more precisely measure the scope of meaning activation over the time course regardless of semantic appropriateness. Method Participants Twenty-four students from introductory psychology at the University of Kansas volunteered for course credit. One additional volunteer was excluded due to excessive errors (exceeding a 15% error rate criterion), and one was replaced due to slow responding (greater than 2.5 standard deviations from the group mean). Participants were native English speakers and had normal or corrected-to-normal vision. Stimuli Stimuli (see Table I) consisted of 120 sentences biased toward the most frequent sense of a sentence-final ambiguous word (96 used by Paul et al., 1992 and an additional 24 selected from Kellas et al., 1989). Sentences were biased through the use of syntactic and pragmatic constraints and care was taken to avoid using any words associatively related to possible interpretations of the homograph. Target stimuli consisted of words high- and low-salient to both the dominant and subordinate sense of each homograph (i.e., resulting in a total of 480 unique targets). Target salience was determined as the production frequency measure from Kellas et al. (1989) weighted by overall order of output. The potential range for weighted production frequency (wpf) is between 1 and 100, in which 100 indicates the maximum possible production frequency (i.e., obtained only


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Table I. Sample Stimuli used in Experiment 1 Target Prime sentence

High-salient

Low-salient

Contextually appropriate It hung from the beam He dropped the bowl He had to wear an old cast I saw a duck She dropped the plant They bought a ring

Support Dish Plaster Quack Green Diamond

Above Cup Hold Paddle Life Promise

Contextually inappropriate It hung from the beam He dropped the bowl He had to wear an old cast I saw a duck She dropped the plant They bought a ring

Light Ball Actors Avoid Factory Bells

Particle Points Action Crouch Labor Call

Table II. Means and Standard Deviations (in parentheses) of Target Stimuli for the Controlled Variables Kucera & Francis

Number of syllables

Number of letters

Bigram frequency

High-salient Dominant Subordinate

111 (185) 125 (160)

1.5 (0.8) 1.5 (0.7)

5.5 (1.7) 5.2 (1.8)

5598 (4150) 5158 (3272)

Low-salient Dominant Subordinate

110 (152) 114 (145)

1.5 (0.7) 1.6 (0.7)

5.5 (1.6) 5.5 (1.5)

5428 (3653) 5757 (4580)

Isolated words

115 (143)

1.5 (0.7)

5.2 (1.6)

5464 (3586)

if the word was the first generated by all respondents). High-salient targets, then, represented the earliest and most frequently generated responses to a given sentence (wpf = 46.6, SD = 15.2 for dominant; wpf = 45.2, SD = 15.9 for subordinate). Low-salient targets represented later and less frequently generated responses (wpf = 4.4, SD = 0.5 for dominant; wpf = 4.3, SD = 0.5 for subordinate). Sentences were simple in structure, and of three to eight words in length. The mean number of words per sentence was 4.67 (SD = .90). As can be seen in Table II, targets were equated across conditions for frequency-of-occurrence in the English language (Kucera & Francis, 1967), summed spatial bigram frequency (Massaro et al., 1980), number of letters, and number of syllables, all p > .15.

