Effect of varying the duration of grain presentation on automaintenance

In a series of three experiments the effects of variation in grain duration on automaintenance were evaluated. In the first experiment, key illumination was followed by grain only when pigeons did not peck the key. Each subject was exposed to 2-, 4-, and 8-second feeder durations in blocks of 10 sessions. Subjects pecked on a high percentage of trials at all feeder durations. The mean peck latency was shorter in the 8-second condition than in the two other conditions in five of six subjects. The conditional probability of pecking given successive keylight-grain pairings did not increase as the number of pairings increased. The second experiment was identical to the first, except that key pecking had no scheduled consequence. Under these conditions, all three subjects showed substantial responding. The recorded measures showed no systematic relationship to feeder duration in this study. In the third experiment, two different stimuli were followed by feeder presentations of either identical (2- or 8-second) or different (2- and 8-second) durations within each session. Subjects tended to respond sooner and with a higher overall rate in the presence of the stimulus associated with the longer feeder duration only when different feeder durations were presented within the same session. This result was confirmed by direct observation of the pigeons. The results of these experiments suggest that the effects of varying grain duration may be small, compared to the effects of varying other variables. The results also suggest that the location as well as the frequency of pecking may be an important measure in the analysis of factors controlling the pigeon's key peck.     

Analyzing the random control procedure: Effects of paired and unpaired CSs and USs on autoshaping the chick's key peck with heat reinforcement

A series of five experiments using a total of 264 subjects investigated the effects of paired and unpaired key light (CS) and heat (US) stimuli on autoshaping the chick's key peck. Experiment 1 established that paired presentations of CS and US promoted a more rapid rise in key pecking than did randomly presented CSs and USs and that the specific sequence of stimuli under the random control procedure affected key pecking performance. Experiment 2 used a trace conditioning procedure to determine the role of the CS-US interval on autoshaping and to define empirically unpaired CSs and USs. Key pecking declined as the trace delay interval was increased from 0 to 25 sec; at 25 sec, no conditioning of key pecking occurred. Experiments 3–5 assessed the effects on autoshaped key pecking of (a) number of daily CS-US pairings, (b) added unpaired CS presentations, and (c) added unpaired US presentations, since paired and random control schedules differed in all of these respects. Reduction in the number of CS-US pairings slowed the acquisition of key pecking as did the concurrent addition of nonreinforced CSs and unsignaled USs. These results support theories of association formation that stress the effects of both paired and unpaired CSs and USs.     

Conditioned suppression of an avoidance response by a stimulus paired with food

Three food-deprived Long-Evans rats were exposed to a non-discriminated shock avoidance procedure. Superimposed upon this operant avoidance baseline were periodic presentations of a conditioned stimulus that was paired with food, the unconditioned stimulus. These pairings resulted in increases in the rate of shock over that recorded when the conditioned stimulus was not present. A traditional suppression ratio failed to reveal any differential effect of the conditioned stimulus on the overall rate of avoidance responding, although all subjects showed a consistent pattern of pausing and postshock response bursts during presentations of the conditioned stimulus. When food was withheld during a final extinction phase, the conditioned stimulus ceased to occasion increases in shock rates and disruptive postshock response bursts were eliminated. An analysis of conditioned suppression procedures is proposed that stresses not only operant-Pavlovian or appetitive-aversive incompatibility, but also the manner in which the baseline schedule of reinforcement affects operant behavior changes that are elicited by the superimposed Pavlovian procedure.     

The role of the response-reinforcer contingency in negative automaintenance

When a response key is briefly illuminated before a grain reinforcer is presented, key pecking is reliably developed and maintained in pigeons, even if pecking prevents reinforcement (negative automaintenance). This experiment demonstrated that pigeons are sensitive to a negative response-reinforcer contingency, even though it does not eliminate responding. Within individual pigeons, two kinds of trials were compared: red key trials, in which reinforcement was negatively contingent on responding, and white key trials, in which reinforcement was unrelated to responding. Reinforcement frequency in non-contingent trials was yoked to the obtained reinforcement frequency in negatively contingent trials. All eight pigeons pecked substantially more on the non-contingent key than on the negative key, and preferred the non-contingent key to the negative key on occasional “choice” trials where both were presented together. When the stimuli correlated with the two conditions were reversed, the pigeons' behavior also shifted. These response differences are taken as evidence that pigeons are sensitive to the negative response-reinforcer contingency.     

