Are abstract and concrete concepts organized differently? Evidence from the blocked translation paradigm

Using the blocked-translation paradigm with healthy participants, we examined Crutch and Warrington’s hypothesis that concrete and abstract concepts are organized by distinct principles: concrete concepts by semantic similarities and abstract ones by associations. In three experiments we constructed two types of experimental blocking (similar vs. associative) for both abstract and concrete words. In Experiment 1, we first attempted to transfer previous findings observed in patients by Crutch and Warrington with semantic impairment to healthy participants. In Experiment 2 only noun stimuli were used, and we further included two semantically categorical conditions that differed by a degree of semantic similarity (close vs. distant). In Experiment 3, verbs were used exclusively. Consistent results were obtained across all three experiments: Significant interference effects were observed for abstract items that were blocked by an associative relationship and by a semantic similarity, and foritems that were blocked by an associative relationship and by a semantic similarity, and for concrete items that were blocked by a semantic similarity (category) but not when they were blocked by an association. The effect of similarity-close was greater than that of similarity-distant in the noun experiment. We argue that the results are in conflict with Crutch and Warrington’s proposals, and can be accommodated by a theory of cooperating similarity and association connections for concrete and abstract concepts, with the association bearing more weight for abstract concepts.concepts, with the association bearing more weight for abstract concepts. Most cognitive theories about the conceptual1 representation are developed on the basis of studies with concrete items and the empirical and theoretical generalizability to abstract items remains controversial. There is the widely documented phenomenon of the concreteness advantage effect, that is, in comparison with abstract words, concrete ones are processed faster, are more resistant to damage, are acquired earlier, and are easier to recall, other things being equal (e.g., Coltheart, Patterson, & Marshall, 1980; Kroll & Merves, 1986; Walker & Hulme, 1999; see Paivio, 1991, for a review). In contrast, the reverse concreteness effect has also been reported. Some patients suffering from brain damage exhibited selective impairment of concrete word processing while abstract word processing skills remained intact (e.g., Bachoud-Lévy & Dupoux, 2003; Breedin, Saffran, © Cambridge University Press 2012 0142-7164/12 $15.00 Applied Psycholinguistics 2 Zhang et al.: Representation of abstract and concrete concepts & Coslett, 1994; Cipolotti & Warrington, 1995; Macoir, 2009; Marshall, Pring, Chiat, & Robson, 1996; Mattioli, 2008; Papagno, Capasso, & Miceli, 2009; Sirigu, Duhamel, & Poncet, 1991; Warrington, 1975, 1981; Warrington & Shallice, 1984; Yi, Moore, & Grossman, 2007). In addition, recent neuroimaging studies have found that abstract and concrete word processing led to the activation of distinct cortical regions, although the results are yet inconsistent (e.g., Noppeney & Price, 2004; Sabsevitz, Medler, Seidenberg, & Binder, 2005; Tolentino & Tokowicz, 2009; Zhang, Guo, Ding, & Wang, 2006). These observations motivated a variety of theories about the conceptual representations of concrete and abstract words. One school assumes common mechanisms for all words/concepts, attributing the concrete/abstract differences to some quantitative differences, including the number of conceptual features (Plaut & Shallice, 1991, 1993) or the extent of contextual support (Schwanenflugel & Shoben, 1983; Schwanenflugel & Stowe, 1989). A related theory (Paivio, 1986) assumes richer coding types for concrete words (verbal and imagery) than abstract words (verbal). Such theories provide a ready account for the concreteness advantage effect but cannot explain the reverse concreteness effect. Theories assuming qualitative differences between the concrete and abstract concepts explain the double dissociation profiles more easily. The first such theory was proposed by Breedin et al. (1994), postulating that the two types of concepts rely on different types of conceptual features, with concrete concepts containing more perceptual features and abstract ones more functional features. This distinction is rooted in the acquisition process, which is different for the two types of concepts. Sensory experience is a key factor for concrete concepts, and language contexts, such as multiple sentence exposure, is essential for abstract concepts. Besides potential differences in the representational contents of concrete and abstract concepts, a recent influential theory put forward by Crutch and Warrington (CW), which is the target hypothesis of the current article, has proposed fundamental differences between these two types of concepts in terms of organizational principles2 (Crutch, 2006; Crutch, Connell, & Warrington, 2009; Crutch, Ridha, & Warrington, 2006; Crutch & Warrington, 2005, 2007). This theory assumes that abstract concepts are organized by semantic association and concrete ones by semantic similarity, with concepts belonging to the same semantic category (e.g., animals) being represented closely. Words with intermediate concreteness involve both types of organizational principles. The target theory, which will be addressed as the organizational hypothesis, was primarily motivated by the behavioral patterns of patients whose cognitive impairments involved conceptual representation. In the first study of this research series, Crutch and Warrington (2005) evaluated the effects of various semantic contexts on the word comprehension performance of a patient (AZ) whose comprehension impairment originated from the semantic access process due to a refractory deficit. The study employed a spoken word to written word matching task, and the target word