Books that suggested ways to improve certain sides of the brain had more to do with social values and commercial interest rather than science. Those who bought into this myth seeked to find a mystical and intuitive rationale for world views and day to day problem solving.
If a family member who read the book ‘Drawing on the Right Side of the Brain’ (Edwards, 1980) and was convinced this phenomenon was true I’d simply explain to them that both sides of the brain are conscious while performing any tasks. For example when giving a speech in front of a large audience, your left hemisphere would concentrate on your word choice. While your right hemisphere would concentrate on the intonation and volume for your voice. It is impossible to perform a single task only using one hemisphere of the brain at a time, unless you are split