Production–comprehension asymmetries and the acquisition of evidential morphology

• We compare evidential production and comprehension directly, using matched stimuli.
• Evidential comprehension lags behind production, even for the same events.
• Difficulty in comprehension persists across different comprehension tasks.
• The asymmetry between perspectives also emerged in a non-evidential context.
• We offer a psycholinguistic explanation for the production–comprehension asymmetry.

Although children typically comprehend the links between specific forms and their meanings before they produce the forms themselves, the opposite pattern also occurs. The nature of these ‘reverse asymmetries’ between production and comprehension remains debated. Here we focus on a striking case where production precedes comprehension in the acquisition of Turkish evidential morphology and explore theoretical explanations of this asymmetry. We show that 3- to 6-year-old Turkish learners produce evidential morphemes accurately (Experiment 1) but have difficulty with evidential comprehension (Experiment 2). Furthermore, comprehension failures persist across multiple tasks (Experiments 3–4). We suggest that evidential comprehension is delayed by the development of mental perspective-taking abilities needed to compute others’ knowledge sources. In support for this hypothesis, we find that children have difficulty reasoning about others’ evidence in non-linguistic tasks but the difficulty disappears when the tasks involve accessing one’s own evidential sources (Experiment 5).