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[Choice between probability and value of alimentary reinforcement as means for revealing individual typological features of dog behavior].

Individual typological features of behavior of dogs were investigated by the method of choice between the low-valuable food available constantly and food of high quality presented with low probability. Animals were subjected to instrumental conditioning with the same conditioned stimuli but different types of reinforcement. Depression of a white pedal was always reinforced with meat-bread-crumb mixture, depression of a black pedal was reinforced with two pieces of liver (with probabilities of 100, 40, 33, 20, or 0%). The choice of reinforcement depended on probability of valuable food and individual typological features of the nervous system of a dog. Decreasing the probability of the reinforcement value to 40-20% revealed differences in behavior of dogs. Dogs of the first group, presumably with the weak type of the nervous system, more frequently pressed the white pedal (always reinforced) than the black pedal thus "avoiding a situation of risk" to receive an empty cup. They displayed symptoms of neurosis: whimper, refusals of food or of the choice of reinforcement, and obtrusive movements. Dogs of the second group, presumably with the strong type of the nervous system, more frequently pressed the black pedal (more valuable food) for the low-probability reward until they obtained the valuable food. They did not show neurosis symptoms and were not afraid of "situation of risk". A decrease in probability of the valuable reinforcement increased a percentage of long-latency depressions of pedals. It can be probably suggested that this phenomenon was associated with increasing involvement of cognitive processes, when contributions of the assessments of probability and value of the reinforcement to decision making became approximately equal. Choice between the probability and value of alimentary reinforcement is a good method for revealing individual typological features of dogs.

Animals↗
PubMed1985

Influences of delay and rate of reinforcement on discrete-trial choice.

An adjusting procedure was used to measure pigeons' preferences among alternatives that differed in the duration of a delay before reinforcement and of an intertrial interval (ITI) after reinforcement. In most conditions, a peck at a red key led to a fixed delay, followed by reinforcement, a fixed ITI, and then the beginning of the next trial. A peck at a green key led to an adjustable delay, reinforcement, and then the next trial began without an ITI. The purpose of the adjusting delay was to estimate an indifference point, or a delay that made a subject approximately indifferent between the two alternatives. As the ITI for the red key increased from 0 s to 60 s, the green-key delay at the indifference point increased systematically but only slightly. The fact that there was some increase showed that pigeons' choices were controlled by more than simply the delay to the next reinforcer. One interpretation of these results is that besides delay of reinforcement, rate of reinforcement also influenced choice. However, an analysis that ignored reinforcement rate, but considered the delays between a choice response and the reinforcers on subsequent trials, was able to account for most of the obtained increases in green-key delays. It was concluded that in this type of discrete-trial situation, rate of reinforcement exerts little control over choice behavior, and perhaps none at all.

Animals↗
PubMed1979

The use of contingent reinforcement for improving the personal appearance and hygiene of chronic psychiatric inpatients.

Chronic psychiatric patients were Ss in a study designed to evaluate the effectiveness of contingent reinforcement to improve personal appearance and hygiene. Ss were divided into four groups matched on age and years of hospitalization. Group 1 was rated on personal appearance and received contingent material reinforcement and verbal reinforcement. Group 2 was rated and received only contingent verbal reinforcement. Group 3 was rated, but received no contingent reinforcement, and Group 4 was control. It was concluded that (1) both contingent verbal reinforcement and contingent material plus verbal reinforcement can be used to improve personal appearance; (2) contingent material plus verbal reinforcement is more effective for improving personal appearance than using only contingent verbal reinforcement; (3) rating patients without using contingent reinforcement does not result in significant improvement; and (4) simply presented video-taped information for improving personal appearance does not cause significant improvement.

Activities of Daily Living↗
PubMed2005

The static strength and modulus of fiber reinforced denture base polymer.

OBJECTIVES: Partial fiber reinforcements have been employed to strengthen dentures both during repair and in the manufacturing process. The reinforcing fibers can be evenly distributed in the denture base polymer or alternatively fiber-rich phase in the denture base polymer can form a separate structure. The aim of this study was to determinate static three-point flexural strength and modulus of denture base polymer that had been reinforced with different fiber reinforcements. METHODS: The test specimens (3 x 5 x 50 mm) were made of auto-polymerized denture base polymer and reinforced with different fiber reinforcements. The test groups were: (A) no fibers; (B) non-impregnated polyethylene fibers; (C) light-polymerized monomer impregnated glass fibers; (D) porous polymer preimpregnated glass fibers and (E) light-polymerized monomer-polymer impregnated glass fibers. The fibers were oriented parallel to the long axis of the specimen and embedded into the denture base resin on the compression side (n=7) or tension side (n=7). Dry specimens were tested with three-point static flexural strength test set-up at crosshead speed of 5 mm/min. RESULTS: The statistical analysis by two-way analysis of variance showed that the brand and the location of the fiber reinforcements significantly influenced the flexural strength (p<0.0001). However, the location of the fiber reinforcements did not influence the flexural modulus (p<0.722). SIGNIFICANCE: The results suggest that impregnated and preimpregnated fibers reinforce denture base polymer more than non-impregnated fibers. Fiber reinforcements placed on the tensile side resulted in considerably higher flexural strength and flexural modulus values compared with same quantity of fibers placed on the compression side.

