Red Keylight Research Articles

Selective attention in pigeon temporal discrimination

Cues can vary in how informative they are about when specific outcomes, such as food availability, will occur. This study was an experimental investigation of the functional relation between cue informativeness and temporal discrimination in a peak-interval (PI) procedure. Each session consisted of fixed-interval (FI) 2- and 4-s schedules of food and occasional, 12-s PI trials during which pecks had no programmed consequences. Across conditions, the phi (ϕ) correlation between key light color and FI schedule value was manipulated. Red and green key lights signaled the onset of either or both FI schedules. Different colors were either predictive (ϕ = 1), moderately predictive (ϕ = 0.2-0.8) or not predictive (ϕ = 0) of a specific FI schedule. This study tested the hypothesis that temporal discrimination is a function of the momentary conditional probability of food; that is, pigeons peck the most at either 2 s or 4 s when ϕ = 1 and peck at both intervals when ϕ < 1. Response distributions were bimodal Gaussian curves; distributions from red- and green-key PI trials converged when ϕ ≤ 0.6. Peak times estimated by summed Gaussian functions, averaged across conditions and pigeons, were 1.85 and 3.87 s; however, pigeons did not always maximize the momentary probability of food. When key light color was highly correlated with FI schedules (ϕ ≥ 0.6), estimates of peak times indicated that temporal discrimination accuracy was reduced at the unlikely interval, but not the likely interval. The mechanism of this reduced temporal discrimination accuracy could be interpreted as an attentional process.

Control by past and present stimuli depends on the discriminated reinforcer differential.

The extent to which a stimulus exerts control over behavior depends largely on its informativeness. However, when reinforcers have discriminative properties, they often exert less control over behavior than do other less reliable stimuli such as elapsed time. We investigated why less reliable cues in the present often overshadow stimulus control by more reliable cues presented in the recent past, by manipulating the reliability and duration of stimulus presentations. Five pigeons worked on a modified concurrent schedule in which the location of the response that produced the last reinforcer was a discriminative stimulus for the likely time and location of the next reinforcer. In some conditions, either the location of the previous reinforcer, or the location of the next reinforcer, was signaled by a red key light. This stimulus was either Brief, occurring for 10 s starting a fixed time after the most recent reinforcer, or Extended, being present at all times between food deliveries. Brief and Extended stimuli that signaled the same information had a similar effect on choice when they were present, but control by Brief stimuli weakened as time since stimulus offset elapsed. Control was divided among stimuli in the present and recent past according to the apparent reliability of the information signaled about the next reinforcer. More reliable stimuli in the present degraded, but did not erase, control by less reliable stimuli presented in the recent past. Thus, we conclude that less reliable stimuli in the present control behavior to a greater degree than do more reliable stimuli in the recent past because these more reliable stimuli are forgotten, and hence their relation to the likely availability of food cannot be discriminated.

Categorical Discrimination of Sequential Stimuli: All SΔ Are Not Created Equal

Pigeons were exposed to a novel variation of a stimulus discrimination task previously used with rats as a slot machine analog. We sought to replicate and extend characterizations of structural characteristics of responding, determine relations between those characteristics and identify predictors of individual differences in performance. Pecking during a “collect” phase produced food if and only if the keylight was red for the entire sample phase. In other trial types, the keylight was green, or started red and turned green after one or two pecks. The opportunity to respond was available for 5 s in all collect phases, permitting multiple responses per trial. Pigeons were less likely to peck in collect phases when sample stimuli were not all red, and when they did peck, it was at a lower rate. However, consistent with reactions to near wins in other slot machine tasks, there was more responding in collect phases that followed sample phases when the red keylight turned green after two pecks. Among initial response characteristics, response rate in trials that resembled near wins was the best predictor of terminal responding. Supporting their characterization as measures of stimulus control, collect proportions were negatively correlated with response times in the sample phase. Supporting their characterization as measures of conditioned reinforcing value, latency and response rate in collect phases were positively correlated, but neither was systematically correlated with proportion or sample phase response times. Ultimately, isolating measures of stimulus control and conditioned reinforcement may help determine the mechanisms responsible for near-win effects.

