An investigation of economic interactions between social reinforcement and heroin or cocaine in rats.

The primary goal of the present study was to determine the economic relationship between heroin and social reinforcement in rats: are they substitutes, independents, or complements? In Experiment 1, one group of rats was given a budget of responses that they could allocate between heroin and social reinforcement offered at various combinations of prices. A second group chose between two levers that each resulted in social reinforcement at varying prices when pressed. There was no relationship between the relative allocation of responses between heroin and social reinforcement and changes in their relative prices, indicating that these reinforcers are best viewed as independents.

Cocaine and heroin interact differently with nondrug reinforcers in a choice situation.

The present study used a rat choice model to test how cocaine or heroin economically interacted with two different nondrug reinforcers along the substitute-to-complement continuum. In Experiment 1, the nondrug alternative was the negative reinforcer timeout-from-avoidance (TOA)-that is, rats could press a lever to obtain a period of safety from footshock. One group of rats chose between cocaine and TOA and another group chose between heroin and TOA.

Purchase task sensitivity to drug and nondrug reinforcers in opioid-agonist treatment patients.

The behavioral economics of substance abuse has been increasingly recognized as a method of determining the value of abused substances for individuals who use those substances. It has been hypothesized that such analyses could serve as a clinical tool and that demand functions can be targeted predictors for the level of intervention necessary. This study evaluated the sensitivity of a demand task in 2 patient groups in a medication assisted treatment program (methadone maintenance), those who had used opioids in the last 2 months and those who had not used opioids in at least 18 months.

Rats (Rattus norvegicus) find occupancy of a restraint tube rewarding.

Two experiments evaluated whether rats' occupancy of a restraint tube is reinforcing. In Experiment 1, each rat in the 0-min group moved freely in a chamber where a wall blocked access to a restraint tube. After 10 min the wall was removed, permitting 15 min of chamber access and tube entry.

Heroin choice depends on income level and economy type.

Rationale: In a previous study, investigating choice between heroin and a non-drug alternative in animals and reductions in income (i.e., choices/day) caused the percentage of income spent on heroin to progressively decrease.

Opening the cocaine economy by providing within-session access to a cheaper source of cocaine makes demand for it more elastic.

Previous studies found that opening the cocaine economy by providing postsession access to cocaine had no effect on animals' demand for cocaine, whereas postsession access to saccharin or food made demand for these nondrug reinforcers more elastic. It is possible that there was no effect of economy type on cocaine taking in these earlier studies because of the delay to the postsession cocaine in the open economy. The present experiment tested whether forming an open economy by providing additional within-session cocaine, rather than postsession cocaine, would make rats' demand for cocaine more elastic.

The effect of economy type on heroin and saccharin essential value.

According to behavioral economics, reinforcer value should be lower in an open economy than in a closed economy. An animal model was used to determine how economy type affected the value of heroin and saccharin. In a first phase, separate groups of rats worked for heroin or saccharin.

Like chimpanzees (Pan troglodytes), pigeons (Columba livia domestica) match and Nash equilibrate where humans (Homo sapiens) do not.

Martin, Bhui, Bossaerts, Matsuzawa, and Camerer (2014) found that chimpanzee pairs competing in matching-pennies games achieved the Nash equilibrium whereas human pairs did not. They hypothesized this outcome may be due to (a) chimpanzee ecology producing evolutionary changes that give them a cognitive advantage over humans in these games, and (b) humans being disadvantaged because the cognition necessary for optimal game play was traded off in evolution to support language. We provide data relevant to their hypotheses by exposing pairs of pigeons to the same games.

The effect of economy type on demand and preference for cocaine and saccharin in rats.

Background: Economy type is an important determinant of reinforcer value. This study investigated the effect of open and closed economies on demand and preference for cocaine and saccharin in rats.

Methods: In the first phase, rats were trained to lever press for cocaine infusions or saccharin.

Does a rat free a trapped rat due to empathy or for sociality?

This report evaluates whether a rat releasing a trapped rat from a restraint tube is better explained as due to its empathic motivation or to the pursuit of social contact. In the first condition, each of six rats chose in an E maze between entering an empty goal box versus entering a goal box where its entrance caused a rat trapped in a restraint tube to be released. Rats preferred the goal box with the trapped rat over the empty goal box.

The effect of nicotine pre-exposure on demand for cocaine and sucrose in male rats.

