Petrusz, S. C., and Turvey, M. T. (2010). On the distinctive features of ecological laws. Ecological Psychology (22), 44-68.

 

 

 

 

Excerpts from "On the Distinctive Features of Ecological Laws"

 

Stephanie C. Petrusz and M. T. Turvey

Center for the Ecological Study of Perception and Action

University of Connecticut

 

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As has been the stance among ecological theorists for some time (e.g., Kugler & Turvey, 1987; Michaels & Carello, 1981; Turvey, Shaw, Reed & Mace, 1981; Warren, 2006), we here defend the view that the laws of perception and action are full-blooded laws of nature in the sense of the laws of physics. What we wish to explore further are the character of laws of nature in general and ways to stave off attempts to separate the laws of the sciences of the animate from those of the sciences of the inanimate. We consider several lines of argument but ultimately conclude that the functions of perceiving-acting systems and the relations in the world that underwrite them have little in common with notions of lawfulness, causation, and the mathematical language of science that have been prevalent historically. We therefore propose newer ways of construing such notions.

 

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Gibson’s work spanning four decades, and summarized through selective samples in Reed and Jones (1982), led him to inquire about the laws of perception and behavior and to question whether standard physics was up to the challenge of determining such laws. A particularly telling quotation is the following (Gibson, 1979/1986, p. 100):

 

“Ecological events are various and difficult to formalize. But when we attempt to reduce them to elementary physical events, they become impossibly complex, and physical complexity then blinds us to ecological simplicity. For there are regularities to be found at the higher level, regularities that cannot now be encompassed by the simple equations of mechanics and physics. The movements of animals, for example, are lawful in ways that cannot yet be derived from the laws of orthodox mechanics, and perhaps never can be.”

 

Behind the quotation is Gibson’s personal belief that theorizing about perception and behavior had to be founded upon precise causal relations (see Gibson’s autobiography, 1967/1982) and his studied opinion that the causal relations in question were not those of Newton’s mechanics.

For Gibson, the laws of perception and behavior must be ecological, that is, they must be defined at the scale of organisms and their environments and they must, in some deep sense yet to be articulated, be defined in terms of organisms and their environments (Gibson, 1979/1986).

 

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In important respects, Gibson’s concerns have overlapped with the concerns of Rosen (1991, 2000): What kind of physics is required to explain the abilities of living things? What form must laws of nature take to express the causality of biological phenomena? In Rosen’s (2000, p. 33-34) words:

 

“[o]rganisms, far from being a special case, an embodiment of more general principles or laws we believe we already know, are indications that these laws themselves are profoundly incomplete…far from being a special case of these laws, and reducible to them, biology provides the most spectacular examples of their inadequacy. The alternative is not vitalism, but rather a more generic view of the scientific world itself, in which it is the mechanical laws that are the special cases.”

 

The issues enshrined in the foregoing questions and quotation were recognized by Kant in The Critique of Judgment (1790/2000, Sections 64-66) via the contrast of organism as other-organized (a machine) with organism as self-organized (a thing that makes itself up as it goes along). The contrast drawn by Kant is paraphrased in the following two paragraphs (see Chemero & Turvey, 2007a).

For any given thing that we recognize as a machine, for example, a clock or an airplane, the following characteristics seem to hold. The parts of the thing exist for, but not by means of, each other. The parts act together to meet the thing’s purpose; their actions, however, have nothing to do with the thing’s construction. The thing and its parts rely upon efficient causes arising from outside themselves for their origin and function.

For any given thing that we recognize as an organism, for example, a fly or a tree, the following characteristics seem to hold. The parts of the thing are both causes and effects of the thing; they are not only the means but also the ends. The parts construct and maintain themselves as a unity, each existing by virtue of, and for the sake of, the others and the whole. The thing and its parts are themselves the source of the efficient causes for their origin and function.

The notion of an ecological property and the notion of a system that self-organizes have this is common: the parts are not definable outside of the whole that they comprise—they are not fractionable. ...The wing of a bird, the product of a long-term self-organizing process, is a combination of engine and airfoil that cannot be fractionated (Rosen, 2000, Essay 19). Propulsion and lift are spatially inseparable functions and neither can be defined outside of the wing that they comprise.

 

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It has been argued that biological and psychological phenomena in particular are only explainable by means of a reduction to basic entities like genes and neurons, and ultimately the power of even those building blocks will be shown to derive from still more basic units. The reductivist position that there is a fundamental level of analysis, a basic science with a claim on fundamental entities and explanations, has a kind of elegance about it, but like others who are concerned with those disciplines that reductivism would explain away we believe that the approach is incorrect.

 

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Because living things are so relatively few and localized, and the universe so large, it may seem that living things are oddities, lumps in the pudding. It is our belief that this view has contributed to the notion that the living are special cases of the physical, and therefore to the notion that theories of the living must be reducible to theories of the non-living physical. The more this enterprise of such reduction fails, the more those for whom explanation just is reduction come to see living things as intractable to any lawful understanding of the universe. We prefer to take a different tack.

