Chapter 1 Introduction
1.2 Research questions
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explore the processing of biased homophones in Chinese. The results indicated that both frequency and context were critical at an early time. Thus, it was compatible with interactive access hypothesis. In sum, it is uncontroversial that the context plays an important role in arriving at the appropriate meaning; however, whether contextual effect is acting early or late in the time course of ambiguity resolution remains unclear in Chinese.
1.2 Research questions
The present study conducts two eye movement experiments to reveal the continuous and incremental processing of semantic ambiguity resolution. Experiment 1 manipulates three types of Chinese two-character words in sentence reading task:
low frequent biased homographs (A), low frequent unambiguous word (LF), and high frequent unambiguous word (HF) and these words are all embedded in sentential contexts. More specifically, the biased homographs are incorporated in the subordinate-biased context. Experiment 2 uses visual world paradigm to probe the time course of lexical ambiguity resolution in an instructional eyetracking-during-listening task. The spoken sentences are similar to those in
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Experiment 1 and the visual stimuli are four disyllabic printed words containing dominant and subordinate semantic associates and two other unrelated distractors.
Specific research questions to be addressed are as follows:
(1) Does the subordinate bias effect exist in lexical ambiguity resolution of reading Chinese homographs? And if the SBE was established, when does the contextual influence occur in Chinese lexical ambiguity resolution (early or late)?
(2) We attempt to differentiate between the reordered and selective access model in lexical ambiguity resolution. The reordered access model proposes the competition account of the SBE; however, the selective access model posits that the SBE is in essence a word frequency effect. Which account (i.e. competition or frequency account) could be supported from the present data? .
(3) What is the fate of the unselected meaning? The reordered access model assumes that the activations of the unselected meaning passively decay. In contrast, the selective access model assumes that the unselected meaning was not accessed at all.
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8
Literature Review
2.1 Issues of lexical ambiguity resolution
Modular and interactive access hypotheses made different assumptions about the timing of contextual influence. Over the past few decades, researchers have used various approaches to investigate lexical ambiguity resolution. For example, cross-modal priming and eye-tracking methods have provided a substantial body of empirical evidence on theoretical accounts of how ambiguous words are processed. In particular, the subordinate bias effect has been found in eye movement studies when the preceding context supported the infrequent meaning of biased homographs. The existence of the SBE suggests that both linguistic context and relative frequency of the alternative meanings play an important role in lexical ambiguity resolution.
2.1.1 Processing models of lexical ambiguity resolution
A central issue in psycholinguistics is whether the successful and rapid meaning access is modular or interactive processing in nature. Although all models of lexical ambiguity resolution agree that context allows readers to determine the relevant
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meaning of a homograph, the perspectives on the time locus of contextual influence are diverse. Modular access hypothesis (Fodor, 1983) proposed the autonomous bottom-up processing in which lower levels of information (lexical module) were not directly influenced by the higher levels of information (discourse module). That is, the contextual information does not penetrate lexical access at the early stage. A contrasting hypothesis, interactive access hypothesis (Marslen-Wilson & Tyler, 1980;
McClelland & Elman, 1986) contended that the simultaneous bottom-up and top-down processing was operated interactively. Higher and lower levels of information can interact with each other at the early stage; therefore, contextual information can influence the activation of lexical meaning in early time. Models associated with the modular and interactive view were generated with their empirical evidence. Under the modular view, multiple and order access models were formed.
According to the interactive view, reordered and selective access models were proposed. Four models of lexical ambiguity resolution are reviewed in the subsequent part in the order of considering the role of context and then meaning dominance in lexical ambiguity resolution.