Acrylic Resins↗
PubMed2006

Influence of triaxial braid denier on ribbon-based fiber reinforced dental composites.

OBJECTIVES: The aim of the study was to compare the mechanical characteristics of two ultrahigh molecular weight polyethylene (UHMWPE) fiber-based triaxial braided reinforcements having different denier braider yarns used in fiber reinforced dental composites to elucidate differences in response and damage under flexural loading. METHODS: Two commercially available triaxial braided reinforcing systems, differing in denier of the axial and braider yarns, using ultra high molecular weight polyethylene (UHMWPE) were used to reinforce rectangular bars towards the tensile surface which were tested in flexure. Mechanical characteristics including energy absorption were determined and results were compared based on Tukey post-test analysis and Weibull probability. Limited fatigue testing was also conducted for 100, 1000, and 10,000 cycles at a level of 75% of peak load. The effect of the braid denier on damage mechanisms was studied microscopically. RESULTS: The use of the triaxially braided ribbon as fiber reinforcement in the dental composite results in significant enhancement in flexural performance over that of the unreinforced dental composite (179% and 183% increase for the "thin" and "dense" braid reinforced specimens, respectively), with a fairly ductile, non-catastrophic post-peak response. With the exception of strain at peak load, there was very little difference between the performance from the two braid architectures. The intrinsic nature of the triaxial braid also results in very little decrease in flexural strength as a result of fatigue cycling at 75% of peak load. Use of the braids results in peak load levels which are substantially higher than those corresponding to points at which the dentin and unreinforced dental composites would fail. The total energy at peak load level is 56.8 and 60.7 times that at the level that dentin would fail if the reinforcement were not placed for the "thin" and "dense" reinforced braid reinforced composites, respectively. SIGNIFICANCE: The research shows that in addition to enhancement in flexural performance characteristics, the use of a triaxial braid provides significant damage tolerance and fatigue resistance through its characteristic architecture wherein axial fibers are uncrimped and braider yarns provide shear resistance and enable local arrest of microcracks. Further, it is demonstrated that the decrease in braider yarn denier does not have a detrimental effect, with differences in performance characteristics, being in the main, statistically insignificant. This allows use of thinner reinforcement which provides ease of placement and better bonding without loss in performance.

Composite Resins↗
PubMed2003

Stimulus control over induction produced by upcoming food-pellet reinforcement.

Research has demonstrated that rats increase their rate of lever pressing for sucrose reinforcement when food-pellet reinforcement will soon be available within the session. Recent results suggest that this increase occurs because stimuli in the session come to signal different levels of overall reinforcement. The present experiment tested this idea by having rats respond in two types of session. In one, they pressed lever A for 1% sucrose reinforcers in the first half of the session and lever B for food-pellet reinforcers in the second half (the opposing lever was retracted in the respective half). In the other, they pressed lever B for 1% sucrose reinforcers in the first half and lever A for 1% sucrose reinforcers in the second. Thus, the presence of lever A in the first half of the session was predictive of upcoming food-pellet reinforcement, but only lever B was ever used to obtain food pellets. Subjects responded at a higher rate on lever B in the first half of the session than on lever A, despite food-pellet reinforcement being unavailable in such sessions. Furthermore, they responded at a higher rate on lever B during probe sessions in which both levers were available. These results demonstrate that stimulus control over induction occurs when a stimulus becomes differentially associated with a heightened level of reinforcement. However, questions remain as to whether this association is Pavlovian or whether stimuli with "predictive value" may ever lead to induction.

Journal Article↗
PubMed2003

Fatigue resistance of removable orthodontic appliance reinforced with glass fibre weave.