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An additional 24 trials were included to serve as practice immediately preceding the experimental trials. Finally, 28 sentences were constructed for reading speed calibration (described below) and 60 isolated words were used to obtain an estimate of baseline naming prior to the experimental session. Each sentence was paired with the four possible targets an equal number of times across the experiment but only appeared once per participant. Therefore, four stimuli lists were required in order to match each target type to each sentence. Within each of the four stimuli lists, three variations were created in which naming delays rotated equally through stimuli. These procedures ensured that, within each sentence-target pairing, each target stimulus was presented at every naming delay an equal number of times across participants and all participants were exposed to an equal number of trials within each naming delay. Apparatus Stimuli were presented on a NEC Multisync-Plus VGA monitor driven by a 12 MHz IBM-AT compatible microcomputer. A GrasonStadler microphone (model #E7300A-2), attached to a Grason-Stadler #E7300A-1 voice operated relay (VOR) interfaced with the microcomputer to signal verbal responses. Procedure Participants were tested individually in a single session lasting about 40 minutes. Each participant was seated approximately 60 cm from the color monitor such that targets subtended an average visual angle of about 1.6◦ horizontally, and .5◦ vertically. All stimuli presented to participants were synchronized to the vertical retrace interval of the monitor. To obtain a baseline measure of naming latency (cf. McRae et al., 1990), 60 isolated words were presented to participants, one word at a time. To allow for practice, only responses to the final 30 words were used to estimate participants’ normal naming intervals. The stimulus characteristics of these 30 words approximated those of the experimental trials (see Table II). On each trial, a visual alerting signal was presented (+ + +) prior to the word to be named. The delay between the alerting signal and the target varied depending on the ISI condition in which the participant was randomly assigned. Participants were instructed to name each word aloud quickly and accurately. The average response time served as the participant’s normal naming interval. To control for individual differences in reading speed, sentence presentation rates were calibrated for each participant (cf. Paul et al., 1992).


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A set of 28 sentences, similar to the test stimuli, were presented one word at a time at an initial rate of 200 ms per word (all characters were shown in lower-case except for the first letter of the first word in each sentence which was capitalized). The display format resembled that used in the moving window procedure of McConkie and Rayner (1975), in which only a single word was visible at any given time (cf. Just et al., 1982). Participants were presented with the first word of the sentence and as soon as it disappeared the next word to the right appeared briefly and so on across the screen to the end of the sentence. This method was used to ensure that each participant’s reading speed would be based on consistent leftto-right reading, and not include strategies of back-tracking for memorization or waiting until the entire sentence was presented before reading it (thus over-estimating reading speed). Participants were instructed to read each sentence silently for comprehension. After each trial, participants answered a comprehension question and then reported whether the display rate was “too fast,” “too slow,” or “about right.” Presentation rate was subsequently adjusted by the experimenter (modulations of about 17 ms). Prior to the delayed naming task, participants were instructed that sentences would be displayed in a manner similar to the calibration trials except that each word of the sentence would remain on the screen until the sentence was fully presented (cf. Just et al., 1982: Cumulative condition). The presentation procedure differed from the calibration procedure in order to make sentence and target stimuli maximally distinct from one another during the experimental trials. After the sentence-final word was displayed, the entire sentence was removed from the screen simultaneous with the presentation of a target which appeared two character spaces to the right of where the sentence prime had ended. Targets were printed in upper-case letters to additionally distinguish them from the primes. Participants were to name the target quickly and accurately as soon as brackets enclosed the word (e.g., [KING]). To prevent participants from developing the strategy of ignoring the sentences, comprehension questions were asked on a random 20% of the trials. Errors were recorded by the researcher during the experimental session and included mispronunciations, responses made prior to the naming cue, trials in which extraneous noises triggered the VOR, and responses that failed to initially trigger the VOR. Results The baseline procedure resulted in mean naming times of 538 ms (SD = 45 ms) and reading calibration resulted in average reading times of 209 ms (SD = 33 ms) per word. Comprehension errors were approximately 4.5% overall.

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Table III. Means (M) and Standard Deviations (SD) in Milliseconds, and Error Proportion (E) for Target-Dominance, Salience, and Naming-Delay for Experiment 1 Naming delay Immediate