Emergent relations in pigeons following training with temporal samples

In two experiments, we investigated emergent conditional relations in pigeons using a symbolic matching-to-sample task with temporal stimuli as the samples and hues as the comparisons. Both experiments comprised three phases. In Phase I, pigeons learned to choose a red keylight (R) but not a green keylight (G) after a 1-s signal. They also learned to choose G but not R after a 4-s signal. In Phase II, correct responding consisted of choosing a blue keylight (B) after a 4-s signal and a yellow keylight (Y) after a 16-s signal. Comparisons G and B were both related to the same 4-s sample, whereas comparisons R and Y had no common sample. In Phase III, R and G were presented as samples, and B and Y were presented as the comparisons. The choice of B was correct following G, and the choice of Y was correct following R. If a relation between comparisons that shared a common sample were to emerge, then responding to B given G would be more likely than responding to Y given R. The results were generally consistent with this prediction, suggesting, for the first time in pigeons, the emergence of novel relations that involve temporal stimuli as nodal samples.

Resistance to change and preference for variable versus fixed response sequences.

In Experiment 1, 4 pigeons were trained on a multiple chain schedule in which the initial link was a variable-interval (VI) 20-s schedule signalled by a red or green center key, and terminal links required four responses made to the left (L) and/or right (R) keys. In the REPEAT component, signalled by red keylights, only LRLR terminal-link response sequences were reinforced, while in the VARY component, signalled by green keylights, terminal-link response sequences were reinforced if they satisfied a variability criterion. The reinforcer rate for both components was equated by adjusting the reinforcer probability for correct REPEAT sequences across sessions. Results showed that initial- and terminal-link responding in the VARY component was generally more resistant to prefeeding, extinction, and response-independent food than responding in the REPEAT component. In Experiment 2, the REPEAT and VARY contingencies were arranged as terminal links of a concurrent chain and the relative reinforcer rate was manipulated across conditions. For all pigeons, initial-link response allocation was biased toward the alternative associated with the VARY terminal link. These results replicate previous reports that operant variation is more resistant to change than operant repetition (Doughty & Lattal, 2001), and show that variation is preferred to repetition with reinforcer-related variables controlled. Behavioral momentum theory (Nevin & Grace, 2000) predicts the covariation of preference and resistance to change in Experiments 1 and 2, but does not explain why these aspects of behavior should depend on contingencies that require repetition or variation.

CONTINGENT STIMULI SIGNAL SUBSEQUENT REINFORCER RATIOS

Conditioned reinforcer effects may be due to the stimulus' discriminative rather than its strengthening properties. While this was demonstrated in a frequently-changing choice procedure, a single attempt to replicate in a relatively static choice environment failed. We contend that this was because the information provided by the stimuli was nonredundant in the frequently-changing preparation, and redundant in the steady-state arrangement. In the present experiments, 6 pigeons worked in a steady-state concurrent schedule procedure with nonredundant informative stimuli (red keylight illuminations). When a response-contingent red keylight signaled that the next food delivery was more likely on one of the two alternatives, postkeylight choice responding was reliably for that alternative. This effect was enhanced after a history of extended informative red keylight presentation (Experiment 2). These results lend support to recent characterizations of conditioned reinforcer effects as reflective of a discriminative, rather than a reinforcing, property of the stimulus.

Reinforcement: food signals the time and location of future food.

