Multistable perception
Multistable perception , change of shape , or change of perception characterizes a phenomenon of spontaneously changing interpretations of a perception, which is rare in everyday life . Systematically produced stimuli that induce change in shape are called tilt figures .
definition
Unpredictable and deliberately unavoidable “changes” in perception occur above all when looking at visual illusions that allow more than one type of stimulus interpretation (so-called tilting figures, technical term: ambiguous patterns ). Well-known examples include a. the Necker cube and some pictures by MC Escher and Salvador Dalí . Either the meaning of an image changes when you change your point of view (e.g. alternately seeing a face or just a pile of stones in front of you) or the impression of depth (as in the case of the Necker cube) or other aspects such as the direction of movement of some dynamic stimulus patterns, the figure -Background ratio of a two-dimensional image or the coherence of a visual object up to the alternation of perception and non-perception of the stimulus itself. Interestingly, these effects also occur in very simple patterns. A simple cross with straight bars of equal length that are at right angles to one another can lead to the fact that one perceives the horizontal bar in front of the vertical one and this in front of the horizontal one.
The fascinating thing about multistable perceptions is their absolutely endogenous character and the dissociation of the perception from the actual stimulation . For changes in perception to occur, neither changes in the stimuli themselves nor active changes on the part of the observer, such as eye movements or deliberate attention to the stimulus pattern.
Tilting figures are related to picture puzzle , in which the task is to look for a specific object in a picture.
Influence on art and culture
Ambiguous figures that are perceived multistable, can already be found in mosaics of antiquity . In the visual arts , MC Escher and Salvador Dalí (and, more rarely, Paul Klee too ) have dealt with multistable perceptions. Some works of Op Art trigger similar spontaneous reorganizations of perception.
In philosophy , Ludwig Wittgenstein's meditations on a multistable stimulus ( William James ' line drawing of a rabbit, which can also be interpreted as a duck's head), and the metaphorical use by Thomas S. Kuhn in connection with his theory of the paradigm shift should be mentioned. Inspired by the neurophysiological findings of recent years, multistable perceptual phenomena have rekindled the interest of the philosophy of mind .
Scientific background
The earlier psychophysics was initially not interested in the variety of perceptual phenomena. With the advent of Gestalt psychology (especially Berlin) in the early 20th century, this changed drastically, and multi-stable perceptual phenomena also became a popular research object. With the demise of this school, interest in multistable phenomena decreased again. Since the 1980s, however, multistable phenomena have once again been of central interest in perceptual psychology . The central assumption is that seeing is an active sensory process during which the brain tries to meaningfully interpret the activation of the receptors . The active processes of the “organization of perception” (see also: Gestalt Laws ) seem to prevent a clear solution if they are in conflict with one another . In this situation, the visual system seems to be forced to “reorganize”, that is to say to switch back and forth from one probable interpretation option to one or more other, more or less equally probable approaches.
A certain control over the process of perception change can be learned. Some eye movements (like blinking and saccades ) can induce such changes to some degree. Some stimulus manipulations also allow external control of the changing states of perception. However, all of these influences have proven to be inadequate for preventing or generating the different modes of perception and only seem to have a modulatory effect on the actually controlling processes.
The rate (speed) of the change of perception varies greatly from person to person and between different perceptions. Correlations with the intelligence quotient , with personality variables, the consumption of stimulants or certain brain damage have been reported several times. However, later studies failed to confirm some of these results. However, there seems to be a consistent decrease in the rate of change with increasing age.
The role of visual attention as a trigger for spontaneous changes in perception is controversial. Despite mutual influences, however, there seems to be a clear dissociation between the processes of multistable perception and attention effects - these are thus related but independent mechanisms.
Neurobiological explanations
Most theories on multistable perception phenomena are based on reciprocal relationships between the alternative forms of perception (percepts) or the ( neural ) mechanisms on which they are based . All of these “classic” models assume that the “dominance” of a state of perception causes the “inhibition” of the alternative forms of perception. The dominance of a percept is ended by the fact that “saturation” or “fatigue” leads to a flattening of the inhibition of the rival state. This increasingly gains the upper hand until it becomes strong enough (“supra-threshold”) to inhibit the previously dominant state. After a certain time, this new state will also tire and the first system state will be resumed. This process can be repeated ad infinitum. In electrical engineering , such circuits can easily be implemented as " flip-flop " multivibrators . In a more biologically oriented modification of this principle, the mutual inhibition of two neurons (or a group of nerve cells) can lead to a similar behavior.
However, several arguments speak against the adoption of such a simple mechanism. Above all, the stochastic nature of the change process poses a major challenge for all "classical" models of reciprocal interrelationships of the rival percepts: Perception does not oscillate (as expected in a system that sways back and forth), but jumps from a state at unpredictable intervals the next. Furthermore, it seems difficult to explain the large inter-individual differences in the change rate with this model. Functional magnetic resonance imaging ( fMRI ) during spontaneous jumps in perception also showed that this mainly activates “higher” brain areas (i.e. in the parietal and frontal lobes), whose functions are mostly associated with action planning and other cognitive phenomena.
See also
literature
- David Alais & Randolph Blake (eds.), Binocular Rivalry , MIT Press, 2005, ISBN 0-262-01212-X
- David Hubel : Eye and Brain. Neurobiology of seeing , Heidelberg: Spectrum of Science, 1995.
Individual evidence
- ↑ (see also Multistable phenomena: changing views in perception ( Memento of September 27, 2008 in the Internet Archive ) Leopold, DA, Logothetis, NK Trends in Cognitive Sciences 1999 (3) 7])