International Encyclopedia of Systems and Cybernetics

There are many significant limits to perception. D.H. MEADOWS et al. put this in the most general terms as follows: Although the perspectives of the world's people vary in space and time, every human concern falls somewhere on a space time graph" (D.H. MEADOWS et aI., 1977, p. 19)

(See the graph "Cognitive spaces", an adapted form of the timegraph)

Physiological limits

J.P. CHANGEUX writes: "An alteration in environmental properties becomes an event for the concerned organism only to the point that its physical characteristics enter within the sensibility domain of its receptors. What may be an event for an insect, possibly will not be one for a vertebrate, and conversely. However, the diversification of receptors types in the superior animals allows them to perceive the event in a more complete manner, even if still limited and partial" (1972, p.391).

A good example is the case of the frog put in cold water, very slowly heated. As the frog does not perceive the quite progressive temperature increase, it is in great danger to be boiled before becoming aware of it.

Once the event becomes registrated as a signal at the level of the sensorial receptor, it is converted into an electrical impulse or action potential.

"Only the frequency or the number of these action potentials may vary in relation to the stimulus nature or intensity and then, only within narrow limits…

"The sensorial organs thus transform the specific and various signals from the external world in conventional ones. When crossing the boundaries of the organism, the signal loses, apparently, its specificity, its information content. Actually, the specificity of the received and transmitted signal is not lost: it is taken up through the specificity of connections, the lines linking the sensorial collectors with specific neural relays in the nervous center" (p.39).

However, during this internalization process, much of the original potential information is lost. According to H.von FOERSTER: "Since there are only a hundred million sensory receptors and about ten-thousand billion synapses in our nervous system, we are 100.000 times more receptive to changes in our internal than in our external environment" (1981, p.300).

It could be added that only during this century man learned to register and translate through technical means some alterations of the environment (X rays, electromagnetic waves, for example) in order to enable his sensorial receptors to perceive them, at least indirectly: we still do not know what we would "see" or "hear" if we were sensorially better endowed.

We use these interpretations, aquired by learning, to observe the world around us. Such observations are by no means pristinely pure. Our physiological observing subsystems act as filters. We do not see, hear, smell, or feel everything that could be observed, not being able to perceive, for example, infrared, ultraviolet light, or ultrasonic waves. On the contrary, we may perfectly "see" lights or shades that are optical illusions. Thus, the information we obtain possess no absolute ontological value.

Psychological and mental limits

We perceive in accordance with our frames of reference, which are constructed in a progressive way by learning and training in specific environments.

In this way a painter becomes much more able to distinct shades of colors, and a musician the specific tonality of different instruments and the sounds harmonics.

In a similar fashion, a trained physician will produce better and swifter diagnostics than a student.

On the contrary, the untrained person is barred to see, hear or understand many signs in any specific trade.

One lesson is that the non-systemist will generally be unable to see not very obvious interrelations among elements in a system or events in a situation.

Perceptions are also oriented – or stunted – by our specific needs or interests. This is "perceptive intentionality" (See above and hereafter).

Cultural limitations

The way perceptions are trained and educated strongly depends upon the cultural settings.

Esquimos learn to recognize many important and distinct aspects of snow, while old seafarers knew much about winds and waves.

The ways to represent perspective have been very different in Western and in Far-Eastern painting.

Cultural limitations do also change through time. Modern Western perspective was unknown in Medieval painting.

Limits to perception lead frequently to serious misunderstandings between people and to deficient awareness in complex situations.