Effects of previous delay of reward,generalized effort,and deprivation on impulsiveness

Two experiments investigated the effects of learning and motivational variables upon rats' degree of impulsiveness (choice of a small, immediate reward versus a large, delayed reward). In Experiment 1, food was presented in one of four ways for 24 sessions: fixed-ratio lever pressing requirement, continuous-reinforcement lever-pressing requirement, long intervals between free food presentations, or short intervals between free food presentations. Exposure to the long intervals produced less subsequent impulsiveness in 48 choice trials than did the short intervals, there being no effect of the instrumental requirement. In Experiment 2, there were 48 choice trials in which two hunger levels were combined factorially with two delays of reward for the self-control alternative. Hunger level did not affect implusiveness when there was a short delay, but high hunger increased the impulsiveness when there was a long delay. These results indicate that impulsiveness is affected by prior learning and current motivation. Implications for Baum, Rachlin, and Green's matching formula and for frustration theory are discussed.     

Yes,they can! Efficient physical effort mobilization according to task difficulty in schizophrenia

The current literature has largely highlighted a deficit of effort-based decision-making for reward in schizophrenia. However, not all studies have dissociated effort from reward, while other studies emphasize that difficulty is the main determinant of effort rather than reward. In this study, 33 individuals with schizophrenia and 32 healthy controls were recruited to perform a decision-making isometric force task. According to motivational intensity theory, task difficulty (i.e., required force) but not reward was manipulated from easy to impossible. Accuracy between force exerted and force required, and choice to perform a task or not were our effort measures. Clinical variables including depression, defeatist beliefs, and apathy were assessed. Our results demonstrated that the schizophrenia group chose to perform easy, moderate, and difficult tasks and exerted the necessary effort to succeed similarly to the non-clinical group. No association between effort and clinical variables was found. Our findings provide new understandings related to effort mechanisms in schizophrenia.

     

On the distinction between open and closed economies.

Open and closed economies have been assumed to produce opposite relations between responding and the programmed density of reward (the amount of reward divided by its cost). Experimental procedures that are treated as open economies typically dissociate responding and total reward by providing supplemental income outside the experimental session; procedures construed as closed economies do not. In an open economy responding is assumed to be directly related to reward density, whereas in a closed economy responding is assumed to be inversely related to reward density. In contrast to this predicted correlation between response-reward relations and type of economy, behavior regulation theory predicts both direct and inverse relations in both open and closed economies. Specifically, responding should be a bitonic function of reward density regardless of the type of economy and is dependent only on the ratio of the schedule terms rather than on their absolute size. These predictions were tested by four experiments in which pigeons' key pecking produced food on fixed-ratio and variable-interval schedules over a range of reward magnitudes and under several open- and closed-economy procedures. The results better supported the behavior regulation view by showing a general bitonic function between key pecking and food density in all conditions. In most cases, the absolute size of the schedule requirement and the magnitude of reward had no effect; equal ratios of these terms produced approximately equal responding.     

The physical properties of bar-pressing behaviour and the problem of reactive inhibition

Many of the terms used in the literature on reactive inhibition are vague, subjective or incorrect. The weighted bar is not a suitable device in the study of this problem, since it records irrelevant aspects of behaviour. An experiment using apparatus which gives a continuous record of the force which a rat applies to a knob produces the following results. After much practice, pressing becomes sharp and brief and the amount of activity per reward is reduced. Under conditions of no (intentional) secondary reward the amount of activity during extinction is at first positively correlated with the average activity per reward during training, but the correlation diminishes as extinction proceeds. With auditory secondary reward there is no correlation.     

Effects of effort on response rate

Pigeons were trained to peck for food reinforcement, and the minimum effective force for a peck was varied. In a single-key situation, the response rate was unaffected up to a certain force value, beyond which increments caused a proportional decrement in response rate. Transient enhancement and suppression effects were observed following a change in the force requirement. A change from a high force requirement to a low force requirement resulted in a temporary enhancement of response rate above the stable performance level, whereas a change from a low to a high requirement produced a temporary suppression of the rate below the stable rate. In a two-key situation, the response rate on a key with a given force remained unaffected by the force requirement on the other key. When the rate of response was plotted against the required force, the resultant function was remarkably similar to that obtained from the single-key experiment. When the rates of reinforcement on the two keys differed, the decrement in response rate produced by an increase in the force requirement was proportionally greater on the key with the lower rate of reinforcement.     

