Showing papers on "Reinforcement published in 1988"

Associations between the discriminative stimulus and the reinforcer in instrumental learning.

Abstract: Trois experiences effectuees avec des rats mettent a l'epreuve le declenchement d'associations entre le stimulus discriminatif et le renforcateur par le fait de renforcer une reponse en presence du stimulus discriminatif

Matching theory in natural human environments.

Abstract: Matching theory is a mathematical account of behavior, many aspects of which have been confirmed in laboratory experiments with nonhuman and human subjects. The theory asserts that behavior is distributed across concurrently available response alternatives in the same proportion that reinforcement is distributed across those alternatives. The theory also asserts that behavior on a single response alternative is a function not only of reinforcement contingent on that behavior, but also of reinforcement contingent on other behaviors and of reinforcement delivered independently of behavior. These assertions constitute important advances in our understanding of the effects of reinforcement on behavior. Evidence from the applied literature suggests that matching theory holds not only in laboratory environments, but also in natural human environments. In addition, the theory has important therapeutic implications. For example, it suggests four new intervention strategies, and it can be used to improve treatment planning and management. Research on matching theory illustrates the progression from laboratory experimentation with nonhuman subjects to therapeutic applications in natural human environments.

Geogrid reinforcement of granular bases in flexible pavements

Abstract: A comprehensive laboratory research program to investigate geogrid reinforcement of granular base layers of flexible pavements was carried out at the University of Waterloo and involved repeated load tests on varying thicknesses of reinforced and unreinforced granular bases. Other controlled variables included reinforcement location and subgrade strength. The purpose of this paper is to explain geogrid reinforcement mechanisms in granular base applications through analysis of stress, strain, and deflection measurements. The results of that research are first compared with fabric reinforcement and failure criteria. For high-deformation systems both fabric and grid can be effective in tension membrane action, but for low-deformation systems the interlock and confining action of a grid is required to provide effective reinforcement. The Waterloo work showed that permanent deformation of both types of systems can be significantly reduced by using geogrid reinforcement in the granular base. The reinforcement mechanisms involved with geogrid reinforcement of granular bases, and how the stress-strain-deflection response of the structure varies, are discussed. It is concluded that, for optimum effect, geogrid reinforcement should be placed at the base-subgrade interface of thin base sections and near the midpoint of thicker bases. Moreover, the zone of such placement should not involve elastic tensile strains in the grid that are greater than 0.2 percent. Under these conditions, geogrid reinforcement can be highly effective in reinforcing the granular base material and thereby extend the life of a structure.

RC Bridge Decks Under Pulsating and Moving Load

Abstract: Tests were conducted on 1/6.6‐scale reinforced‐concrete bridge deck slabs under static load, pulsating load applied at a fixed point, and moving constant wheel‐load. Both isotropic and orthotropic reinforcing arrangements were considered. The current AASHTO design approach (orthotropic reinforcement) appears to be overconservative. The moving wheel‐load results in far more damage than the fixed pulsating load, and the cracking pattern due to the former loading is segmental (gridlike) and more extensive. The failure mode for all reinforced model decks is that of punching shear and not flexure. It is concluded that the reinforcement content in a bridge deck can be reduced significantly and satisfy both serviceability and strength requirements.

From contrast to reinforcement: role of response contingency in anticipatory contrast.

Abstract: Intake of a 0.15% saccharin solution is suppressed if access to the saccharin is followed by access to 32% sucrose in brief daily pairings. The present series of four experiments was concerned with factors that lead to this anticipatory contrast effect (suppressed saccharin intake) rather than a reinforcement effect. In Experiment 1, anticipatory contrast was obtained with an autoshaping procedure (no lick requirement on the initial tube), and degree of contrast did not vary as a function of intersolution interval in the range of 0-15 s. Experiments 2 and 3 showed that requirements of 10, 100, 200, or 400 licks on the first tube available led to a reinforcement effect in latency, but a requirement of 0 licks (autoshaping procedure) led to a contrast effect in licks and latency. In Experiment 4, a group with a 200-contingent-lick requirement showed a reinforcement effect in latency, but a group yoked to this contingent group showed a contrast effect in both latency and licks. Overall, the results suggest that anticipatory contrast occurs under conditions of a "relaxed" instrumental contingency. The data are discussed in terms of control of behavior by stimulus-stimulus, response-stimulus, and stimulus-response associations, and the results are related to behavioral contrast, to flavor-outcome associations, and to "misbehavior" produced by Pavlovian-instrumental interactions.