in each trial was presented with several other words that were either associatively related or semantically similar to the target. For concrete words, in comparison to unrelated conditions, AZ’s matching performance was poorer in the semantically similar condition (categorically related, e.g., goose– crow–sparrow–pigeon), but was not influenced by associative blocking (e.g., Applied Psycholinguistics 3 Zhang et al.: Representation of abstract and concrete concepts farmer–cow–barn–soil). By contrast, her matching performance of abstract words was hindered in the associatively related condition (e.g., exercise–healthy–fitness– jogging), and not in the semantically similar condition (synonyms, e.g., boil–fry– bake–cook). The pattern that performances on concrete items were influenced by semantically similar (categorical) blocking and abstract items by associative blocking was subsequently replicated with another patient with a similar semantic refractory access deficit (Crutch et al., 2006), a patient with phonological-deep dyslexia (Crutch & Warrington, 2007), and a patient with global aphasia (Crutch & Warrington, 2010). Furthermore, Crutch (2006) carried out post hoc analyses of the reading errors of several deep dyslexia cases and observed that the semantic substitution errors for concrete word targets had a higher percentage of being categorically related to the target, and that those for abstract words were more likely to be associatively related. Finally, in a recent study the group has generalized the findings to healthy participants using a semantic odd one out task, where they observed facilitation effects for similarity-based connections with concrete words and for association-based connections with abstract words (Crutch et al., 2009). Consistent with this line of results for the associative results, Duñabeitia et al. (2009) found greater and earlier effects of associative concrete words for abstract than for concrete words using the visual world paradigm with eye movement measures. However, there are reasons to be cautious about the generalizability of the results obtained by Crutch and colleagues (Crutch, 2006; Crutch et al., 2006; Crutch & Warrington, 2005, 2007). First, the main results in Crutch and Warrington (2005) were not replicated by a later study with the same paradigm and a patient with the same type of deficit as that of AZ. Hamilton and Coslett (2008) observed that their patient’s matching performance for both concrete words and abstract words was significantly influenced by semantically similar blocking and by associative blocking. They speculated that Crutch et al.’s (2006) failure to observe the associative effect for concrete words and the semantic similarity effect for abstract words might be because their patient was already at floor for these items. Furthermore, a recent study (Papagno et al., 2009) reported a semantic dementia patient whose profile could not be explained by the organizational hypothesis. The patient showed the reverse-concreteness effect, that is, an advantage with abstract concepts, but she was not better with associative knowledge than semantically categorical knowledge. Therefore, it remains to be assessed to what extent CW’s findings can be generalized to other subjects and other semantically related experimental situations. There are additional caveats to consider in CW’s series of studies. The main issue concerns the confounds of the abstract/concrete manipulation with grammatical class. First, in the main experiments in Crutch and Warrington (2005), the concrete words were predominantly nouns (98%) and the abstract words contained nouns (57%), verbs (36%), and adjectives (7%). Therefore, although the results might be explained by the concreteness dimension, it is equally possible that they were caused by the grammatical class difference. Indeed, there is a rich neuropsychological and neuroimaging literature suggesting that nouns and verbs might be processed differently on the semantic level, the morphosyntactic level and/or the lexical level (e.g., Bedney, Caramazza, Grossman, Pascual-Leone, Applied Psycholinguistics 4 Zhang et al.: Representation of abstract and concrete concepts & Rebecca, 2008; Caramazza & Hillis, 1991; McCarthy & Warrington, 1985; Rapp & Caramazza, 1998; Shapiro, Shelton, & Caramazza, 2000; see Laiacona & Caramazza, 2004, for a review of patients showing noun/verb dissociations). The interpretation of these dissociations is still a matter of debate, with some theories assuming distinct representations for noun concepts and verb concepts (e.g., Bedney et al., 2008; Huttenlocher & Lui, 1979) and others assuming the same organizational principle for knowledge of all grammatical classes (e.g., Vigliocco, Vinson, Barber, Druks, & Cappa, in press; Vigliocco, Vinson, Lewis, & Garrett, 2004). The point here is simply that the results observed in Crutch & Warrington (2005, 2006) might be explained by a variable orthogonal to the concrete/abstract dimension. The second issue is more theoretical in nature. For the semantically similar condition in their line of work, concrete items were from the same semantic category (e.g., lemon–banana) and abstract items were near-synonyms (e.g., clean– neat). Different instructions were given in the collection of semantic similarity ratings (“Concrete words, e.g., dog, cat, mouse, horse, sheep—all animals; abstract words, e.g., loud, noisy, blaring, rowdy, deafening—words with a very similar meaning: synonyms or near-synonyms,” see Crutch & Warrington, 2007). It is theoretically possible that these two types of semantic relationship are not to be equated, as it has been previously suggested that once the categorical membership was controlled for, the semantic distance (measured by the amount of feature overlap) yields a different type of effect in tasks such as picture naming (Mahon, Costa, Peterson, Vargas, & Caramazza, 2007). Note that this issue can potentially also be applied to the associative variable, although it is less extreme. Associated