Are two words seen as one object? How age-of-acquisition affects the recognition and naming of pictorial representations of compound words

Adults recognize objects learned in childhood (e.g., "unicorn") faster than those learned later (e.g., "taxes"). This phenomenon is known as the Age-of-Acquisition (AoA) effect. The integrated account proposes that this effect stems from higher demands on semantic processing or arbitrary input-output mappings. To investigate this, 48 British English-speaking students completed an object decision task and a spoken picture naming task using 150 compound words. Compound words were selected because their mapping to multiple morphemes requires increased semantic processing. In addition to individual task performance, we calculated a subtractive measure (naming latency minus object decision latency) for each item per participant. Results showed that early-acquired objects were identified and named more quickly than late-acquired objects. The analysis of the subtractive measure also revealed significant AoA effects. These findings suggest that the influence of AoA and semantic predictors is more pronounced in picture naming than in object decision. This supports the representation account, indicating that the AoA effect is rooted in semantic and phonological representations. Furthermore, the robust AoA effect observed in the subtractive analysis bolsters the mapping account, suggesting the effect also resides in the connections between these representations. Overall, these results align with the integrated account of the AoA effect.