Control Stimuli in Experimental Code-Switching Research

The current study investigates whether there is variation among different types of control stimuli in code-switching (CS) research, how such stimuli can be used to accommodate heterogeneity, and how they can also be used as a baseline comparison of acceptability. A group of native Spanish–English bilinguals (n = 20) completed a written acceptability judgment task with a 7-point Likert scale. Five different types of control stimuli were included, with three types considered to be completely acceptable (complex-sentence switches, direct-object switches, and subject–predicate switches) and two types considered to be completely unacceptable (pronoun switches and present–perfect switches). Additionally, a set of present–progressive switches were included as a comparison, as their acceptability status is still actively debated. The participants as a whole exhibited the expected grammatical distinctions among the control stimuli, but with a high degree of individual variability. Pronoun switches and auxiliary verb switches were rated significantly lower than the complex-sentence switches, direct-object switches, and subject–predicate switches. These results show that control stimuli can also establish a baseline comparison of acceptability, and recommendations for inclusion in experimental CS research are provided.