concrete items may not be “connected” in the same way as associated abstract items. Finally, a methodological note is that in the rating collections for similarity and association strength, an ∼−3 (extreme associative) ∼0 (unrelated) ∼+3 (similarity—category/synonym) rank was used, forcing the participants to choose between associative or similar relationships (Crutch & Warrington, 2007). Such a rating system may artificially increase the difference between association and similarity, and cannot reflect truthfully cases where word sets were both associatively and semantically related. In light of these considerations, the current study aims at evaluating the organizational hypothesis about the abstract and concrete conceptual organizations in healthy subjects, taking into consideration the theoretical and methodological issues outlined above. As Crutch (2006) suggested, their hypothesis about the conceptual structure should make similar predictions for any semantically mediated processes across different types of subjects. In doing so, we need a task that involves semantic processing and that can be employed with abstract items. The spoken word to written word matching task is not suitable for healthy subjects because it can be achieved with minimum semantic activation, and a task such as picture naming is not feasible because abstract items cannot be depicted. Crutch et al. (2009) adapted a semantic odd one out judgment task for healthy subjects and observed facilitation effects rather than the interference effects with patients, raising questions whether the same mechanisms apply for both cases. We therefore turned to a paradigm developed by Kroll and Stewart (1994)—the Applied Psycholinguistics 5 Zhang et al.: Representation of abstract and concrete concepts blocked translation—where semantic relationship produced interference effects. In this paradigm, bilingual subjects translate words into another language, and words are arranged into experimental blocks in similar ways to those in Crutch and Warrington (2005). It has been observed that, at least in the first language (L1) to second language (L2) translation version of the paradigm, when the words in a set were from the same semantic category, the translation latencies were prolonged in comparison to those in unrelated sets (see also La Heij, Dirkz, & Kramer, 1990; La Heij, Hooglander, Kerling, & Van der Veldon, 1996). More recently, a common task called cyclic semantic blocking, in which a set of pictures were named multiple times in different types of blocks, also demonstrated a similar semantic interference effect (Belke, Meyer, & Damian, 2005; Damian, 2003; Damian & Als 2005; Damian et al., 2001; Maess, Friederici, Damian, Meyer, & Levelt, 2002). Although the exact mechanisms of the translation task and the semantic effects in such blocked settings are still equivocal (e.g., Belke et al., 2005; Biegler, Crowther, & Martin, 2008; Damian, 2003; Damian & Als, 2005; Damian, Vigliocco, & Levelt, 2001; Jefferies & Lambon Ralph, 2006; Maess et al., 2002; Schnur, Schwartz, Brecher, & Hodgson, 2006), the involvement of the conceptual and word retrieval components in this task make it suitable to elucidate the characteristics of the conceptual structure. Specifically, in different blocks, we asked participants to translate into L2 words small sets of L1 words that were semantically similar (similarity block), associatively related (associative block), or unrelated (unrelated block). The types of words (concrete vs. abstract) were also manipulated. We follow the prevailing notion of semantic effects in blocked naming and speculate the following for the mechanisms underlying the potential interference effects. It is commonly assumed that lexical access in production, either when naming a picture or translating a foreign word, is a competitive process, such that the stronger other candidates are activated, the harder it is to select the target lexical node (e.g., Kroll & Stewart, 1994; Levelt, Roelofs, & Meyer, 1999; Roelofs, 1992; but see Mahon et al., 2007), which in our current case is the target L2 lexical node. In experimental blocks where words are closely related in their conceptual space (e.g., semantic category coordinates), activation spreads among the (L2) items more strongly than unrelated blocks, leading to greater competition for (L2) target selection. Besides transferring CW’s results to healthy subjects with the blockedtranslation task (Experiment 1) using their stimuli (Crutch & Warrington, 2005, their experiments 4 and 5), we attempted to address the several methodological issues outlined above in their study. We separated the variable concreteness and grammatical class by carrying out separate experiments using only noun stimuli (Experiment 2) or verb stimuli (Experiment 3). In the noun experiment (Experiment 2), we further included additional conditions varying the degree of semantic similarity within the same categorical relationships to assess the effect of a comparable kind of semantic similarity in concrete and abstract items. Finally, throughout the three experiments, we carried out separate ratings for associative and similarity strength independently, and used an identical procedure and instructions to collect rating values (semantic similarity and association) for concrete and abstract words. If the organizational hypothesis were correct, we would predict in all experiments Applied Psycholinguistics 6 Zhang et al.: Representation of abstract and concrete concepts interference effects for semantic similarity blocking for concrete words but not for abstract words, and associative blocking for abstract words but not for concrete words. The predictions from the alternative theories (e.g., Breedin et al., 1994), which attribute more weights to the association connections for abstract concepts than for concrete concepts, are less straightforward and will depend on the actual weights being given to various types of semantic features/connections for a particular concept.