Effect of drugs on response-duration differentiation VII: response-force requirements

Rats were trained to press a lever for at least 1 s but for less than 1.3 s. The force required to press the lever was then increased or decreased by 10, 15, or 20 g. Increases in the force requirements for lever pressing decreased timing accuracy, but decreases in the force requirement had the opposite effect. Accuracy decreases at increasing force requirements were characterized by an increase in the relative frequency of responses that were too short to meet the reinforcement criterion. In contrast, increases in accuracy when the force requirements were decreased were characterized by increases in response durations that met the reinforcement criterion and decreases in the relative frequency of responses that were too short to produce the reinforcer. Phencyclidine (PCP) and methamphetamine produced dose-dependent decreases in accuracy that were associated primarily with increases in the relative frequency of short response durations, although methamphetamine also produced increases in long response durations at some doses. When the effects of PCP were determined with the force requirement increased by 10 g or decreased by 15 g, the cumulative response-duration distribution shifted toward even shorter response durations. When the effects of methamphetamine were determined with the force requirement on the lever increased by 10 g, the cumulative frequency distribution was shifted toward shorter response durations to about the same extent as it had been before force requirements increased; however, when the force required to press the lever was decreased by 15 g, these shifts toward shorter response durations almost completely disappeared. These results show that increases and decreases in the force requirements for lever pressing have different effects on the accuracy of temporal response differentiation.     

I'm worth more than you! Effects of reward interdependence on performance,cohesion, emotion and effort during team competition

ObjectivesTo examine the effects of reward structures on the performance of a motor task. To evaluate the effects of reward interdependence on performance, cohesion, emotion, and effort during intergroup (team) competition.DesignAn experimental design was used to compare the effects of reward interdependence (no, low, high) on performance of a strength and endurance task.MethodParticipants (N = 111) performed a 3-min handgrip task as a member of a team of four under three reward interdependence conditions (no; low, with an even split of prize money; high, with an uneven split of prize money) in head-to-head competitions against another team. Task performance was assessed using the cumulative force production total. Task-related cohesion, enjoyment, anxiety and effort were measured using self-report scales.ResultsPerformance was better with rewards than no reward, and better with high than low reward interdependence. Team cohesion was highest with low reward interdependence. Effort was greater with rewards than no reward. Anxiety and enjoyment did not vary among the reward conditions. Mediation analyses indicated that increased cohesion mediated improvements in performance from no reward to low reward interdependence conditions, and increased effort mediated improvements in performance from no reward to both low and high reward interdependence conditions.ConclusionPerformance of a simple physical task in team competition was facilitated by rewards, with optimal performance associated with unequal rewards (i.e., performance-related pay). The benefits of performing with rewards compared to no rewards were explained by increased cohesion and effort. Social interdependence theory can help explain performance of simple motor tasks during team-based competitions. The findings have implications for the pay structures adopted by sports teams.     

Some punishing effects of response-force

The present experiment explored the punishing effect of different response-force requirements by means of a two-operant design analogous to a two-component chain schedule. The first component of the chain required a lever pull through 0.25 in. (0.64 cm) at 1 lb (4.45 N) of force. The second component required a lever pull through an additional 0.75 in. (1.90 cm) with the force varied between sessions from 1 lb to 50 lb (4.45 N to 223 N). Completion of the second component of the chain was reinforced after variable intervals averaging 1 min. The average rate of first-component response decreased as the force requirement for second-component responses was increased. This rate reduction did not appear to be due to increased response duration, “fatigue”, or differing rates of reinforcement. If the force requirement for the second-component response is viewed as a consequence for the first-component response, then the results of the experiment show that a high force requirement is a punisher.     

Effects of differing response-force requirements on food-maintained responding in CD-1 mice

The effect of force requirements on response effort was examined using outbred (CD-1) mice trained to press a disk with their snout. Lateral peak forces greater than 2 g were defined as threshold responses (i.e., all measured responses). Different force requirements were used to define criterion responses (a subclass of threshold responses) that exceeded the requirement. The reinforcer was sweetened, condensed milk, and it was delivered upon response termination. All mice were exposed to two ascending series of criterion force requirements (2, 4, 8, 16, and 32 g). Increasing the force requirement decreased criterion response rates, but increased threshold response rates. The time-integral of force (area under the force-time curve for individual responses, which is proportional to energy expenditure for each response) increased with the increase in the force requirement. These results conflict with the hypothesis that higher force requirements have aversive qualities and suggest that increased force requirements are more analogous to intermittent schedules of reinforcement. These data suggest that estimations of effort or energy expenditure should be measured independently of the force requirement. Individual differences in responding were found for the CD-1 outbred stock.     