Baseline + 600 ms

Baseline

M

SD

E

M

SD

E

M

SD

E

High salient targets Dominant Subordinate

655 693

68 92

.08 04

412 423

47 49

.05 .05

391 382

64 65

.07 .03

Low salient targets Dominant Subordinate

691 696

78 73

.12 .10

439 429

55 52

.08 .05

391 390

50 58

.06 .08

A 2 (Target Dominance) × 2 (Salience) × 3 (Naming Delay) within subjects analysis of variance (ANOVA) was performed on mean response times, excluding error trials and responses slower than 1000 ms and faster than 200 ms. Table III contains subject means, standard deviations, and errors for each condition, and outcomes reported were significant at p < .05 unless otherwise indicated. The analysis revealed significant main effects of both salience, F (1, 23) = 13.52, MSE = 946.12, and naming-delay, F (2, 46) = 354.90, MSE = 6983.81. In addition, there were significant two-factor interactions of target-dominance with salience, F (1, 23) = 5.14, MSE = 748.84, and target-dominance with naming-delay, F (2, 46) = 4.97, MSE = 916.48. These outcomes were qualified by the significant three factor interaction of target-dominance, salience, and naming-delay, F (2, 46) = 3.78, MSE = 892.03. No other outcomes were significant. To visually simplify the priming outcomes, the results are presented in Fig. 1 as relative facilitation scores (response times to contextually inappropriate targets minus response times to contextually appropriate targets). In this case, because sentence contexts constrained the dominant senses of the sentence-final homographs, dominant-related targets are considered contextually appropriate (i.e., priming would be revealed through faster responses to dominant targets relative to responses to subordinate targets). As can be seen in Fig. 1, the interaction was due to priming only for highsalient targets at the immediate delay. Responses to dominant targets were faster (655 ms) than to subordinate targets (693 ms). Error Rates Although overall errors were few (5.7%), an ANOVA was performed on arcsin-transformed errors (cf. Winer, 1971, p. 400) to evaluate the


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Fig. 1. Average relative facilitation (responses to contextually inappropriate relative to contextually appropriate targets, or: subordinate (S) minus dominant (D) across naming delays for high- and low-salient targets.

possibility of speed-accuracy trade offs. No evidence of speed-accuracy trade offs was indicated to qualify conclusions concerning the latency outcomes.6 Discussion For the immediate naming condition, results converged closely with Paul et al., (1992) Experiment 2. That is, both outcomes support models claiming that initial activation of lexically ambiguous words within a sentence may be influenced by a prior context. In the present study, responses to dominant (i.e., contextually appropriate), high-salient targets were facilitated relative to subordinate (i.e., contextually inappropriate) targets. Unlike Paul et al. the present study failed to show significant priming for low-salient targets for immediate-naming, perhaps because 6

Errors tended to increase somewhat from baseline to the baseline +600 conditions as response latencies decreased. This is typical of delayed-naming tasks (e.g., Balota et al., 1989; Balota & Duchek, 1988; Connine et al., 1990; Rossmeissl & Theios, 1982) and appears to be due to an increase in anticipatory responses. At long naming delays, participants are more likely to pronounce the target before the cue to respond is presented.

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of the unusual nature of the task (i.e., some trials required delayed responses). The baseline naming delay was designed to assess the relatively late occurring interaction of context and target (if any) at the estimated moment in which processes leading to the execution of an articulatorymotor program were completed. According to the results, these processes primed naming responses but only for high-salient targets. The late involvement of context was clearly not apparent for low-salient targets. The simplest explanation for the rapid diminish in priming across the naming-delays is that, with dominant-constraining sentences, related and unrelated targets are easy to resolve, so do not require substantial postaccess processing. That is, because the most common interpretation of the homograph is also the sense constrained by the sentence, there is little additional benefit from a semantically consistent (dominant) target. Obviously, such a conclusion begs a comparison with subordinate constraining sentences. Such sentences would not be expected to enjoy the same degree of semantic activation (i.e., from both meaning-dominance and sentence context) necessary to overwhelm conflicting, or semantically inappropriate, information. It is also important to recognize that the priming effects observed in the immediate naming condition may be the result of benefits in responding to contextually appropriate targets, inhibition in responding to contextually inappropriate targets, or both. If on-line reading involves integrating new information (e.g., from a target) with the current semantic representation (cf. Carpenter & Daneman, 1981; Colombo & Williams, 1990; Sharkey & Sharkey, 1992), naming responses may be slowed only when attempts are made to integrate contextually inappropriate information (Colombo & Williams, 1990). In the present study, it is not possible to determine whether the differences in naming times were due to response slowing to subordinate targets and/or due to speeded responding to dominant (contextually appropriate) targets. However, it is clearly the case that context had some immediate influence on target naming. The overall conclusions drawn from the present results are that context can influence initial activation levels of meanings of ambiguous words. This is consistent with previous conclusions regarding context sensitivity and does not rely on providing evidence of activation or no activation to alternate meanings of the homograph (i.e., comparisons with “neutral” conditions). In addition, variations in performance were observed according to the strength of the semantic relationship between prime and target. This outcome suggests that activation to weakly related information is not sustained and consequently is unlikely to be as easily integrated with a prior context as strongly related information.


