Stimulus control in fixed interfood intervals

The control exerted by various portions of fixed-time and fixed-interval schedules was assessed with a trace-conditioning procedure. The intervals were segmented into 10 bins. In all but 1 of those bins, the stimuli were presented in different random orders on each trial. In 1 bin, the stimulus was the same on each trial. The position of this trace stimulus was varied across phases. The results indicated that a trace stimulus can come to control behavior and that differential control can extend to even the second tenth of an interfood interval. The results were interpreted as indicating that traditional explanations of the rate loss in earlier portions of an interfood interval are inadequate and that models such as Palya’s (1993) bipolar model or Miller and Schachtman’s (1985) comparator model may provide a principled framework with which to understand within-trial effects.     

Stimulus control in multiple variable-ratio schedules of reinforcement

One component of a multiple variable-ratio 150 variable-ratio 150 schedule remained unchanged while the reinforcement schedule of the other component was periodically changed to extinction and then returned to variable ratio 150. When the reinforcement schedule of the changed component was an unmodified variable ratio 150 schedule, the magnitude of negative contrast during baseline recovery was equal to the magnitude of positive contrast observed during the previous change from multiple variable-ratio 150 variable-ratio 150 to multiple variable-ratio 150 extinction. When the schedule of the changed component was modified during baseline recovery so that responses terminating interresponse times greater than the average baseline interresponse time in the unchanged component were not reinforced, the magnitude of the unchanged-component response rate decrease was reduced. The magnitude of negative contrast was attenuated even though response and reinforcement rates in the variable component increased to levels at or above their prior multiple variable-ratio 150 variable-ratio 150 baseline levels. The results support a general theory that negative contrast results from both (1) the removal of certain positive-contrast-producing operations and (2) changes in the interresponse time-reinforcer relations that occur as a byproduct of schedule manipulations.     

Stimulus control following training on a conditional discrimination

Pigeons were trained on a conditional discrimination in which responding was reinforced either in the presence or in the absence of a vertical line, depending on the color of the key and the chamber’s illumination. When subsequently tested for generalization along the line-orientation dimension, all subjects showed a decremental gradient when the Unes were combined with the color that had signaled reinforcement in the presence of the vertical line. In addition, most subjects showed an incremental gradient when the lines were combined with the color that had signaled no reinforcement in the presence of the vertical line.     

Fluid intelligence and discriminative operant learning of reinforcement contingencies in a fixed ratio 3 schedule

Although intelligence has traditionally been identified as the ability to learn (Peterson, 1925), this relationship has been questioned in simple operant learning tasks (Spielberger, 1962). Nevertheless, recent pieces of research have demonstrated a strong and significant correlation between associative learning measures and intelligence ( [Kaufman et al., 2009] and [Williams et al., 2008] ). The present paper aims to examine the relationship between intelligence and learning, complying with the experimental conditions of discriminative conditioning in a relatively complex free operant task. To that end, a sample of 1600 subjects applying for an ab initio Air Traffic Control training course was tested. The task is expected to allow identifying the specific influence of intelligence on the discrimination between stimulus dimensions. The results show how the relation among learning and intelligence strengthen on those trials which are critical in terms of discrimination.     

Stimulus control of topographically tagged responding

Pigeons’ responses on an operant key were reinforced according to either multiple variable-interval variable-interval or multiple variable-interval extinction schedules. The multiple-schedule components were signaled by line-tilt stimuli on a second key (signal key). Signal-key responses never produced reinforcement, and operant-key responses were not reinforced if they followed within 1 sec of a signal-key response. Behavioral contrast was not observed on the operant key, although there was a small, but reliable, increase in signal-key responding in the variable-interval component of the multiple variable-interval extinction condition. Generalization tests were interspersed between sessions of multiple variable-interval extinction training. Generalization gradients along the line-tilt dimension exhibited peak shift for both operant-key and signal-key responding following intradimensional (line tilt) discrimination training. Line-tilt generalization gradients following interdimensional discrimination did not exhibit peak shift. Gradients following intradimensional discrimination were sharper than gradients following interdimensional discrimination for both operant-key and signal-key responding. It was concluded that dimensional stimulus control of topographically tagged responding maintained by the stimulusreinforcer relation parallels that maintained by the response-reinforcer relation.     

