Orthographic and phonological effects in the picture–word interference paradigm: Evidence from a logographic language

One important finding with the picture–word interference paradigm is that picture-naming performance is facilitated by the presentation of a distractor (e.g., CAP) formally related to the picture name (e.g., “cat”). In two picture-naming experiments we investigated the nature of such form facilitation effect with Mandarin Chinese, separating the effects of phonology and orthography. Significant facilitation effects were observed both when distractors were only orthographically or only phonologically related to the targets. The orthographic effect was overall stronger than the phonological effect. These findings suggest that the classic form facilitation effect in picture–word interference is a mixed effect with multiple loci: it cannot be attributed merely to the nonlexical activation of the target phonological segments from the visual input of the distractor. It seems instead that orthographically only related distractors facilitate the lexical selection process of picture naming, and phonologically only related distractors facilitate the retrieval of target phonological segments. The picture–word interference paradigm, a variant of the Stroop task (1935), has been widely used in psycholinguistic research, especially in the field of spoken word production (Glaser & Dungelhoff, 1984; Glaser & Glaser, 1989). In this paradigm, participants are required to name pictures that have distractor words superimposed upon them. Two kinds of picture–distractor relationships have been found to affect picture-naming performance. When the distractor word (e.g., DOG) belongs to the same semantic category as the picture (e.g., “cat”1), it takes longer © 2009 Cambridge University Press 0142-7164/09 $15.00 Applied Psycholinguistics 30:4 638 Bi et al.: Picture–word interference to name the picture than when the distractor word is unrelated to the target (e.g., PEN). This has been called the semantic interference effect. When the distractor (CAP) is related to the picture name (“cat”) by phonological properties, the picture is named more quickly than when it is accompanied by an unrelated distractor. This is commonly referred to as the phonological facilitation effect. The dominant interpretation of these two effects is that they reflect different processing levels of picture naming. The semantic interference effect is the result of competition at the lexical selection stage, and the phonological facilitation effect is because of the priming of the target phonological nodes by the distractor (e.g., Meyer & Shriefers, 1991; Posnansky & Rayner, 1978; Schriefers, Meyer, & Levelt, 1990; Starreveld & La Heij, 1995). Based on such assumptions, the paradigm has been used to develop various theories of lexical access, concerning both the organization and the dynamics of speech production. However, the interpretations of both the semantic and the phonological effects are still controversial. For example, there is disagreement about the locus of the semantic interference effect: it has been argued that this effect does not reflect competition at the stage of lexical selection but interference at the stage of response selection (Costa, Mahon, Savova, & Caramazza, 2003; Finkbeiner & Caramazza, 2006; Janssen Schrim, Mahon, & Caramazza, 2008; Mahon, Costa, Peterson, Vargas, & Caramazza, 2007; Miozzo & Caramazza, 2003). As for the phonological facilitation effect reported in the literature, it remains controversial whether this effect is the result of the priming of target phonological segments or the facilitation on earlier stages of target production (e.g., Damian & Martin, 1999; Roelofs, Meyer, & Levelt, 1996; Starreveld, 2000; Starreveld & La Heij, 1995). However, there has always been a crucial confound in the study of the phonological effect in picture–word interference. Because almost all studies were conducted in alphabetic languages with medium to high grapheme–phoneme correspondence, the “phonological” distractor is also similar to the target word in visual form (consider CAP and “cat”), and therefore, it is unclear whether the facilitation effect produced by such distractors should be attributed to the phonological relatedness between target and distractor or the orthographic relatedness between target and distractor. Although Lupker (1982) conducted experiments to examine the contribution of orthographic versus phonological relatedness of the distractor to the target, his study has not received much attention, and the theoretical implications of the results have not been considered in depth (but see Roelofs et al., 1996). Instead, researchers have focused on the phonological aspect of the relationship and assumed that the facilitation is an output effect resulting from the priming of the target phonological nodes (e.g., Shriefers et al., 1990; Starreveld & La Heij, 1995).2 Does the confounding of orthographic and phonological relatedness matter in the interpretation of the mechanism responsible for the observed facilitation effects? Detailed analyses of how an orthographically and/or phonologically related distractor may affect the target-naming process are presented below, using the example of the pairs “cat”/KEY and “cat”/CELL for phonological and orthographic relatedness, respectively. Two kinds of processes need to be considered to determine how a distractor word may affect picture naming: the word perception process and the Applied Psycholinguistics 30:4 639 Bi et al.: Picture–word interference picture-naming process. It is widely accepted that the picture-naming process involves at least the