Bilingualism and inhibitory control influence statistical learning of novel word forms

Abstract

We examined the influence of bilingual experience and inhibitory control on the ability to learn a novel language. Using a statistical learning paradigm, participants learned words in two novel languages that were based on the International Morse Code. First, participants listened to a continuous stream of words in a Morse code language to test their ability to segment words from continuous speech. Since Morse code does not overlap in form with natural languages, interference from known languages was minimized. Next, participants listened to another Morse code language composed of new words that conflicted with the first Morse code language. Interference in this second language was high due to conflict between languages and due to the presence of two colliding cues (compressed pauses between words and statistical regularities) that competed to define word boundaries. Results suggest that bilingual experience can improve word learning when interference from other languages is low, while inhibitory control ability can improve word learning when interference from other languages is high. We conclude that the ability to extract novel words from continuous speech is a skill that is affected both by linguistic factors, such as bilingual experience, and by cognitive abilities, such as inhibitory control.

Keywords: Morse code; Simon task; bilingualism; inhibitory control; language acquisition; statistical learning.

Figure 1

The Morse code words used in the two languages. Long tones, or dashes, are 300 ms long, and short tones, or dots, are 100 ms long. Numbers in parentheses indicate the length of the pause, either 100 or 300 ms. Short pauses separate tones within a letter, and long pauses separate letters within a word.

Figure 2

Morse code listening streams in the low and high-interference conditions. The dots and dashes represent short (100 ms) and long (300 ms) tones respectively, while the short and long gaps represent silences of 100 and 300 ms respectively. In the low-interference condition (A), words are marked by statistical probabilities between letters (the transitional probability within words is 100%, e.g., T is always followed by A, but the transitional probability between words is 50%, e.g., A is followed by either E or I). In the high-interference condition (B), the gap between words is reduced, and the statistically defined words (TA, EM, IN) compete with words defined by the long pauses (AE, MT, AI, as well as MI, NT, NE). Each participant was exposed to both the low- and high-interference conditions. The order of the two conditions was fixed, with the low-interference condition always occurring first, but the language used in each condition was counterbalanced across subjects. In the example above, the same language is shown in both the low-interference condition and the high-interference conditions in order to highlight the difference between conditions.

Figure 3

Effects of second language proficiency and inhibitory control on learning the new language in the low-interference condition. (Asterisks indicate a significant difference from chance, alpha of 0.05. Error bars indicate 1 SE).

Figure 4

Relationship between second language proficiency and learning of word forms in the low-interference condition.

Figure 5

Effects of second language proficiency and inhibitory control on learning the new language in the high-interference condition. Positive scores indicate learning of statistical cues and negative scores indicate learning of pause cues. (Asterisks indicate a significant difference from chance, alpha of 0.05. Error bars indicate 1 SE).

Figure 6

Relationship between inhibitory control (assessed by the Simon task) and learning of word forms in the high-interference condition.