We investigated the extent to which a reader’s prior knowledge about words specifically, the quality of semantic knowledge is associated with efficiently recognizing words in context during a natural, sentence reading task. The pattern of results suggests vocabulary knowledge is associated with
qualitative differences in lexical processing, evident in early eye movement measures, and differences in comprehension processes, evident in late eye movement measures. By manipulating lexical-semantic relatedness and word frequency, we demonstrate differential effects for readers with high- and low-quality semantic knowledge partially supporting predictions of the RSF [
9]. High quality knowledge was related to faster initial reading times and less rereading behavior overall. The interaction between lexical quality, co-occurrence and frequency indicates that readers across the range of vocabulary knowledge are sensitive to lexical context, which sometimes facilitated recognition and comprehension as predicted, particularly for those with high quality semantic knowledge. However, contrary to predictions, low quality semantic knowledge was associated with
longer gaze durations (and a trend in FF) on low frequency words in related context compared to when the same low frequency words in unrelated context. This suggests that for readers with the lowest quality semantic knowledge, there was a higher processing demand associated with a large cost when recognizing low frequency words in related context. This will be discussed in further detail below.
4.1. Individual Differences in Lexical Quality
The current study measured the vocabulary and spelling knowledge of a sample of skilled, adult readers – college students. As such, participants are assumed to be a relatively skilled subset of the general population with experience reading a wide variety of texts independently for comprehension. Despite this characterization, a wide range of vocabulary and spelling skill was observed in the current sample. Although high spelling knowledge was associated with faster reading time overall and an increased probability of skipping the target word, the effect of spelling on all target word reading measures was additive. Thus, the differences in word recognition associated with spelling knowledge appear to be quantitative differences; highly skilled spellers are faster readers than less skilled spellers.
Although accurate orthographic representations, indexed by spelling skill, can enable the rapid activation of precise semantic representations, indexed by vocabulary skill, no significant interactions of spelling and vocabulary were observed, suggesting independent effects on word recognition. Instead, vocabulary knowledge uniquely interacted with frequency and relatedness on all target word reading measures resulting in a pattern indicative of qualitative differences in word recognition processes. These results suggest a critical role for vocabulary knowledge when reading words in context.
4.2. Semantic Quality and Vocabulary Knowledge
For below average readers, the post-hoc analyses of gaze duration and total time revealed a similar pattern of effects. The results suggest that the difference in total reading time for high and low frequency targets in the related condition is due in large part to an increase in reading times for low frequency words (relative to low frequency, unrelated targets), not faster reading of high frequency words. This could indicate that readers with low vocabulary knowledge had difficulty recognizing low frequency words in lexically related context and returned to reread resulting in a delayed effect of frequency. Although the effect was not significant in gaze duration, variation among those below average in vocabulary skill was larger compared to the other skill groups. Reading times were however numerically longer on low compared to high frequency target words. Taken together, the results are most compatible with the interpretation that the interactive effects on target word reading are largely attributable to difficulty processing low frequency words in related context.
For the readers above average in vocabulary knowledge, the difference between reading times for high and low frequency words in the unrelated condition indicates that, despite their high vocabulary knowledge, there is no evidence to suggest a reduced frequency effect as predicted by the LQH. Additionally, the post-hoc analysis of gaze duration resulted in a marginally significant, but unpredicted, effect of word frequency; above average readers took longer to read high frequency target words in related context compared to the same high frequency words in unrelated context. This suggests the interaction effect on gaze duration for the highest skilled readers is best characterized by longer reading times on high frequency words, not faster reading of low frequency words, as predicted. However, the post-hoc analysis of total time resulted in a null effect of relatedness on high frequency words and instead indicated that low frequency related target words were read significantly faster than low frequency, unrelated target words. Together the results suggest that readers with above average vocabulary knowledge, unlike those below average in vocabulary, were able resolve any initial difficulty recognizing related, high frequency words without the need to reread.
4.3. Context Effects and the RSF
By accounting for reader-specific vocabulary knowledge, the current study demonstrated that readers sometimes took longer to read target words in lexically related context; this finding is inconsistent with traditional models of lexical context effects. Lexical context, defined by word-to-word associations, is thought to facilitate word recognition through spreading activation wherein the currently active areas of long-term memory (LTM) yield activation in other, related areas of LTM. This automatic, pre-activation of lexically related candidates facilitates word recognition through a speeded search process [
21,
52]. In this account, word recognition following a lexically related word should be faster than, or equivalent to, recognition of the same word when it is unrelated to previous words. However, in the current study, the interactive effects on target word reading measures are best characterized in terms of slower reading times, not faster. This demonstrates that lexically related context is not necessarily facilitative, and may instead make word recognition more demanding, a finding incompatible with an automatic spreading activation account of lexical context effects.
Alternative accounts of lexical context effects based on word-to-text integration processes make similar predications regarding the facilitative effect of lexical context during word recognition. Previous research has suggested situational model priming wherein word recognition is facilitated when the word fits with the text representation, can account for lexical context effects [
16]. Situation model priming was also incorporated into the Reading Systems Framework (RSF), a broad view of the reading architecture that further accounts for the effects of lexical quality [
9]. The RSF clarifies situation model priming by incorporating a backwards memory mechanism to describe how readers integrate new words into developing text representations. According to the RSF, as lexical entries become active candidates for word recognition their representations activate associated parts of LTM; when these activated areas of LTM ‘resonate’ with the areas of LTM activated by the text representation, word recognition may be facilitated [
30]. However, this model also predicts that word recognition and/or integration with the text representation should be easier when words are related. That is, in the experimental sentences from the current study, “He examined his
arms and
elbow when he fell yesterday,” and “He examined his
teeth and
elbow when he fell yesterday,” ‘elbow’ should be more easily incorporated into a situation model and/or should ‘resonate’ more strongly with the text representation when it follows the related prime word ‘arms’ than when it follows ‘teeth.’ A lexical quality account may propose that low skill readers have difficulty forming a text representation and/or that low quality semantic representations do not ‘resonate’ with text representations very strongly. However, in both instances, it should be no more difficult to recognize the word ‘elbow’ following ‘arms’ than ‘teeth’ nor should it be more difficult to integrate into the text representation. The finding that readers sometimes had longer reading times in the related condition suggests that recognizing and/or integrating words in lexically related contexts may actually be more challenging for some readers than recognizing and/or integrating the same words in unrelated contexts, inconsistent with predictions derived from situation model priming.
