Albert Einstein had a lifelong love of music (particularly the works of Bach and Mozart), once stating that life without playing music would be inconceivable to him. In some interviews Einstein even attributed much of his scientific intuition to music, with his son Hans recounting that "whenever he felt that he had come to the end of the road or into a difficult situation in his work, he would take refuge in music, and that would usually resolve all his difficulties." Something in the music, according to Michele and Robert Root-Bernstein in "Psychology Today", "would guide his thoughts in new and creative directions." It has been said that Einstein considered Mozart's music to reveal a universal harmony that Einstein believed existed in the universe, "as if the great Wolfgang Amadeus did not 'create' his beautifully clear music at all, but simply discovered it already made. This perspective parallels, remarkably, Einstein’s views on the ultimate simplicity of nature and its explanation and statement via essentially simple mathematical expressions." A review suggests that music may be effective for improving subjective sleep quality in adults with insomnia symptoms. Music is also being used in clinical rehabilitation of cognitive and motor disorders.