The understanding of decision-making systems has come together in recent years to form a unified theory of decision-making in the mammalian brain as arising from multiple, interacting systems (a planning system, a habit system, and a situation-recognition system). This unified decision-making system has multiple potential access points through which it can be driven to make maladaptive choices, particularly choices that entail seeking of certain drugs or behaviors. We identify 10 key vulnerabilities in the system: (1) moving away from homeostasis, (2) (...) changing allostatic set points, (3) euphorigenic signals, (4) overvaluation in the planning system, (5) incorrect search of situation-action-outcome relationships, (6) misclassification of situations, (7) overvaluation in the habit system, (8) a mismatch in the balance of the two decision systems, (9) over-fast discounting processes, and (10) changed learning rates. These vulnerabilities provide a taxonomy of potential problems with decision-making systems. Although each vulnerability can drive an agent to return to the addictive choice, each vulnerability also implies a characteristic symptomology. Different drugs, different behaviors, and different individuals are likely to access different vulnerabilities. This has implications for an individual's susceptibility to addiction and the transition to addiction, for the potential for relapse, and for the potential for treatment. (shrink)

To study animal welfare empirically we need an objective basis for deciding when an animal is suffering. Suffering includes a wide range ofunpleasant emotional states such as fear, boredom, pain, and hunger. Suffering has evolved as a mechanism for avoiding sources ofdanger and threats to fitness. Captive animals often suffer in situations in which they are prevented from doing something that they are highly motivated to do. The an animal is prepared to pay to attain or to escape a situation (...) is an index ofhow the animal about that situation. Withholding conditions or commodities for which an animal shows (i.e., for which it continues to work despite increasing costs) is very likely to cause suffering. In designing environments for animals in zoos, farms, and laboratories, priority should be given to features for which animals show inelastic demand. The care ofanimals can thereby be based on an objective, animal-centered assessment of their needs. (shrink)

Current theories of addiction try to explain what addiction is, who experiences it, why it occurs, and how it develops and persists. In this article, I explain why none of these theories can be accepted as a comprehensive model. I argue that current models fail to account for differences in embodiment, interaction processes, and the experience of addiction. To redress these limiting factors, I design a proposal for an enactive account of addiction that follows the enactive model of autism proposed (...) by Hanne De Jaegher. (shrink)

Heyman's analysis of addiction suggests that drug taking is irrational. The irrationality of drug taking, however, may depend on the acceptance of mainstream society's view of what is valuable. Consideration of the addict's viewpoint and cultural aspects of drug taking may be useful in trying to fathom the “rationality” of drug taking.

Heyman's target article is an analytical tour de force, but it makes too hard a distinction between voluntary and driven behavior. It is more fruitful to think about brain and behavior as shifting, interacting “agents,” represented by multiple neural circuits. This has the virtue of better connecting behavioral analysis with wet neuroscience.

Addictive behavior has never seemed rational because it persists in spite of drastic aversive consequences. This is a particular problem for models of addiction such as operant psychology which hold that behavior is controlled by its consequences. Inspite of claims to the contrary, Heymans target article illustrates how operant psychology resolves this contradiction. By using the matching law, Heyman suggests a mechanism that explains why delayed aversive events may not control behavior, and a conceptual framework in which we can understand (...) successful therapies. (shrink)

Heyman's target article makes a strong case for a behavioral approach to addiction, yet some important assumptions require justification, and promising behavioral alternatives to the author's melioration approach should be considered. In particular, the behavioral economic approach to addiction appears well developed and comprehensive. How does the melioration approach complement or improve on a behavioral economic account?

Research findings on addiction are contradictory. According to biographical records and widely used diagnostic manuals, addicts use drugs compulsively, meaning that drug use is out of control and independent of its aversive consequences. This account is supported by studies that show significant heritabilities for alcoholism and other addictions and by laboratory experiments in which repeated administration of addictive drugs caused changes in neural substrates associated with reward. Epidemiological and experimental data, however, show that the consequences of drug consumption can significantly (...) modify drug intake in addicts. The disease model can account for the compulsive features of addiction, but not occasions in which price and punishment reduced drug consumption in addicts. Conversely, learning models of addiction can account for the influence of price and punishment, but not compulsive drug taking. The occasion for this target article is that recent developments in behavioral choice theory resolve the apparent contradictions in the addiction literature. The basic argument includes the following four statements: First, repeated consumption of an addictive drug decreases its future value and the future value of competing activities. Second, the frequency of an activity is a function of its relative (not absolute) value. This implies that an activity that reduces the values of competing behaviors can increase in frequency even if its own value also declines. Third, a recent experiment (Heyman & Tanz 1995) shows that the effective reinforcement contingencies are relative to a frame of reference, and this frame of reference can change so as to favor optimal or suboptimal choice. Fourth, if the frame of reference is local, reinforcement contingencies will favor excessive drug use, but if the frame of reference is global, the reinforcement contingencies will favor controlled drug use. The transition from a global to a local frame of reference explains relapse and other compulsive features of addiction. (shrink)

It is difficult to accommodate compulsive drug use that destroys regulation by consequences in a unitary framework of melioration or maximization, especially as both are strategies of behavioral regulation. The “contradiction” of addictive behavior despite aversive consequences is an illusory issue because consequences that do not decrease addictive behavior cannot be considered punishing.

