The importance of fine-tuning for intentional agency

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Why fine-tuning is required for agency


Charles Abramson. Picture courtesy of the Public Information Office, Oklahoma State University.

We have seen that many animals are capable of learning to perform certain actions for the sake of the consequences they learn to associate with them (e.g. the attainment of a reinforcement). Most psychologists refer to such behaviour as operant behaviour, but Abramson calls this kind of behaviour "instrumental conditioning", and reserves the term "operant behaviour" for a special sub-set. He observes that if we adopt the commonly-used definition of operant behaviour, then

...such behavior is present in all animal groups. However, if operant behavior is defined in terms of its functional influence on the environment and the ability to use an arbitrary response, then... [it] is limited to vertebrates and perhaps some species of mollusks, crustaceans, and insects. A rule of thumb I have found useful... is that in operant behavior, an animal must demonstrate the ability to operate some device - and know how to use it, that is, make an arbitrary response to obtain reinforcement. (1994, p. 151, italics mine).

Abramson provides an illustration of behaviour conforming to his more restrictive definition:

For example, we know that rats can be taught to press a lever in various directions and with various degrees of force. They can also be trained to run down an alley with speeds selected by the experimenter... I would be more convinced that an invertebrate has operant responses if they can adjust their, for example, swimming speed to fit the contingencies. (personal email, 2 February 2003, italics mine).

Abramson's description of operant behaviour could be expressed using the notion of fine-tuning. If an animal can adjust and fine-tune its responses to a variable stimulus, then we could say that it has control over its responses, and is able to engage in operant behaviour. The word "control", like "try", has mentalistic overtones and is amenable to an agent-centred intentional stance, although it is not yet clear that fine-tuning requires a mentalistic intentional stance.

If, on the other hand, the animal cannot fine-tune its responses to the stimulus, then it lacks control over them and is only capable of instrumental behaviour.

Mental states such as beliefs and desires are primarily identified through the performance of intentional acts, which presuppose the notions of trying and control. For organisms that are incapable of fine-tuning their bodily movements, it is impossible to ascertain whether they are acting intentionally, because their actions lack the flexibility that enables us to identify the underlying mental states. As we have seen, behaviours such as directed movement, navigation and action selection require only fixed action patterns:

A.13 An organism must be capable of fine-tuning its bodily movements before it can be identified as having cognitive mental states.

Which organisms are capable of fine-tuning?

Case study 1: The nervous system of cnidaria


The box jellyfish Chironex fleckeri. Courtesy of www.barrierreefaustralia.com.

The phylum cnidaria (commonly known as coelenterates), makes up the most "primitive" group of "true" animals (Eumetazoa). The group includes animals such as jellyfish, sea anemones, corals and freshwater hydra. Their relationships to other animals, nervous system and sensory capacities are described in an Appendix.

Cnidaria have a rudimentary nervous system, described by Abramson:

Neurons are located regularly over the surface of the animal, and, like a net, they are in contact with those nearest to it. The effect of such an arrangement is that a stimulus applied to any part of the animal will be directed to all parts, much like sticking your finger in a cup of jello will make the whole mass move... The propagation of a nerve impulse is not transmitted along a linear chain of neurons, but radiates from its point of origin. Such a system is not conducive to fine control of motor movements (1994, p. 176, italics mine).

Fine-tuning behaviour may suggest the capacity for control over one's actions, and hence agency. So far, we have found that all cellular organisms, including bacteria and plants, are capable of directed movement. However, directed movement is an insufficient criterion for agency. I shall discuss fine-tuning in more detail in my model of operant agency, below.

A.14 Only organisms with central nervous systems are capable of fine-tuning their bodily movements for the performance of intentional acts.
This allows us to define a flexibility criterion for intentional agency:

F.8 Internally generated flexible behaviour appears to be confined to organisms with central nervous systems. It is found in most but possibly not all phyla of animals with central nervous systems. (Flatworms may not be capable of it, but many other phyla of worms are.)

We can also formulate a biological criterion for intentional agency:

B.5 An organism must have a central nervous system in order to qualify as having cognitive mental states.

Case study 2: Operant conditioning in C. elegans worms?

The roundworm Caenorhabditis elegans (length approximately 1 mm). Courtesy of The Sanger Institute.

The relationships between the different groups (or phyla) of worms, and other animals, are discussed in further detail in an Appendix. Of special interest here are roundworms, or nematodes, the group to which the well-studied C. elegans belongs.

Two studies were recently conducted which suggest that C. elegans worms may indeed be capable of modifying their responses to obtain a reinforcement. These studies are outlined in an Appendix. Caution is advised, as the studies produced some conflicting results, for reasons that are not altogether clear. It would be premature to draw any conclusions from this research, but at least it suggests how one might proceed in attempting to verify operant behaviour - as defined by Abramson - in a species of animal.

First, it is important to construct a complete pictorial catalogue of the behavioural patterns (in particular, movement patterns) of that species - i.e. an ethogram.

Second, it is essential to learn what attracts them and what repels them.

Third, the animals have to be able to control (or fine-tune) one of their patterns of behaviour, in order to obtain a "reward" or avoid a "punishment".

There is still one question we have not answered. How do we identify "control" over patterns of behaviour, or fine-tuning? For example, is an increase in a worm's innate tendency to turn when it becomes too hot or cold an instance of controlled behaviour, or is it an aversive reaction to change? The answer is not always clear-cut. However, if the worm were able to adjust, say, the speed of its movement in an arbitrary fashion as the temperature rose or fell, in order to obtain a more "comfortable" temperature setting, this would be a bona fide instance of "controlled behaviour". I will discuss this issue further in the next section, in connection with Dretske's account of belief.

Summary

There is tentative evidence that some worms may be capable of undergoing operant conditioning, if we define this as fine-tuning one's bodily movements to attain a goal. It remains unclear whether such fine-tuning requires an agent-centred intentional stance.

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