 

Animate systems are more general

Following Rosen (1991, 2000), we wish to consider living systems as the more general.

 

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George Gaylord Simpson, the 20^th century’s most influential paleontologist, said it best (Simpson, 1964, pp. 106-107), particularly if one adds psychology to “biology”:

 

[l]iving things have been affected for…billions of years by historical processes…The results of those processes are systems different in kind from any nonliving systems and almost incomparably more complicated. They are not for that reason necessarily any less material or less physical in nature. The point is that all known material processes and explanatory principles apply to organisms, while only a limited number of them apply to nonliving systems…Biology, then, is the science that stands at the center of all science…where all the principles of all the sciences are embodied…

 

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Aristotle and Newton

The first systematic categorization of causes is due to Aristotle. His analysis was perhaps closer to intuitions than to modern philosophical practices. His four causal categories are, in a way, each answers to a question of how something in the world comes to be as it is. What something is made out of is the material cause. The form that something takes, its shape, is the aptly named formal cause. The process to create such a thing, the forces applied to the raw materials to get it to achieve the shape it possesses, is the efficient cause. And the final piece of the puzzle, the reason why or purpose for which a thing is made, is the final cause. Figure 1a depicts the four causal categories. The material cause is the marble. The formal cause is the shape of the statue, while the efficient cause is the action of the sculptor on the block. And the final cause is the purpose to which the statue is put: adornment, or commemoration, perhaps.

The Aristotelian account, developed before the advent of experimental science, is built around a causal analysis of how things at the human-observable scale, or what we have already called the ecological scale, come to be as they are. Newtonian science, however, developed from the study of heavenly bodies. It thus inherited the abstraction away from the ecological scale to unobservable scales—the very large and then the very small. Newtonian predicates, restricted by available means of observation, became the descriptors of classical physics, such as mass, velocity, position, and momentum.

Newton’s three laws make no reference either to cause or to process. It was Newton’s concern to produce mathematical expressions of the functioning of the world, not to guess at its underpinnings (Koyré, 1957). Because it was not the job of Newtonian science to explain, the causal richness of the Aristotelian picture was set aside in favor of a more austere ontology of bodies, states, and forces.

Rosen’s (1988, 1991) perspective on Newton’s program is expressed in Figure 1, panels b and c. Environment is encoded as force F and system is encoded into a formalism in which the only entailment is a recursion rule such that, given the phase () at ,

()(+ ).                                                                                (1)

Newtonian force preserved the character of the Aristotelian efficient cause, but became purely impinging, with no flavor of agency. As for why bodies behave as they do, there is only the history of the forces contacting them and the resulting changes in the state variables. Searching for purpose would be meaningless. Therefore the Aristotelian final cause is completely ejected from the Newtonian picture.

After Newton, then, we are left with an impoverished account of causes, though a much-expanded mathematical vocabulary. It might seem difficult to describe very many situations with such a minimal causal language, but Newton added a further insight. Affairs did not come about as a result of the interplay of different types of causes, but rather by the repeated action of forces—as expressed in Equation 1 and depicted in Figure 1c. This idea of recursion, of the state change at successive time points brought about by iteratively applying the same forces, more or less completed the Newtonian ontology.

But despite Newton’s avoidance of making causal claims, a notion of cause restricted in the abovementioned ways was already packed into this notion of recursion. Causes were now exogenous, forward-running, linearly chained processes (Hanson, 1969), a state of affairs that did rather well for planets, particles and, with suitable expansions, for many macroscopic bodies in a variety of conditions. Attempts to expand the Newtonian system’s explanatory power into the realm of living systems, however, have often been less than fruitful. Newtonian physics seems up to the task of explaining that an organism will fall when certain conditions hold but not that an organism will jump when certain conditions hold. As Rosen (1991, 2000) implied and we have emphasized, it seems odd in the extreme to assert that organisms, which are made up of physical stuff, lie somehow outside the laws of physics. So if the laws of physics are insufficient to explain the behavior of living systems, it seems more likely that the laws of physics are incomplete, rather than that the functioning of organisms is simply intractable to physics. It is this conviction that serves as the departure point for the most crucial question we wish to ask: what is missing from physics? What must the missing pieces look like in order to account for the behaviors of animate systems? The answer will include an acknowledgement that the idea of cause implicit in Newtonian physics is insufficient, and that the notion of cause must be either altered or rejected entirely.

 

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If we treat an animal jumping up on a surface as a kind of textbook exercise, then we consider such quantities as initial velocity, upward force, force due to gravity, height of target, and mass of animal. If we do that, we are describing at best a trajectory, not an action. Nothing has been said about how the animal perceives that it can, and perceives when it should, jump up on some parts of the environment and not others. We may say that an animal of a size capable of producing so much force may jump onto a surface in some range of heights. But does this mean that it is these properties that feature in our descriptions in virtue of which the animal makes the jump? Does the organism perceive its situation in terms of kilograms, meters, and Newtons? Even for fairly sophisticated animals such properties are not meaningful in terms of actions. They are at best meaningful only in terms of descriptions, and then only for such creatures as are capable of abstract symbolizing. Whereas very few species (and perhaps only one) are capable of the latter, very many species leap from one place to another in the course of negotiating their surroundings. Our discussion above of property-based accounts of law highlighted the advantage of treating laws as relations that exist between intensions rather than extensions. Now we will take another step and say that the relations in virtue of which organisms successfully perceive and act are secured by not just any properties, but by those properties specifically that are meaningful to organisms, and that these properties come with the physics, the laws, that perception and action abide.