It has long been understood that food deliveries may act as signals of future food location, and not only as strengtheners of prefood responding as the law of effect suggests. Recent research has taken this idea further--the main effect of food deliveries, or other "reinforcers", may be signaling rather than strengthening. The present experiment investigated the ability of food deliveries to signal food contingencies across time after food. In Phase 1, the next food delivery was always equally likely to be arranged for a left- or a right-key response. Conditions were arranged such that the next food delivery was likely to occur either sooner on the left (or right) key, or sooner on the just-productive (or not-just-productive) key. In Phase 2, similar contingencies were arranged, but the last-food location was signaled by a red keylight. Preference, measured in 2-s bins across interfood intervals, was jointly controlled by the likely time and location of the next food delivery. In Phase 1, when any food delivery signaled a likely sooner next food delivery on a particular key, postfood preference was strongly toward that key, and moved toward the other key across the interreinforcer interval. In other conditions in which food delivery on the two keys signaled different subsequent contingencies, postfood preference was less extreme, and quickly moved toward indifference. In Phase 2, in all three conditions, initial preference was strongly toward the likely-sooner food key, and moved to the other key across the interfood interval. In both phases, at a more extended level of analysis, sequences of same-key food deliveries caused a small increase in preference for the just-productive key, suggesting the presence of a "reinforcement effect", albeit one that was very small.

Time versus response indices affect conclusions about preference pulses

Using data from two conditions of an experiment that arranged response-contingent foods and red keylight illuminations, we compared time-indexed and response-indexed preference pulses. The interpretation of red keylight effects (relative to food effects) differed according to whether time or behaviour was used to index choice in the post-event period: preference after a red keylight was more extreme than after a food in the response pulses while preference after a food was more extreme than after a keylight in the time pulses. This was due to different response latencies following the two events in combination with a tendency for initial preference to decrease as latency increased: responding began sooner after non-foods and responding that began later, after any event, tended towards indifference. Our finding suggests that preference pulses ought to be indexed according to time since the last event delivery, particularly if the response-contingent events may result in systematically different response latencies.

Memory for empty time intervals in pigeons

Pigeons were trained to discriminate short (2 sec) and long (8 sec) empty intervals that began each trial. In group consistent, onset of an empty interval was marked by a brief presentation of red keylight, and termination of the interval was marked by a brief presentation of green keylight. In group inconsistent, red and green served equally often as the first and second markers across trials. Testing revealed that, in group consistent, (1) birds were sensitive to the relation between marker color and marker type and (2) presentation of the second marker did not initiate timing a new interval. Testing also revealed a robust choose-long effect at delays longer than the training delay and indifference between the comparisons on no-sample trials. Both of the latter findings differ from those typically obtained when filled intervals are employed. It was concluded that pigeons process filled and empty intervals differently.

Olanzapine, an atypical antipsychotic, increases rates of punished responding in pigeons

The effects of olanzapine [LY 170053; 2-methyl-4-(4-methyl-1-piperazinyl)-10H-thieno[2, 3b] [1,5]benzodiazepine), a potential atypical antipsychotic, were determined in pigeons whose keypeck responding was punished. These effects were compared to the anxiolytic agents chlordiazepoxide and pentobarbital, and to other antipsychotic agents. Keypeck behavior was maintained under a multiple FR30 FR30 schedule, signalled by white and red stimulus lights, respectively. Each component of the schedule alternated every 3 min with a 30-s timeout. During the white keylight component, responding was maintained by food presentation. During the red keylight component, responding was maintained by food and simultaneously suppressed by electric shock presentation, with response rates being only about 5% of those during the white stimulus light. Olanzapine (0.01-1.0 mg/kg) increased punished responding at doses below those which had an effect on unpunished responding. Clozapine (0.01-1.0 mg/kg), ritanserin (0.1-3.0 mg/kg), and, to a lesser extent, risperidone (0.1-1.0 mg/kg) were also effective at increasing punished responding. Generally, the maximum effect seen with olanzapine was equal to that seen with ritanserin, and it exceeded that seen with clozapine. However, these effects were generally less than those seen with chlordiazepoxide and pentobarbital. Haloperidol (0.01-0.1 mg/kg) was completely without effect on punished responding, while it caused decreases in unpunished behavior. These results provide further evidence that olanzapine has a profile in behavioral tests unlike the typical antipsychotic haloperidol. Moreover, this profile is similar to clozapine, a clinically effective antipsychotic with an atypical profile.