following stages: concept activation, lexical selection, and phonological encoding. This generic model will be used as a guide in our current discussion. Although the received view of lexical access is that the lexical layer is further divided into a lemma layer, which specifies the syntactic properties of a word, and a lexeme layer, which specifies the syntactically determined morphemes (e.g., Bock & Levelt, 1994; Dell, 1986; Garrett, 1980; Levelt, 1989; Roelofs, 1992, 1997) this view has been contested (Caramazza, 1997; Caramazza & Miozzo, 1997; Caramazza, Costa, Miozzo, & Bi, 2001). There is an unresolved controversy about the dynamics of the access process: whether activation flows between layers in a discrete (e.g., Levelt, Roelofs, & Meyer, 1999), cascading (e.g., Caramazza, 1997), or interactive fashion (e.g., Dell, 1986). The consequences of adopting a distinction between a lemma and a lexeme level and of adopting feedback connections for the interpretation of the effects of distractors on picture naming will be discussed in the General Discussion. On the word perception side, a written word is assumed to activate its orthographic, semantic, and phonological representations. The details of the activation flow among these representations have received much attention but remain controversial. Many models have been proposed, including logogen models (Morton, 1969), serial search, and verification models (Forster, 1976), interactive activation (McClelland & Rumelhart, 1981), fuzzy logic models (Massaro & Cohen, 1991), and so on. Here, the one assumption we are committed to is that of spreading activation. It is assumed that the lexical orthographic representation of the distractor word is always activated by the visual input. From the orthographic representation, the lexical phonological representation receives activation either through its semantic representation (e.g., Hillis & Caramazza, 1995), or by direct lexical mapping between orthographic and phonological representations (e.g., Bub, Cancelliere, & Kertesz, 1985). The semantic representation also receives activation, either directly from the lexical orthographic representation (e.g., Coltheart, 1978) or indirectly via phonology (e.g., Lukatela & Turvey, 1994a, 1994b). The phonological segments that compose the word are activated both by the lexical phonological representation and through nonlexical grapheme– phoneme conversion (GPC) from the visual input. Although there is much debate in the literature on reading concerning the detailed timing and routes of activation among these representations, the central issue here is how the picture-naming process might be affected by a visual word input, namely, where and how the contact(s) between wordand picture-based processes occur. Consider a distractor word that is phonologically, but not visually related to the target (KEY for “cat”). There are at least two ways in which the presentation of KEY may affect the naming of a picture of a “cat.” One is that, upon seeing the word distractor, its lexical phonological representation /ki:/ is activated, either directly (Route P, Figure 1) or via its semantic representation. This lexical phonological representation, in turn, sends activation to its phonological segments (/k/, /i:/), parts of which (e.g., /k/) may be shared by the target. Also, the distractor can prime the target phonological segments through the GPC process. For instance, the grapheme “k” in KEY activates the phoneme /k/ through the GPC process, leading to the facilitation of phonological encoding of the target (Route G, Figure 1). Figure 1. How a phonological distractor word (e.g., KEY) and an orthographic distractor (e.g., CELL) affects production (“cat”). Note: The connection between the corresponding items in the orthographic lexicon and the phonological lexicon could either be direct or via the conceptual system (see text). A direct line is drawn for the sake of simplicity. Orthographic lexical item CELL, once activated by the visual input, also activates its own semantic representation and phonological lexical representation. Only the activation that influences the target (“cat”) is depicted. GPC, grapheme–phoneme conversion. Applied Psycholinguistics 30:4 641 Bi et al.: Picture–word interference Now consider an orthographically related word that does not share any phonology with the target, for example, the distractor CELL for the picture of “cat.” Upon seeing the visual input CELL, the orthographic representations of all visual neighbors (CELL, CEILING, CALL, CAR, etc.) should be activated, including the target CAT (McClelland & Rumelhart, 1981). The phonological lexical nodes of the activated orthographic representations are then activated either directly through orthographic to phonological lexical connections or through the semantic system (lexical orthographic to semantic to lexical phonological). Therefore, the target phonological lexical node “cat” is primed by the presentation of a visually similar distractor CELL (Route O, Figure 1). In some cases, the orthographic distractors can prime target phonological segments through the GPC process; in the present example, the grapheme “c” in CELL might activate the phoneme /k/, which is also part of the target’s phonological content (Route G, Figure 1). The point of this analysis is that there are multiple potential routes that are responsible for the facilitation effect observed with phonologically and orthographically related distractors (e.g., CAP for “cat”). An important study that shed light on the contributions of these possible routes was conducted by Lupker (1982). In two picture–word experiments conducted in English, Lupker