Transfer of approach responding between punishment, frustrative nonreward, and the combination of punishment and nonreward

Rats trained to make an approach response with either partial reward, intermittent punishment, or a combination of partial reward and intermittent punishment, were tested for persistence to extinction, punishment with reward, or punishment during extinction. Partial reward, alone or with punishment, produced greates resistance to extinction, while intermittent punishment, alone or with partial reward, produced greatest persistence to punishment with reward. Transfer of persistence from partial reward to punishment with reward and intermittent punishment to extinction was also demonstrated. However, partial reward alone did not increase persistence to punishment during extinction, whereas intermittent punishment and partial reward combined with intermittent punishment did increase such persistence. These results were interpreted in Amsel's (1958, 1962) conditioning-model theory by extending the hypothesized similarity of frustrative nonreward and punishment.     

Confirmation of linear system theory prediction: Rate of change of Herrnstein's kappa as a function of response-force requirement

Four human subjects worked on all combinations of five variable-interval schedules and five reinforcer magnitudes (¢/reinforcer) in each of two phases of the experiment. In one phase the force requirement on the operandum was low (1 or 11 N) and in the other it was high (25 or 146 N). Estimates of Herrnstein's κ were obtained at each reinforcer magnitude. The results were: (1) response rate was more sensitive to changes in reinforcement rate at the high than at the low force requirement, (2) κ increased from the beginning to the end of the magnitude range for all subjects at both force requirements, (3) the reciprocal of κ was a linear function of the reciprocal of reinforcer magnitude for seven of the eight data sets, and (4) the rate of change of κ was greater at the high than at the low force requirement by an order of magnitude or more. The second and third findings confirm predictions made by linear system theory, and replicate the results of an earlier experiment (McDowell & Wood, 1984). The fourth finding confirms a further prediction of the theory and supports the theory's interpretation of conflicting data on the constancy of Herrnstein's κ.     

Reward enhances backward inhibition in task switching

Recently, effects of reward incentives on interference-induced cognitive adjustments have drawn much attention. It has been demonstrated that reward can reduce or eliminate switch costs which occurred when alternating between different tasks. However, it still remains a question how reward affects inhibitory processes underlying task switching. The present study examined this issue by combining a task-switching paradigm with performance-contingent reward. Results showed that the inhibitory processes were modulated by reward, with n-2 repetition costs incremented after reward delivery. Data suggest that reward-triggered reduction or elimination of switch costs may reflect enhancing inhibitory processes which are motivated by reward signals and targeted at the irrelevant task set. These findings shed new light on the role of reward in cognitive control.     

Role of Reward Sensitivity and Processing in Major Depressive and Bipolar Spectrum Disorders

Since Costello’s (1972) seminal Behavior Therapy article on loss of reinforcers or reinforcer effectiveness in depression, the role of reward sensitivity and processing in both depression and bipolar disorder has become a central area of investigation. In this article, we review the evidence for a model of reward sensitivity in mood disorders, with unipolar depression characterized by reward hyposensitivity and bipolar disorders by reward hypersensitivity. We address whether aberrant reward sensitivity and processing are correlates of, mood-independent traits of, vulnerabilities for, and/or predictors of the course of depression and bipolar spectrum disorders, covering evidence from self-report, behavioral, neurophysiological, and neural levels of analysis. We conclude that substantial evidence documents that blunted reward sensitivity and processing are involved in unipolar depression and heightened reward sensitivity and processing are characteristic of hypomania/mania. We further conclude that aberrant reward sensitivity has a trait component, but more research is needed to clearly demonstrate that reward hyposensitivity and hypersensitivity are vulnerabilities for depression and bipolar disorder, respectively. Moreover, additional research is needed to determine whether bipolar depression is similar to unipolar depression and characterized by reward hyposensitivity, or whether like bipolar hypomania/mania, it involves reward hypersensitivity.     

The order of continuous,partial and nonreward trials and resistance to extinction

In the first experiment rats were given either 16 or 48 nonrewarded or continuously rewarded trials prior to 24 continuously or partially rewarded trials, followed by extinction. Increased resistance to extinction was found for increasing numbers of nonrewarded trials when they were followed by partial reward, but not when followed by continuous reward. Similarly, more continuously rewarded trials followed by partial reward tended to increase resistance to extinction. Because of the theoretical importance of the effect of continuous reward followed by partial, a second experiment was performed where the range of the number of continuously rewarded trials was extended to 0, 48, and 96. Contrary to many theoretical predictions, resistance to extinction increased as a function of increasing amounts of continuous reward.     