Contextual control of Pavlovian bidirectional occasion setting

Three pigeons were trained in a lighted context on a bidirectional occasion-setting task in which a tone feature (F) signaled food after the green keylight (L:G-, L:FG+) and no food after the red keylight (L:R+, L:FR-). They acquired the former feature-positive (F-P) discrimination and the latter feature-negative (F-N) discrimination at almost equal speed. Another three birds were trained with a F-P discrimination task in a light context (L:G-, L:FG+) and with a F-N discrimination task in a dark context (D:G+, D:FG-). The keylight was always green and two contextual conditions were changed randomly trial by trial. In this training, the F-P discrimination was acquired faster than the F-N discrimination. Then, all birds received a more complex amalgam contingency in which all eight types of trials were presented in the session (D:R-, D:G+, D:FR+, D:FG-, L:R+, L:G-, L:FR-, L:FG+). After they learned the amalgam training, the outcomes of two trial types were changed (D:R+, D:G-), but this treatment failed to reverse the pattern of responding in the remaining trial types.

Anticonflict effects of buspirone and chlordiazepoxide in pigeons under a concurrent schedule with punishment and a changeover response.

A procedure was developed with pigeons to extend the experimental analysis of punished behavior and the effects of anxiolytic drugs. Under this procedure the completion of a fixed-ratio requirement on a changeover key switched between two variable-interval schedules of reinforcement that were programmed on a second response key. Under one schedule, correlated with a green keylight, key pecks produced only food; under the second schedule, correlated with a red keylight, key pecks produced both food and electric shock. Pigeons were switched into the component with shock if they did not enter that component within 5 min. Parameter values of the variable-interval schedules were manipulated systematically and the effects of two clinically active anxiolytic drugs, buspirone and chlordiazepoxide, were examined. Responding was suppressed during the component with shock (punishment) and, under non-drug conditions, pigeons infrequently switched into the punishment component; changeover responses occurred rapidly when switched into the punishment component. Both buspirone (0.1-3.0 mg/kg) and chlordiazepoxide (3.0-30 mg/kg) increased punished responding at doses that had little effect on unpunished responding; d-amphetamine (0.3-5.6 mg/kg), which was studied only under one parameter of the variable-interval schedule, produced greater decreases in rates of punished responding than in unpunished responding.(ABSTRACT TRUNCATED AT 250 WORDS)

CONTEXT SPECIFICITY OF OPERANT DISCRIMINATION PERFORMANCE IN PIGEONS

In an experiment designed to investigate odors as potential retrieval cues in pigeons' memory (i.e., as conditional stimuli), 8 pigeons first learned to peck a red keylight (S+, reinforced) and not a blue one (S-, extinguished) in the presence of either a eucalyptus oil or isoamyl acetate odor. They were repeatedly switched between two chambers with the same odor to habituate any reaction to the switching that would be required for eventual testing for conditional control by the odors. Next, the birds learned the reversal (blue S+, red S-) in the presence of the alternative odor in one of these chambers. When the birds were then switched to the alternative chamber for additional training, although the odor was still appropriate to the reversal problem, behavior appropriate to the original training condition recurred. Testing indicated that reversal performance was specific to the one chamber in which it had been trained.

Backward associations: Differential learning about stimuli that follow the presence versus the absence of food in pigeons

During training intended to establish positive and negative backward associations, pigeons received periodic 3-sec illuminations of a grain magazine, with food simultaneously available on 50% of the illuminations. For backward-positive subjects, a red keylight followed food trials only; for backward-negative subjects, it followed no-food trials only. During this training, the birds hardly ever pecked the red stimulus (no evidence of backward conditioning). However, when the red stimulus subsequently preceded and signaled grain for all birds, the backward-positive subjects pecked sooner and more often than did the backward-negative subjects, and control subjects performed at an intermediate level. Increases in the amount of original training did not significantly change the facilitatory effects of the backward-positive stimulus, but seemed to enhance the retarding effects of the backward-negative stimulus. These group differences cannot be attributed to what happened after the backward stimuli during original training. The features of the present technique that could possibly have produced strong and long-lasting positive and negative backward associations are discussed in comparison to prior research that has indicated weak or transitory evidence of true backward conditioning.

