Alone or with someone else in the lab? Influence of a second participant in a go/no-go lexical decision task

The goal of this research was to investigate whether a simple linguistic task, such as lexical decision, is affected by the presence of another person jointly performing the task. Previous studies showed that, in a lexical decision task, nonword frequency (the frequency of the word from which the nonword was derived) had either null effects or negatively affected RTs, so that high frequency nonwords were responded to more slowly than low frequency nonwords. Such effect critically reversed in the case of a go/no-go task in which participants were required to respond only to nonwords. This difference was particularly evident in the first quantile of the RTs distribution (Perea et al. 2005). In the Individual condition of the present study participants individually performed a go/no-go task, responding only when the stimulus was a nonword. In the Joint condition a second participant (confederate) joined the task and responded just to words. The results showed a modulation of the frequency effect in the first quantile according to condition so that high frequency nonwords yielded faster responses only in the Individual condition. Results are discussed in terms of task-sharing processes and time criteria.