Perception psychology is the study of the ability that allows biological organisms to obtain information about the outside world and the world within us, often with the intention of being able to interact with the outside world.
Psychophysics is the field of psychology that studies the connections between physical stimuli, their neuropsychological counterparts and corresponding sensory experiences. The research is conducted with the aim of establishing statutory obligations, invariants or psychophysical principles, primarily in perception and cognitive psychology, psychophysiology, neuropsychology and in environmental psychology and social psychology.
Source: National Committee for Psychology, at the Royal. Academy of Sciences.