The motion vision is part of the visual perception and the ability to perceive movement. Our world consists of movement, of changes in spatial relationships. However, we not only see real movement, but also apparent movement .
Movement vision accompanies us in everyday life and is important to find our way around the world.
Differentiation of movement signals
- Retinal movement: when the image on the retina shifts and various receptors are stimulated one after the other, movement is perceived. The eye does not follow the object. The further away the object, the less the retinal displacement.
- Eye movement : Movement is perceived although the image remains at the same retinal point because the object is being followed with the eyes or even with the whole head. Your own movement and that of the object are offset against each other.
The movement of the eyes makes it clear that movement cannot only be explained by a shift on the retina.
Other important components in motion vision
Body sensations : People themselves often move, but not their surroundings - trees and houses, for example, stand still when people walk or drive past them. In such cases, too, various areas of the retina are stimulated by these stationary objects when walking or driving past. Nevertheless, we do not experience these objects as moving, but ourselves. The environment is perceived as stable, because the brain "offsets" all other body sensations with the visual perceptions, and as a result of the unconscious assessment of different sensory impressions, the conclusion can be drawn that The houses around us do not move, but we ourselves are in motion and subject to a subjective localization.
The experience : In addition to the various body sensations, experience (our acquired knowledge that not the houses, but only we ourselves can move) also causes you to experience yourself as moving. Over time you also learn that objects that are further away appear smaller than those that are closer to us. For example, you can tell that a car is moving towards you when it gets bigger and bigger.
Functions of movement perception
Being able to see movement is an extremely important skill. Motion vision is vital for both animals and humans.
- Recognize dangers : by perceiving movement, animals recognize when an attacker is moving towards them. It can also protect people from danger. For example, humans can see the movement of cars or falling objects and react accordingly.
- Generate attention : by seeing movement, attention is drawn to the object. For example, if you are in a large group, you can draw attention to yourself by waving.
- Recognize objects : through movement, an object can stand out from its background or helps to make its shape more recognizable.
- Information about the environment: since we can see movement, we receive important information about our environment. Gestures provide information on the intensity of a conversation, for example. It can also be helpful when interacting with the environment. We can recognize a hand coming towards us as an offer to shake hands and thereby adapt our movement and extend our hand as well.
- Spatial perception : our brain also uses the movement information for spatial perception . A well-known example of this is the parallax of movement .
Real and apparent movement
In the broader sense, apparent movement is understood as the perception of movement in objects that do not really move in the physical sense. In a narrower sense, this means stroboscopic movement . This is the perception of movement when viewing a sequence of slightly varied individual images. This gained a great deal of importance in the film: Images are presented in rapid sequence - usually 24 to 30 different individual images per second. The movements depicted in these images appear realistic. In a broader sense, other illusions of movement are also referred to as apparent movement, for example the landscape that appears to be flying past when looking out of the train window.
The development of suitable movement patterns has played a central role in research into movement vision since Helmholtz . Traditionally, light beams were directed using movable mirrors and oscilloscopes were used. Today, experimental movement patterns are almost exclusively created as pseudo-movement with computers, although it is known that the human eye reacts differently to pseudo and continuous movements at up to 300 frames per second. Well-known movement patterns are Julesz patterns , summations of Gaussian blobs or point patterns (e.g. biological movement ).
Explanations of movement perception
Gibson's ecological perception theory
James Jerome Gibson developed an ecological theory of perception. This deals with the information from the environment that is used for perception. Gibson uses the term optical field to describe information in the environment, a structure made up of contours, surfaces and textures of the environment. He was asked how movements of the observer change this optical field.
According to Gibson, movement is perceived through a local disturbance that occurs when the moving object in the optical field conceals different parts one after the other and then reveals them again.
You can see movement when you follow the moving object with your eyes and it leads to a stationary image on the retina or when the eyes are stationary and there is an image shift on the retina. In both cases a local disturbance occurs in the optical field.
If you look around with your eyes from left to right, however, there is a shift on the retina, although actually no object is moving. According to Gibson, this is a so-called global optical flow . If you look from left to right in a room, objects such as a cupboard, table or chair move from right to left. This optical flow shows that the environment does not move and we also do not perceive any movement.
According to Gibson, information about the movement or non-movement of an object is obtained directly from the environment. Perception and the environment are closely related. For him, it is not the retinal shift that determines the perception of movement, but events in the optical field. We see movement when something moves in our optical field relative to the whole. However, when this optical field moves as a whole, as when looking around the room or standing still, we perceive no movement.
In contrast to Gibson's ecological approach, Bernhard Hassenstein and Werner Reichardt looked at movement vision on the neural level. The Reichardt detector ensures that movement in a certain direction causes a neuron to fire. The detector is excited when a stimulus first arrives at location A and then a short time later at location B. However, the detector can also be inhibited. This happens when the stimulus moves in the opposite direction. This model can also be used to explain pseudo movements.
- Retinal Image Shift (SRB) signal: when the gaze is stationary and an object is moving in the field of view
- Motor signal (MS) : ensures that you follow a moving object with your eyes, as a signal has been sent from the brain to the eye muscles
- Efficiency copy (E) : this is a copy of the motor signal that is sent to other areas of the brain instead of the muscles of the eye
According to the reactivity principle, movement is only perceived when the comparator (a neural structure in the brain that serves as a comparison instance) receives either only an efference copy or only a retinal image displacement signal. If so, a movement signal is sent to the cortex and movement is sensed. However, if the comparator receives both signals, they compensate each other, the cortex receives no movement signal and no movement is perceived. With this principle, our visual system can distinguish between proper movement (especially eye movement) and external movement.
Movement perception in the brain
The MT area in the middle cortex and the MST area in the medial superior temporal cortex play an important role in motion vision . It is assumed that the MT area is primarily relevant for processing movement information. An example of the importance of the MT area can be seen when this area is destroyed as is the case with actinetopsia . Those affected then no longer have the ability to perceive movement. This is why one speaks of movement blindness. Everyday actions such as pouring a cup become impossible because the liquid even seems frozen.
- Julia Groß: Always on the move. September 3, 2011, accessed February 23, 2017 .
- Heiko Hecht: Movement Perception . In: Joachim Funke, Peter A. Frensch (Hrsg.): Handbuch der Allgemeine Psychologie- Kognition . tape 5 . Hogrefe, Göttingen / Bern / Vienna 2006, ISBN 3-8017-1846-8 , pp. 182-189 .
- E. Bruce Goldstein: movement perception . In: Karl Gegenfurtner (Ed.): Perception Psychology . 9th edition. Springer, Berlin / Heidelberg 2015, ISBN 978-3-642-55073-7 , pp. 174-194 .
- Max Neunecker, Andreas Orth, Jörg Trojan, Michael Witthöft: Movement Seeing : Introduction. Retrieved February 23, 2017 .
- Apparent movement. In: Dorsch, Lexikon der Psychologie, Hogrefe Verlag, Bern. MA Wirtz, accessed on May 8, 2019 .
- Kerstin Witte: Basics of sports motor skills in the bachelor's degree. Springer Spektrum,, Berlin 2018, ISBN 978-3-662-57867-4 , p. 66 ( Google books ).