Stimulus control in multiple temporal discriminations

In multiple fixed interval (FI) schedules, rats are trained to discriminate different FIs that are signaled by different stimuli. After extensive training, the different stimuli often acquire control over performance, observed by an earlier increase in responding for stimuli that signal shorter FIs, as compared with stimuli that signal longer FIs. The order in which the different FIs are trained, either intermixed across cycles or in blocks of several cycles, may seem irrelevant given that average performance at asymptote may be similar. In this study, rats were trained in two procedures with multiple FIs presented intermixed within sessions or in blocks of one interval per session. Similar performance was observed at asymptote, but an inspection of early cycles in each session revealed that different stimuli acquired control over performance only when trained intermixed within each session. Although the stimuli reliably signaled the upcoming FI, when trained in successive blocks of 60 cycles, rats rapidly adjusted performance early in the sessions on the basis of the temporal aspects of the task, and not on the basis of the stimulus presented in the current cycle. These results are discussed in terms of overshadowing of the stimuli by temporal cues and in terms of conditions under which a stimulus acquires control over performance.     

Stimulus control of immunization against chronic learned helplessness

Two experiments investigated the effectiveness of multiple (five) sessions of signaled eseapable-shock pretraining in preventing (immunizing against) the shack-escape impairment produced by an equal number of sessions of signaled inescapable shock. In Experiment 1, rats were exposed to 50 pairings per session of a white-noise stimulus with escapable shock during the immunization phase. Subsequently, they were exposed to 50 pairings per session of a different (houselight) stimulus with inescapable shock. Shock-escape performance in a shuttlebox test with constant illumination revealed no evidence of immunization relative to the performance of rats given five prior sessions of light-signaled inescapable shock only. Experiment 2 was identical in all respects to Experiment 1, except that both the escapable- and the inescapable-shock phases for animals in the immunization treatment group involved the same stimulus (houseüght) as a shock signal. Under these circumstances, the prior escapable-shock training significantly reduced the shuttle-box escape deficit engendered by chronic exposure to signaled inescapable shock; performance in the shuttle-box was not reliably different from that of rats exposed to signaled escapable shock alone. These findings suggest that, under chronic conditions, the development of stimulus control using Pavlovian conditioning procedures may serve to modulate the normally prophylactic influence on later shock-escape acquisition of serial exposure to escapable and inescapable shocks.     

Goal setting,responsibility training,and fixed ratio reinforcement: Ten-month application to students with emotional disturbance in a public school setting

Reviews of treatment strategies for students with emotional disturbance (ED) have noted that most studies (a) do not involve entire classes or groups of classes, (b) are not conducted in public schools, and (c) do not report data for an entire 10-month school year (September to June). This study applied goal setting (GS), responsibility training (RT), and fixed ratio reinforcement (FRR) to three classes of students with ED in a public elementary school from September to June. GS included daily, weekly, and monthly goals for behavior and work earnings (points). RT included a level system with different reinforcers and privileges for each level, and nonisolated time out with problem solving. FRR included reward contingencies for behavior and work earnings. Data for 10 months indicated that (a) goals were consistently earned at high levels, (b) the percentage of students attaining higher RT levels progressively increased, and (c) time-out levels progressively decreased, with year-end spikes below prior peak levels. Findings supported the use of GS, RT, and FRR for students with ED in public school to encourage appropriate behavior and work effort over 10 months. Method limitations and research implications are discussed.     

Stimulus generalization in monkeys following discrimination training with gray stimuli

Eight rhesus monkeys were trained on a successive discrimination problem with light gray and dark gray stimuli. Following training, generalization tests were given with variable stimuli ranging from white to black. Responses and response latencies were recorded. Responses were faster to the training stimulus values than to middle grays or to the extreme values on the lightness continuum. The theoretical implications of this as compared to other possible findings are developed.     

Prior fixed ratio training and durable persistence in rats

Following barpress training with different terminal fixed ratios (FR), rats were given the interpolated experiences of runway acquisition and extinction (as part of another experiment) followed by 2 months of vacation. Then they were tested in FR 10 barpress reacquisition, FR 10 barpress extinction, consistently reinforced runway reacquisition, and a second runway extinction. In a start (response initiation) measure, resistance to extinction during the FR 10 extinction and in the second runway extinction was positively related to the terminal FR values of the initial barpress training, an indication of highly durable differential persistence effects attributable to the initial training to different terminal fixed ratios of barpress responding.     

