The effects of context, meaning frequency, and associative strength on semantic selection: Distinct contributions from each cerebral hemisphere

Abstract

The visual half-field procedure was used to examine hemispheric asymmetries in meaning selection. Event-related potentials were recorded as participants decided if a lateralized ambiguous or unambiguous prime was related in meaning to a centrally-presented target. Prime-target pairs were preceded by a related or unrelated centrally-presented context word. To separate the effects of meaning frequency and associative strength, unambiguous words were paired with concordant weakly-related context words and strongly-related targets (e.g., taste-sweet-candy) that were similar in associative strength to discordant subordinate-related context words and dominant-related targets (e.g., river-bank-deposit) in the ambiguous condition. Context words and targets were reversed in a second experiment. In an unrelated (neutral) context, N400 responses were more positive than baseline (facilitated) in all ambiguous conditions except when subordinate targets were presented on left visual field-right hemisphere (LVF-RH) trials. Thus, in the absence of biasing context information, the hemispheres seem to be differentially affected by meaning frequency, with the left maintaining multiple meanings and the right selecting the dominant meaning. In the presence of discordant context information, N400 facilitation was absent in both visual fields, indicating that the contextually-consistent meaning of the ambiguous word had been selected. In contrast, N400 facilitation occurred in all of the unambiguous conditions; however, the left hemisphere (LH) showed less facilitation for the weakly-related target when a strongly-related context was presented. These findings indicate that both hemispheres use context to guide meaning selection, but that the LH is more likely to focus activation on a single, contextually-relevant sense. KeywordsLexical Ambiguity; Cerebral Hemispheres; Context Effects; ERP; N400; LPC Based on evidence from studies using the visual half-field (VF) procedure with neurologicallyintact individuals (e.g., Burgess and Simpson, 1988), as well as studies involving participants with unilateral brain damage (e.g., Tompkins, Baumgartner, Lehman, and Fassbinder, 2000), it has been argued that the cerebral hemispheres differ in their processing of lexical semantics.Corresponding Author: Aaron M. Meyer, Beckman Institute, University of Illinois, 405 N. Mathews Ave., Urbana, IL 61801, meyeram@uiuc.edu, (217) 244-9638. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NIH Public Access NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptMore specifically, it has been...

The divided visual world paradigm: Eye tracking reveals hemispheric asymmetries in lexical ambiguity resolution

“…Other studies that have examined the processing of non-literal aspects of language have similarly yielded evidence that the RH is able to flexibly integrate an unexpected meaning based on prior context (e.g., in a joke such as "When I asked the bartender for something cold and full of rum, he recommended his wife. "; Coulson and Williams, 2005).Compared to our ERP experiments (Meyer and Federmeier, 2007), the RH advantage for a broader or more flexible use of context was more apparent in the gaze data of the current experiments. This pattern suggests that the advantage may result from or at least be more prominent in active tasks.…”

“…This effect of context was longer-lasting in the RVF-LH (and a tendency for the same pattern was also seen in the RVF-LH for the unambiguous condition). The effect of context was apparent in the behavioral data as well, as relatedness judgment accuracy was higher in the UR ambiguous condition compared to the discordant (RR) condition for both VFs.Different from the pattern seen in Experiment 1, but replicating the pattern seen in our ERP study (Meyer and Federmeier, 2007), in the RH, meaning activation in the unambiguous UR condition preceded activation in the ambiguous UR condition. Since the UR conditions were controlled for associative strength with the prime, this pattern indicates that processing in the RH is affected by meaning frequency, over and above the effects of associative strength.…”

“…Thus, based on the N400 facilitation effects we observed (Meyer and Federmeier, 2007), for both experiments we predicted initial above-baseline gaze for all related targets in the unrelated context (UR) condition, except for subordinate-related targets presented on LVF-RH trials (the ambiguous UR condition in Experiment 2). This pattern would indicate that the LH maintains multiple meanings, while the RH selects the dominant meaning or activates the subordinate meaning more slowly…”

“…These findings, along with those of other studies using similar materials (e.g., Kandhadai and Federmeier, 2007), are inconsistent with the main tenet of the coarse coding hypothesis, which argues that meaning activation is broader in the RH, including both strongly-related information such as the dominant meaning and weakly-related information such as subordinate meanings (Beeman et al, 1994;Jung-Beeman, 2005). Instead, studies that have manipulated SOA or utilized measures that allow continuous sampling of cognitive processing have found evidence that the subordinate meaning is activated in both hemispheres, but with a different time course in each (Burgess and Simpson, 1988;Meyer and Federmeier, 2007; see also Coulson and Severens, 2007, for similar findings in the context of pun comprehension).However, several aspects of our ERP, gaze, and behavioral data suggest that the RH might have an advantage in making broader or more flexible use of context information. First, compared to the LH, the RH showed greater N400 priming when a weakly-biased context preceded strongly-related targets, and the LH also showed reduced N400 priming (compared to the unrelated context condition) when a strongly-biased context preceded weakly-related targets.…”

“…However, deficits in context-based meaning selection have also been observed in patients with unilateral RH damage (McDonald et al, 2005;Tompkins et al, 2000). Thus, it may be that the functions of both hemispheres are essential to normal meaning processing, although the literature to date does not provide a clear picture of what those asymmetric functions are.Building on work using VF presentation methods with ERP measures to examine hemispheric differences in language comprehension (see, e.g., review by Federmeier, Wlotko, and Meyer, in press), we (Meyer and Federmeier, 2007) examined hemispheric asymmetries in ambiguity resolution, focusing on the effects of context, meaning frequency, and associative strength.ERPs were recorded as neurologically-intact participants decided if a lateralized ambiguous or unambiguous prime was related in meaning to a centrally-presented target. Prime-target pairs were preceded by a centrally-presented context word that could be related or unrelated in meaning.…”