Effects of self-control training for elementary students with emotional and behavioral disorders

Progressive delay training (PDT) has been used to promote self-controlled choices (i.e., selecting a larger, later reward over a smaller, immediate reward) for people with a variety of developmental characteristics. However, the efficacy of PDT has not been evaluated in children with emotional and behavioral disorders (EBD), who often have co-occurring symptoms of impulsivity. The purpose of this study was to evaluate the effects of PDT with a rule-following requirement on the impulsive choices of 6 elementary students with EBD using a modified changing criterion design. Results indicated that PDT alone did not improve self-control, but a modified version of PDT with a rationale and rule for selecting the delayed reward promoted self-control for 3 participants. The remaining 3 participants continued to make impulsive choices despite further modifications to the PDT protocol. We discuss implications of our results and directions for future research on treating impulsivity in children with EBD.     

Transfer of effort across behaviors

A series of experiments investigated the effects of required force and number of responses per reinforcer upon the subsequent performance of a second behavior. In the first experiment, a group of rats required to complete five round trips in an alley per food pellet subsequently bar-pressed for food at a greater rate than a group rewarded for each round trip or a control group that did not receive the alley experience. In the second experiment, a group required to apply a 70-g bar-press force subsequently shuttled for food at a greater rate than a group required merely to touch the lever or a control group that did not undergo the lever-press manipulation. The third experiment found that the force effect persisted across all five test sessions and was attributable to differences both in response speed and interresponse time. The fourth experiment found that both the necessary bar-press force and number of bar presses per reward affected subsequent shuttling in extinction. Two alternative interpretations of these results were compared: (a) the degree of accustomed effort per reinforcer becomes a generalized component of instrumental behavior or (b) high effort increases the habituation frustration-produced disruptive responses.     

Conscious and unconscious reward cues can affect a critical component of executive control

The present study investigates whether updating an important function of executive control can be driven by unconscious reward cues. Participants had to memorize several numbers and update those numbers independently according to a sequence of arithmetic operations. At the beginning of each trial, a reward (1 euro or 5 cents) was presented, either subliminally or supraliminally. Participants could earn the reward if they found the correct response on the updating task. Results showed better performance when a high (conscious or unconscious) reward was at stake compared to a low reward. This suggests that subliminal information can influence a component process of executive control traditionally thought to require consciousness.     

Strength of a Secondary Reinforcement as a Function of the Quality of Food Reward

Thirty-two children were presented 18 stories containing either a good, neutral, or negative act which was followed by either a reward or punishment. It was predicted that Ss' responses would be influenced by the sanctions. It was also predicted that the type of story (good, neutral, or bad) would influence the extent to which a child judged the act independent of the effects of the sanction (reward or punishment).

These predictions were supported. Ss made more positive responses to acts followed by reward than to those followed by punishment. However, an examination of a Content × Sanction interaction found the sanction of reward relatively ineffective for the stones with negative content.     

Variation of Isometric Response Force in the Rat

Hungry, unrestrained rats (N = 7) were rewarded for pressing a response beam in excess of 11 different force requirements. Changes in peak force production as a function of peak force requirement were examined by analyses of the first four moments of distributions of peak response forces: constant error, the within-subject standard deviation, skewness, and kurtosis. Results were similar to those previously obtained with human subjects: Constant error was positive at low and negative at high force requirements, the within-subject standard deviation increased as a negatively accelerating function of force requirement, and skewness and kurtosis were positive at low force requirements and decreased to negative values at the highest increments. Additional analyses of response kinetics indicated that rats, like humans, meet increasing force requirements by altering the rate of rise of force. The performance similarities suggest that common processes are engaged by the human and rat motor control systems to solve the problem of generating forces that are appropriate to the prevailing environmental constraints.     

Imagery and strength of craving for eating,drinking, and playing sport

The elaborated intrusion (EI) theory of desire (Kavanagh, Andrade, & May, 2005) attributes the motivational force of cravings to cognitive elaboration, including imagery, of apparently spontaneous thoughts that intrude into awareness. We report a questionnaire study in which respondents rated a craving for food or drink. Questionnaire items derived from EI theory formed a single factor alongside factors for anticipated reward/relief, resistance, and opportunity. In a multiple regression predicting strength of craving, the first three factors accounted for 36% of the variance. Opportunity did not enter the model. In a second study, the difference between individuals’ strong and weak cravings to take part in a sporting activity was shown to be related to visual, auditory, and general imagery, and to anticipated reward or relief from engaging in the activity. Implications for treatment of craving-related disorders are discussed in the light of these results and of other research indicating that interference with imagery can reduce the strength of craving.