Schematic illustration of hypothetical representation of abstract and concrete words within a specific location context (e.g., church ). Abstract words have stronger connections to other concrete words whereas concrete words are not strongly linked to other abstract words. Therefore, training abstract words will activate related concrete words whereas training concrete words will not activate related abstract words. 

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... refers to the ease in which a visual representation of a word can be accessed. Concreteness is the degree to which a word’s referents can be perceived through the senses. Imageability and concreteness are highly correlated (Paivio, Yuille, & Madigan, 1968), although notable exceptions exist. For example, emotion words such as anger are rated high for imageability but low for concreteness; also, very low-frequency nouns such as armadillo are rated high for concreteness but low for imageability. Abstract words (e.g., religion ) typically have low imageability and concreteness, while concrete words (e.g., gavel ) share high imageability and concreteness. In behavioural studies, normal participants exhibit longer lexical decision times for abstract words than for concrete words (Bleasdale, 1987; de Groot, 1989; James, 1975), longer word association times for abstract than concrete words (de Groot, 1989), better recall of concrete word pairs and sentences than abstract word pairs and sentences (see Paivio, 1991 for a review), and increased ease of predication (generating semantic features) for concrete over abstract words (Jones, 1985). This behavioural preference for concrete over abstract words is referred to as a concreteness effect. Many theories have been proposed to account for the concreteness effect. The dual coding theory (DCT) posits that there are two systems for encoding words into semantic memory: verbal or linguistic and nonverbal or sensory. Abstract words are encoded into the semantic system with only verbal information, whereas concrete words are encoded into the semantic system with both verbal and multi- modal sensory information (Paivio, 1991). Schwanenflugel, Harnishfeger, and Stowe (1988) proposed the context availability theory (CAT) as an alternative to the DCT. In it they posit that the concreteness effect is due to the relative difficulty of retrieving the relevant contextual information (world knowledge) associated with the word(s) under consideration. Abstract words have less contextual information associated with them because they are weakly associated with many concepts, as opposed to concrete words, which are strongly associated with just a few concepts (Schwanenflugel et al., 1988). Considering behavioural evidence from patients with aphasia provides further insights into how imageability and concreteness affect lexical retrieval. In general, patients with aphasia exhibit an exaggerated concreteness effect. Increased performance on words with higher imageability and/or higher concreteness has been well documented during single and paired word repetition (Martin, Saffran, & Dell, 1996), single word reading (Newton & Barry, 1997), word recognition (Crutch & Warrington, 2005), and reading comprehension (Barry & Gerhand, 2003). Nickels and Howard (1995) investigated various factors affecting naming performance in people with fluent and nonfluent aphasia, and found that imageability and concreteness significantly predicted naming performance for their participants. To explain reading deficits in deep dyslexia, the normal isolated centrally expressed (NICE) model proposed by Newton and Barry (1997) posits that lexicalisation (the process in which a semantic representation activates the phonological form) is driven by concreteness. Concepts with higher concreteness values will produce strong and specific activations of the word form, with less spreading activation to other word forms, resulting in fewer errors in lexical retrieval. Further, the NICE model proposes that abstract words are loosely associated with many different concepts, whereas concrete words are strongly associated with only a few concepts. In contrast to the extensive literature in behavioural psycholinguistics, the utility of considering imageability and concreteness has only been examined in the context for remediation of reading deficits (Kim & Beaudoin-Parsons, 2007) and not for treatment of lexical retrieval deficits in aphasia. The present study was based on our previous treatment work extending the complexity account of treatment efficacy hypothesis (Thompson & Shapiro, 2007) within the semantic domain (Kiran, 2007). Specifically, Kiran (2007) argued that training the more complex atypical examples in a category results in generalisation to the less-complex typical examples because atypical items are less representative of their category than typical items. These findings have been borne out in three studies examining generalisation from atypical to typical examples and vice versa using animate categories ( birds , vegetables ) (Kiran & Thompson, 2003), inanimate categories ( clothing , furniture ) (Kiran, 2008), and in well-defined categories ( shapes ) (Kiran & Johnson, 2008). However, these three studies have only examined lexical retrieval of typical/atypical examples within a category in the context of picture naming. In the present study we examine the effect of abstractness in treatment within categories defined by their specific location (e.g., church , courthouse ). Because abstract words cannot be pictured, we examine lexical retrieval of concrete and abstract words in a category generation task. Based on the NICE model, we hypothesised that abstract concepts are defined through their relationship with concrete concepts and other abstract concepts. Concrete concepts, on the other hand, are defined through visual characteristics, somatosensory experience, and their relationship with other concrete concepts. These differences in semantic representation make abstract concepts more complex than concrete words. As an example, in a contextual category such as ‘‘ church ’’ activation of an abstract word such as ‘‘ prayer ’’ entails activation of related concrete words such ‘‘ candle ’’, ‘‘ bible ’’, ‘‘ hymn ’’. In contrast, a concrete word such as ‘‘ candle ’’ will activate other related concrete words but not necessarily activate abstract words such as ‘‘ solace ’’ or ‘‘ penance ’’ (see Figure 1). Therefore, the current study aimed to determine the effectiveness of a treatment for lexical retrieval that is based on models of lexical processing by utilising abstractness as a mode of complexity. It was hypothesised that training abstract words in a category will result in generalisation to untrained target concrete words in the same category. However, training concrete words in a category will result in the retrieval of trained concrete words, but not generalisation to target abstract words. Four monolingual English speakers with anomic aphasia and relatively high-level language skills participated in the study (see Table 1 for a complete description of participant demographics). The diagnosis of anomic aphasia was determined by administration of the Western Aphasia Battery (WAB; Kertesz, 1982). Results showed that all participants presented with fluent speech, naming deficits, and mildly impaired comprehension. All participants showed impaired naming on the Boston Naming Test (Kaplan, Goodglass, & Weintraub, 2001). Subtests of the Psycholinguistic Assessment of Language Processing in Aphasia (PALPA; Kay, Lesser, & Coltheart, 1992) and the Pyramids and Palm Trees Test (PAPT; Howard & Patterson, 1992) revealed that all participants presented with mild semantic impairments with performances ranging between 75% and 100% accuracy. Lower accuracy on low-imageability pairs compared to high-imageability pairs was observed on both synonym judgement tasks on the PALPA (see Table 2 for complete pre-testing results). Development of categories. First, we identified eight location categories ( hospital , school , park , church , office , courthouse , restaurant , and museum ). A total of 14 normal young adults were provided with the list of eight locations and were asked to write down at least 15 words that they associated with each place. They were instructed to consider nouns, verbs, adjectives, high- and low-frequency words, and high- and low-imageability words. Then categories were eliminated in which (a) too few abstract words were obtained ( office , restaurant ), or (b) too many examples overlapped in two categories ( school , park ). Based on these criteria, four ...