For investigators to be able to make claims
For investigators to be able to make claims about language, they must examine the language experiences of the children in their studies instead of relying on reverse inference (Poldrack, 2011). Many of the children in Noble et al.’s (2012) sample were Hispanic/Latino (42%) or African American (13%). Due largely to differences in parental education − which is how Noble et al. operationalized SES − Hispanic-American children from lower SES backgrounds are significantly more likely than are their higher-SES counterparts to grow up speaking Spanish in the home (Hakimzadeh and Cohn, 2007). Similarly, lower-SES Black-American children are significantly more likely to grow up hearing a variation of Standard American English (SAE) often referred to as African American Vernacular English (AAVE) (Smitherman, 2003; Wyatt, 1995). Bilingualism has shown to be related to differences in patterns of neural activation (Buchweitz and Prat, 2013). Thus, children’s language, and in particular bilingualism, may be confounded with SES in a way that the researchers did not control. Given this confound, it diazoxide is worth considering the following alternative explanation for Noble et al.’s (2012) finding of an interaction of age and SES in the LIFG. Schools in the United States, among other more formal settings, demand the use of SAE (Smitherman, 2003; Valdes-Fallis, 1978), but most lower-SES Hispanic and Black children continue to use Spanish and AAVE, respectively, when interacting with friends and family (Rickford and Rickford, 2002; Valdes-Fallis, 1978). This is particularly true when these individuals express strong emotion (Harris, 2004). This switching between language variants, termed code-switching, has received considerable attention in the study of bilingual children as a possible mechanism through which bilinguals may develop superior executive function capacities (Bialystok, 1999; Carlson and Meltzoff, 2008; Emmorey et al., 2008), although we should note that this is still an area in which there is considerable debate (Duñabeitia and Carreiras, 2015). Typically developing children recruit bilateral IFG for executive function tasks, particularly those that require switching between tasks (Aron et al., 2003). In fact, one study showed that bilinguals are more likely than monolinguals to differentially recruit the LIFG, and this increased recruitment of LIFG during switching tasks mediated their superior performance on the task itself (Garbin et al., 2010). Thus, because the lower-SES children in Noble et al.’s study may have had superior task-switching abilities relative to their peers, the decreasing volume of LIFG with age may be evidence of an advanced trajectory of executive function development, such that synaptic pruning begins at earlier ages, allowing them to reach adult-level proficiency more rapidly (Shaw et al., 2006). While this alternative explanation is speculative, it highlights the difficulty of using reverse inference to interpret neural differences, particularly over development. One can interpret these differences as reflecting either a deficiency or an advantage simply by drawing on different literatures. Indeed, in the absence of longitudinal data, structural MRI measures during childhood and adolescence may be particularly subject to different interpretations (Mills and Tamnes, 2014). In this example, it is unclear whether decreased cortical volume represents underdevelopment of synaptic connections or more advanced pruning. Noble et al. (2012) were meticulous in implementing controls for such confounding factors as gender and age, and were appropriately cautious in offering their interpretations of their data. Nevertheless, it is important to recognize that the reification inherent in cross-group studies of SES makes the isolation of any particular variable of interest, and hence the interpretability of any findings, particularly difficult. At this point, we believe that there is simply not sufficient evidence to support linking structural brain differences to underlying language deficits in lower-SES children.