LOS NOTICIEROS NACIONALES QUE SE MANTIENEN EN EL SISTEMA PÚBLICO: NOTICIAS UNO Y CM& 

Based on findings of previous research on behavioural tests of hemispheric asymmetry with respect to either stuttering or bilingualism, the following hypotheses are proposed.

2.7.1 Comparison of MWS and MWNS

Comparisons of MWS and MWNS have been conducted in previous research investigating cerebral hemispheric processing in the disorder of stuttering. These earlier behavioural studies assessing hemispheric asymmetry in MWS (see Sections 2.4.3.1, 2.4.4.1, and 2.4.5.1) have indicated an asymmetry to the right hemisphere for language processing in MWS compared to MWNS.

Research Question: How do MWS compare to MWNS on functional cerebral hemispheric language processing?

Hypothesis 1

MWS have greater right-hemisphere dominance for functional cerebral hemispheric language processing over MWNS.

Hypothesis 1a: MWS will have significantly greater right-hemisphere dominance than MWNS on a dichotic listening paradigm.

Hypothesis 1b: MWS will have significantly greater right-hemisphere dominance than MWNS on a visual hemifield paradigm.

Hypothesis 1c: MWS will have significantly greater right-hemisphere dominance than MWNS on a dual-task paradigm.

2.7.2 Comparison of BWNS and MWNS

Comparisons of BWNS and MWNS have been conducted in previous research investigating cerebral hemispheric processing in the field of bilingualism. These earlier behavioural studies assessing hemispheric asymmetry in sequential BWNS (see Sections 2.4.3.2, 2.4.4.2, and 2.4.5.2) have indicated a greater asymmetry to the left hemisphere for language processing in BWNS compared to MWNS.

Research Question: How do BWNS compare to MWNS on functional cerebral hemispheric language processing?

Hypothesis 2

BWNS have greater left-hemisphere dominance for functional cerebral hemispheric language processing over MWNS.

Hypothesis 2a: BWNS will have significantly greater left-hemisphere dominance than MWNS on a dichotic listening paradigm.

Hypothesis 2b: BWNS will have significantly greater left-hemisphere dominance than MWNS on a visual hemifield paradigm.

Hypothesis 2c: BWNS will have significantly greater left-hemisphere dominance than MWNS on a dual-task paradigm.

2.7.3 Comparison of BWS and MWS

A comparison of BWS and MWS has not been conducted in previous research investigating cerebral hemispheric processing in the disorder of stuttering. Despite earlier behavioural studies assessing hemispheric asymmetry in MWS (see Sections 2.4.3.1, 2.4.4.1, and 2.4.5.1) or sequential BWNS (see Sections 2.4.3.2, 2.4.4.2, and 2.4.5.2), it is not known whether BWS and MWS have the same level of hemispheric asymmetry in language processing.

Research Question: How do BWS compare to MWS on functional cerebral hemispheric language processing?

Hypothesis 3

BWS have greater left-hemisphere dominance for functional cerebral hemispheric language processing over MWS.

Hypothesis 3a: BWS will have significantly greater left-hemisphere dominance than MWS on a dichotic listening paradigm.

Hypothesis 3b: BWS will have significantly greater left-hemisphere dominance than MWS on a visual hemifield paradigm.

Hypothesis 3c: BWS will have significantly greater left-hemisphere dominance than MWS on a dual-task paradigm.

2.7.4 Comparison of BWS and BWNS

A comparison of BWS and BWNS has not been conducted in previous research investigating cerebral hemispheric asymmetry in the disorder of stuttering. Despite earlier studies assessing hemispheric asymmetry in MWS (see Sections 2.4.3.1, 2.4.4.1, and 2.4.5.1) or sequential BWNS

(see Sections 2.4.3.2, 2.4.4.2, and 2.4.5.2), it is not known how BWS and BWNS differ with respect to hemispheric asymmetry in language processing.

Research Question: How do BWS compare to BWNS on functional cerebral hemispheric language processing?

Hypothesis 4

BWS have greater right-hemisphere dominance for functional cerebral hemispheric language processing over BWNS.

Hypothesis 4a: BWS will have significantly greater right-hemisphere dominance than BWNS on a dichotic listening paradigm.

Hypothesis 4b: BWS will have significantly greater right-hemisphere dominance than BWNS on a visual hemifield paradigm.

Hypothesis 4c: BWS will have significantly greater right-hemisphere dominance than BWNS on a dual-task paradigm.

2.7.5 Rationale for Hypotheses 1 to 4

Findings for MWS on dichotic listening, visual hemifield and dual-task paradigms indicate atypical cerebral lateralisation (Foundas et al., 2004; Moore, 1976; Sussman, 1982). Bilateral hemispheric involvement has been found for speech and non-speech processing, as well as for motor control (Choo, Robb, Dalrymple-Alford, Huckabee, & O'Beirne, 2010; Fox et al., 2000). With respect to bilingualism, meta-analyses have found that sequential bilinguals display strong left hemisphere dominance in their first and second language (Hull & Vaid, 2006, 2007). Moreover, it has been suggested that sequential bilinguals demonstrate greater left hemisphere reliance for language compared to simultaneous bilinguals and monolinguals (Vaid, 1987). Therefore, both MWS and sequential bilinguals appear to show divergent patterns of language processing. The past finding of a spread of cerebral activation among PWS and a reliance of left hemisphere activation among sequential bilinguals presents an interesting paradox in regard to the BWS. Therefore, research examining BWS compared to MWS, as well as their non-stuttering

controls, may provide new and important insight not only into the disorder of stuttering but also into the phenomenon of bilingualism. However, at present, there are no behavioural studies of hemispheric asymmetry that have investigated BWS.

2.7.6 Significance for Hypotheses 1 to 4

The aim of this research was to examine the relationship between stuttering and bilingualism to hemispheric asymmetry for the processing and production of language. As no previous studies have investigated BWS, evaluations of this particular population were required to gain further knowledge of the interaction of the two cerebral hemispheres during language processing and production. The examination of possible associations between stuttering and bilingualism may assist in determining the predictive value of these factors on language lateralisation. This could ultimately contribute to a better understanding of the disorder stuttering, as well as the nature of bilingualism.