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One aspect of strength which was not evaluated in Experiment 1 concerns the homograph itself. According to Rayner and Pollatsek (1989, p. 233), there are two sources which contribute to the strength of a context containing an ambiguous word. One source is the context itself which affects how much activation a particular meaning receives (e.g., Paul et al., 1992; Van Petten & Kutas, 1987; Vu et al., 1998). The other source is the dominant sense of a homograph which will compete for activation with the less frequent meaning if the context is not biasing (cf. Swinney, 1979). Therefore, a logical next step to examining integration processes as a function of prime-target strength, is to evaluate context effects similarly to Experiment 1 but for the subordinate meaning of each homograph. This second experiment will also address an alternative account of a portion of the results from Experiment 1. The results of Experiment 1 discount strong versions of context-independent activation (i.e., that initial meaning activation is unaffected by prior context) but neither an ordered access account (Hogaboam & Perfetti, 1975) nor a reordered access account (e.g., Duffy et al., 1988; Rayner et al., 1994) can be discounted out of hand. It could be that, given the relatively impoverished sentences, the dominant meaning of a homograph is activated first no matter what the nominal bias of the context happens to be. Despite the fact that neither possibility is supported in similar studies of this nature (Kellas et al., 1991; Paul et al., 1992), strictly speaking, both an ordered access as well as a reordered access explanation can account for the results of Experiment 1 without appealing to context sensitive views. Therefore, in addition to addressing concerns of the strength of the semantic relationship between prime and target, Experiment 2 will allow stronger tests of these alternative accounts. It is worth reviewing at this point, that in terms of addressing our primary research goals, Experiment 1 has provided at least a partial picture of comprehension processes extending beyond initial activation. These processes either do not appear to require anything more than a rapid (or continued) suppression of low-salient information, or, they simply reflect the gradual decay of high-salient information following comprehension (i.e., there is no reason to sustain activation to a functionally unambiguous interpretation of a simple sentence). What remains to be determined is whether performance with subordinate-constraining sentences yields similar patterns, and if not, whether the nature of the activation to low-salient information comes from direct or indirect sources. Finally, should lowsalient information become initially activated as expected based on previous research, we hope to determine if this information is kept activated over the time course examined, or, if it disappears somehow (e.g., actively suppressed or allowed to decay).

