Fixed-ratio discrimination: effects of intermittent reinforcement

Four pigeons had discrimination training that required the choice of a left side-key after completing a fixed-ratio 10 on the center key, and a right side-key choice after fixed-ratio 20. Correct choices were reinforced on various fixed-interval, fixed-ratio, random-interval, and random-ratio schedules. When performance was examined across successive 15-second intervals (fixed-interval and fixed-ratio schedules) accuracy was high in the first 15-second interval, decreased in one or several of the next 15-second intervals, and then increased again as reinforcement was approached. When performance was examined across correct trials on fixed-interval and fixed-ratio schedules, accuracy was lowest immediately after reinforcement, followed by a systematic increase in accuracy as the number of correct choices increased. These patterns were due primarily to errors on fixed-ratio 20 trials. Systematic accuracy patterns did not occur on random-interval or random-ratio schedules. The results indicate that when choice patterns differed on fixed-interval and fixed-ratio schedules, the differences were due to the method of data analysis.     

Inverse relation between choice and local response rate with a schedule of response-produced blackouts

Pigeons were exposed to a two-key concurrent chains schedule in which identical frequencies and distributions of food presentations generated different response rates in the terminal links. An inverse relation between local rate of response in the terminal links and relative frequency of response in the initial links was observed. The high response rate was produced in one terminal link by a second-order schedule in which responding produced brief blackouts of the response key. Responding under the same schedule in the other terminal link did not produce blackouts. Under initial training and after spatial reversal of the terminal-link schedules, two of three pigeons had lower relative frequencies of response in the initial member of the chain with the higher terminal link response rate. The third pigeon showed no change in preference at reversal.     

Effects of response-produced stimuli upon conditional discrimination performance

In zero-delay matching procedures the performance of three groups of pigeons was examined when exteroceptive stimuli, response-produced stimuli associated with the completion of either of two fixed ratios, or a compound of exteroceptive and response-produced stimuli were available as samples. Exteroceptive samples were found to control a higher level of matching accuracy than response-produced samples, while compound samples controlled a higher level of accuracy than did exteroceptive samples alone. When all subjects were placed on a transfer procedure, during which the previously used red and green samples were replaced by horizontal and vertical lines, the availability of sample-specific fixed-ratios facilitated acquisition of the task.     

A comparison of the punishing effects of response-produced shock and response-produced time out

Electric shock and time out were compared as punishers in the squirrel monkey. At the parameters investigated, both suppressed responding to about the same degree. Scheduling punishment intermittently or administering pentobarbital reduced the effectiveness of both punishers. The effects of the punishers were different in that responding suppressed by shock recovered more within a session than responding suppressed by time out. Responding was suppressed after some shock-punishment components, but less often after time-out-punishment components. The similarities of the two punishers were more striking than the differences.     

Fixed-ratio pausing: Joint effects of past reinforcer magnitude and stimuli correlated with upcoming magnitude

Pigeons responded on fixed-ratio schedules ending in small or large reinforcers (grain presentations of different duration) interspersed within each session. In mixed-schedule conditions, the response key was lit with a single color throughout the session, and pausing was directly related to the past reinforcer (longer pauses after large reinforcers than after small ones). In multiple-schedule conditions, different colors accompanied the ratios ending in small and large reinforcers, and pausing was affected by the upcoming reinforcer as well as the past one. Pauses were shorter before large reinforcers than before small ones, but they continued to be longer after large reinforcers than after small ones. The influence of the past reinforcer was modulated by the magnitude of the upcoming reinforcer; in the presence of the stimulus before the small reinforcer, the effect of the past reinforcer was enhanced relative to its effect in the stimulus before the large reinforcer. These results show that pausing between ratios is jointly determined by two competing factors: past conditions of reinforcement and stimuli correlated with upcoming conditions.     

Fixed-ratio reinforcement of spaced responding

Responses by rats were reinforced with food under a second-order schedule involving fixed-ratio reinforcement of temporally spaced responses. Requirements of 20, 8, and 3 responses were examined. The typical characteristic of spaced responding was maintained under the ratio schedules: interresponse time distributions were similar to those typically seen, and were not noticeably affected by the ratio value. Comparison of total response rate, correct response rate, and accuracy showed correct response rate to be the most consistently affected by changes in the ratio value. Substantial evidence of schedule control was seen only for correct responses. Incorrect response records were erratic, but rates generally declined as reinforcement was approached. Correct response records were characterized by increasing rate as reinforcement was approached. It was suggested that the pattern of fixed-ratio performance revealed may be affected by the behavioral unit examined.     

Alcoholic blackouts: Phenomenology and legal relevance

Alcohol-induced amnestic periods (blackouts) are common to alcoholic and nonalcoholic drinkers. The use of alcoholic amnesia as evidence of incompetence to stand trial or in mitigation of criminal responsibility hinges upon the reversibility of amnesia and upon the voluntariness of intoxication and of the ensuing blackout. After discussions of the phenomenology of alcoholic blackouts and the role of alcoholic and nonalcoholic amnesia in criminal law, it is argued that the voluntary nature of alcohol consumption should not mitigate behavioral consequences in any drinker.     

