Intermodality differences in statistical learning: phylogenetic and ontogenetic influences

In Basque–Spanish bilinguals, statistical learning (SL) in the visual modality was more efficient on nonlinguistic than linguistic input; in the auditory modality, we found the reverse pattern of results. We hypothesize that SL was shaped for processing nonlinguistic environmental stimuli and only later, as the language faculty emerged, recycled for speech processing. This led to further adaptive changes in the neurocognitive mechanisms underlying speech processing, including SL. By contrast, as a recent cultural innovation, written language has not yet led to adaptations. The current study investigated whether such phylogenetic influences on SL can be modulated by ontogenetic influences on a shorter timescale, over the course of individual development. We explored how SL is modulated by the ambient linguistic environment. We found that SL in the auditory modality can be further modulated by exposure to a bilingual environment, in which speakers need to process a wider range of diverse speech cues. This effect was observed only on linguistic, not nonlinguistic, material. We conclude that ontogenetic factors modulate the efficiency of already existing SL ability, honing it for specific types of input, by providing new targets for selection via exposure to different cues in the sensory input.