From the late 1930s to the mid-1940s, Dove's approach became more intellectual and objective as he experimented further with abstraction and with spatial, geometric, and color relationships, and became increasingly aware of the growing abstract tendencies in art. His primary objective became color harmony and experimentation. Although he still gained initial inspiration from nature and continued to paint in an intuitive manner, he now reduced elements to their simplest forms and either stressed flatness or spatial ambiguity. He focused on the arrangement of forms in space and the selection of colors, such as in Yellow, Blue-Green and Brown, painted in 1941. He expressed his great interest in color abstractions with the titles of his paintings, unlike his earlier paintings that referenced the place or object that he was re-creating. His late works, expressions of pure color and form, anticipated the creations of then-emerging Abstract Expressionists like Adolph Gottlieb and Mark Rothko.