Vestiges of unused foreign languages learned as children may be deeply embedded in people's memory banks, British researchers say.

Many children who learn a foreign language may believe they have no recollection of the neglected language.

However, researchers at the University of Bristol say study participants who had learned Hindi and Zulu as children living abroad could remember phonemes -- the smallest sounds in a language.

The study participants did not recognize vocabulary words, but they were able to quickly relearn and correctly identify vocabulary tests phonemes the researchers say would have been difficult for native English speakers to recognize.

The findings, published in Psychological Science, suggest being exposed as young children to foreign languages, even if they do not continue to speak them, can have a lasting impact on speech perception.

"Even if the language is forgotten -- or feels this way -- after many years of disuse, leftover traces of the early exposure can manifest themselves as an improved ability to relearn the language," the study authors said in a statement.