tried to distinguish the contribution of the orthographic and phonological relatedness of the distractor on the processing of the target. He found that both phonologically (but not orthographically) related distractors and orthographically (but not phonologically) related distractors facilitated picture naming. In Experiment 1, each picture (e.g., “bear”) was paired with a distractor with similar orthography and different phonology (e.g., YEAR), or an unrelated distractor (e.g., WORK), or nonwords with different degrees of orthographic similarity (e.g., XXXT, XXR, or DFRP). In Experiment 2, the picture targets (e.g., “plane”) were paired with distractors of similar phonology and different spelling (e.g., BRAIN), distractors sharing both sound and spelling (e.g., CANE), unrelated words, and nonwords with orthographic and phonological properties parallel to the word conditions. Lupker’s (1982) major findings were the following: (a) phonological distractors facilitated picture naming (by 23 ms in Experiment 2); (b) orthographically similar distractors facilitated picture naming (by 56 ms in Experiment 1); and (c) when both orthography and phonology were shared between distractor and picture name, the magnitude of the facilitation effect (55 ms in Experiment 2) was similar to that found when only orthography was shared (56 ms in Experiment 1). As discussed above, an orthographic distractor (“bear”-YEAR) may affect either the target lexical node or its phonological segments through GPC processes. The fact that facilitation from these kinds of distractors was indeed observed suggests that either or both of these processing layers are affected in the picture–word naming task. Similarly, the observed facilitation effect from phonologically related distractors (“plane”-BRAIN) suggests that the phonological content of the target is primed. However, we need to view these results with caution. Because it is difficult to disentangle orthography and phonology in English, the orthographically related pairs sometimes also share phonological properties and the phonologically related pairs sometimes share orthographic properties. In addition, the item sets in the experiments were rather small—12 pictures in Experiment 1 and 9 pictures in Experiment 2. Because item analyses were not performed in the study, it is not Applied Psycholinguistics 30:4 642 Bi et al.: Picture–word interference clear how reliable the results are over different items. Furthermore, the observation that the magnitude of the orthographic facilitation effect is similar to that of the orthographic plus phonological effect, and is larger than that of the phonological facilitation effect, is based on “eyeball” comparisons across two experiments with different stimuli and participants. Thus, it is not obvious that these differences in the magnitude of effects are interpretable. Two studies (Weekes, Davies, & Chen 2002; Zhou, Zhuang, Wu, & Yang, 2003) have attempted to more clearly separate the effects of orthographic and phonological relatedness by using Chinese. The basic writing units of Chinese are characters, which are logographic in nature with highly arbitrary symbol–sound correspondence (e.g., DeFrancis, 1989; Li, 1993; Wang, 1973; Yin & Rohsenow, 1994; Zhou, Shu, Bi, & Shi, 1999). Two related characteristics of the language make it ideal for the study of phonological and orthographic effects in picture naming. Because symbol–sound correspondence is highly opaque in general, and is completely arbitrary for many characters, one can test whether the orthographic and phonological facilitation effects still exist when target phonology cannot be primed through a GPC route. Furthermore, it is common to find homophones with distinct visual forms (e.g., the first character of the word and , both pronounced as /hu2/3), or two orthographically similar characters with different pronunciations (e.g., , /hu2/ vs. , /gua1/). Therefore, Chinese offers the opportunity to manipulate phonological and orthographic relatedness in a factorial design, thereby allowing us to identify the locus or loci of the putative phonological facilitation effect (e.g., Chen, Cheung, & Flores d’Arcais, 1995; Cheng & Shih, 1998; Feng, Miller, Shu, & Zhang, 2001; Hue, 1992; Perfetti & Tan 1998; Shen & Forster, 1999; Wong & Chen, 1999; Zhou & Marslen-Wilson, 1999a; Zhou, Marslen-Wilson, Taft, & Shu, 1999). The primary goal of Weekes et al.’s (2002) study was to investigate the locus of the semantic interference effect by comparing it with the orthographic/phonological effects. Similarly to Lupker (1982), they found that both orthographically only and phonologically only related distractors produced significant effects. However, contrary to Lupker’s study, the magnitudes of the two effects were comparable and the phonological and the orthographic effects were additive. In Zhou et al.’s (2003) study, they reported that the phonological effect was larger than the orthographic effect, although no direct statistical comparison was carried out between these two conditions. The interaction between these two types of effects was not assessed. There are certain methodological limitations in these studies, however. Weekes et al. (2002) did not control the visual complexity of distractors in different conditions nor the degree of orthographic/phonological similarity across conditions (B. S. Weekes, personal communication, 2008). Zhou et al. (2003) constructed the unrelated condition by pairing the orthographic distractors with targets. Hence, the three types of distractors (phonologically, orthographically, and semantically related distractors) were presented in the experiment an unequal