① Perceptual initiative. Perceptors don't passively record all the details of stimuli like cameras. On the contrary, perception is an active process, which processes the stimulus, loses some details of the stimulus, retains its basic characteristics, and organizes the stimulus experience in the form of concepts, so that the objective stimulus becomes an image with a complete structure in perception.
② the organization of perception. In the ever-changing and colorful world, the perceiver is limited by the channel, and it is impossible to input all the information that acts on the senses all the time. Therefore, people can only respond to the basic characteristics of stimuli and organize many isolated stimuli into a meaningful whole.
How does perception arise in the activities of the nervous system? On this issue, Gestalt school put forward the hypothesis of perceptual experience and the theory of nervous system isomorphism. According to this theory, there is a corresponding relationship between the perceptual image of stimulus and its performance in the central nervous system, that is, the perceptual phenomenon conforms to the characteristics of the nervous system. For example, in the organization principle of perception, some stimuli can be perceived as complete graphics, while others are perceived as background, because nerve cells in the cerebral cortex have the characteristics of electromagnetic fields. The force distribution in the magnetic field makes some excitation areas attract each other and others repel each other, thus forming a certain structure or "gestalt". This gestalt in the brain is the graphic-background structure in human perceptual experience. In the case of optical illusion, perception is distorted because its performance in the central nervous system is distorted. Gestalt school's perception theory is a kind of transcendentalism, which holds that perception is the inherent attribute of nervous system and ignores the role of knowledge and experience in perception. Another influential viewpoint of perceptual psychology is the reasoning theory about the basic nature of perception. Its basic assumption is that perceptual experience is a mixture, part of which comes from current feelings and most of which is extracted from information stored in the brain. According to the experience gained in life, people infer the nature of objects from the stimuli acting on the senses.
W. James, an American psychologist, described this theory as follows: "Now it is enough to prove the general law of perception: some of what people perceive through their senses comes from the objects in front of people, and the other part (maybe most of it) always comes from people's own hearts." He believes that people infer the nature of objects that may produce such stimuli according to the stimuli that triggered the senses at that time. This inference is based on the sensory experience formed in one's life, so it is a highly probable possibility. H.von Helmholtz has long pointed out that perceptual reasoning is an automatic and unconscious process.
Another basic assumption of perceptual reasoning theory is that the sensory information input instantly is extremely preliminary, vague or incomplete, so it is impossible to determine what the corresponding external physical stimulus is. In any perceptual process, the near-end stimuli (such as retinal images) acting on the senses can only provide clues, but can not provide a true and complete description of the far-end stimuli (external objective things). Therefore, we must evaluate the true nature of proximal stimulation according to the clues provided by proximal stimulation and a series of assumptions about the world based on past experience. The result of this evaluation is human perception.
The reasoning theory of perception is a reconstruction theory, that is, people can reconstruct the objective world through perception. This theory must assume that people live in an orderly and diverse world, because only in this world can the input of fragments become clues, so that people can infer what the sensory input comes from and what the missing input fragments are. If in a chaotic world, it is impossible to provide an understanding of the rest if only one piece of knowledge about the world is available. In such a world, past experience will not help to infer the nature of external things. The representative figure of this theory is J.J. Gibson. Contrary to the reasoning theory of perception, his point of view is that the stimulus in nature is very complete, and the perceiver is in direct contact with the environment, which can completely produce the perceptual experience corresponding to the stimulus from all sides to the senses, without assuming a reasoning process at all.
Gibson distinguished between stimulus and stimulus information. Although the observer's retina is stimulated by light in the dense fog, the light is uniform at this time, so he can't see anything. This shows that the stimulus of light does not necessarily contain stimulus information, but the perceived information is contained in the difference of external light. No matter the observer observes the surrounding space at any point, the distribution of ambient light is different. This difference or structure of ambient light is an important visual stimulus, which contains spatial information. Distance is not an abstract space between the observer and the object, it is obtained by directly sensing the distribution of physical light.
The psychophysical correspondence theory of perception completely excludes the initiative of perception and the role of past experience, and the role of these factors in the process of perception is undeniable.
Some psychologists have found that eye movements and hand touch movements play an important role in perception. When people observe complex graphics, eye movements can help them perceive the graphics. When people perceive the surrounding environment, the active participation of limbs is easier to adapt to the new environment.
With the development of modern cognitive psychology, the research of perception focuses on the information processing process of visual graphics. These studies include the formation and development of graphic perception, graphic aftereffect, image recognition and so on. In image recognition, people put forward template matching, prototype matching theory and "pan-magic" recognition model. The cognitive view of perception emphasizes the role of representation and concept in perception, and holds that perception is a part of human advanced cognitive activities.