The perception process is broadly described as the way in which living things take sensory input and assign meaning to it in their minds so that purposeful action can be taken in response to stimuli. With human beings, this means that our awareness and interaction with people and objects in our environment must first be experienced by the five senses in some form or another before judgments can be made as to what the experiences mean. Though psychology states that all individuals may see the world in a different light, the important aspect of the perception process is one of selection. Much of what the senses experience must be tuned out so that the mind can organize important sensory input and interpret it for meaningful action. It is in the final stage of the perception process, or interpretation, where individuals most directly display their subjective views of the world around them.
While the process of perception is thought to generally have three stages, it is possible to extend this to five, especially where human beings are concerned. Perception is generally thought of as a continuum of experience where the selection of sensory input is first brought to conscious awareness, then is organized in some manner, and then interpreted. All living things go through this basic perception process to one degree or another as a more elaborate definition of the stimulus-response behavior of living things.
More advanced life forms, however, also have periods of reflection and adaptation that are added to the final stage of interpretation. Measuring perception itself may be based on the ability for an organism to store memories of past experiences and alter interpretation of similar events as they arise. This can, therefore, lead to changes in behavioral response where the perception process is continually updated and refined using current learning experiences and memories simultaneously.
Types of perception that differ between lower life forms and those that are more immediately aware of their own existence may vary based on the perception process having an element of Gestalt theory to it. Gestalt theory originated in Germany in the mid-1900s as a result of research by three German psychologists, but it was Max Wertheimer among them who categorized it as defining the nature of human perception in 1924. Gestalt theories of perception focus on the idea that the behavior of an entire system, or individual mind, is not directly determined or controlled by stimuli that can be classified or organized into separate components.
Where Gestalt theory differs from classical psychology in defining the perception process can be illustrated with an example of a musical score. Standard psychological views of the process of perception tell us that a person consciously selects each individual note of a musical composition in his or her mind as they are heard, organizes them, and then interprets them as a recognizable song. The Gestalt theory perception process instead states that the human mind hears the totality of the musical composition as a whole, even if parts of it are muffled or missing. The perception process can therefore be seen as one where the mind experiences the totality of reality and then breaks it if necessary into separate parts, or where it assembles points of stimuli in its environment into a subjective meaning for what the world around it actually is.