2.1 Participants
Thirty right-handed Chinese (L1)-English (L2) bilingual university students with normal or corrected-to-normal vision were recruited in the experiment. All participants were born in China and had no immigration or study abroad experience. On average, the participants began learning English in traditional classroom settings at the age of 8.40 years (SD = 2.18, range: 6-13). No participant reported neurological, cognitive, or motor impairments. Research ethics approval was obtained from the Committee of Protection of Participants at Beijing Normal University and all participants provided written informed consent before beginning the experiment. One participant was excluded because of excessive EEG artifacts. The final sample consisted of 29 participants (10 males, 19 females, mean age: 22.66, range: 19-27).
To gather information about the participants’ language proficiency, we administered the Oxford Quick Placement test (OPT; Geranpayeh, 2003) and asked participants to provide self-ratings of their language abilities on a 6-point scale (1 = no knowledge; 6 = perfect knowledge) (Liu et al., 2021; Liu et al., 2023a; 2023b). The mean score from the OPT was 36.63 (SD = 5.52), which falls within the A2 level of the Common European Framework of Reference. The average self-ratings of L1 proficiency were: listening (M = 5.62, SD = .49), speaking (M = 5.17, SD = .54), reading (M = 4.59, SD = .78), and writing (M = 5.1, SD = .77). For L2 proficiency, the self-ratings were: listening (M = 3.62,SD = 1.05), speaking (M = 3.45, SD = .74), reading (M = 3.03, SD = .98), and writing (M = 3.31,SD = 1.2). Paired-sample t -tests revealed that the participants’ L1 was significantly stronger than L2 in all four domains: listening (t = 10.41, p < .001), speaking (t = 11.65, p < .001), reading (t = 8.81,p < .001), and writing (t = 7.81, p < .001). These self-ratings and OPT scores are similar to those reported on intermediate Chinese-English bilinguals in prior research (Kang et al., 2017; Liu et al., 2016; Liu et al., 2021; Liu et al., 2023b; Yuan et al., 2021; Wu et al., 2019), suggesting unequal proficiency between their two languages.