In one of his lectures Jordan Peterson says that psychological constructs are difficult to validate, and therefore that it is desirable to have up to five levels of validation for any such construct, including psychometric, neuroscientific, pharmacological, evolutionary etc. An example might be one of the Big Five Personality Traits Conscientiousness-Orderliness, which is validated with reference to disgust, which has evolutionary value (avoidance of disease) and behavioural correlates (eg., facial expression).
This provides a research paradigm for psychology and related disciplines. For example, in Second Language Acquisition (SLA) it is posited that language is acquired naturally when certain conditions are met, in particular, there is sufficient compehensible input and noticing. The idea is that given adequate comprehensible input the learner will notice certain linguistic features which is a necessary condition of acquisition. Moreover, there will be a natural progression in learning innately determined by the structure of the language acquisition system.
Other theories, such as Social Constructivism,
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