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In the standard Proportion-Congruent (PC) paradigm, performance is compared between a list containing mostly congruent (MC) stimuli (e.g., the word RED in the color red in the Stroop task; Stroop, 1935) and a list containing mostly incongruent (MI) stimuli (e.g., the word BLUE in red). The PC effect, the finding that the congruency effect (i.e., the latency difference between incongruent and congruent stimuli) is typically larger in an MC list, has been interpreted by the popular conflict-monitoring account (Botvinick et al., 2001) as reflecting a proactive process whereby attention to task-relevant information is adapted based on how frequently conflict from task-irrelevant information arises. Recently, however, alternative accounts of the PC effect have emerged that assume either that the PC effect reflects processes other than proactive conflict adaptation (e.g., stimulus-response contingency learning) or that proactive conflict adaptation is only engaged as a last resort (e.g., when contingency learning cannot be used to minimize interference). We examined these ideas in three experiments in which proactive conflict adaptation could be evaluated independently from processes that are normally confounded with it in the PC paradigm, while still allowing those processes, particularly contingency learning, to be used to minimize interference. Consistent with the conflict-monitoring account of the PC effect, but inconsistent with all the alternative accounts of the PC effect, evidence for proactive conflict adaptation emerged in all experiments. Although multiple processes may be engaged in the PC paradigm, this paradigm remains a valid tool for examining proactive conflict adaptation, its typical use.

According to some accounts, the bilingual advantage is most pronounced in the domain of executive attention rather than inhibition and should therefore be more easily detected in conflict adaptation paradigms than in simple interference paradigms. We tested this idea using two conflict adaptation paradigms, one that elicits a list-wide proportion-congruent effect and one that elicits an item-specific proportion-congruent effect. In both cases, the relevant finding is that congruency effects are reduced when the proportion of congruent to incongruent items is smaller. These effects are validated measures of proactive and reactive control, respectively, and are aspects of executive attention known to be associated with individual differences in working memory capacity. We reasoned that if bilingualism affects executive attention in a similar way as does working memory capacity, indices of proactive and reactive control should be comparably associated with continuous variation in language status and working memory capacity. In two experiments, we replicated previous findings that working memory capacity is associated with variation in congruency effects (suggesting greater reliance on proactive control). In contrast, language status had no consistent association with performance, save for a hint that bilingualism may be associated with greater reliance on reactive control. Thus, the bilingual advantage may exist, but not in proactive control or any other aspects of executive attention that have been proposed thus far.

Using two-character Chinese word targets in a masked priming lexical-decision task, Gu and colleagues (2015) demonstrated a significant transposed character (TC) priming effect. More importantly, the priming effect was the same size for single-morpheme words and multiple-morpheme words, suggesting that TC priming effects are not influenced by morphemic structure. In Chinese, there are, however, two types of single-morpheme words, single-morpheme simple words (e.g., [Chinese characters omitted] [similar to "practice" in English]) and single-morpheme complex words (e.g., [Chinese characters omitted] [similar to "carpet" in English in that both components are words themselves and, hence, when presented in transposed order, may activate morphological information reflecting the individual components rather than the word itself]), a contrast that Gu et al. did not examine. In Experiment 1, we replicated Gu et al.'s finding of equal TC priming effects for their single- and multiple-morpheme words, although our priming effects were noticeably smaller than theirs. In Experiment 2, we split the single-morpheme condition in order to examine the TC priming effects for single-morpheme simple words, single-morpheme complex words and multiple-morpheme words. The results showed that the single-morpheme complex words produced the smallest priming effect, indicating that transposed morphemes can influence masked priming in Chinese; however, apparently only in an inhibitory fashion.

In the Stroop task, congruency effects are typically larger forcolor words presented mainly in their congruent color than forcolor words presented mainly in incongruent colors.However, the nature of this item-specific proportioncongruent (ISPC) effect is debated: It might be produced byeither conflict-adaptation processes (e.g., focus attention totask-relevant information when the word BLUE appears)and/or a more general contingency-learning process (e.g.,anticipate a green response when the word BLUE appears).We re-examined the role of conflict-adaptation processes inthis paradigm in two experiments. In both experiments, aconflict-adaptation effect emerged on stimuli matched oncontingency. Further, in Experiment 2, we found separateeffects of adaptation to the frequency of conflict specific tothe color and word dimensions of individual stimuli. Theseresults challenge the contingency-learning account of theISPC effect and suggest that conflict-adaptation processes inthis paradigm may depend on both task-relevant and task-irrelevant information.

