Despite the expanding size and scope of studies on the plasticity of the brain associated with learning involving higher-level brain functions such as language acquisition, not much is known about the change in brain functions, mental developments in areas such as self-recognition, and changes in learning strategies during adolescence, even though adolescence has long been viewed as a period accompanied by significant mental development and change in learning mechanisms.
In the present study, we examined functional changes and neuroplasticity of participants around adolescence using psychological and behavioral tests and brain-function measurements involving near-infrared spectroscopy, while half the participants engaged in the task of acquiring phonological distinctions in non-native phonemes in English and the other half engaged in a control task. The behavioral tests indicated that every group that engaged in phonological learning achieved significant improvement in their ability to distinguish phonemes. This result shows that new phonemes can be acquired even after puberty. Brain-function measurements during behavioral tests showed that learning was accompanied by strengthening of brain activation. The details of the strengthening was different across age groups. Examination of the relationship between these behavioral tests, brain-function measurements and the level of self-recognition indicated that those who scored higher on the scale for independent and interdependent construal of self tended to achieve higher levels of acquisition and show stronger brain activation after the training.
These results indicated that learning directed toward acquisition of spoken language causes changes in brain function in all age groups and that the changes seen in pubescent participants have some distinctive features. It was also suggested that there is association between the level of phonological acquisition and the level of self-recognition.