First of all, according to multiple or exhaustive access model (Onifer & Swinney, 1981; Swinney, 1979; Tanenhaus et al., 1979), all of the meanings of an ambiguous word were accessed temporarily and the contextual information can only help to
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select an appropriate meaning at post-lexical stage. The most compelling evidence of exhaustive access came from cross-modal priming studies. Participants were instructed to respond to the visual probes either by making a lexical decision or naming it after hearing the spoken sentences containing an ambiguous word. There were a related probe for each meaning and an unrelated probe. Participants saw one of the three possible probes. The reaction time of semantically related target to either meaning of ambiguous words was compared with that of semantically unrelated controls. For example, Onifer and Swinney (1981) presented sentences either biased for the dominant or for the subordinate meaning of an ambiguous word. Participants made lexical decision for the visual probe which may occur immediate at the auditory offset of the ambiguous words or 1.5 seconds delay. In the immediate condition, participants responded faster to either of the meaning-related probes than to an unrelated probe, thus, facilitation occurred for both dominant and subordinate meaning irrespective of context. In the delayed condition, facilitation was limited to one contextual-relevant probe as the time was lengthened between the occurrence of the ambiguous words and the probe. This implies that context only operates at post-lexical stage to select a single meaning after all meanings have been initially accessed. However, some researchers noted that the lexical decision or naming task is sensitive to backward priming or susceptible to guessing strategies, respectively, and
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thus the results may reflect post-lexical integration instead of lexical access (Balota & Chumbley, 1984).
The selective access model (G.B. Simpson, 1981; Tabossi et al., 1987; Tabossi &
Zardon, 1993) was developed to capture the results in the cross-modal priming studies.
When the appropriate context conditions were given, participants were faster to respond to a probe related to the contextually-appropriate meaning of an ambiguous word than to a probe related to contextually-inappropriate meaning. This is consistent with the notion that the access may be limited to the information derived from the context. To summarize, the discrepancy between multiple and selective access models lies in the locus (early versus late) of contextual information affecting meaning activation of ambiguous words. However, neither of them considered the meaning dominance of ambiguous words, which is an important factor in lexical ambiguity resolution.
Two competing models were proposed with the consideration for meaning dominance. The ordered access model is proposed by Hogaboam and Perfetti (1975) and G.B. Simpson and Burgess (1985). They maintained that, like the exhaustive model, the preceding context cannot influence on lexical access until the post-lexical stage of selecting appropriate meaning. However, the meaning was not parallel activated but the order of the activation was determined by the relative frequencies of
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alternative meanings of the ambiguous words, with the most frequent meaning being retrieved first (e.g., Hogaboam & Perfetti, 1975; Onifer & Swinney, 1981;
Schvaneveldt & Meyer, 1976; G.B. Simpson & Krueger, 1991). On the contrary, Duffy et al. (1988) proposed the reordered access model to account for their eye-movement results. The lexical access was exhaustive but the meaning activation was determined by both preceding contextual information and meaning dominance.
Generally, the most frequent meaning was activated but the contextual information can also boost the activation of context-appropriate meaning of an ambiguous word at the early stage. This led to the competition between multiple meanings when they were both available for the readers. To summarize, four models of lexical ambiguity resolution are classified with respect to considering the role of context and meaning dominance, and they are presented in Table 1.
Table 1. Different types of models of lexical ambiguity resolution Variables
Multiple access No
Late
Ordered access Yes
Interactive hypothesis
Selective access No
Early Reordered access Yes
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2.1.2 Empirical evidence for lexical ambiguity resolution
2.1.2.1 Eye-tracking paradigm and lexical ambiguity resolution
Readers move their eyes through lines in order to acquire information. Readers recognize words, access meaning and in the end integrate all the information in the course of understanding a text. In eye-tracking experiment, reader’s eye movements were monitored and recorded when the eyes proceed with a series of jumps (saccades) and stops (fixations). When readers recognize words and further integrate the obtained meanings into the constructed context for comprehension, the characteristics of words affect two types of decisions, where and when to move the eyes (Tsai & McConkie, 2003).There are some advantages of the eye-tracking paradigm comparing to cross-modal paradigm. First, the whole experiment is under the natural circumstance of reading sentences or texts. Second, unlike cross-modal paradigm, it is more sensitive to the on-line linguistic processing with readers’ eye fixation duration and fixation probability being measured.
A large number of eye movement studies have investigated lexical ambiguity resolution (K. S. Binder, 2003; Dopkins, Morris, & Rayner, 1992; Duffy et al., 1988;
Kambe, Rayner, & Duffy, 2001; Pacht & Rayner, 1993; Rayner, Cook, Juhasz, &
Frazier, 2006; Rayner & Duffy, 1986; Rayner et al., 1994; S. C. Sereno, 1995; S. C.