The aim of this study was to measure the fatigue resistance of fibre-reinforced composite (FRC) reinforced polymeric parts of a removable orthodontic appliance beside the clasp. The effect of quantity and position of FRC-reinforcement were investigated. In addition, the influence of water storage on the fatigue properties was determined. The test specimens for eight groups (n=6) were manufactured from autopolymerizing acrylic resin. Polymethylmethacrylate pre-impregnated woven glass fibre was used as reinforcement of acrylic resin specimens at the region of steel wire clasp. The test specimens of the control group were not reinforced. In the second group, the test specimens were reinforced with one fibre layer (thickness: 0.06 mm) on the tension side, and in the third and fourth group with two fibre layers. Fatigue resistance was measured by applying repeated bending force to the clasp. The highest fatigue resistance values were achieved when the test specimens were fibre-reinforced with two fibre layers. The lowest fatigue resistance values resulted when the test specimens were not reinforced (P=0.046, anova). Water storage had a tendency to decrease the fatigue resistance in all fibre reinforced test specimen groups. The results suggest that use of the woven polymer pre-impregnated glass FRC-reinforcement increases the fracture resistance of orthodontic appliance made of acrylic polymer.

Absorption↗
PubMed1969

Interval reinforcement of choice behavior in discrete trials.

Pigeons were trained to peck at red or green keys presented simultaneously in discrete trials. In one experiment, reinforcements were arranged by concurrent variable-interval schedules. The proportion of responses to green approximately matched the proportion of reinforcements produced by pecking green. Detailed analysis of responding revealed a systematic decrease in the probability of switching from green to red within sequences of trials after reinforcement. This trend corresponded to sequential changes in the relative frequency of reinforcement, and not to sequential changes in probability of reinforcement. In a second experiment, reinforcements were scheduled probabilistically every seventh trial. Even though there were no contingencies on pecking during the first six post-reinforcement trials, choices of green on the first response after reinforcement matched the proportion of reinforcements for pecking green. These results extend the generality of overall matching under concurrent reinforcement.

Journal Article↗
PubMed1969

Collateral responding during differential reinforcement of low rates.

Two pigeons were trained to peck either of two response keys for food, under two different variable-interval schedules. When responding stabilized, the schedule on the left key (reinforcement-key) was changed to a differential-reinforcement-of-low-rates schedule, and responses on the right key (extinction-key) were no longer reinforced. The mean interresponse time of responses on the reinforcement-key approximated the temporal requirement of the reinforcement schedule on that key. Collateral responding on the extinction-key was maintained by one of the birds. A "run" of these collateral responses was defined as a sequence of responses on the extinction-key occurring between two responses on the reinforcement-key. For this one bird, collateral behavior, measured by mean time per run and mean number of responses per run, was an increasing function of the temporal requirements of the reinforcement schedule on the reinforcement key, and it was strongly positively correlated with the mean interresponse time of responses on the reinforcement-key. However, from an analysis of the results, the collateral behavior did not appear to have mediated the temporal spacing of responses on the reinforcement-key.

Journal Article↗
PubMed1971

Some temporal parameters of non-contingent reinforcement.

In each baseline session, pigeons were exposed to a multiple schedule in which each of five distinctive stimuli was correlated with a different frequency of reinforcement. In one component, responses were reinforced with a probability of 0.10 (random-ratio schedule); in the other four components, responses were reinforced with different scheduled temporal frequencies averaging 30 to 240 sec between reinforcements (random-interval schedules). For periods lasting 30 sessions, contingent reinforcement was discontinued and reinforcement was presented independent of responding at irregular intervals averaging 30, 60, or 120 sec, while the sequence of stimuli continued. After each such period, the baseline was reinstated for 30 sessions. The data indicated that: (1) The rate of responding in the presence of all stimuli decreased as exposure to the non-contingent reinforcement procedure was prolonged, at all the frequencies of reinforcement employed; (2) The rate under the random-ratio schedule declined faster than the rates under all the random-interval schedules, presumably because the decrease in reinforcement frequency under this stimulus condition was greatest; (3) The decline in rates of responding under the stimuli correlated with the random-interval schedules tended to be greatest for the stimuli paired with the lowest frequencies of reinforcement.

Journal Article↗
PubMed1974

Effects of random reinforcement sequences.

Rats were exposed to a random sequence of reinforcement on two levers, such that there was no way to predict from the previous reinforcement which lever would deliver reinforcement next. The rats showed a tendency to repeat the choice that had just produced reinforcement, despite the absence of an overall contingency that differentially reinforced such repetition. However, this tendency decreased with continued exposure to the schedule. Runs of successive reinforcements on a lever increased the probability of pressing that lever, but only slightly, and only in the earlier phases of training. The more quickly a press was made after reinforcement the more likely it was to be on the lever that had delivered that reinforcement. Repetition of choice followed by reinforcement should be viewed as a naturally occurring behavior in the rat, but not necessarily as a behavior that will continue without differential reinforcement of repetition.