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EXPERIMENT 2 Experiment 2 is conceptually identical to Experiment 1 with the exception that the contexts constrained the subordinate sense of the sentence-final homograph. Consequently, the most straightforward expectancy is that Experiment 2 will replicate the first experiment in terms of immediate context effects. That is, facilitation of contextually appropriate (in this case, subordinate) targets relative to contextually inappropriate (or dominant) targets should converge with Experiment 1 on a context sensitive view of initial meaning activation. This outcome is also reasonable to expect given that previous studies comparing dominant and subordinate primes similar to those used here produced context-sensitive outcomes (e.g., Kellas et al., 1991; Paul et al., 1992). In terms of later-occurring contributions to sentence comprehension, although they have never been directly evaluated with regard to meaning dominance, certain differences between the present experiments are reasonable to expect. For example, due to the relative infrequency with which the subordinate sense is used, activation levels of dominant information are typically greater than for subordinate information (cf. Simpson, 1984). However, there is evidence that the contribution of a constraining context appears sufficient to compensate for this meaning frequency effect initially (Kellas et al., 1991; Paul et al., 1992). The means by which context overcomes meaning frequency effects could be due either to the activation of subordinate information only (i.e., subordinate activated only), or increased activation to subordinate information above that for dominant (i.e., both dominant and subordinate activated). In the first case, late occurring contributions to performance are expected to be identical to those of Experiment 1. This is because, functionally, the most critical source of influence would be contextual constraint rather than meaning frequency. In the second case, reliance on later (ongoing) processes would presumably be required to maintain activation levels of weaker subordinate concepts above activation levels of dominant. Activation of the inappropriate dominant meaning of the homograph could result in two ways. First, the context may not be sufficiently strong enough to prevent initial multiple activation. Second, if the context is strong enough to prevent activation of the dominant sense, later activation of this sense might occur via backward priming during the naming-delay interval (although this was not observed in Experiment 1). In either case, it seems necessary that part of the integration process would be to boost activation levels of appropriate information above those of inappropriate information. These processes would probably operate only until dominant information no longer competed with appropriate subordinate information


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(i.e., until activation levels of dominant related targets are reduced) or until a response is made. Under these circumstances, then, it is very reasonable to expect context effects at the longer naming delays.

Method Participants Participants were 24 volunteers from psychology courses at the University of Kansas who did not participate in Experiment 1. An additional individual was excluded due to excessive errors (more than 15%). Participants received course credit, were native English speakers and had normal or corrected-to-normal vision.

Stimuli As can be seen in Table IV, targets for Experiment 2 were those used in Experiment 1. The only stimulus change was that sentence primes were used that constrained the homograph toward its less frequent (subordinate) sense. The mean number of words per sentence was 4.97 (SD = 1.08). All other aspects of Experiment 2 were identical to Experiment 1 including apparatus and procedure. Table IV. Sample Simuli used in Experiment 2 Target Prime sentence

High-salient

Low-salient

Contextually appropriate There was a faint beam We went to bowl They were all part of the cast I had to duck They closed the plant It began to ring

Light Ball Actors Avoid Factory Bells

Particle Points Action Crouch Labor Call

Contextually inappropriate There was a faint beam We went to bowl They were all part of the cast I had to duck They closed the plant It began to ring

Support Dish Plaster Quack Green Diamond

Above Cup Hold Paddle Life Promise

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Results The baseline assessment procedure resulted in average naming time estimates of 534 ms (SD = 41 ms) and the reading speed calibration procedure resulted in an average reading speed of 253 ms (SD = 31 ms). Comprehension errors averaged 6.3% overall. A 2 (Target Dominance) × 2 (Salience) × 3 (Naming Delay) within subjects analysis of variance (ANOVA) was performed on participants’ mean response times excluding error trials and responses slower than 1000 ms and faster than 200 ms. The analysis revealed significant main effects for all variables. The effect of target-dominance, F (1, 23) = 26.63, MSE = 646.01, resulted because contextually appropriate (subordinate-related) targets were responded to more quickly (503 ms) than contextually inappropriate (dominant-related) targets (518 ms). Both the main effect of salience, F (1, 23) = 16.56, MSE = 1013.17, and the main effect of naming-delay, F (2, 46) = 619.18, MSE = 3990.68, were qualified by the interaction of salience with naming-delay, F (2, 46) = 3.42, MSE = 701.66. This interaction essentially shows that facilitation in responding to high-salient targets relative to lowsalient targets tended to decrease as naming-delay increased. Table V contains participant means, standard deviations, and errors for all conditions, and Fig. 2 is provided to facilitate visual comparisons between experiments. All reported outcomes were significant at p < .05. Error Rates As in Experiment 1, response errors were few (5.2%). An ANOVA on arcsin-transformed errors revealed no effects which would indicate the presence of a speed-accuracy trade off (see footnote 5). Table V. Means (M) and Standard Deviations (SD) in Milliseconds, and Error Proportion (E) for Naming Delay, Salience, and Target-Dominance for Experiment 2 Naming delay Immediate