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Sereno et al., 2006; S. C. Sereno, J. M. Pacht, & K Rayner, 1992; Sheridan, Reingold,
& Daneman, 2009; Wiley & Rayner, 2000) Most of the studies focus on two variables:
(1) the meaning dominance1, and (2) the instantiated meaning of supporting context.
Meaning dominance concerns the relative frequency of alternative meaning of ambiguous words, thus, two types of homographs were differentiated. Balanced homographs have two fairly equally frequent meaning, and the biased homographs
have one highly frequent meaning (dominant meaning) and one or more less frequent meanings (subordinate meaning). For example, a balanced homograph such as case, with one meaning related to legal proceeding, the other related to containers and both of which are equally common in the language. In contrast, a biased homograph, like port, the dominant meaning “harbor” is more prevalent in the language than its
subordinate meaning, “a type of wine”.
Duffy et al. (1988) embedded the biased and balanced homographs in disambiguating information which either preceded or followed the two types of homographs, thus creating four conditions. Each type of homograph had an unambiguous control word matched with same word frequency and length. In general, when preceding contexts instantiated the subordinate meaning of biased homographs, reading times were longer on biased homographs compared with those of balanced
1 Meaning dominance could be operationally defined as the probability that a particular meaning associated with the homograph itself is given as the first response in word-association norming tasks.
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homographs or control words. On the contrary, in the neutral contexts, readers fixate longer on balanced homographs than on biased homographs or unambiguous control words. The example sentences and findings are summarized in Table 2.
Table 2. The materials and results summarized from Duffy, Morris, and Rayner (1988)
Meaning Dominance
Preceding Context
Balanced / control Biased / control
Prior context (Subordinate biasing)
Because they heard it from so far away, the bark/howl was
difficult to identify.
When she finally served it to her guests, the port/soup was a great
success.
Pattern of fixation
times(GD) Balanced = control Biased > control Prior context
(neutral)
Unfortunately the bark/howl was difficult to identify, because they
heard it from so far.
Last night the port/soup was a great success, when she finally
served it to her guests.
Pattern of fixation
times(GD) Balanced > control Biased = control Note: the ambiguous targets were presented in bold.
The results demonstrated that processing difficulty resulted from certain combination of contextual information and meaning dominance, such as, when the preceding context biased for the subordinate meaning, gaze duration was longer on biased homographs than on its unambiguous control words. The SBE reveals that longer processing time is needed when the preceding contexts support infrequent
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meaning of the biased homographs (e.g. with the infrequent meaning generated less than 8% of the time). However, the SBE is not consistently observed under certain conditions2. For example, Wiley and Rayner (2000) found no SBE when the ambiguous words were not strongly biased for frequent meaning (e.g. with the probabilities of infrequent meaning generated between 8% and 30% of the time) and the titles of the context passages were given to disambiguate the vague passage. It seems that SBE is consistently established only when the subordinate meaning is very infrequent but not moderately infrequent (see discussion in Duffy, Kambe, & Rayner, 2001, p. 36).
2.2 Subordinate Bias Effect (SBE) revisited
The existence of SBE implied that the language processing was likely to be interactive since the prior context influenced ambiguous word processing in an early
time. Two models based on interactive hypothesis were thus proposed. The reordered
2 In a number of experiments, Kellas and colleagues (Martin, Vu, Kellas, & Metcalf, 1999; Hoang Vu, Kellas, Metcalf, & Herman, 2000; H. Vu, Kellas, & Paul, 1998) have reported effective elimination of SBE through strong contextual manipulations. On the contrary, numerous others failed to eliminate the SBE from eye movement monitoring of skilled readers by manipulating characteristics of context, such as, contextual constraint, topic and conceptual repetition (Dopkins et al., 1992; Kambe et al., 2001;
Morris & Binder, 2002; Rayner et al., 1994).
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access model assumed that both meaning frequency and prior contextual information can influence ambiguous word processing, on the contrary, selective access model proposed that prior context determined and selected the appropriate meaning immediately regardless of the meaning dominance. Therefore, the reordered and selective access models accounted for the established SBE by proposing competition and frequency account respectively. The former assumed that the dominant meaning was activated, while, the latter was not. Sereno,et al. (1992) and Sereno,et al. (2006) have tested these two accounts. They argued that the appropriate control words should correspond to the frequency of component meaning since the overall word-form frequency was much higher than the subordinate meaning frequency. If only the context-appropriate meaning was activated, it was comparably fair to compare the fixation times between the homograph and its meaning frequency matched controls.
