New in, old out: Does learning a new language make you forget previously learned foreign languages?

Area of Science:

• Cognitive Psychology
• Neuroscience
• Linguistics

Background:

• Anecdotal evidence suggests a negative impact of learning new foreign languages (FLs) on previously acquired ones.
• The phenomenon of language attrition and interference in multilingualism requires empirical investigation.

Purpose of the Study:

• To empirically test whether learning a third language (L3) hinders the retrieval of words from a second language (L2).
• To investigate the immediate and consolidated effects of L3 learning on L2 retrieval.

Main Methods:

• Two experiments were conducted with Dutch native speakers (L1) who knew English (L2) but not Spanish (L3).
• Participants learned Spanish translations for previously known English words and were then tested on their English recall.
• Testing involved picture naming tasks, with variations in session timing to assess consolidation effects.

Main Results:

• Learning Spanish translation equivalents significantly impaired the speed and accuracy of recalling English words.
• Interference effects were observed immediately after learning new Spanish words.
• Consolidation time (1 day vs. immediate testing) did not significantly alter the observed interference effects.

Conclusions:

• Learning a new foreign language incurs a retrieval cost for other foreign languages.
• Interference effects emerge rapidly after new language acquisition and do not require extended consolidation periods.
• These findings provide empirical support for the claim that multilingual learning involves inherent interference.