Until now it had been demonstrated that emotion is reduced when one expresses oneself in a language other than the mother tongue and that the decision-making process of an emotive nature varies depending on the language context. Thus, people are more emotional in their own language and are likely to take more rational decisions in a non-native communicative context.

Albert Costa, ICREA researcher at the Department of Information and Communication Technologies  (DTIC) and leader of the research group into Speech Production and Bilingualism (SPB) at the Center for Cognition and Brain (CBC) at UPF, together with Jon Andoni Duñabeitia, researcher at the Basque Center on Cognition, Brain and Language, has participated in a study published in the advanced online edition of the journal Psychonomic Bulletin & Review, in which he explores the interaction between the act of deliberately lying and the processing of a second language, other than the mother tongue.

Since lying requires an emotional component, the researchers started from the assumption that this emotion could be attenuated if the lie is expressed in a language other than the mother tongue.  Costa and Duñabeitia have studied the interaction between the lie and the use of a non-native language, two actions that are capable of causing the speaker stress.

In this study, native Spaniards with a good command of English were asked to name photographs of animals out loud. Within each group, depending on the instructions, a description of the animal that the participants were seeing was elicited (true enunciations) or they were asked to deliberately lie, naming an animal other than the one in the picture they were presented with (false statements, or "lies").

Lying and speaking in a foreign language are stressful actions

Pupil dilation was the primary measure for evaluating the results of the experiment. Pupil dilation is an indicator associated with the emotional response and increased cognitive load. The authors found that, as expected, stressful variables increase the emotional response. That is to say, the dilation of the pupil is greater when speaking in a foreign language and also when people tell lies, even if they utter them in their own language.

As Costa states, "it is important to note that the extent of the effects of the lie was comparable in the two languages: lying in English turned out to be as emotional as lying in native Spanish". This result is rather unexpected, since it suggests that the participants using a foreign language were not able to distance themselves emotionally from the repercussions of their lie.

However, as Duñabeitia expressed, "given that speaking in a non-native language involves a greater cognitive load, the logical prediction would have been that lying in English should be more troublesome than lying in Spanish, and the results show that this is not so". At the same time, in spite of the higher cognitive load associated with speaking in a language other than the native tongue, the results of the study show that a certain type of emotional distance is operating in the other language, because the "effort" of lying has not turned out to be disproportionately greater in the native language.

Reference work:

Jon Andoni Duñabeitia, Albert Costa (2015), " Lying in a native and foreign language",  Psychonomic Bulletin and Review, print version in press.