Anticonflict effects of the 5-HT1A compound flesinoxan

The new phenylpiperazine derivative flesinoxan, a potent and selective serotonin(1A) (5-HT(1A)) agonist, was examined under a procedure that has proved to be a reliable and sensitive method for detecting novel anxiolytic drugs believed to produce their effects at the 5-HT( 1A) receptor subtype. Key pecking by pigeons was maintained by the presentation of food following every 30th response in the presence of a white keylight; during an alternate component, correlated with a red keylight, every 30th response produced food and electric shock which suppressed responding (punishment). Flesinoxan doses from 0.001 to 0.3 mg/ kg, intramuscularly, produced significant increases in punished responding at doses that did not affect unpunished responding. Doses of flesinoxan between 1.0 and 3.0 mg/kg also increased punished responding but produced decreases in responding that was not punished. In a second study flesinoxan substituted for the 5-HT(1A) anxiolytic buspirone under a drug discrimination procedure, providing further evidence that the behavioural effects offlesinoxan are mediated by 5-HT(1A) mechanisms. Based on these findings, it would appear that flesinoxan should be a useful compound in the clinical management of anxiety.

TOPOGRAPHICAL VARIATIONS IN BEHAVIOR DURING AUTOSHAPING, AUTOMAINTENANCE, AND OMISSION TRAINING

Three pigeons were exposed to an autoshaping and automaintenance procedure while a computer-controlled tracking system continuously recorded the position of the bird's head as it moved freely in the experimental chamber. Although only 2 birds pecked the key during the conditional stimulus (red keylight), all 3 birds exhibited stable patterns of approaching the conditional stimulus and withdrawing from the intertrial stimulus (white keylight). Subsequent exposure to an omission procedure, in which pecks on the red key cancelled the presentation of food upon the termination of the red keylight, greatly reduced key pecking, but approaching and pecking in the vicinity of the conditional stimulus were maintained at high levels. When the omission contingency was removed key pecking increased. During all phases the birds withdrew from the area of the white key and engaged in repetitive back-and-forth or circuiting movements during this intertrial stimulus. The data document (a) the strong control the conditional stimulus in autoshaping and automaintenance exerts over approach to the key and pecking motions whether or not the conditional stimulus elicits key pecking at a high level; and (b) withdrawal from the vicinity of the key and the occurrence of stereotypic behavior during the intertrial interval.

The Emergence of Establishing Stimulus Control

The development of control of four pigeons’ keypecks by a stimulus that appeared to serve a novel function was examined. In the presence of a red key light, a peck on a white key produced food. However, before food delivery could occur, the white key light had to be produced by a peck on a green key. Of interest was whether subjects would eventually peck the green key to produce the white keylight only after onset of the red keylight. Such an outcome would be consistent with the description of establishing stimulus control (Michael, 1982). Acquisition of apparent establishing stimulus control was observed in the responding of each pigeon and was maintained in the responding of three of the four birds. Four response patterns described performances on over 93% of the trials for these three pigeons. A latencies per opportunity analysis showed that these same three pigeons responded as if key pecks were controlled by onset of the red keylight. When a variable-time schedule controlled onset of the red keylight, pigeons were more likely to wait for onset of the red keylight to peck the green key when time to red keylight onset was relatively short. These results provide support for the existence of a fourth stimulus function, but leave open the question of the utility of the term, establishing stimulus, as a label for that function.