 

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Though we have spent some time arguing against some of the hallmarks of Newtonian science, we do not question that these meaningful properties are physical ones. Rather, the realization that the physical properties that feature in physical accounts of the world are unlikely to be the same ones that feature in the content of perceptions and actions demands that a psychological theory – a theory of perception and action at the scale of organisms and their environments – make use of terms that, although physical, are not the same terms as those in the theories of the other sciences. In short, we are looking for a physical account of meaningful properties: a semantic physics. The entities that would feature in such an account would be those that are meaningful and relevant to the lives of organisms. As Mace (2005) discusses, objects like sheets of brass are no less real or physical than the atoms of zinc and copper that make them up, but a reductivist approach to physics is concerned with explaining the properties of brass by reference to the properties of its constituent atoms. A property like reflectance can be explained by the atomic properties, but the use in antiquity of brass for mirrors is explained not just by the reflectance of the metal but also by its appeal and usefulness to the people who made the mirrors. A semantic physics requires explanations for those properties that are meaningful to organisms, and what is meaningful to an organism depends on the organism, as we shall see.

 

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It was Russell’s (1927) conviction that differential equations were the proper mathematical language for the laws of nature. Bunge (1979) disagreed, arguing that there was no reason to yoke lawfulness to any particular mathematics. Differential equations are not in general sufficient to describe all systems for which we would like laws. In particular, nonlinear systems are not always tractable to such an approach. Instead, nonlinear dynamics and complex systems theory often examine systems for which analytical solutions to differential equations are extraordinarily difficult to come by, or just unavailable, and for which such equations are in any case inadequate to capture the behavior of the system (West & Deering, 1995).

 

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...behavior is guided by the capacities of the organism-environment system as a whole, by intentions and the opportunities for realizing them. These capacities are in some sense dependent on lower-level physical features, as laid out in many reductivist accounts, but such accounts fail to consider that because of the nonfractionable nature of the higher level features, lower-level features are not fully determining of higher-level ones.

 

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Physical systems that do not exhibit hallmarks of the animate are simple cases of those that do. So laws of living systems should be in agreement with the more strictly “physical” sciences, but a deficit in connecting the two should not be regarded as evidence that the only laws that govern animate systems are those that govern their physical components. The causal entailment of animate systems exceeds that of physical (inanimate) systems. Animate systems are more general.

 

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selections from the list of references:

 

Gibson, J.J. (1966). The senses considered as perceptual systems. Boston: Houghton Mifflin.

Gibson, J.J. (1979/1986). The Ecological Approach to Visual Perception. Hillsdale, New Jersey: Lawrence Erlbaum Associates.

Kant, I. (1790/2000). The Critique of Judgment. (Translated J. H. Bernard). Amherst, MA: Prometheus Books.

Koyré, A. (1957). From the Closed World to the Infinite Universe. Baltimore: The Johns Hopkins Press.

Michaels, C.F. & Carello, C. (1981). Direct perception. Englewood Cliff, NJ: Prentice-Hall.

Rosen, R. (1991). Life itself. New York: Columbia University Press.

Rosen, R. (2000). Essays on life itself. New York: Columbia University Press.

Ruby, J.E. (1986). The origins of scientific ‘law’. Journal of the History of Ideas, 47, 341-359.

Russell, B. (1927). An outline of philosophy. London: Allen & Unwin.

Searle, J. (1983). Intentionality: An essay on the philosophy of mind. Cambridge: Cambridge University Press.

Shaw, R. E., Turvey, M. T., & Mace, W. M. (1982). Ecological psychology: The consequence of a commitment to realism. In W. Weimer & D. Palermo (Eds.), Cognition and the symbolic processes II (pp. 159-226). Hillsdale, NJ: Erlbaum.

Swenson, R. E., & Turvey, M. T. (1991). Thermodynamic reasons for perception-action cycles. Ecological Psychology, 3, 317-348.

Turvey, M. T., Shaw, R. E., Reed, E. S., & Mace, W. M. (1981). Ecological laws of perceiving and acting: In reply to Fodor and Pylyshyn (1981). Cognition, 9, 237-304.

Turvey, M. T., & Shaw, R. E. (1995). Toward an ecological physics and a physical psychology. In R. Solso & D. Massaro (Eds.), The science of the mind: 2001 and beyond (pp. 144-169). Oxford: Oxford University Press.

Zilsel, E. (1942). The genesis of the concept of physical law. The Philosophical Review, 51, 245-279.

Figure 1. (a) Aristotle’s four causal categories; (b) Newton’s revision; (c) Newton’s recursion: state variables and the repeated application of force.

 

 

Figure 1