Stimulus control of behavior during the postreinforcement pause of FI schedules

Pigeons were given the opportunity to terminate certain segments of fixed intervals by pecking a control key. When 30-sec segments of negative and positive stimuli alternated across the interreinforcement interval (Experiment 1), most birds terminated a large proportion of negative segments. However, few control-key responses were made during the negative segment immediately following food presentation. Under schedules during which only one negative segment was programmed, during the first 30 sec of 1-min intervals (Experiment 2), control-key responses, when they occurred at all, were made after several seconds of the interval had elapsed. Similar findings were obtained when a peck on the control key merely changed the color on the food key (Experiment 3). These findings suggest that the post-reinforcement extinction state (Schneider, 1969) during fixed-interval schedules consists of two phases: an immediate postreinforcement inhibitory phase, followed by a second phase during which a control-key response may occur. These two phases and their associated behavior may be related to Staddon’s (1977) distinction between interim and facultative activities.     

Stimulus delay and the reduction of errors in the transfer of stimulus control

Pigeons initially trained on a simultaneous discrimination of line orientation (S1) were subsequently transferred to a wavelength discrimination (S2). Three transfer procedures were employed. The abrupt-transfer Ss were “abruptly” switched from S1 to the S2 dimension. The stimulus-compounding Ss were trained on a compound stimulus consisting of S1 and S2 displayed in superimposition prior to the presentation of S2 alone. The stimulus-delay Ss were trained on a compound stimulus in which the presentation of the S1 component was delayed for successively longer intervals as a result of a correct response to the preceding trial. Stimulus-delay Ss transferred by responding to S2 prior to the presentation of S1 and the resulting formation of the compound. Ss transferred by the stimulus-compounding and the abrupt-transfer procedures displayed 5 and 10 times as many errors to the S2 dimension, respectively, as Ss receiving the stimulus-delay procedure.

     

Transfer of discriminative control during stimulus fading conducted without reinforcement

Using trial-and-error training, eight pigeons did not learn to discriminate between 45° and 135° lines, but did learn to discriminate between red and green colors. Control by line tilt was induced by stimulus fading that did not include reinforcement while fading out the colors. After establishing the red–green discrimination, low-intensity lines were superimposed on colors and were gradually faded in. All of this was done using reinforcement. At the end of the line fade-in, the lines had not acquired control of responding. Finally, color intensity was gradually faded out in the absence of reinforcement, and the lines acquired discriminative control by six of the eight pigeons. Thus, reinforcement during the color fade-out was not necessary for the acquisition of discriminative control by the lines during fading. Acquisition of control by lines was attributed to overshadowing, the reduction of stimulus blocking by generalization, and the evocation of correct responding by the colors while the participants were attending to the lines. This last process was also responsible for the induction of discriminative control during sensory preconditioning, higher order conditioning, and response transfer in equivalence classes. Errors, however, were not correlated with discrimination learning during stimulus fading. Finally, transfer of control occurred very quickly with or without errors.     

Stimulus control of anticipatory responding in instrumental learning as revealed in serial learning tasks

Items in a fixed series A-B-C can be anticipated employing either item information (e.g., ItemA cues signal Item B) or position information (e.g., Position 2 cues signal Item B). Identical fixed series of rewarded and nonrewarded trials were employed in investigations reported by Capaldi and Miller (1988), Capaldi, Alptekin, Miller, and Birmingham (1997), and Burns, Dunkman, and Detloff (1999). These series were learned employing item cues according to Capaldi and colleagues and position cues according to Burns et al. (1999). Burns et al.’s (1999) conclusions were based on rats’ behavior when shifted to novel series, which could reveal position learning but not item learning. Employing the acquisition conditions of Burns and co-workers but shifts to series that could reveal item learning, evidence for item learning was obtained in two experiments. The most reasonable interpretation of the above set of findings is that rats employ a compound of both types of cues to signal items. To our knowledge, no set of prior findings so strongly suggests a similar conclusion.     

