Observing responses in pigeons

Pigeons were trained on an observing-response procedure in which periods of VR 100 and EXT alternated unpredictably during a white light (mixed stimulus). During VR 100, responses on a food-producing key (the first key) were intermittently reinforced. Responses on the observing key (the second key) produced a green light (positive stimulus) when VR 100 was in effect, and a red light (negative stimulus) for EXT. The birds did not respond on either key during the negative stimulus, but they responded on the food-producing key when the positive stimulus appeared. When observing responses produced the positive or negative stimulus on FR, observing responses were maintained until the FR reached a maximum; beyond this, only food-producing responses occurred. When observing responses did not produce either stimulus, the observing-response rates fell to zero. With prolonged exposure to an FR 20 schedule of observing, observing-response rates during EXT were higher than during VR 100. Chlorpromazine hydrochloride decreased the total response output but markedly increased observing-response rates except when it was administered before sessions of observing response extinction.     

Effects of d-amphetamine and chlordiazepoxide on spaced responding in pigeons

The effects of d-amphetamine and chlordiazepoxide were studied in pigeons on performance (1) under a schedule that reinforced responses on a key (food key) if they were more than 20 sec apart, (2) under the same schedule when responses also were required on a collateral key during the interresponse time on the food key, and (3) under the same schedule when responses were required on a collateral key during the interresponse time on the food key and collateral-key responses could produce a stimulus correlated with the availability of food. Under all three spaced-responding schedules, d-amphetamine and chlordiazepoxide at low dose levels slightly increased the frequency of short interresponse times on the food key for about half the birds, and either did not affect the interresponse time patterns of the other birds, or lengthened the durations slightly. At higher dose levels, d-amphetamine and chlordiazepoxide increased the frequency of long interresponse times or abolished responding in all birds. Changes in the pattern of interresponse times on the food key did not seem to depend on changes in the rate or pattern of collateral-key responses.     

Stimulus control and response bias in an analogue prey-detection procedure

The present study compared the performance of 6 pigeons trained to detect luminance differences in two different signal-detection procedures. Exposed to a three-key array, the pigeons were trained to peck the left key when the brighter of two light intensities had been presented on the center key and to peck the right key when the dimmer of two light intensities had been presented on the center key. Procedure A was a standard signal-detection procedure in which left/bright and right/dim responses produced food reinforcement and left/dim and right/bright responses produced periods of timeout. Procedure B was designed to simulate some of the contingencies operating in a prey-detection situation. Left-key responses produced reinforcement following the brighter center-key stimulus and a period of timeout following the dimmer center-key stimulus. Right-key responses always produced a short period of timeout irrespective of the stimulus. Within each procedure, the duration of timeout arranged for false alarms (left/dim responses) was varied between 3 s and 120 s. Measures of accuracy and response bias were compared between the two procedures. The timeout manipulation produced systematic, but relatively small, changes in these measures when right/dim responses (i.e., correct rejections) produced reinforcement (Procedure A). Arranging timeout for right/dim responses in Procedure B produced greater variability in accuracy and response bias than did arranging reinforcement, but this variability was not related to timeout duration. Overall, discrimination accuracy was considerably higher when right/dim responses produced timeout than when they resulted in reinforcement, and accuracy was accompanied by a large bias toward the response associated with reinforcement. These results are consistent with a recently proposed model of signal detection.     

Effects of d-amphetamine and pentobarbital under concurrent fixed-ratio schedules.

Pigeons were studied under a two-key concurrent fixed-ratio schedule of food presentation. During the first five sessions, the fixed-ratio requirements were 30 responses on one key (major key) and 120 responses on the other key (minor key): responding occurred almost exclusively on the major key. When the fixed-ratio requirements were then made equal at 30 responses on both keys, responding continued to predominate on the major key. The asymmetric distribution of responses persisted when the concurrent fixed-ratio fixed-ratio schedule was interrupted with periods during which the major key was associated with extinction while the other key remained associated with a fixed-ratio schedule. Additionally, in some subjects the fixed-ratio requirements were increased. These schedule modifications decreased the asymmetry in responding but did not eliminate it. d-Amphetamine decreased rates on both keys and slightly increased the asymmetric distribution of responses, while pentobarbital reversed the distribution of responses by increasing low rates and decreasing high rates. The pigeons maintained their original asymmetric distribution of responses during the 1 1/2-year-long study, despite schedule alterations and drug administrations.     