In the Stroop task, congruency effects (i.e., the color-naming latency difference between incongruent stimuli, e.g., the word BLUE written in the color red, and congruent stimuli, e.g., RED in red) are smaller in a list in which incongruent trials are frequent than in a list in which incongruent trials are infrequent. The traditional explanation for this pattern is that a conflict-monitoring mechanism adjusts attention to task-relevant versus task-irrelevant information in a proactive fashion based on list-wide conflict frequency. More recently, however, multiple alternative explanations have been advanced that could explain the pattern without invoking this form of proactive control: Individuals might only adapt to conflict frequency specific to individual items (as opposed to list-wide conflict frequency), they could learn word-color contingencies (e.g., how often a particular word and color are paired), or they could adapt attention based on whether the words are informative of the color (even if many word-color pairings are incongruent) in the list as a whole. To examine this issue, we designed a new paradigm that should eliminate any impact of these alternative mechanisms. In that paradigm, the proportion of neutral (e.g., XXX in red) and incongruent stimuli was manipulated across lists. Paralleling the results in the original paradigm, there was a smaller latency difference between incongruent and neutral stimuli in a list in which incongruent trials were frequent than in a list in which incongruent trials were infrequent, suggesting that proactive control in response to list-wide conflict frequency is a process humans can and do use.

A word's exterior letters, particularly its initial letter, appear to have a special status when reading. Therefore, most orthographic coding models incorporate assumptions giving initial letters and, in some cases, final letters, enhanced importance during the orthographic coding process. In the present article, 3 masked priming experiments were carried out, using the conventional lexical-decision task, the sandwich priming lexical-decision task and the masked priming same-different task, in an attempt to examine a number of those models with a specific focus on the implications of the models' assumptions concerning the different letter positions. The related primes and targets were 6-letter strings that differed in 2 letter positions, initial (e.g., "jnckey-HOCKEY"), middle (e.g., "hojney-HOCKEY"), or final ("hockjn-HOCKEY"), with the middle-letters different primes being the primes that maintained both end letters. To the extent possible, the predictions of the models were derived by using easyNet, the simulation program recently developed by Adelman, Gubian, and Davis (2017). In all experiments, the final-letters different primes were the most effective primes with there being no clear distinction between the other 2 prime types, a pattern that none of the models predicted. The lack of an advantage for the middle-letters different primes suggests that the orthographic code driving masked priming is not one that places a special emphasis on the identities of the exterior letters.

A consistent finding in the Stroop literature is that congruency effects (i.e., the color-naming latency difference between words presented in incongruent vs. congruent colors) are larger for mostly-congruent items (e.g., the word RED presented most often in red) than for mostly-incongruent items (e.g., the word GREEN presented most often in yellow). This "item-specific proportion-congruent effect" might be produced by a conflict-adaptation process (e.g., fully focus attention to the color when the word GREEN appears) and/or by a more general learning mechanism of stimulus-response contingencies (e.g., respond "yellow" when the word GREEN appears). Under the assumption that limited-capacity resources are necessary for learning stimulus-response contingencies, we examined the contingency-learning account using both Stroop and nonconflict (i.e., noncolor words written in colors) versions of a color identification task while participants maintained a working memory (WM) load. Consistent with the contingency-learning account, WM load modulated people's ability to learn contingencies in the nonconflict task. In contrast, across 3 experiments, WM load did not affect the item-specific proportion-congruent effect in the Stroop task even though we employed a design (the "2-item set" design) in which contingency learning should be the dominant process. These results imply that the item-specific proportion-congruent effect is not merely a byproduct of contingency learning but a manifestation of reactive control, a mode of control engagement that may be especially useful when WM resources are scarce.