Autoshaping and automaintenance of a key-press response in squirrel monkeys

Following exposure for a minimum of 500 to 600 trials, three of four naive squirrel monkeys eventually pressed a response key, illumination of which always preceded delivery of a food pellet. Three other naive monkeys did not press the key when the pellets were delivered randomly with respect to key illumination. Despite some similarities to autoshaping using pigeons, the data indicate many points of difference when squirrel monkeys are used as subjects. Although key-food pairings were shown to be important in the acquisition of the key-press response, they were ineffective in maintaining the response when either a negative response-reinforcer dependency was introduced, or when there was no scheduled response-reinforcer dependency (fixed trial). Not all demonstrations of autoshaping can be considered to be under the control of those processes that are primarily responsible for the phenomena obtained in pigeons.     

Lever-contact responses in rats: automaintenance with and without a negative response-reinforcer dependency

Pairing the presentations of one lever (cueing lever) with food led to the acquisition and persistence of lever contacts by rats. This behavior did not occur with a second lever, which was presented randomly with regard to food delivery. This finding obtained whether food delivery was independent of cueing-lever contacts (positive automaintenance) or dependent on the absence of cueing-lever contacts (negative automaintenance). The general findings were: (1) cueing-lever contacts on the positive automaintenance procedure occurred on a higher proportion of trials and at higher rates when contacts occurred than on the negative automaintenance procedure; (2) instances of the cueing lever's failure to support responding were more frequent on the negative than the positive automaintenance procedure; and (3) the topography and median contact duration of positively automaintained responding differed from negatively automaintained responding. These findings agree substantially with the automaintenance literature on pigeons, suggesting that similar processes may characterize automaintained responding in both pigeons and rats.     

Effects of varying cycle length in a tau reinforcement schedule

A temporally defined reinforcement schedule within the tau system of classification was studied, with pigeons as subjects and with cycle length as the independent variable. As cycle length decreased, response rates increased, responses-per-reinforcement went through a maximum, while the number of reinforcements-per-session increased. The first two functions are attributed to changes in the discriminability of the τ^D and τ^Δ components of the cycle, while the latter seems to result from changes in the relative durations of reinforcement time and τ^Δ time.     

The effects of varying levels of treatment integrity on child compliance during treatment with a three-step prompting procedure

The effects of three levels of treatment integrity (100%, 50%, and 0%) on child compliance were evaluated in the context of the implementation of a three-step prompting procedure. Two typically developing preschool children participated in the study. After baseline data on compliance to one of three common demands were collected, a therapist implemented the three-step prompting procedure at three different integrity levels. One integrity level was associated with each demand. The effects of the integrity levels were examined using multielement designs. The results indicate that compliance varied according to the level of treatment integrity that was in place.     

Effects of pair collaboration and word-frequency in recognition memory: a study with the remember-know procedure

The present study investigated the effects of pair collaboration and word-frequency on recognition memory, using the "remember-know" procedure. The aim was to test the predictions of the information-exchange hypothesis (Clark, Hori, Putnam & Martin, 2000), which states that collaborative facilitation occurs when participants are able to share their recollective memories with other members of the group. Results showed that recognition performance was significantly better in the collaborative than in the individual condition, and better for low-frequency than for high-frequency words. The advantage of collaborating dyads was produced by an increase of correct hits, coupled with a significant reduction of false alarms. Furthermore, the analysis of the "remember" (R) and "know" (K) responses indicated that the effects of both pair collaboration and word-frequency were larger on recollection than on familiarity processes. It is concluded that, in a collaborative condition, arguments based on the retrieval of the contextual details associated with the target words are more effective than those based on familiarity in increasing the proportions of correct hits. In addition, it is proposed that collaboration may lead to a reduction of the probability to accept new items on the basis of familiarity (K) responses.     

Positive reinforcement and suppression from the same occurrence of the unconditioned stimulus in a positive conditioned suppression procedure

Responding of rats was maintained on a variable-interval schedule of food reinforcement. The same response also produced a blinking light followed by electrical brain stimulation according to a fixed-interval schedule. This conjoint schedule produced two behavioral changes. First, instead of a steady rate of responding throughout the session, which would be characteristic of the variable interval food schedule alone, responding between occurrences of the light-brain stimulation pairings became positively accelerated and thus was more characteristic of the fixed-interval schedule of these pairings. Second, food responding was suppressed during the light that preceded brain stimulation. These results indicate that positive reinforcement and suppression resulted from the same occurrence of the light-brain stimulation combination. This finding suggests that stimuli such as conditioned reinforcers that precede an unconditioned reinforcer may have a suppressive effect upon responding in their presence that is being maintained by another reinforcer.     

Acquisition and maintenance of autoshaped key pecking as a function of food stimulus and key stimulus similarity.

