The brain’s hemispheres and controlled search of the lexicon: Evidence from fixated words and pseudowords Barbara J. Rutherford ⇑ , Jeffrey R. Mathesius Psychology Department, University of British Columbia, Okanagan, Kelowna, British Columbia, Canada article info Article history: Accepted 1 March 2012 Available online 28 April 2012 Keywords: Laterality Phonology Orthography Semantics Controlled processing Lexical search Priming Cerebral hemispheres Lexical decision Visual field abstract Difference between the brain’s hemispheres in efficiency of intentional search of the mental lexicon with phonological, orthographic, and semantic strategies was investigated. Letter strings for lexical decision were presented at fixation, with a lateralized distractor to the LVF or RVF. Word results revealed that both hemispheres were capable of using each of the three strategies, but the right hemisphere had better base- line processing of orthography and was better at processing semantics. Pseudoword results supported the right hemisphere advantage for orthography and showed a left hemisphere advantage for phonology and assessment of possible semantic relationships. Taken together, the data support the idea that the right hemisphere uses orthography to make efficient decisions about novelty of an item, while the left engages in grapheme-to-phoneme conversion to test hypotheses about unfamiliar items. The convergence of data with previous research reveals that the procedure, as well as analyses of pseudowords, inform laterality research. Ó 2012 Elsevier Inc. All rights reserved. 1. Introduction The lexicon long has been suggested to include phonological, orthographic, and semantic information (e.g. Morton, 1969). Also long suggested is that the hemispheres have a different preferred strategy or strategies when invoking controlled processing to con- duct an intentional search of the lexicon (Chiarello, 1985). However, laterality in the use of phonological, orthographic, and semantic strategies for intentional search is not always found in priming studies (for phonological processing, see Chiarello, 1985; Crossman & Polich, 1988). Moreover, when found, sometimes the findings are contradictory (for orthographic processing, see Chiarello, 1985; Crossman & Polich, 1988; for semantic processing, see Chiarello, 1985; Koivisto, 1997). Priming studies that load controlled processing of lexical infor- mation encourage the conscious processing of a potential relation- ship between two lexical items (Collins, 1999; Neely, 1977). Two tasks, explicit judgement and lexical decision, are commonly used. Explicit judgement involves a conscious decision that a dimension of a phonological, orthographic, or semantic relationship does or does not exist between two words (Crossman & Polich, 1988; Khateb et al., 2000). Priming is evidenced by gains to speed and accuracy of response when there is a relationship compared to when there is not. Lexical decision investigates priming by pre- senting successive letter strings in which the preceding prime string either is or is not related to the succeeding target string on a dimension of phonology, orthography, or semantics (Chiarello, 1985; Peleg & Eviatar, 2009; Yochim, Kender, Abeare, Gustafson, & Whitman, 2005). Speed and accuracy of a decision that the target is a word is facilitated when there is a relationship, likely as a con- sequence of spread of activation from the prime to lexical repre- sentations that are associated (Collins & Loftus, 1975), whether the association is phonological, orthographic, or semantic. To encourage conscious processing of a relationship, participants are made aware of the predictive value of a prime by using primes that are perceptually clear, an SOA that is 500 ms or more, or by setting the probability of a relationship to be high (Collins, 1999; Neely, 1977). In turn, attention can be restricted to information in the lex- icon expected by the priming context (Collins, 1999). Critical to the contention of probability of relationship is the operational defini- tion of ‘high’. Examples from laterality research include relatedness proportions of 25% (Collins, 1999), 30% (Chiarello, 1985), and 33% (Yochim et al., 2005) of the total stimulus set of words and non- words in lexical decision, and 33% (Khateb et al., 2000) in explicit judgement. In a seminal series of lexical decision experiments with normal subjects, Chiarello (1985) built on evidence derived from tests of commisurotomy patients and patients with unilateral damage to examine the possibility that the hemispheres may have different 0278-2626/$ - see front matter Ó 2012 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.bandc.2012.03.004 ⇑ Corresponding author. Address: Psychology Department, University of British Columbia, Okanagan, 3333 University Way, Kelowna, British Columbia, Canada V1V 1V7. Fax: +1 250 807 8439. E-mail address: barbara.rutherford@ubc.ca (B.J. Rutherford). Brain and Cognition 79 (2012) 188–199 Contents lists available at SciVerse ScienceDirect Brain and Cognition journal homepage: www.elsevier.com/locate/b&c