Why Understanding Positive and Negative Feedback is Important

Why Understanding Positive & Negative Feedback Is Important:

Positive and negative feedback refer to characteristics of complex systems, the understanding of which is important in the science of ecology. Gregory Bateson (1979), for example, suggests that the two types of systems operate according to very different patterns, each of which has a distinctive logic.

Negative feedback systems are referred to as “deviation /inhibiting/ systems.” The classic mechanical example of a negative feedback system is the relationship between a thermostat and a furnace, where the user is able to set the optimum value, or the desired temperature. Consequently, when the temperature of the room exceeds this optimum value, the furnace will be shut off, allowing the temperature of the room to drop. When the temperature falls below the optimum value, however, the furnace is turned on. This leads to an oscillation in temperature around the optimum value which mirrors the patterns of relationship which characterize all complex organic systems.

Complex organic systems include everything from biological organisms themselves, to ecosystems and the biosphere as a whole. In general, organic systems behave very differently from mechanical systems. As Bateson points out:

“…there are no monotone values in biology. A monotone value is one that either only increases or only decreases…Desired substances, things, patterns, or sequences that are in some sense good’ for the organism…are never such that more of the something is always better than less of the something. Rather, for all objects and experiences there is a quantity that has an optimum value. Above that quantity, the variable becomes toxic. To fall below that value is to be deprived” (1979:56).

Blood sugar is an excellent example, as insulin dependent diabetics know all too well. Both too much and too little is bad for human health, and diabetics must try to maintain blood sugar within its optimum range to avoid the negative health effects of either extreme. Populations of predators and prey also naturally oscillate around optimum levels. There are optimum levels of plant nutrients in ecosystems, optimum levels for pH or acidity in bodies of water, and there is also an optimum amount of carbon dioxide and other greenhouse gases in the atmosphere, all of which are maintained within their optimum range under normal circumstances. Interfering with these natural processes by maximizing one of these variables leads to ecological problems: nutrient pollution from too many nutrients, acid rain that kills lakes, and global warming, respectively.

In sum, optimization is the norm in organic systems, and too much or too little of any variable is generally a bad thing. Bateson defines the negative feedback systems which are the norm for organic systems as exhibiting an “ethics of optima.”

The “ethics of maxima” which characterizes the logic behind capitalist economics, however, is quite different. It is consistent not with the negative feedback systems typical of other living systems, but rather with “positive feedback” systems. Positive feedback systems are referred to as “deviation /amplifying/ systems.”

In other words, positive feedback systems tend to move consistently in the direction of one of the extremes. An intensification leads to further intensification; a decrease leads to a further decrease in some variable. The classic mechanical example of positive feedback is the breakdown in the intended, or optimum relationship between a microphone, amplifier and speaker system. For if the sound coming out of the speakers feeds back into the microphone, it creates a “vicious circle” through which the signal is continually amplified each time it comes back around the cycle. This leads to the familiar, high pitched squeal of “feedback” with which we are all familiar in popular language. It also leads to the eventual /collapse/ of the system.

The opposite pattern of positive feedback is illustrated by the relationship between a camera and screen, where the image being recording includes a playback of that image. This leads to a diminishing pattern of images within images which eventually become too small to register on the pixels of the screen displaying the image. Thus resulting in its /disappearance/.

Thus, where negative feedback systems tend to /maintain themselves/ by oscillating about an optimum value, positive feedback systems tend to /escalate/ out of control, leading to their own /destruction/. One pattern is /sustainable/ while the other is /self-destructive/.

A thermostat-furnace system which went into positive feedback mode, for example, would be unable to compensate for increases in temperature by shutting the furnace off. Instead, if the room became hotter the message would be that the room needed to be made even hotter still. And eventually the house would burn down as a consequence.

Human cancers follow a similar pattern. Cancer is, after all, a unidirectional explosion of cell growth which damages the organism of which it is a part. This is because it is “growth” which is unregulated by the usual negative feedbacks governing the reproduction of normal, healthy cells in a normal, healthy human being.

This is precisely what the logic of economics promotes, however,-that more is always better. More profit, more production, more population, more fossil fuels, more artificial fertilizers, etc. Unlimited economic growth, it would seem, follows the logic of cancer, rather than the logic of healthy cells. This is why Bateson concluded that, “we may find that money, too becomes toxic beyond a certain point. In any case, the philosophy of money, the set of presuppositions by which money is supposedly better and better the more you have of it, is totally antibiological” (1979:56).

In other words, the logic behind endless economic growth is a positive feedback system, which is inherently unsustainable and destructive. As a living system, then, contemporary economics is destined to destroy itself unless negative feedbacks are introduced in order to compensate for this imbalance, and bring our production and distribution systems back into balance with ecological realities.

References, suggested readings:

Gregory Bateson (1979) Mind & Nature: A Necessary Unity, Bantam.

Roger Lewin, (1992) Complexity: Life at the Edge of Chaos, Collier Books.