The aim of the present study was to determine how nicotine pre-exposure affects the elasticity of demand for intravenous cocaine and for sucrose pellets in adult male rats. In Experiment 1, demand for cocaine was assessed in rats that had nicotine in their drinking water. Nicotine pre-exposure significantly decreased rats' willingness to defend cocaine consumption as the price (measured as the number of responses per cocaine infusion) increased compared with a control group with no nicotine pre-exposure.

Heroin and saccharin demand and preference in rats.

Background: Several recent studies have investigated the choice between heroin and a non-drug alternative reinforcer in rats. A common finding in these studies is that there are large individual differences in preference, with some rats preferring heroin and some preferring the non-drug alternative. The primary goal of the present study was to determine whether individual differences in how heroin or saccharin is valued, based on demand analysis, predicts choice.

Does a rat release a soaked conspecific due to empathy?

In Experiment 1, rats choosing in an E maze preferred to release a rat standing in a pool of water to dry ground over a rat already standing on dry ground. Five additional experiments showed that the choosing rat's preference for releasing the wet rat was maintained by two separable outcomes: (1) the social contact offered by the released rat and (2) the reinforcing value of proximity to a pool of water. These results call into question Sato et al.

Essential values of cocaine and non-drug alternatives predict the choice between them.

This study investigated the relationship between reinforcer value and choice between cocaine and two non-drug alternative reinforcers in rats. The essential value (EV, a behavioral economic measure based on elasticity of demand) of intravenous cocaine and food (Experiment 1) or saccharin (Experiment 2) was determined in the first phase of each experiment. Food had higher EV than cocaine, whereas the EVs of cocaine and saccharin did not differ.

Scaling reward value with demand curves versus preference tests.

In Experiment 1, six capuchins lifted a weight during a 10-min session to receive a food piece. Across conditions, the weight was increased across six different amounts for three different food types. The number of food pieces obtained as a function of the weight lifted was fitted by a demand equation that is hypothesized to quantify food value.

Dose and elasticity of demand for self-administered cocaine in rats.

The present experiment tested whether the elasticity of demand for self-administered cocaine in rats is dose-dependent. Subjects lever pressed for three different doses of intravenous cocaine - 0.11, 0.

Preference pulses and the win-stay, fix-and-sample model of choice.

Two groups of six rats each were trained to respond to two levers for a food reinforcer. One group was trained on concurrent variable-ratio 20 extinction schedules of reinforcement. The second group was trained on a concurrent variable-interval 27-s extinction schedule.

The copyist model and the shaping view of reinforcement.

The strengthening view of reinforcement attributes behavior change to changes in the response strength or the value of the reinforcer. In contrast, the shaping view explains behavior change as shaping different response units through differential reinforcement. In this paper, we evaluate how well these two views explain: (1) the response-rate difference between variable-ratio and variable-interval schedules that provide the same reinforcement rate; and (2) the phenomenon of matching in choice.

A randomized, double-blind, crossover study to evaluate the depth response relationship of intradermal capsaicin-induced pain and hyperalgesia in healthy adult volunteers.

Objective: The purpose of this study was to evaluate pain and hyperalgesia in response to different depths of intradermal (ID) capsaicin injections in healthy volunteers.

Design: Double-blind, cross-over study.

Setting: Clinical Research Laboratory.

Inter-response-time reinforcement and relative reinforcer frequency control choice.

In Conditions 1 and 3 of our Experiment 1, rats pressed levers for food in a two-component multiple schedule. The first component was concurrent variable-ratio (VR) 20 variable-interval (VI) 90 s, and the second was concurrent yoked VI (its reinforcement rate equaled that of the prior component's VR) VI 90 s. In Condition 2, the VR was changed to tandem VR 20, differential reinforcement of low rates (DRL) 0.

Preference pulses induced by reinforcement.

Eight rats responded on concurrent Variable-Ratio 20 Extinction schedules for food reinforcement. The assignment of variable-ratio reinforcement to a left or right lever varied randomly following each reinforcer, and was cued by illumination of a stimulus light above that lever. Postreinforcement preference levels decreased substantially and reliably over time when the lever that just delivered reinforcement was now in extinction; however, if that lever was once again associated with variable ratio, this decrease in same-lever preference tended to be small, and for some subjects, not in evidence.

Desire for social contact, not empathy, may explain "rescue" behavior in rats.

Ben-Ami Bartal et al. (Science 334:1427-1430, 2011) showed that a rat in an open space (free rat) would touch the front door of a restraining tube to open its rear door, thereby enabling a rat trapped within (trapped rat) to enter a larger space that was farther away from the free rat. Since opening the rear door distanced the trapped rat from the free rat, Ben-Ami Bartal et al.