A preliminary investigation of the consequences that define the mand and the tact.

Abstract: Skinner (1957) proposed that the mand and the tact differed with respect to their unique antecedents and consequences. The present study examined the specific reinforcement characteristic of the mand, and the nonspecific reinforcement characteristic of the tact. A severely mentally impaired individual who used sign language served as subject. A concurrent-chain with latency measures and choice was used. The results showed that specific reinforcement produced stronger verbal behavior than nonspecific reinforcement, but only when response strength was measured in terms of latency and choice. These data lend support to Skinner's assertion that the mand and the tact are different operants. These results also have practical significance in that they may lead to more effective work with individuals who have speech and language impairments.

Effects of prior response-contingent reinforcement on superstitious behavior

Abstract: Three pigeons were exposed to fixed-time (FT) 15 sec, fixed-interval (FI) 15 sec for performing an arbitrary response, a reversal back to FT 15 sec, and then extinction (no reinforcement). During each phase, a computer-controlled tracking system continuously recorded the position of the bird’s head as it moved freely in the experimental chamber. During the first exposure to FT 15 sec, all 3 birds developed a pattern of feeder-wall-directed behavior with occasional circular excursions from the feeder immediately following reinforcement. During FI 15 sec, all birds performed the arbitrary operant, which consisted of contacting a virtual target sphere near the rear of the chamber, and did not engage in feeder-wall-directed behavior. During the reversal back to FT 15 sec, the birds developed a behavior sequence consisting of moving in the direction of the target sphere after reinforcement, followed by feeder-wall-directed behavior prior to the next reinforcement. During extinction, either moves toward the target sphere or wall-directed behavior occurred separately, interspersed with reappearance of the two as a sequence, followed by cessation of both members of the behavior sequence. These findings indicate that prior reinforcement of an arbitrary response can affect the location and form of superstitious behavior that develops near the beginning of the interreinforcement interval, but that other factors (e.g., immediacy of reinforcement) affect the location and form of the behavior near the end of the interval. The findings can be interpreted in the context of superstitious chaining.

DSP4 and Herrnstein's equation: further evidence for a role of noradrenaline in the maintenance of operant behaviour by positive reinforcement.

Abstract: The effect of the selective noradrenaline neurotoxin DSP4 on steady-state operant behaviour was examined using a quantitative behavioural paradigm based on Herrnstein's (1970) equation, which defines a hyperbolic relationship between steady-state response rate and reinforcement frequency in variable-interval schedules. Eleven rats received injections of DSP4 (two doses of 50 mg/kg, intraperitoneally), and 12 rats received injections of the vehicle alone. The rats were trained to steady state in a series of six variable-interval schedules of sucrose reinforcement, affording scheduled reinforcement frequencies of 4–360 reinforcers per hour. Herrnstein's equation was fitted to the data obtained from each rat and to the averaged data obtained from the two groups. The value ofKH (the parameter expressing the reinforcement frequency needed to maintain the half-maximal response rate) was higher in the DSP4-treated rats than in the control rats; the value ofRmax (the parameter expressing the maximum response rate) did not differ significantly between the two groups. At the end of the behavioural experiment the rats were sacrificed for determination of the concentrations of catecholamines in the brain by high-performance liquid chromatography. The levels of noradrenaline in the parietal cortex, hippocampus and cerebellum of the DSP4-treated rats were less than 20% of those of the control rats. The results provide further evidence that central noradrenergic neurones are involved in the maintenance of operant behaviour by positive reinforcement.