Considerable research effort has been devoted to investigating semantic priming effects, particularly, the locus of those effects. Semantically related primes might activate their target's lexical representation (through automatic spreading activation at short stimulus onset asynchronies (SOAs), or through generation of words expected to follow the prime at longer SOAs). Alternately, semantically related primes might aid responding after target identification (i.e., postlexically). In contrast, masked orthographic priming effects appear to be lexical and automatic. Lexical processing of targets is facilitated by orthographically similar nonword primes and often inhibited by orthographically similar word primes (Davis & Lupker, 2006). Using the lexical-decision task (LDT), we found additivity between the facilitative effects of visible semantic primes and the facilitative effects of masked orthographically similar nonword primes at long and short SOAs, consistent with a postlexical locus of the semantic priming effects. Also consistent with this conclusion, semantic primes affected the skew of the distribution (larger effects on longer latency trials), whereas masked orthographic primes did not. In a final experiment, visible primes that were semantically related to the masked orthographic word primes did not make those primes more effective lexical inhibitors of orthographically similar targets (independent of SOA). Taken together, our findings suggest that the impact of a semantic prime is not to increase the lexical activation of related concepts. Rather, they suggest that the locus of semantic priming effects in LDTs is postlexical, in that discovering the existence of a relationship between the prime and target biases participants to make a "word" response.

Perceptual learning accounts of orthographic coding predict that transposed-letter (TL) priming effects should be smaller when the prime and target stimuli are not presented in their canonical (left-to-right horizontal in English) orientation (Dehaene, Cohen, Sigman, & Vinckier, 2005; Grainger & Holcomb, 2009). In contrast, abstract letter unit accounts would propose that TL priming effects should be essentially unaffected by presenting stimuli in most unfamiliar text orientations (Witzel, Qiao, & Forster, 2011). In the present experiments, we examined masked TL priming effects with primes and targets presented in 3 different text orientations (e.g., 0 degrees, as well as 90 degrees and 180 degrees rotations). Results revealed that the magnitude of the TL priming effect with native English readers was equivalent for stimuli presented in these three orientations, providing support for abstract letter unit accounts of orthographic coding.

Does visuospatial orientation influence repetition and transposed character (TC) priming effects in logographic scripts? According to perceptual learning accounts, the nature of orthographic (form) priming effects should be influenced by text orientation (Dehaene, Cohen, Sigman, & Vinckier, 2005; Grainger & Holcomb, 2009). In contrast, Witzel, Qiao, and Forster's (2011) abstract letter unit account argues that the mechanism responsible for such effects acts at a totally abstract orthographic level (i.e., the visuospatial orientation is irrelevant to the nature of the relevant orthographic code). The present experiments expanded this debate beyond alphabetic scripts and the syllabic Kana script used by Witzel et al. to a logographic script (Chinese). Experiment 1 showed masked repetition and TC priming effects with primes and targets presented in both the conventional left-to-right horizontal orientation and the vertical top-to-bottom orientation, replicating Witzel et al. Experiment 2 showed masked repetition and TC priming effects even when both the primes and targets were presented in the right-to-left orientation, a rare but existent text orientation in Chinese. In Experiment 3, the primes, but not the targets, were presented in the right-to-left orientation. Priming effects were again obtained regardless of the fact that the primes and targets appeared in different orientations. Experiment 4, which involved primes and targets presented in a completely novel bottom-to-top orientation, also produced a TC priming effect. These results support abstract letter/character unit accounts of form priming effects while failing to support perceptual learning accounts.

The present experiment provides an investigation of a promising new tool, the masked priming same-different task, for investigating the orthographic coding process. Orthographic coding is the process of establishing a mental representation of the letters and letter order in the word being read which is then used by readers to access higher-level (e.g., semantic) information about that word. Prior research (e.g., Norris & Kinoshita, 2008) had suggested that performance in this task may be based entirely on orthographic codes. As reported by Lupker, Nakayama, and Perea (2015a), however, in at least some circumstances, phonological codes also play a role. Specifically, even though their 2 languages are completely different orthographically, Lupker et al.'s Japanese-English bilinguals showed priming in this task when masked L1 primes were phonologically similar to L2 targets. An obvious follow-up question is whether Lupker et al.'s effect might have resulted from a strategy that was adopted by their bilinguals to aid in processing of, and memory for, the somewhat unfamiliar L2 targets. In the present experiment, Japanese readers responded to (Japanese) Kanji targets with phonologically identical primes (on "related" trials) being presented in a completely different but highly familiar Japanese script, Hiragana. Once again, significant priming effects were observed, indicating that, although performance in the masked priming same-different task may be mainly based on orthographic codes, phonological codes can play a role even when the stimuli being matched are familiar words from a reader's L1.