Benzodiazepine-like effects of inosine on punished behavior of pigeons

Behavioral effects of the putative endogenous benzodiazepine receptor ligand, inosine, were studied alone and in combination with the benzodiazepine antagonist Ro 15-1788. Keypeck responses were maintained by food under a multiple fixed-interval 3-min, fixed-interval 3-min schedule of food delivery. Under the multiple schedule, the first response after 3 min produced food in the presence of either white (no punishment) or red keylights and, in addition, each 30th response produced a brief electric shock (punishment) when the keylight was red. Inosine increased the low rates of punished responding (10–100 mg/kg IM) and the higher rates of unpunished responding (30 mg/kg). The benzodiazepine antagonist Ro 15-1788 (0.03 mg/kg, IM) antagonized the rate-increasing effects of inosine but had no effect when given alone. Combinations of inosine (30 mg/kg) with higher doses of Ro 15-1788 (0.1–1 mg/kg) decreased responding much like Ro 15-1788 alone. The marked rate-decreasing effects of 1000 mg/kg inosine were not affected by concurrent administration of Ro 15-1788 (0.01–1 mg/kg). The behavioral effects of inosine alone resembled effects of benzodiazepines but not those of benzodiazepine antagonists. The response rate-increasing effects of inosine may be due to its benzodiazepine receptor binding properties, whereas the rate decreases produced by higher doses of inosine appear to be unrelated to benzodiazepine receptors.

Behavioral effects and benzodiazepine antagonist activity of Ro 15-1788 (flumazepil) in pigeons

The selective benzodiazepine receptor antagonist, Ro 15–1788, produced behavioral effects in pigeons at doses at least 100 times lower than those previously reported to possess intrinsic pharmacological activity in mammals. In contrast to its effects in mammalian species, in pigeons, Ro 15–1788 does not exhibit partial agonist activity. Keypeck responses of pigeons were studied under a multiple fixed-interval 3-min, fixed-interval 3-min schedule in which the first response after 3-min produced food in the presence of red or white keylights. In addition, every 30th response during the red keylight produced a brief electric shock (punishment). Under control conditions, punished responding was suppressed to 30% of unpunished response levels. Ro 15–1788 (0.01 mg/kg, i.m.) increased unpunished response rates by 33% without affecting rates of punished responding. Doses of 0.1 to 1.0 mg/kg Ro 15–1788 produced dose-related decreases in both punished and unpunished responding. As in characteristic of other benzodiazepines, midazolam (0.1 and 0.3 mg/kg, i.m.) markedly increased punished responding but had little effect on rates of unpunished responding. Ro 15–1788 antagonized the increases in punished responding and also reversed the rate-decreasing effects of higher doses of midozolam. However, the effectiveness of Ro 15–1788 as a benzodiazepine antagonist was limited by its intrinsic activity: rate-decreasing doses of Ro 15–1788 were unable to completely reverse behavioral effects of midozolam. Midazolam was an effective antagonist of the behavioral effects of Ro 15–1788 (up to 0.1 mg/kg) but midazolam did not influence the rate-decreasing effects of 1.0 mg/kg Ro 15–1788 across a 100-fold dose range. In the pigeon, the behavioral effects of relatively low doses of Ro 15–1788 (0.01–0.1 mg/kg) appear to be related to benzodiazepine receptor mechanisms, whereas other systems appear to be involved in the effects of higher doses.

Effects of barbiturates and other sedative hypnotics in pigeons trained to discriminate phencyclidine from saline.

Pigeons were trained to peck the center key (lighted white) of three response keys to turn off the center keylight and to light one of the side keys with a red keylight and the other side key with a green keylight. Five responses (fixed-ratio component) on either side key relighted the center key. Food was delivered following 10 fixed-ratio components on the red key if 1.5 mg/kg phencyclidine had been given before the session. The position of the red and green keylights on the side keys varied randomly each time they were lighted by a peck on the center key. Subsequently, increasing doses of phencyclidine, barbital, amobarbital, phenobarbital, methaqualone, methyprylon, diazepam, oxazepam, and d-amphetamine were substituted for the training dose of phencyclidine, using a cumulative dosing procedure. At low doses of the sedative hypnotics, birds pecked the keylight color associated with saline. At higher doses, birds pecked both key colors. At the highest doses of pentobarbital and amobarbital, some birds responded almost exclusively On he color associated with phencyclidine. When responding on keys of both colors occurred following administration of phencyclidine or other sedative hypnotics, this responding was controlled by key position rather than by key color.