Effect on subsequent fixed-interval schedule performance of prior exposure to ratio and interval schedules of reinforcement

In three experiments, we examined the effect on the patterns of responding noted on fixed interval (FI) schedules of prior exposure to a range of interval and ratio schedules. Rats leverpressed for food reinforcement on random ratio (RR), random interval (RI), or variable interval (VI) schedules prior to transfer to FI schedules. In Experiment 1, prior exposure to an RR schedule retarded the development of typical FI patterns of responding. Exposure to a yoked RI schedule produced even greater retardation of typical FI performance. This effect was replicated in Experiment 2, using a within-subjects design. Rats responded on a multiple RR-RI schedule prior to a multiple FI-FI schedule. Typical FI performance emerged more slowly in the component previously associated with the RI than with that associated with the RR. In Experiment 3, exposure to an RR schedule retarded the development of FI performance to a greater extent than did exposure to a VR schedule. The latter schedule was programmed to allow the possibility that inhibitory control would develop after reinforcement. These results confirm that ratio schedules independently result in the disruption of FI responding. This effect was not long lasting and cannot be used plausibly to explain species differences in responding to FI schedules. However, it does suggest that temporal control—as manifested by the transfer of inhibitory control from one schedule to another—could facilitate movement between interval schedules.     

Sustained attention: Stimulus control determined by schedule of cue production interacting with cue duration

In a study of sustained attention (“vigilance”), pigeons performed a conditional discrimination in a 3-key operant chamber. Pecking a white center key initiated a 0.2- or 2.0-sec cue (a red or green disk). The side keys then displayed white disks, and a peck on the right or left key was reinforced depending on whether the preceding cue was red or green. Pecks on the white center key initiated the cue according to one of two schedules of cue production (FR 1 or VI 7.5 sec). Control of side key choices by 0.2-sec cues was disturbed by transition from FR 1 to VI 7.5, and recovered after the schedule of cue production changed from VI 7.5 back to FR 1. Control of choices by 2.0-sec cues was not affected by changing schedules of cue production. Rates of pecking the cue were higher than rates of cue-producing responses.     

Cognitive theories as reinforcement history surrogates: The case of likelihood ratio models of human recognition memory

B. F. Skinner (1977) once argued that cognitive theories are essentially surrogates for the organism’s (usually unknown) reinforcement history. In this article, we argue that this notion applies rather directly to a class of likelihood ratio models of human recognition memory. The point is not that such models are fundamentally flawed or that they are not useful and should be abandoned. Instead, the point is that the role of reinforcement history in shaping memory decisions could help to explain what otherwise must be explained by assuming that subjects are inexplicably endowed with the relevant distributional information and computational abilities. To the degree that a role for an organism’s reinforcement history is appreciated, the importance of animal memory research in understanding human memory comes into clearer focus. As Skinner was also fond of pointing out, it is only in the animal laboratory that an organism’s history of reinforcement can be precisely controlled and its effects on behavior clearly understood.     

Stimulus generalization decrement in latent inhibition to a compound following exposure to the elements or the compound

In two experiments using the taste-aversion paradigm, we attempted to replicate a result reported by Holland and Forbes (1980), in which exposure to the elements of a compound produced more interference with future conditioning (latent inhibition) to the compound than did exposure to the compound itself. In our first experiment, a compound of HC1 and sucrose was used and the amount of fluid consumed during exposure and the first conditioning trial was controlled. Rather than finding enhanced interference produced by exposure to the elements, we found reduced interference relative to exposure to the compound. In Experiment 2, a compound of NaCl and sucrose was used and a method similar to that used by Holland and Forbes was employed. We replicated the result of our Experiment 1. We interpret these results as posing problems for some associative accounts of latent inhibition but as being easily explained as an instance of stimulus generalization decrement.     

Fatigue reliability analysis of fixed offshore structures： A first passage problem approach

INTRODUCTION Offshore production and drilling platforms are, in general, large and complex structural systems, usually fabricated using steel tubular members interconnected through welded joints. These structures are predomi- nantly subjected to oscillatory environmental loads and fatigue characterizes a primary mode of failure of their components. The fatigue damage at any point in the structure depends on the complete stress history during the structure’s service life. The calculation …