Models of written word recognition in languages using the Roman alphabet assume that a word's visual form is quickly mapped onto abstract units. This proposal is consistent with the finding that masked priming effects are of similar magnitude from lowercase, uppercase, and alternating-case primes (e.g., beard-BEARD, BEARD-BEARD, and BeArD-BEARD). We examined whether this claim can be readily generalized to the 2 syllabaries of Japanese Kana (Hiragana and Katakana). The specific rationale was that if the visual form of Kana words is lost early in the lexical access process, alternating-script repetition primes should be as effective as same-script repetition primes at activating a target word. Results showed that alternating-script repetition primes were less effective at activating lexical representations of Katakana words than same-script repetition primes--indeed, they were no more effective than partial primes that contained only the Katakana characters from the alternating-script primes. Thus, the idiosyncrasies of each writing system do appear to shape the pathways to lexical access.

There is broad consensus that printed complex words are identified on the basis of their constituent morphemes. This fact raises the issue of how the word identification system codes for morpheme position, hence allowing it to distinguish between words like "overhang" and "hangover", and to recognize that "preheat" is a word, whereas "heatpre" is not. Recent data have shown that suffixes are identified as morphemes only when they occur at the end of letter strings (Crepaldi, Rastle, & Davis, 2010, "Morphemes in Their Place: Evidence for Position-Specific Identification of Suffixes," "Memory & Cognition, 38", 312-321), which supports the general proposal that the word identification system is sensitive to morpheme positional constraints. This proposal leads to the prediction that the identification of free stems should occur in a position-independent fashion, given that free stems can occur anywhere within complex words (e.g., over"dress" and "dresser"). In Experiment 1, we show that the rejection time of transposed-constituent pseudocompounds (e.g., "moonhoney") is longer than that of matched control nonwords (e.g., "moonbasin"), suggesting that honey and "moon" are identified within "moonhoney", and that these morpheme representations activate the representation for the word "honeymoon". In Experiments 2 and 3, we demonstrate that the masked presentation of transposed-constituent pseudocompounds (e.g., "moonhoney") facilitates the identification of compound words ("honeymoon"). In contrast, monomorphemic control pairs do not produce a similar pattern (i.e., "rickmave" did not prime "maverick"), indicating that the effect for "moonhoney" pairs is genuinely morphological in nature. These results demonstrate that stem representations differ from affix representations in terms of their positional constraints, providing a challenge to all existing theories of morphological processing. (Contains 7 tables and 3 footnotes.)

Studies using the lexical decision task with English stimuli have demonstrated that homophones are responded to more slowly than nonhomophonic controls. In contrast, several studies using Chinese stimuli have shown that homophones are responded to more rapidly than nonhomophonic controls. In an attempt to better understand the impact of homophony, we investigated homophone effects for Japanese kanji words in a lexical decision task. The results indicated that, whereas a processing disadvantage emerged for homophones when they have only a single homophonic mate (as in the English experiments), a processing advantage occurred for homophones when they have multiple homophonic mates (as in the Chinese experiments). On the basis of these results, we discuss the nature of the processes that may be responsible for producing the processing advantages and disadvantages for homophones. (Contains 8 tables and 11 footnotes.)

In most current models of word recognition, the word recognition process is assumed to be driven by the activation of letter units (i.e., that letters are the perceptual units in reading). An alternative possibility is that the word recognition process is driven by the activation of grapheme units, that is, that graphemes, rather than letters, are the perceptual units in reading. If so, there must be representational units for multiletter graphemes like CH and PH, which play a key role in this process. We examined this idea in four masked priming experiments. Primes were created by transposing, replacing entirely, or removing one component of either multiletter graphemes or two adjacent letters that each represented a grapheme, using both English and Spanish stimuli. In none of the experiments was there any evidence of differential priming effects depending on whether the two letters being manipulated formed a single grapheme or formed two separate graphemes. These data are most consistent with the idea that multiletter graphemes have no special status at the earliest stages of word processing and, therefore, that word recognition is, indeed, driven by the activation of units for individual letters. (Contains 9 tables, 3 figures and 6 footnotes.)

Three experiments are reported investigating the role of letter order in orthographic subset priming (e.g., "grdn"-GARDEN) using both the conventional masked priming technique as well as the sandwich priming technique in a lexical decision task. In all three experiments, subset primes produced priming with the effect being considerably larger when sandwich priming was used. More importantly, there was very little difference in the degree of priming produced by subset primes with transposed (i.e., "gdrn") vs. nontransposed ("grdn") internal letters. The priming effects with transposed letter subset primes contradict Peressotti and Grainger's claim that letter order must be maintained in order to produce subset priming effects (i.e., their "relative position priming constraint"). (Contains 3 footnotes and 6 tables.)