Journal Article↗
PubMed1976

Short-term memory in the pigeon: the previously reinforced response.

Eighteen pigeons served in a discrete-trials short-term memory experiment in which the reinforcement probability for a peck on one of two keys depended on the response reinforced on the previous trial: either the probability of reinforcement on a trial was 0.8 for the same response reinforced on the previous trial and was 0.2 for the other response (Group A), or, it was 0 or 0.2 for the same response and 1.0 or 0.8 for the other response (Group B). A correction procedure ensured that over all trials reinforcement was distributed equally across the left and right keys. The optimal strategy was either a winstay, lose-shift strategy (Group A) or a win-shift, lose-stay strategy (Group B). The retention interval, that is the intertrial interval, was varied. The average probability of choosing the optimal alternative reinforced 80% of the time was 0.96, 0.84, and 0.74 after delays of 2.5, 4.0, and 6.0 sec, respectively for Group A, and was 0.87, 0.81, and 0.55 after delays of 2.5, 4.0, and 6.0 sec, respectively, for Group B. This outcome is consistent with the view that behavior approximated the optimal response strategy but only to an extent permitted by a subject's short-term memory for the cue correlated with reinforcement, that is, its own most-recently reinforced response. More generally, this result is consistent with "molecular" analyses of operant behavior, but is inconsistent with traditional "molar" analyses holding that fundamental controlling relations may be discovered by routinely averaging over different local reinforcement contingencies. In the present experiment, the molar results were byproducts of local reinforcement contingencies involving an organism's own recent behavior.

Journal Article↗
PubMed1978

Inhibiting function of reinforcement: magnitude effects on variable-interval schedules.

In two experiments, the performance of rats under constant-probability and arithmetic variable-interval schedules respectively was compared when the concentration of a liquid reinforcer was varied within sessions; in other sessions, half of the reinforcers were randomly omitted. When the discriminative function of the reinforcer as a signal for a decrease in the probability of reinforcement was attenuated (the constant-probability schedule) the postreinforcement pause duration was nevertheless an increasing function of reinforcer magnitude. This relationship was also present, but more marked, when the temporal discriminative function of the reinforcer was enhanced (the arithmetic schedule). These results suggested that reinforcement has an unconditioned suppressive effect on the reinforced response distinct from any discriminative function it may acquire. The reinforcement-omission effect, where response rate accelerates following omission, was observed when the reinforcer functioned as an effective temporal discriminative stimulus, but not when such temporal control was absent.

Journal Article↗
PubMed1979

Choice and number of reinforcers.

Pigeons were exposed to the concurrent-chains procedure in two experiments designed to investigate the effects of unequal numbers of reinforcers on choice. In Experiment 1, the pigeons were indifferent between long and short durations of access to variable-interval schedules of equal reinforcement density, but preferred a short high-density terminal link over a longer, lower density terminal link, even though in both sets of comparisons there were many more reinforcers per cycle in the longer terminal link. In Experiment 2, the pigeons preferred five reinforcers, the first of which was available after 30 sec, over a single reinforcer available at 30 sec, but only when the local interval between successive reinforcers was short. The pigeons were indifferent when this local interval was sufficiently long. The pigeons' behavior appeared to be under the control of local terminal-link variables, such as the intervals to the first reinforcer and between successive reinforcers, and was not well described in terms of transformed delays of reinforcement or reductions in average delay to reinforcement.

Journal Article↗
PubMed1982

Topography of signal-centered behavior in the rat: Effects of deprivation state and reinforcer type.

In a series of three experiments, groups of food-deprived and water-deprived rats were given pairings of a retractable lever (CS(+)) with response-independent deliveries of either solid or liquid reinforcers. In Experiment 1 food-deprived rats given a solid-pellet reinforcer differentially tended to sniff, paw, mouth, and bite the CS(+) lever more often than a lever that was not paired with food (CS(-)), whereas food-deprived rats given a liquid reinforcer tended to differentially sniff, paw, and lick the CS(+) lever. 23(1/2)-hour water-deprived rats given liquid reinforcers showed very little CS(+) contact. In Experiment 2 increasing the severity of water deprivation from 23(1/2) to 47(1/2) hours significantly increased CS(+) contact. In Experiment 3, subjects that were simultaneously food and water deprived and given a water reinforcer failed to exhibit differential CS(+) contact, but subjects that were simultaneously food and water deprived and given a food reinforcer did acquire differential CS(+)-contact behavior. These results suggest that (a) even under a single motivational state the nature of signal-centered behavior can be determined by type of reinforcer, (b) although water reinforcement produces less signal contact than food reinforcement, this can be facilitated with more severe water-deprivation levels, and (c) high CS-contact rates using food reinforcement are not simply a product of reductions in body weight with food deprivation.