number of times: orthographically related distractrors were presented twice as often as the other distractors. This makes a direct comparison of the phonological and orthographic distractors problematic because the fact that orthographic distractors led to less interference than phonological distractors in picture naming may be an effect of distractor repetition and not a difference Applied Psycholinguistics 30:4 643 Bi et al.: Picture–word interference between phonology and orthography. This difference in distractor repetition might temporarily change the activation level of distractor words. In addition, given that lexical activation levels modulate the word interference effect in the word–picturenaming paradigm (see the distractor word frequency effect; Miozzo & Caramazza, 2003), the orthographic and the phonological effects might be contaminated by a possible distractor word repetition effect. More critically for the theoretical interpretations of the orthographic/ phonological effects, in these two studies the authors did not explicitly manipulate or control for the potential GPC factor. Although Chinese has highly opaque symbol–sound correspondences, it has been proposed that GPC or a GPC-like mechanism is not completely absent in Chinese. Over 80% of modern Chinese characters are so-called “compound characters” composed of a “semantic radical” and a “phonetic radical” (Perfetti & Tan, 1998; Zhu, 1988). The semantic radical relates to the meaning, typically the semantic category of the character. The phonetic radical, which is usually also a Chinese character by itself, provides cues to the pronunciation of the whole character, although these cues are often unreliable. The position of the phonetic radical is not fixed either. Studies have shown that in reading such compound characters, the phonological properties of the phonetic radicals are automatically activated and influence reading performance (e.g., Bi, Han, Shu, & Weekes, 2007; Hue, 1992; Law & Wang, 2005; Lee et al., 2004; Lee, Tsai, Su, Tzeng, & Huang, 2005; Peng, Yang, & Chen, 1994; Seidenberg, 1985; Shu & Zhang, 1987; Weekes & Chen, 1999; Yin & Butterworth, 1992; Zhou & Marslen-Wilson, 1999b; but see Coltheart, Rastle, Perry, Langdon, & Ziegler, 2001). It remains controversial whether such a GPC-like procedure, which is often referred to as a “sublexical” mechanism, is nonlexical or lexical in nature (see Zhou & Marslen-Wilson, 1999b). For our current purposes what is relevant is whether orthographic and/or phonological distractors might affect target production without going through their corresponding lexical representations. In other words, the point is whether procedures similar to Route G in Figure 1 can be applied in the Chinese experiments. If yes, it would influence the interpretation of the effects in the following ways. If the orthographic distractors are compound characters and the phonetic radical is phonologically similar to the target name, the orthographic effect could have resulted from sublexical processes (Route G, Figure 1) alone, or the combination of the sublexical and the “lexical” routes (Route O). Similarly, If phonological distractors are compound characters and the phonetic radicals in these characters were phonologically similar to the target name, then the phonological effect could have resulted from sublexical (Route G, Figure 1) alone or the combination of sublexical (G) and the “lexical phonology” routes (Route P). In light of these considerations, it is important to control for such potential GPC-like sublexical origins for the phonological/orthographic effects even in experiments using Chinese, and this is what we did here. In this article, we report two experiments using Mandarin Chinese to further investigate the mechanisms responsible for the putative phonological/orthographic facilitation effect. We paired each target picture with an unrelated distractor or a distractor that is related to the picture’s name only orthographically, only phonologically, or both orthographically and phonologically. Critically, the distractors were constructed in a way to maximally reduce the application of GPC-like Applied Psycholinguistics 30:4 644 Bi et al.: Picture–word interference mechanisms. The rationale is as follows: if the phonological facilitation effect is merely because of the activation of the phonological segments through GPC processes (Route G, Figure 1), we should not find facilitation effects in any of the related conditions because the nonlexical symbol–sound correspondence is not applicable for our Chinese stimuli; the target phonemic segments do not receive direct activation via GPC from the visual input of the written distractor. If we do observe a facilitation effect from the phonologically only related distractors, it could only arise through the “lexical phonology route” (Route P). This is because the phonologically only related distractors (e.g., /hu2/) share with the target items (“ ” , /hu2-li0/) nothing but phonological properties. Furthermore, there is no visual information of these distractors ( , ) that could provide cues for the target sound (/hu2/) through any nonlexical GPC process. A possible explanation for such an outcome is that the visual form activates the lexical phonological representation ( , , /hu2/), which in turn, activates the phonetic segments shared with the target (“ ,” /hu2-li0/). If we observe a facilitation effect from a distractor that is related to the target only orthographically (e.g., , /gua1/) and if the contribution of GPC process is ruled out, we would have to attribute the cause of such an effect to processes internal to the “lexical route” (Route O).