Performance in a lexical decision task is crucially dependent on the difficulty of the word-nonword discrimination. More wordlike nonwords cause not only a latency increase for words but also, as reported by Stone and Van Orden (1993), larger word frequency effects. Several current models of lexical decision making can explain these types of results in terms of a single mechanism, a mechanism driven by the nature of the interactions within the lexicon. In 2 experiments, we replicated Stone and Van Orden's increased frequency effect using both pseudohomophones (e.g., BEEST) and transposed-letter nonwords (e.g., JUGDE) as the more wordlike nonwords. In a 3rd experiment, we demonstrated that simply increasing word latencies without changing the difficulty of the word-nonword discrimination does not produce larger frequency effects. These results are reasonably consistent with many current models. In contrast, neither pseudohomophones nor transposed-letter nonwords altered the size of semantic priming effects across 4 additional experiments, posing a challenge to models that would attempt to explain both nonword difficulty effects and semantic priming effects in lexical decision tasks in terms of a single, lexically driven mechanism. (Contains 2 tables and 5 footnotes.)

Recent studies have found that masked word primes that are orthographic neighbors of the target inhibit lexical decision latencies (Davis & Lupker, 2006; Nakayama, Sears, & Lupker, 2008), consistent with the predictions of lexical competition models of visual word identification (e.g., Grainger & Jacobs, 1996). In contrast, using the fast priming paradigm (Sereno & Rayner, 1992), orthographically similar primes produced facilitation in a reading task (H. Lee, Rayner, & Pollatsek, 1999; Y. Lee, Binder, Kim, Pollatsek, & Rayner, 1999). Experiment 1 replicated this facilitation effect using orthographic neighbor primes. In Experiment 2, neighbor primes and targets were presented in different cases (e.g., "SIDE"-tide); in this situation, the facilitation effect disappeared. However, nonword neighbor primes (e.g., "KIDE"-tide) still significantly facilitated reading of targets (Experiment 3). Taken together, these results suggest that it is possible to explain the priming effects from word neighbor primes in fast priming experiments in terms of the interactions between the inhibitory and facilitory processes embodied in lexical competition models. (Contains 4 tables, 1 figure and 11 footnotes.)

An orthographically similar masked nonword prime facilitates responding in a lexical decision task (Forster & Davis, 1984). Recently, this masked priming paradigm has been used to evaluate models of orthographic coding--models that attempt to quantify prime-target similarity. One general finding is that priming effects often do not occur when prime-target similarity is moderate, a result that the authors interpret as being due to uncontrolled effects of lexical inhibition. In the present research, a new version of the masked priming paradigm, sandwich priming, was introduced in an effort to minimize the impact of lexical inhibition. Masked sandwich priming involves briefly presenting the target itself prior to the presentation of each prime. Results indicate that the new paradigm was successful. The predicted priming effects were observed for Guerrera and Forster's (2008) T-All primes (e.g., "avacitno"-VACATION) and for primes differing from their targets at 3 letter positions (e.g., "coshure"-CAPTURE)--effects that are not found with the conventional masked priming paradigm. In addition to demonstrating the usefulness of the sandwich priming technique, these results also support the assumption that inhibitory processes play an important role in lexical processing. (Contains 4 figures, 1 table and 3 footnotes.)

When asked to list semantic features for concrete concepts, participants list many features for some concepts and few for others. Concepts with many semantic features are processed faster in lexical and semantic decision tasks [Pexman, P. M., Lupker, S. J., & Hino, Y. (2002). "The impact of feedback semantics in visual word recognition: Number-of-features effects in lexical decision and naming tasks." "Psychonomic Bulletin & Review," 9, 542-549; Pexman, P. M., Holyk, G. G., & MonFils, M.-H. (2003)." Number-of-features effects and semantic processing." "Memory & Cognition," 31, 842-855]. Using both lexical and concreteness decision tasks, we provided further insight into these number-of-features (NoF) effects. We began by replicating the effect using a larger and better controlled set of items. We then investigated the relationship between NoF and feature distinctiveness and found that features shared by numerous concrete concepts such as "has four legs" facilitate decisions to a greater extent than do distinctive features such as "moos". Finally, we showed that NoF effects are carried by shared visual form and surface, encyclopedic, tactile, and taste knowledge. We propose a decision-making account of these results, rather than one based on the computation of word meaning. (Contains 10 tables.)