Heyman explains useful ways to bring addictive drug use under environmental control. We doubt that relapse is explained by drug features such as immediate reinforcement, clouding of judgment, and so forth. Relapse may require explanation in terms of enduring sensitization of incentive neural substrates, but even if its causal assumptions are wrong, Heyman's model makes useful predictions for behavioral control.

Heyman's analysis of addiction in terms of matching to local relative value can be supplemented by stimulus-control processes. Stimulus equivalence can broaden the set of situations that occasion addictive behavior, and the situation-reinforcer correlation can enhance its persistence. The joint effects of stimulus-control and reinforcement processes may complicate treatment.

Heyman's view that addiction can be viewed as a natural outcome predictable by melioration and the matching law is provocative. Remaining to be explained more fully, however, are exactly how his view is an improvement on other reinforcement-based accounts. Included in these elaborations should be an account of how different “bookkeeping schemes” are developed and controlled and what new approaches to treatment and prevention of drug addiction are indicated.

The matching law accounts for both addictive behavior and the usefulness of a person's evaluating choices in overall categories. To explain why overall bookkeeping, once learned, does not easily win out over local bookkeeping, another implication of matching is needed: intertemporal bargaining. The role of melioration, though probably important for new addiction is separate.

The academic journey to a widely acknowledged Machine Consciousness is anticipated to be an emotional one. Both in terms of the active debate provoked by the subject and a hypothesized need to encapsulate an analogue of emotions in an artificial system in order to progress towards machine consciousness. This paper considers the inspiration that the concepts related to emotion may contribute to cognitive systems when approaching conscious-like behavior. Specifically, emotions can set goals including balancing explore versus exploit, facilitate action in (...) unknown domains and modify existing behaviors, which are explored in cognitive robotics experiments. (shrink)

Heyman's target article contributes to our understanding of addictions by offering solutions to several paradoxes and by recognizing the stable nature of addictive behavior. Previous classical and operant conditioning models have emphasized molecular processes, such as acquisition and extinction, and have failed to address the aggregate effects of long-term exposure to the contingencies of drug and alcohol use.

Melioration is not superior and may be inferior to other extensions of behavioral choice theory to addiction studies. Progress in the addiction field will be accelerated by the demise of the disease model rather than by attempting to resolve the contradictions it has created.

Over the years, many theories have been proposed to account for the aberrant behavior of drug dependent individuals. Heyman posits that the existing theories of drug dependence are inadequate to explain the complex processes inherent in human drug-taking. He proposes that incongruous behaviors that comprise addiction, such as continued drug use in spite of adverse consequences, can be explained by application of the matching law approach. While the matching law theory of addiction explains certain aspects of human behavior, its application (...) to the area of addiction must be subjected to experimental verification. (shrink)

Neuroscientists and psychologists have proposed a variety of well-supported theories to explain addiction. Many of these theories suggest that addiction results from a single process or dysfunction across all of its forms. The authors of the current review, in contrast, have used a well-defined theoretical account of decision-making to outline the variety of dysfunctions that could account for addictive behavior.

Heyman proposes that external stimuli can promote a switch from a local to a global frame of reference for evaluating the consequences of behavior and that such a change might be critical to breaking the grip of drag addiction. Could incentive stimuli promote a switch in the opposite direction and thus contribute to relapse in the recovered addict?

Extreme sensations – thirst, pain – can focus attention on local consequences at the expense of the overall, perhaps for good evolutionary reasons. Maybe the same phenomenon evolves from prolonged use of addictive substances. The matching law explains mistaken choice, not how a person who has confronted personal catastrophe manages to ignore it in making a locally induced choice.

Extraversion has two central characteristics: (1) interpersonalengagement, which consists of affiliation (enjoying and valuing close interpersonal bonds, being warm and affectionate) and agency (being socially dominant, enjoying leadership roles, being assertive, being exhibitionistic, and having a sense of potency in accomplishing goals) and (2) impulsivity, which emerges from the interaction of extraversion and a second, independent trait (constraint). Agency is a more general motivational disposition that includes dominance, ambition, mastery, efficacy, and achievement. Positive affect (a combination of positive feelings and (...) motivation) is closely associated with extraversion. Extraversion is accordingly based on positiveincentivemotivation. (shrink)

Two issues are raised. (1) What is the nature of the drug effect Heyman thinks confers value to drugs? (2) What is the evidence that drug use decreases the value of drugs and of conventional incentives over the long-term? There is considerable evidence for the opposite; a persistent increase in the sensitivity of neural systems that mediate drug value.