In the following subsections, we focus on the two accounts for SBE based on the reordered access and selective access model and their explanations of the fate of the dominant meaning.
2.2.1 Reordered versus selective access model
Duffy et al. (1988) proposed the reordered access model for lexical ambiguity resolution. The model makes four basic assumptions: first, lexical access is exhaustive
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and all possible meanings are accessed when the word form is activated. Second, meaning dominance determines the relative activation of multiple meanings. Third, lexical access is an interactive process, in which the preceding context participates in the initial access of word meaning and increase the contextually-appropriate interpretation of an ambiguous word. Fourth, the activation level of the contextually-inappropriate meaning is unaffected. The SBE has served as a test ground for investigating the assumption that access is exhaustive. The most accepted account of SBE is proposed by reordered access model which maintains that the dominant meaning is activated due to its relative frequent meaning and the subordinate meaning is boosted by context. Both meanings compete for selection, thus resulting in the longer gazes on ambiguous words. The competition was apparently manifested in eye movement behaviors. Reading was disrupted with longer fixation durations and ambiguous words received more regressions when they followed subordinate-instantiated context (Duffy et al., 2001; Kambe et al., 2001).
Duffy et al. (2001) pointed out that although context supported the less likely meaning, the dominant meaning was not eliminated in the process. Rayner et al. (2006) suggested that the subordinate bias effect resulted from the automatic processing of the dominant meaning. Contextual information does not override the access of dominant meaning.
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According to the selective access model, the SBE was a word frequency effect.
In other words, a single meaning was activated without retrieving the other meanings associated with that form. It takes longer processing time to access to the infrequent meaning (Kellas & Vu, 1999; S. C. Sereno et al., 1992; G. B. Simpson & Kreuger, 1991). Sereno, et al. (1992) used two control conditions to examine the selective account of SBE as only the frequency effect instead of the meaning dominance which should determine processing time. One control was matched to the form frequency of an ambiguous word, namely HF control. Another LF control word was matched with the frequency of subordinate interpretation, which was estimated as the proportion of form frequency. That is, an interpretation with a meaning bias of .15 was estimated to have a meaning frequency that was 15% of the form frequency of ambiguous words.
They obtained the typical SBE when the form frequency control was used to compare with biased homographs. Additionally, they reported longer fixations in post-target (fixation time on the next two words of target), which indicated that ambiguity continued to next region. On the contrary, when the meaning frequency control was the comparison condition, they found SBE in total viewing time and post-target duration but not in target GD. Sereno, et al. (2006) used similar control words to investigate the SBE. They hypothesized that the use of stronger contexts would decrease the SBE related to the word-form (HF) controls and eliminate the SBE
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related to the word-meaning (LF) controls, as in Sereno, et al.(1992). They reported the SBE with respect to HF words in target measures, but not in spillover measures. In contrast, reverse SBE was found with respect to LF words in target measures, namely shorter fixation times for biased homographs compared with that for LF words. They claimed that the biased homograph represented a special case in which the word form was a high-frequency word, but the context it occurred intended a low-frequency meaning. Therefore, an ambiguous word’s fixation-time can be determined by the contribution of its form and meaning during lexical access process. In terms of word form, the homograph should be processed no faster than an HF control but faster than an LF control (e.g., gaze durations: LF>A≧HF). In terms of word meaning, the homograph should be processed much slower than an HF control but no slower than an LF control (e.g., gaze durations: LF≧A>>HF). This finding indicated that only the subordinate meaning of the homograph was accessed. The comparison of results in Sereno,et al.(1992) and Sereno,et al. (2006) are summarized in Table 3.
To summarize, the studies of Sereno et al. (1992) and Sereno et al. (2006) addressed important claims regarding whether the SBE is due to the different manipulations of the control words. This raised the concern that the SBE, instead of reflecting the competition between two meanings, but the increased time may result from effort to access and integrate a lower frequency word. This provided another