In models of visual word identification that incorporate inhibitory competition among activated lexical units, a word's higher frequency neighbors will be the word's strongest competitors. Preactivation of these neighbors by a prime is predicted to delay the word's identification. Using the masked priming paradigm (K. I. Forster & C. Davis, 1984, J. Segui and J. Grainger, 1990) reported that, consistent with this prediction, a higher frequency neighbor prime delayed the responses to a lower frequency target, whereas a lower frequency neighbor prime did not delay the responses to a higher frequency target. In the present experiments, using English stimuli, it was found that this pattern held only when the primes and targets had few neighbors; when the primes and targets had many neighbors, lower frequency primes delayed responses to higher frequency targets essentially as much as higher frequency primes delayed responses to lower frequency targets. Several possible explanations for these findings are discussed along with their theoretical implications. Considered together, the results are most consistent with activation-based accounts of the masked priming effect.

What is the effect of a word's higher frequency neighbors on its identification time? According to activation-based models of word identification (J. Grainger & A. M. Jacobs, 1996; J. L. McClelland & D. E. Rumelhart, 1981), words with higher frequency neighbors will be processed more slowly than words without higher frequency neighbors because of the lexical competition mechanism embodied in these models. Although a critical prediction of these models, this inhibitory neighborhood frequency effect has been elusive in studies that have used English stimuli. In the present experiments, the effect of higher frequency neighbors was examined in the lexical decision task and when participants were reading sentences while their eye movements were monitored. Results suggest that higher frequency neighbors have little, if any, effect on the identification of English words. The implications for activation-based models of word identification are discussed.

According to parallel distributed processing (PDP) models of visual word recognition, the speed of semantic coding is modulated by the nature of the orthographic-to-semantic mappings. Consistent with this idea, an ambiguity disadvantage and a relatedness-of-meaning (ROM) advantage have been reported in some word recognition tasks in which semantic processing is presumed to be required for responding. To further evaluate this idea, we examined ambiguity and ROM effects in lexical decision and semantic categorization tasks. In the lexical decision task, there was an ambiguity advantage but no ROM effect. In the semantic categorization tasks, we used various semantic categories and found a processing time disadvantage for ambiguous words with less related meanings when the decisions were relatively difficult, but observed no effect when the decisions were easier. These results suggest that both the ambiguity disadvantage and the ROM advantage in the semantic categorization tasks are due to decision-making, rather than semantic-coding, processes. The implications of these results for issues concerning the nature of semantic coding and semantic representations are discussed.

Predictions derived from the interactive activation (IA) model were tested in 3 experiments using the masked priming technique in the lexical decision task. Experiment 1 showed a strong effect of prime lexicality: Classifications of target words were facilitated by orthographically related nonword primes (relative to unrelated nonword primes) but were inhibited by orthographically related word primes (relative to unrelated word primes). Experiment 2 confirmed IA's prediction that inhibitory priming effects are greater when the prime and target share a neighbor. Experiment 3 showed a minimal effect of target word neighborhood size (N) on inhibitory priming but a trend toward greater inhibition when nonword foils were high-N than when they were low-N. Simulations of 3 different versions of the IA model showed that the best fit to the data is produced when lexical inhibition is selective and when masking leads to reset of letter activities.

An ambiguity disadvantage (slower responses for ambiguous words, e.g., bank, than for unambiguous words) has been reported in semantic tasks (L. R. Gottlob, S. D. Goldinger, G. O. Stone, & G. C. Van Orden, 1999; Y. Hino, S. J. Lupker, & P. M. Pexman, 2002; C. D. Piercey & S. Joordens, 2000) and has been attributed to the meaning activation process. The authors tested an alternative explanation; The ambiguity disadvantage arises from the decision-making process in semantic tasks. The authors examined effects of ambiguity on unrelated trials in a relatedness decision task, because these trials are free from response competition created by ambiguous words on related trials. Results showed no ambiguity effect on unrelated trials (Experiments 2, 3c, and 5c) and an ambiguity disadvantage on related trials (Experiments 3a, 3b, 5a, and 5b).