On conditioned reinforcing effects of negative discriminative stimuli

Observing responses by pigeons were studied during sessions in which a food key and an observing key were available continuously. A variable-interval schedule and extinction alternated randomly on the food key. In one condition, food-key pecking during extinction decreased reinforcement frequency during the next variable-interval component, and in the other condition such pecking did not affect reinforcement frequency. Observing responses either changed both keylight colors from white to green (S+) or to red (S−) depending on the condition on the food key, or the observing responses never produced the S+ but produced the S− when extinction was in effect on the food key. Observing responses that produced only S− were maintained only when food-key pecking during extinction decreased reinforcement frequency in the subsequent variable-interval component. The red light conformed to conventional definitions of a negative discriminative stimulus, rendering results counter to previous findings that production of S− alone does not maintain observing. Rather than offering support for an informational account of conditioned reinforcement, the results are discussed in terms of a molar analysis to account for how stimuli acquire response-maintaining properties.     

Some temporal properties of behavioral contrast

Pigeons were rewarded on a variable time interval for pecking a translucent key illuminated with either a 45 degrees or a vertical line. The key illumination changed every 2 min during daily 1-hr sessions. When the rates of pecking were stable, reinforcement was omitted in the presence of the 45 degrees line. Responding in the presence of the vertical line increased. This increase did not disappear when responses to the 45 degrees line were once more reinforced, but when reinforcements for responses in the presence of the 45 degrees line were again omitted, responding to the vertical line increased again. After the second alternation of these two procedures, the increased responding to the vertical line appeared when responses were not reinforced in the presence of the 45 degrees line, and disappeared when reinforcement was available during both stimuli. In a second experiment, the key illumination changed between sessions only, so that 1-hr sessions of reinforcement and non-reinforcement occurred on alternate days. Responding to the vertical line still increased when responding to the 45 degrees line was not reinforced, but the increase tended to disappear during the session.     

A note on chaining and temporal discrimination

Four pigeons were exposed to a two-key DRL procedure. At the start of a trial, key A was illuminated. A response to the lighted key turned it off and simultaneously illuminated key B. Reinforcement was available for responses on key B which followed the initial key A response by more than 2 sec. In the course of exposure to these conditions, all birds acquired superstitious response chains on key A. The distribution of the number of responses on key A preceding a key B response and the distribution of intervals elapsing from the initial key A response to the key B response were of the same form. The suggestion is made that the superstitious responding on key A served to mediate the required delay interval. However, when intervals between successive key A responses were recorded for one subject, they were found to be regularly spaced in time. Thus, the problem remains of how this behavior is itself timed.     

Studies in Vision: IV. The Interactions of Rods and Cones in After-Sensations

Fixed-ratio (FR) size was increased for pigeons (N = 6), while the number of eating responses at reinforcement was either held constant or increased. Also, FR size was held constant while the number of eating responses at reinforcement was increased. Major findings were as follows: (a) when eating responses were held constant, higher FR requirements led to stable key rates and postreinforcement pauses; (b) allowing more eating responses at successively higher FR requirements led to stable key rates and postreinforcement pauses; (c) at high FR requirements which produced low key rates, increasing the number of eating responses at reinforcement increased key rates; and (d) eating response rates varied systematically with key rates.     

Aversive aspects of a schedule of positive reinforcement

Six male White Carneaux pigeons were trained to peck at one of two keys to obtain food on several fixed-ratio schedules of reinforcement. Concurrently, the first response on a second key could, I—change the conditions of visual stimulation and remove the food reinforcement contingency, II—change the conditions of stimulation and have no effect upon the reinforcement contingency, or III—do nothing. The second response on the stimulus change key always restored baseline conditions. When second-key responses produced a stimulus change, the number of such responses was a function of the ratio value on the first key. Typically, second-key responses occurred before the start of fixed-ratio runs. The duration of stimulus change periods was an exponential function of the number of responses required for reinforcement when the possibility for reinforcement was not disturbed by periods of stimulus change (Condition II).     

