Gustav Fechner
Fechner, along with Wilhelm Wundt and Hermann von Helmholtz, is recognized as one of the founders of modern experimental psychology. His clearest contribution was the demonstration that because the mind was susceptible to measurement and mathematical treatment, psychology had the potential to become a quantified science. Theorists such as Immanuel Kant had long stated that this was impossible, and that therefore, a science of psychology was also impossible.
Cognitive psychology
One of the foremost minds with regard to developmental psychology, Jean Piaget, focused much of his attention on cognitive development from birth through adulthood. Though there have been considerable challenges to parts of his stages of cognitive development, they remain a staple in the realm of education. Piaget's concepts and ideas predated the cognitive revolution but inspired a wealth of research in the field of cognitive psychology and many of his principles have been blended with modern theory to synthesize the predominant views of today.