Gradual Decline Hypothesis

The Gradual Decline Hypothesis is a theory proposed within the field of language acquisition and linguistics to explain the process of first language attrition, especially in individuals who acquire a second language. It suggests that native language abilities do not disappear abruptly but instead undergo a slow, progressive weakening over time, often influenced by reduced use and increasing dominance of the second language. This hypothesis stands in contrast to explanations that emphasise sudden shifts or critical periods in linguistic competence.

Background

The study of language attrition has focused on how bilingual or multilingual individuals experience changes in proficiency, fluency, and automaticity in their first language (L1). Researchers observed that in cases where individuals are immersed in environments dominated by a second language (L2), features of the L1 may decline.
The Gradual Decline Hypothesis emerged as a way to account for this phenomenon. It posits that attrition results from incremental reductions in frequency of use, leading to gradual weakening of memory traces and accessibility of linguistic structures.

Core Assumptions

• Incremental Nature: Language attrition does not occur suddenly but unfolds progressively.
• Frequency of Use: The more infrequently certain words, structures, or phonological patterns are used, the more likely they are to weaken.
• Interference: The second language may interfere with the first, influencing word choice, grammar, or pronunciation.
• Variable Decline: Not all aspects of language decline at the same pace; vocabulary and morphosyntactic structures may weaken earlier than core phonological features.

Empirical Evidence

Studies on bilinguals and immigrants have provided evidence for the hypothesis:

• Lexical Retrieval: Reduced speed and accuracy in recalling less common words from the L1.
• Grammar Simplification: Gradual omission of complex syntactic forms in favour of simpler structures.
• Phonological Drift: Subtle shifts in pronunciation influenced by the dominant L2 over time.
• Code-Switching: Increased reliance on L2 words when L1 vocabulary is not readily accessible.

Such findings support the idea that L1 attrition is a slow process, reflecting cognitive and usage-based changes rather than sudden loss.

Comparison with Other Hypotheses

• Critical Period Hypothesis: Suggests that once a certain age is passed, language abilities cannot be regained or preserved. The Gradual Decline Hypothesis differs by focusing on progressive erosion rather than age-related cut-offs.
• Regression Hypothesis: Proposes that language is lost in the reverse order it was acquired. By contrast, the Gradual Decline Hypothesis highlights continuous weakening influenced by use and interference, not strict reversal.
• Abrupt Loss Models: Some theories propose sudden loss of linguistic competence due to trauma or immediate immersion in another language, which the gradual model rejects.

Implications

• Language Maintenance: Highlights the importance of regular practice, exposure, and active use to maintain first language skills in bilingual contexts.
• Education: Suggests that heritage language education should emphasise consistent reinforcement to counteract slow attrition.
• Cognitive Science: Provides insights into how memory, frequency effects, and interference shape linguistic competence.
• Sociolinguistics: Explains patterns in immigrant communities where first-generation speakers maintain strong L1 competence, while second-generation speakers show gradual decline in certain linguistic features.