Biasing the pacemaker in the behavioral theory of timing

In the behavioral theory of timing, pacemaker rate is determined by overall rate of reinforcement. A two-alternative free-operant psychophysical procedure was employed to investigate whether pacemaker period was also sensitive to the differential rate of reinforcement. Responding on a left key during the first 25 s and on a right key during the second 25 s of a 50-s trial was reinforced at variable intervals, and variable-interval schedule values during the two halves of the trials were varied systematically. Responding on the right key during the first 25 s and on the left key during the second 25 s was not reinforced. Estimates of pacemaker period were derived from fits of a function predicted by the behavioral theory of timing to right-key response proportions in consecutive 5-s bins of the 50-s trial. Estimates of pacemaker period were shortest when the differential reinforcer rate most strongly favored right-key responses, and were longest when the differential reinforcer rate most strongly favored left-key responses. The results were consistent with the conclusion that pacemaker rate is influenced by relative reinforcer rate.     

Inhibitory stimulus control in concurrent schedules

Six pigeons were exposed to two keys, a main key and a changeover key. Pecking the main key was reinforced on a variable-interval 5-min schedule when the key was blue and never reinforced when the key displayed a vertical line on a blue background. Each peck on the changeover key changed the stimulus displayed on the main key. Each subject was given two generalization tests, consisting of presentations on the main key of six orientations of the line on the blue background, with no reinforcements being given. In one test changeover-key pecks changed the stimulus; in the other test the changeover key was covered and the experimenter controlled stimulus changes. Both responses to the six stimuli and time spent in the presence of the stimuli gave U-shaped gradients when the changeover key was operative. With most subjects, absolute rates of responding to each stimulus produced unsystematic gradients, whether or not the changeover key was operative.     

Response selection influences inhibition of return

Previous work has suggested that there may be a relationship between the magnitude of inhibition of return (IOR) and the number of possible responses in the perceptual‐motor task. To test this possibility, the present experiment used a display that contained four horizontally aligned cue/target locations. In different blocks of trials, subjects responded to the target either with a one‐response detection key press, a two‐response localisation key press, or a four‐response localisation key press. The results showed the largest magnitude of IOR was found in the one‐response condition and the least in the four‐response condition. These results suggest that IOR may be most effective in inhibiting relatively prepotent responses and the inhibitory effect weakens when responses require more intricate sensorimotor mappings.     

Choice, rate of reinforcement, and the changeover delay

Pigeons distribute their responses on concurrently available variable-interval schedules in the same proportion as reinforcements are distributed on the two schedules only when a changeover delay is used. The present study shows that this equality between proportions of responses and proportions of reinforcements (“matching”) is obtained when the value of the changeover delay is varied. When responses are partitioned into the set of rapid response bursts occurring during the delay interval and the set of responses occurring subsequently, the proportion of neither set of responses matches the proportion of reinforcements. Instead, each set deviates from matching but in opposite directions. Matching on the gross level results from the interaction of two patterns evident in the local response rates: (I) the lengthening of the changeover delay response burst is accompanied by a commensurate decrease in the number of changeovers; (2) the changeover delay response burst is longer than the scheduled delay duration. When delay responses are eliminated by introducing a blackout during the delay interval, response matching is eliminated; the pigeon, however, continues to match the proportion of time spent responding on a key to the proportion of reinforcements obtained on that key.     

Reinforcer effectiveness as a function of reinforcer rate and magnitude: a comparison of concurrent performances

Pigeons' pecks on each of two concurrently available response keys were reinforced under a variable-interval schedule that sometimes allotted food-pellet deliveries to one key and sometimes to the other. The keys differed in the number of reinforcements assigned to each and in the number of pellets delivered during each reinforcement. When the total quantity of food associated with each key during a session was constant, the proportion of responses to a key depended on the particular combinations of reinforcer rate and reinforcer magnitude scheduled on each key. A given quantity of food generated more responding on a key when it was delivered frequently in small amounts than when it was delivered infrequently in large amounts.     