Integration accounts of context effects in reading attribute context effects to difficulty incorporating word meanings into a developing text representation after word recognition is complete. This differs from situation model priming in that integration occurs only after lexical processing has resulted in word recognition. Thus, integration accounts assert that longer initial reading times are due to a failure at a post-lexical stage rather than during lexical word recognition [
53]. When integration failures occur, readers often regress to the place in the text where the difficulty occurred [
54]. In the current study, there was a relatively low but significant probability of regressing from the post-target region into the target word (
M = 13%,
SD = .34). Thus, it does not appear as though most readers left the post-target region to return to the target word specifically. Instead the probability of regressing out of the post-target region suggests that readers had more comprehension difficulty following low frequency, related words and this was most likely for readers low in vocabulary knowledge. Nonetheless, few readers experienced integration failure specific to the target word. Therefore, any integration failure is unlikely to be the result of lexical relatedness but may be due to post-lexical processing and attributed to more general comprehension difficulties.
Moreover, much of the evidence supporting early word-to-text integration effects during word recognition has been conducted with experimental manipulations of plausibility [
55,
56], predictability [
57], message-level context [
13,
14,
16,
58], and discourse processing [
59,
60]. Manipulations of plausibility and predictability are necessarily confounded with message-level context and therefore not good candidates for isolating a lexical effect of context on word recognition. The current study maintained sentence plausibility and predictability such that within frequency conditions, sentences differed by a single prime word but target words remained the same to minimize any effects from differences in message-level context and eliminate word-specific lexical factors. All prime words and targets words were nouns contained within the same sentence clause to ensure that effects were not attributable to syntactic processing (e.g., verb-noun linking) and/or to integrative processing that occurs across clause boundaries [
9]. Therefore, the effects observed in early processing in the current study are not likely attributable to syntactic or contextual differences across conditions. Similarly, the demands on integrative processing are relatively consistent across conditions. Instead, because frequency has long been considered a lexical factor, the interaction of lexical context and vocabulary knowledge with word frequency during initial processing is indicative of a lexical effect.
The presence of the interaction as early as first fixation indicates that lexical relatedness information is available in the earliest stages of word recognition, however the specific effect of relatedness depends on the reader’s vocabulary knowledge. Any effect of lexical context is contingent on readers having previously encoded the word-to-word relationships captured by lexical co-occurrence. Readers across the dimension of vocabulary knowledge were sensitive to these lexically encoded relationships, only those with high vocabulary knowledge benefited from this additional source of input. Lexically related context may therefore be more advantageous in supporting reading comprehension for those readers with a high level of vocabulary knowledge to rely on.
4.4. Lexical-Semantic ‘Dischord’ and Future Directions
Two distinct patterns of reading emerged. Readers assumed to have strong semantic knowledge to rely on appeared to quickly, efficiently activate meaning from lexical processing regardless of condition but lexical context appeared to create an additional early processing demand for high frequency words in related context, consistent with rapid word-to-text identification and integration as predicted by the RSF 9. Readers assumed to have the weakest semantic knowledge also appeared to make use of lexical context to support word recognition, but critically this effect was only observed for high frequency words and did not appear to facilitate word-to-text integration. Moreover, unlike readers with strong semantic knowledge, these readers took more time to process low frequency words when they were related, relative to all other conditions. The longer initial reading measures may indicate difficulty accessing the meaning of low frequency words when they appear in context. Later processing measures further support this interpretation.
One explaination for this finding, consistent with a lexical quality account, is that the multiple sources of lexical input which sometimes produced relatively ‘harmonious’ lexical activation produced under other conditions, for different readers a more discordant pattern of lexical activation, impeding access to or selection of the correct meaning. One source of activation for semantic knowledge is orthographic processing of the target itself (e.g., elbow), which when unrelated produced a decrease in the magnitude of the frequency effect as semantic quality decreased. The other source of input is received from the preceding context, in the current study a lexically related (e.g., arms) or unrelated word (e.g., teeth). As both sources activate lexical semantics at different time points, different lexical candidates compete for selection. One artifact of our experimental materials is that for low frequency targets in particular, the preceding context may strongly activate a high(er) frequency lexical candidate activated via context and via its semantic association with the target. For example, arms may pre-activate hands, and elbow, becoming active via orthographic processing, may further produce activation for an unseen, related word, like hands, a high frequency competitor, one which fits syntactically and thematically in the sentence. The hypothesis that a higher frequency competitor can impede access to meaning can be investigated in future research. A more direct test of this hypothesis could use the fast-priming paradigm developed by Rayner et al. [
61]. This eye tracking technique presents a word within a sentence briefly (e.g., 25ms) before changing to a different word. Though most readers are unaware of a change it nevertheless impacts automatic lexical processing. Future research should continue to explore the nuanced relationships between frequency, context, and semantic quality.