Journal Article↗
PubMed1986

Superimposition of response-independent reinforcement.

Studies that have superimposed response-independent reinforcement (or reinforcers scheduled by contingencies placed on the absence of responding) upon conventional response-dependent schedules are reviewed. In general, providing alternative sources of reinforcement reduced response rates below the levels observed when alternative reinforcement was absent. However, response-rate elevation was sometimes found, particularly when rates of superimposed response-independent reinforcement were low. Superimposition of schedules providing reinforcers contingent on the absence of responding usually produced more severe response-rate decrements than superimposition of response-independent reinforcement. A variant of Herrnstein's equation, which assumes that some of the alternative reinforcers function as if they were delivered by baseline response-dependent source of reinforcement, is in qualitative agreement with the overall body of results obtained, and can predict both increases and decreases in response rate as resulting from superimposed reinforcers.

Journal Article↗
PubMed1989

Effects of relative reinforcer frequency on complex color detection.

Pigeons were trained under a discrete-trials detection procedure in which one of a set of color stimuli was presented on the center key and a single response turned off the stimulus and illuminated two side keys. Single responses to one or the other side key produced occasional reinforcers depending on the value of the color stimulus. In Experiment 1, one color-stimulus set comprised 559, 564, 569, and 574 nm, and right-key pecks were occasionally reinforced following presentations of members of this set. The other stimulus set comprised 579, 584, 589, and 594 nm, and left-key pecks were occasionally reinforced following presentations of members of this set. Across seven experimental conditions, the left/(left + right) relative reinforcer frequency was varied from .1 to .9. In Experiment 2, one stimulus set contained only one member, 574 nm, and right-key responses were occasionally reinforced following its presentation. Over 12 experimental conditions, two manipulations were carried out. First, the number of stimuli comprising the other stimulus set was increased from one (579 nm) to two (579 and 584 nm) to three (579, 584, and 589 nm) and to four (579, 584, 589, and 594 nm), and left-key responses were reinforced occasionally following center-key presentations of members of this set. Second, for each stimulus combination, the left/(left + right) relative reinforcer frequency was varied from .1 to .5 to .9 across three experimental conditions. The principal finding of Experiments 1 and 2 was that reinforcers and stimuli interacted in their effects on behavior. In Experiment 3, pairs of adjacent stimuli (5 nm apart) in the range 559 to 594 nm were presented in each experimental condition, and the left/(left + right) relative reinforcer frequency was held constant at .5. The data from all three experiments were analyzed according to a detection model describing performance in multiple-stimulus two-response procedures. This model provided independent measures of stimulus discriminability, contingency discriminability, and bias. The analysis showed that (a) consistent with the color-naming function, pigeons were better able to discriminate between higher nanometer values than lower nanometer values; (b) their ability to discriminate between the stimuli was independent of the number of wavelengths comprising each stimulus set; (c) they allocated delivered reinforcers very accurately to the previously emitted response; and (d) no consistent biases emerged.

Journal Article↗
PubMed1995

Resistance to reinforcement change in multiple and concurrent schedules assessed in transition and at steady state.

Behavioral momentum theory relates resistance to change of responding in a multiple-schedule component to the total reinforcement obtained in that component, regardless of how the reinforcers are produced. Four pigeons responded in a series of multiple-schedule conditions in which a variable-interval 40-s schedule arranged reinforcers for pecking in one component and a variable-interval 360-s schedule arranged them in the other. In addition, responses on a second key were reinforced according to variable-interval schedules that were equal in the two components. In different parts of the experiment, responding was disrupted by changing the rate of reinforcement on the second key or by delivering response-independent food during a blackout separating the two components. Consistent with momentum theory, responding on the first key in Part 1 changed more in the component with the lower reinforcement total when it was disrupted by changes in the rate of reinforcement on the second key. However, responding on the second key changed more in the component with the higher reinforcement total. In Parts 2 and 3, responding was disrupted with free food presented during intercomponent blackouts, with extinction (Part 2) or variable-interval 80-s reinforcement (Part 3) arranged on the second key. Here, resistance to change was greater for the component with greater overall reinforcement. Failures of momentum theory to predict short-term differences in resistance to change occurred with disruptors that caused greater change between steady states for the richer component. Consistency of effects across disruptors may yet be found if short-term effects of disruptors are assessed relative to the extent of change observed after prolonged exposure.

Journal Article↗