Baseline + 600 ms

Baseline

M

SD

E

M

SD

E

M

SD

E

High salient Targets Dominant Subordinate

699 675

74 67

.06 06

437 426

60 58

.04 .02

400 381

83 65

.06 .05

Low salient Targets Dominant Subordinate

707 693

68 68

.09 .08

465 451

74 69

.01 .03

402 392

81 70

.07 .08


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Fig. 2. Average relative facilitation (responses to contextually inappropriate relative to contextually appropriate targets, or: dominant (D) minus subordinate (S) across naming delays for high- and low-salient targets.

Discussion As expected, the immediate naming results converged with Experiment 1. Responses to contextually appropriate targets were facilitated relative to inappropriate targets, regardless of target salience. Together, the immediate naming conditions of Experiments 1 and 2 do not support context-independent views of initial context effects.7 Therefore, the present research converges with the context-sensitive results of Kellas et al. (1991) who used lexical decision and the modified Stroop results of Paul et al. (1992). In addition, because initial activation was found to be context sensitive regardless of prime dominance (see footnote 7), it cannot be argued that an additional role of the comprehension process is to compensate for initial ordered activation (e.g., Hogaboam & Perfetti, 1975; Rayner et al.,

7

A direct test across experiments verified this conclusion. The interaction of prime-dominance with target-dominance was highly significant, F (1, 46) = 22.80, MSE = 706.03. Responses to contextually appropriate targets (dominant targets following dominant primes and subordinate targets following subordinate primes) were faster than responses to contextually inappropriate targets (dominant targets following subordinate primes and subordinate targets following dominant primes).

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1994). Otherwise, dominant targets would have been responded to more quickly than subordinate targets regardless of contextual constraint. Although the present data rule out a context-independent view, they do not altogether support a strong context-dependent view (i.e., that contextually inappropriate, dominant, information is never activated). Rather, only a context-sensitive view can be supported; contextually appropriate information received greater activation than contextually inappropriate information. In fact, some activation of the contextually inappropriate but dominant sense of the constrained homograph makes the most sense when interpreting the present outcomes. What is new in the present research has to do with the outcomes observed in the delayed-naming conditions. According to the baseline and baseline +600 naming delay conditions, later processes affected naming times for both high- and low-salient targets. This outcome is very different from that of Experiment 1. Because the two experiments were identical except for the meaning of the sentence final homograph constrained by the context, it seems reasonable to infer that meaning frequency does affect the extent to which late occurring processes are initiated. One explanation that would require such late-occurring processes is that, because the dominant sense of an ambiguous word is used more frequently than the subordinate sense, initial activation levels may be relatively high regardless of the context in which it occurs. When the context biases the more frequent interpretation (as in Experiment 1), initial processing is facilitated and subordinate and/or less relevant information represented by a target does not interfere with the message level representation of the text. However, when the context biases a subordinate interpretation, initial activation levels of the dominant sense are nearly as high as those of the subordinate sense despite the fact that these dominant-related concepts are contextually inappropriate. In order for readers to maintain the contextually appropriate interpretation of the sentence, ongoing processes must generate and sustain greater levels of activation to subordinate information. Otherwise, the partial activation of dominant information would interfere with the appropriate semantic interpretation of the sentence. Together, facilitation of contextually appropriate, and/or interference from contextually inappropriate, targets likely resulted in the late-occurring effects observed across naming delays (cf. Colombo & Williams, 1990). It remains to be determined if biasing contexts can be constructed that are strong enough to overwhelm early and late occurring frequency effects. Another potential contribution to the necessity of late occurring processing in Experiment 2 is that bottom-up activation from the dominant related target may have resulted in additional activation to the dominant