Effects of reinforcement context on choice.

Abstract: Two experiments investigated the effects of successive reinforcement contexts on choice. In the first, concurrent variable-interval schedules of primary reinforcement operated during the initial links of concurrent chains. The rate of this reinforcement arranged by the concurrent schedules was decreased across conditions: When it was higher than the terminal-link rate, preference for the higher frequency initial-link schedule increased relative to baseline. (During baseline, a standard concurrent-schedule procedure was in effect). When the initial-link reinforcement rate was lower than the terminal-link rate, preference converged toward indifference. In the second experiment, a chain schedule was available on a third key while a concurrent schedule was in effect on the side keys. When the terminal link of the chain schedule was produced, the side keys became inoperative. Availability of the chain schedule did not affect choice between the concurrent schedules. These results show that only when successive reinforcement contexts are produced by choice responding do those successive contexts affect choice in concurrent schedules.

Application of operant procedures in a group of institutionalized aggressive geriatric patients

Abstract: This study used positive reinforcement schedules versus no reinforcement on a group of 6 highly aggressive, institutionalized elderly patients. Dependent measures included confirmed incidents of physical and verbal aggressive behavior monitored across an ABAB design with a 4-month phase-out period. Results indicated that aggressive behavior can be significantly decreased in a group setting and subsequently generalized to ward behavior. Ancillary aspects of the study included the role of tangible and back-up reinforcers and staff attitude and behavior. Implications for future research are discussed.

Behavioral stereotypy and the generalized matching equation

Abstract: The development of behavioral stereotypy is a common result of exposure to both response-dependent and response-independent reinforcement procedures. The generalized matching equation and two dynamic versions of that equation, which take into account the time differential between reinforcements and their effect on behavior, predict this outcome of many procedures involving reinforcement. Following from the assumption that distinct response topographies, distinct response sequences, or orientations to distinct stimuli can be treated in the equations as distinct classes of behavior, the equations predict that-at least for matching and undermatching-the behavior class that is most biased relative to other behavior classes of the same type will tend to predominate to the exclusion or near exclusion of those behavior classes.

Analysis of the partial reinforcement extinction effect in humans using absolute and relative comparisons of schedules.

Abstract: The partial reinforcement extinction effect (PREE) was analyzed in humans using a quasi-multiple schedule of reinforcement with two discrete trial tasks. The first task was a videogame analog of a shuttle box. Using a joystick, subjects were required to move a cue in one of four directions for reinforcement. The second was a simple concept-formation task consisting of two binary dimensions; responding to one of the four alternatives was reinforced. All subjects were trained on the two tasks on a randomly alternating basis. Two groups were trained on the tasks using either continuous or partial reinforcement schedules for both tasks. An additional two groups received both schedules of reinforcement with continuous reinforcement on

Effects of magnitude of food reinforcement on free-operant response rates

Abstract: In Experiment 1 rats were trained to press a lever on a variable-ratio schedule of food presentation and were then exposed to progressively increasing magnitudes of food reinforcement. Response running rates (rates exclusive of the postreinforcement pause) were found to increase as a function of increasing reinforcement magnitudes. The effect of reinforcement magnitude on response rates inclusive of the postreinforcement pause, however, was less pronounced. Increases in the magnitude of reinforcement were also found to increase the length of the postreinforcement pause. Rats in Experiment 2 were trained to respond on a chained differential-reinforcement-of-low-rate variable-ratio schedule, and were exposed to increasing magnitudes of reinforcement as in Experiment 1. Response running rates increased in the variable-ratio component but decreased in the other component of the schedule. The results are discussed with reference to incentive accounts of reinforcement and the action of reinforcement on the response units generated by the operative contingencies.