On the development of stimulus control

Pigeons were trained to peck one key when presented with white noise at any of five intensities lower than a reference intensity, and to peck another key when presented with white noise at any of five intensities greater than the reference intensity. The shape of the stimulus control curves (proportion of responses to one key versus stimulus intensity) changed from a horizontal line at the beginning of training to the sigmoid form of typical psychometric functions at the end of training. The development of stimulus control is described in terms of a model based on the theory of signal recognition and a concept of attention.     

Preference for mixed-interval versus fixed-interval schedules

Pigeons were trained on a two-link concurrent chain schedule in which responses on two keys were reinforced according to independent variable-interval schedules by the production of a change in key color. Further responses on the key on which the stimulus change had been produced gave a single food reinforcement and a return to concurrent variable-interval conditions. On one key the terminal link was a two-valued mixed-interval schedule, while on the other, the terminal link was a fixed-interval schedule. When the mixed-interval values were kept constant and the fixed-interval values varied, relative response rates in the initial concurrent links matched relative reinforcement rates in the terminal links when these were computed from cubic transformations of the reciprocals of the intervals comprising the terminal link schedules.     

Visual and auditory accessory stimulus offset and the Simon effect

We investigated the effect on the right and left responses of the disappearance of a task-irrelevant stimulus located on the right or left side. Participants pressed a right or left response key on the basis of the color of a centrally located visual target. Visual (Experiment 1) or auditory (Experiment 2) task-irrelevant accessory stimuli appeared or disappeared at locations to the right or left of the central target. In Experiment 1, responses were faster when onset or offset of the visual accessory stimulus was spatially congruent with the response. In Experiment 2, responses were again faster when onset of the auditory accessory stimulus and the response were on the same side. However, responses were slightly slower when offset of the auditory accessory stimulus and the response were on the same side than when they were on opposite sides. These findings indicate that transient change information is crucial for a visual Simon effect, whereas sustained stimulation from an ongoing stimulus also contributes to an auditory Simon effect.     

Signal probability, reinforcement and signal detection.

Five pigeons were trained to detect differences in light intensity. Two stimuli, S1 and S2, differing in intensity, were arranged on the center key of a three-key chamber according to set probabilities. A peck on the center key turned on the two side keys. When S1 was presented on the center key, a peck on the left key was "correct" and when S2 was presented, a peck on the right key was "correct." Correct responses produced reinforcement and incorrect responses produced 3-second blackout. Detection performance was measured under three procedures. The first was a standard signal-detection design in which the probability of S1 was varied and the number of reinforcements obtained for correct responses to S1 was allowed to covary. In the second procedure, the probability of S1 was again varied but the distribution of reinforcements between the two choices was kept equal. In the third procedure, probability of S1 was held constant while the distribution of reinforcements was varied between the two choices. Changes in response bias were a function of variations in the relative reinforcement ratio for the choice responses and not a function of variations in the probability of stimulus presentation. Discriminability remained constant across the three procedures.     

ChoiceKey: A real-time speech recognition program for psychology experiments with a small response set

Psychological experiments often collect choice responses using buttonpresses. However, spoken responses are useful in many cases—for example, when working with special clinical populations, or when a paradigm demands vocalization, or when accurate response time measurements are desired. In these cases, spoken responses are typically collected using a voice key, which usually involves manual coding by experimenters in a tedious and error-prone manner. We describe ChoiceKey, an open-source speech recognition package for MATLAB. It can be optimized by training for small response sets and different speakers. We show ChoiceKey to be reliable with minimal training for most participants in experiments with two different responses. Problems presented by individual differences, and occasional atypical responses, are examined, and extensions to larger response sets are explored. The ChoiceKey source files and instructions may be downloaded as supplemental materials for this article from brm.psychonomic-journals.org/content/supplemental.