The results of a number of recent studies suggest that acquisitions of autoshaped key pecking in pigeons is affected by the similarity of the grain-hopper stimulus and response-key stimulus. In Experiment 1 this hypothesis was tested by training independent groups of pigeons to key peck under six different hopper-stimulus and key-stimulus similarity conditions, and three procedures containing either immediate reinforcement, variable delay of reinforcement, or omission of reinforcement for key pecking. Number of trials to acquisition was found to be related to the similarity variable. Maintained responding was affected by the response-reinforcer contingency. This effect was found both within and between subjects. Under two of the contingencies (automaintenance and omission), maintained responding continued to be affected by the similarity of the hopper stimulus and key stimulus. In Experiment 2 pigeons were given omission training with a hopper light on or off. Both acquisition and maintenance of key pecking were facilitated by the presence of the hopper light. The present findings suggest that much of the responding reported in various automatic shaping and training procedures may reflect the effects of key stimulus/food stimulus similarity.     

Effects of varying the apparent tilt of the inspection figure on a kinaesthetic after-effect

Three experiments were conducted to determine whether kinaesthetic after-effects, measured by settings of a bar to the horizontal, are controlled by the apparent or the physical tilt of the bar during inspection. Two arrangements were used to induce a discrepancy between apparent and physical tilt. Data obtained with one arrangement did not permit a proper test of the issue. With the other arrangement either distorted or undistorted visual information about tilt was present during kinaesthetic inspection. It was found that post-inspection settings were displaced from pre-inspection settings in the direction of the tilt of the inspection figure when there was no discrepancy between information presented by the two modalities. When there was a discrepancy, the displacements attributable to apparent tilt were in the direction opposite to the apparent tilt of the inspection figure. The former effects dissipated rapidly after inspection; the latter did not. It is suggested that after-effects obtained following an inspection period during which there is no discrepancy between physical and apparent tilt are controlled by the physical tilt of the inspection figure and that apparent tilt, when it is an effective variable, operates by modifying the judgemental frame of reference.     

Constraints on Pavlovian conditioning of the pigeon: Relative conditioned reinforcing effects of red-light and tone CSs paired with food

Recent Pavlovian conditioning experiments presented all possible CS-US combinations of red-light and tone CSs and food and shock USs to separate groups of pigeons. Pigeons receiving shock USs demonstrated conditioned head raising followed by prancing to both CSs, but CRs were acquired more rapidly to tone than to red light. Although pigeons receiving food USs rapidly acquired a conditioned response of pecking to the red-light CS, there was no evidence of conditioned responding in groups receiving tone-food pairings. This outcome left open the possibility that Pavlovian pairings of tone and food may have resulted in association formation that was not revealed in performance. The present series of experiments attempted to reveal that association, using an indirect method of assessment, conditioned reinforcement. Experiment 1 demonstrated that both red light and tone paired with food became positive conditioned reinforcers, suggesting that an association between tone and food was formed in the same number of Pavlovian conditioning trials that previously failed to yield any direct evidence of conditioning. Experiment 2, which presented fewer conditioning trials, revealed that the tone-food association was formed less rapidly than the red light-food association. Experiment 3 demonstrated that the observed outcomes were not attributable to unconditioned, rather than conditioned, reinforcing effects of the Css.     

Maintenance of key pecking by response-independent food presentation: the role of the modality of the signal for food

Three pigeons were exposed to a series of procedures in which periods of response-independent food presentation, on a variable-time schedule, alternated with periods in which food was never presented. The stimuli that signalled periods of food availability or non-availability varied from one procedure to the next, and were sometimes key colors, sometimes tones, and sometimes compounds of both. Key pecking was initiated and maintained when key color was a signal for food; key pecking was not initiated when a tone was the signal for food. However, control of key pecking that was already established could be transferred from key color to tone, and subsequently, initiated by the tone. It is suggested that for pigeons, pre-experimental relationships exist among food, visual stimuli, and pecking, and that a similar relationship, which includes auditory stimuli, must be induced in the laboratory.     

Second-order schedules of token reinforcement: effects of varying the schedule of food presentation

In the initial link of a complex schedule, one discriminative stimulus was presented and lever pressing produced tokens on fixed-ratio schedules. In the terminal link, signalled by a second discriminative stimulus, deposits of the tokens produced food. With two rats, the terminal link was presented after each sixth component schedule of token reinforcement was completed. With the other two rats, the terminal link was presented following the first component schedule completed after a fixed interval. During the terminal link, each token deposit initially produced food. The schedule of food presentation was subsequently increased such that an increasing number of token deposits in the terminal link was required for each food presentation. Rates of lever pressing in the initial link were inversely related to the schedule of food presentation in the terminal link. These results are similar to those of experiments that have varied schedules of food presentation in chained schedules. Rates and patterns of responding controlled throughout the initial link were more similar to those ordinarily controlled by second-order brief-stimulus schedules than to those controlled by comparable extended chained schedules.