Laboratory Investigation of Earth Walls Simultaneously Reinforced by Strips and Random Reinforcement

Abstract: The performance of reinforced earth structures depends, among other factors, on the shear strength of the backfill material used in construction. The shear strength can be enhanced by the use of random reinforcement. This paper presents the result of laboratory investigations concerning the effects of several types of random reinforcement on soil strength and, in particular, on the performance of reinforced earth model walls. Six series of experiments were conducted, in which a medium sand randomly reinforced by various metal particles was used as a backfill material for construction of 32 model walls. In construction of the walls standard reinforcement (horizontal metal strips attached to facing units) was used as well. The results obtained from shear box tests and from observation of model wall failures indicate that the presence of random reinforcement could lead to a significant increase in the critical height of model walls. An increase of up to 13% was observed as a result of adding only 0.5% of random reinforcement to the sand used for the construction of model walls. It was also found that fiber-like shapes of random reinforcement particles give a more significant increase in the soil strength and critical height of walls than other shapes tested. It might be reasonably expected that a small quantity of similar random reinforcement used in full-scale constructions could lead to a significant increase of their design height or, alternatively, to a decrease in volume of standard reinforcement needed.

Potentiation of responding on a VR schedule by a stimulus correlated with reinforcement: Effects of diffuse and localized signals

Abstract: In Experiment 1, rats were trained to leverpress on a variable ratio (VR) 30 schedule with a 500-msec delay between the reinforced response and food delivery. Subjects that experienced a signal during the delay responded faster than did control subjects that received the stimulus un-correlated with reinforcement. Higher response rates were obtained when the stimulus used to signal reinforcement was auditory rather than visual. Experiments 2 and 3 compared the effects of signaling reinforcement with either a localized or a diffuse light on responding maintained by VR schedules of reinforcement. Elevated response rates were observed with the diffuse stimulus, but the localized stimulus failed to produce such potentiation. Experiment 3 also examined the conditioned reinforcing power of localized and diffuse visual stimuli. These results are discussed with reference to (1) theories of selective association and sign tracking and (2) their implications for current theories of signaling reinforcement.

Preference for simple interval schedules of reinforcement in concurrent chains: Effects of segmentation ratio.

Abstract: A concurrent-chains procedure was used to examine pigeons' preferences between segmented and unsegmented terminal-link schedules of reinforcement. During the initial link, a pair of independent, concurrent variable-interval 60-s schedules was in effect. In the terminal link, reinforcement was provided by a chain fixed-interval fixed-interval schedule on one key and by a simple fixed-interval schedule with an equal interreinforcement interval in the other. The relative duration between the first and second components (segmentation ratio) in the terminal-link chained schedule was systematically varied while the terminal-link duration was kept constant at either 15 s or 30 s in two sets of conditions. With few exceptions, the simple schedule was preferred to the chained schedule. Furthermore, this preference was inversely related to the size of the segmentation ratio in the segmented schedule. When the segmentation ratio was smaller than 1:1, preference was more extreme for a 30-s condition than for a 15-s condition. However, preference decreased more rapidly in conditions with the longer terminal-link duration when the ratio increased. Taken together, these results were consistent with previous findings concerning the effect of the terminal-link duration on choice between segmented and unsegmented schedules. In addition, the data suggested that segmentation ratio in a segmented schedule constitutes another potent factor influencing preference for the unsegmented schedule.

Corrosion of steel reinforcement in carbonated mortar containing chlorides

Abstract: Synopsis It is well known and accepted that the presence of chlorides and carbonation of the concrete cover are the two main causes of corrosion of reinforcement, and that the simultaneous occurrence of both chlorides and carbonation is expected to increase the likelihood of corrosion This likelihood may be quantified and monitored through the use of electrochemical techniques Polarization resistance and electrochemical impedance measurements on rebars embedded in carbonated mortar containing chlorides have been carried out and the results indicate that these techniques not only allow the extent of corrosion to be estimated but also give information about the effect of the variables on the corrosion process