Complex sentence: Modern theories often stay true to behaviourist means of describing such a trait (sociability, talkativeness, assertiveness etc.) whereas Jungian introversion and extraversion is expressed as a perspective: introverts interpret the world "subjectively", whereas extraverts interpret the world "objectively".
Split into simpler sentences: Modern theories often stay true to behaviourist means of describing such a trait (sociability, talkativeness, assertiveness etc.) whereas Jungian introversion and extraversion is expressed as a perspective. Introverts interpret the world "subjectively", whereas extraverts interpret the world "objectively".