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meaning of the sentence-final homograph (i.e., in a backward sense that would be independent of the sentence context; cf. Koriat, 1981; Peterson & Simpson, 1989). Therefore, although context may have affected initial meaning activation of the ambiguous word, later processes may have resulted in additional activation to the unprimed meaning. Maintenance of the contextually appropriate interpretation of the sentence during later target integration would require greater compensatory activation to contextually appropriate than inappropriate information to maintain coherence. This is supported by results from Van Petten and Kutas (1987) who found facilitation in naming times for multiple senses of homographs. However, a backward priming interpretation does not adequately explain why such bottom-up processes would have resulted in the activation of contextually inappropriate meanings of the homograph in Experiment 2, but not in Experiment 1.

GENERAL DISCUSSION There were three major goals addressed by the present research. First, we have provided a more complete picture of the processes of sentence comprehension by showing not only the traditional immediate patterns but also later occurring processes as they related to both meaning dominance and strength (salience). Of particular importance in the present research is the finding that the integration of new information with ambiguous word meanings only extends into later processes for subordinate senses of the ambiguous words. Apparently, for later integration, additional processing is required to sustain activation levels of these less frequent homograph meanings above activation levels of more frequent meanings. A second goal was to determine the source of activation of lowsalient information. Our findings suggest most strongly that low-salient information is initially activated differently for dominant and subordinate constraining sentences. Whereas we did not find evidence of activation to low-salient information related to dominant constrained homographs, there was evidence of approximately equal activation to both high- and low-salient information related to subordinate-constrained homographs. Finally, we were interested in establishing whether low-salient information was actively inhibited, or simply allowed to decay. The present results, unfortunately do not allow for a simple answer to this question. It appears that activation levels of both high- and low-salient information are reduced in Experiment 2 relative to what was observed for high-salient targets in Experiment 1. However, because priming was apparent across all naming delays, the results do not address the question. To do so would

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likely require much longer naming delays than those used in the present studies. In terms of secondary goals addressed by the present research, it can be said that our findings support context-sensitive models of initial context effects (Kellas et al., 1991; Martin et al., 1992; Paul, 1996; Paul et al., 1992; Van Petten & Kutas, 1987; 1991). In addition, the present research demonstrates the successful use of delayed-naming methodology for assessing later occurring comprehension processes. This conclusion is based on the simple assumption that when sufficient time is allowed to complete all processes associated with naming except execution of the response, any context effects observed must reflect influences that extend beyond (or continue to contribute to) access and identification of that word. These conditions were met by both the baseline and baseline +600 manipulations. The results from these conditions from both experiments demonstrated that processes following initial activation continue to be sensitive to context. These outcomes represent a more complete, albeit more complex, view of online sentence comprehension than has yet been demonstrated. Although the present study was limited in that it utilized only short, relatively impoverished contexts, evidence of context sensitivity and lateoccurring contributions to performance was found. It will be informative to extend these procedures and results to situations which examine how comprehension systems deal with different forms of prior context as well as different forms of ambiguity. This will be important at least for establishing whether context can override the local effects of meaning frequency in ambiguity resolution. In addition, the question of what happens to information that has been activated during comprehension, but found to be less relevant (i.e., low-salient) remains unanswered. It is possible that this question could be answered either by extending the delayed-naming conditions to evaluate longer processing durations, or, by increasing the strength of the contexts used to constrain subordinate senses of the sentence-final homographs.

ACKNOWLEDGEMENTS Special thanks are extended to David Balota, Mark Faust, David Eddington, and Bernard Steinman for their comments on earlier drafts of this manuscript. Preparation of this article was supported by NIA postdoctoral training grant #AG00030. Correspondence concerning this manuscript should be addressed to Stephen T. Paul, Robert Morris University, 6001 University Boulevard, Moon Township, Pennsylvania 15108-1189; E-mail: [email protected].


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