Control of avoidance by a response-produced stimulus

Three pigeons were trained to press a foot pedal to postpone electric shock. The safety signal was a tone of 1000 Hz, which sounded for 5 sec following each press; silence therefore served as a warning signal. After the performance approached asymptote, test sessions were interspersed among the training sessions. Following a warm up, the shock was omitted (extinction), and no tone or a tone of 250, 500, 1000, 2000, or 4000 Hz was presented following each press for the remainder of the session. Gradients of generalization plotted in terms of the number of times the tone was produced on each test peaked at 1000 Hz, indicating that the performance was controlled by the frequency. Since this dimension is orthogonal to absence of tone, the gradient cannot be attributed to differences in the magnitude of change in the warning signal. It was concluded that response-produced stimuli reinforce avoidance behavior.     

Fixed-ratio escape and avoidance-escape from naloxone in morphine-dependent monkeys: effects of naloxone dose and morphine pretreatment.

Lever pressing by rhesus monkeys was maintained by morphine injections during four equally spaced sessions each day. During other periods, lever pressing was maintained by timeout from a continuous naloxone infusion (escape), or by timeout from a stimulus that preceded naloxone injections, or termination of the injections (avoidance-escape). As naloxone dose increased in the escape procedure, response rate increased to a maximum and then decreased. In the avoidance-escape procedure, response rate generally increased as naloxone dose increased, but the changes in rate were small compared to the excape procedure. Substitution of saline for naloxone in the escape procedure led to a very low response rates within three sessions. In the avoidance-escape procedure, rate decrements produced by saline substitution appeared to be related to the behavioral history of the monkey. Previous escape experience led to more rapid decreases in responding when saline was introduced, whereas responding was maintained for 15 sessions in a monkey without prior escape conditioning. Morphine pretreatment produced comparable, dose-dependent decreases in response rates in both procedures. The rate-decreasing effects of morphine were exacerbated when no naloxone was delivered in the escape procedure.     

Decreasing overt discrimination increases covert discrimination: Adverse effects of equal opportunities policies

Building on the moral licensing literature, this paper examines whether highlighting the successful implementation of an equal opportunities policy in a company leads to covert forms of discrimination in hiring decisions (i.e., expressing a preference for a white candidate over an equally qualified black/Moroccan candidate in an ambiguous context). Furthermore, moral self‐image is indirectly tested as a possible underlying mechanism. Two scenario studies first revealed that covert discrimination is more likely after highlighting a successful implementation of an equal opportunities policy in the company (study 1) and that elevated levels of moral self‐image are related to covert discrimination (study 2). Subsequently, a field study revealed that the presence of successful equal opportunities policies positively related to employees’ moral self‐image (study 3).     

Fixed-ratio performance under conditions of delayed reinforcement

Four rats were trained on a schedule in which completion of a fixed number of lever presses initiated a signalled delay period, at the end of which food was delivered. Lever presses made during the delay had no scheduled consequences. Delays of 12, 3, and 0.75 sec were used, and it was found that the latency of the first response after food (the post-reinforcement pause) increased with length of delay. There was, on the other hand, no consistent effect of delay upon rates of responding after the post-reinforcement pause.     

Two-key concurrent responding: response-reinforcement dependencies and blackouts

Two-key concurrent responding was maintained for three pigeons by a single variable-interval 1-minute schedule of reinforcement in conjunction with a random number generator that assigned feeder operations between keys with equal probability. The duration of blackouts was varied between keys when each response initiated a blackout, and grain arranged by the variable-interval schedule was automatically presented after a blackout (Exp. I). In Exp. II every key peck, except for those that produced grain, initiated a blackout, and grain was dependent upon a response following a blackout. For each pigeon in Exp. I and for one pigeon in Exp. II, the relative frequency of responding on a key approximated, i.e., matched, the relative reciprocal of the duration of the blackout interval on that key. In a third experiment, blackouts scheduled on a variable-interval were of equal duration on the two keys. For one key, grain automatically followed each blackout; for the other key, grain was dependent upon a response and never followed a blackout. The relative frequency of responding on the former key, i.e., the delay key, better approximated the negative exponential function obtained by Chung (1965) than the matching function predicted by Chung and Herrnstein (1967).     

The differential reinforcement of reward-produced and response-produced stimuli

In two experiments, groups received successive large-reward trials on odd-numbered days and successive small-reward trials on even-numbered days in the same gray alleyway. This produced a discrimination problem in which the memory of large reward (S^L) was reliably discriminative of large reward and the memory of small reward (S^S) was reliably discriminative of small reward. Intertrial interval (ITI) was varied both between and within groups. In the within-groups manipulation, ITI separating S+ trials differed from that separating S- trials. Experimental groups learned the discrimination, running slower to S^S (S- cue) than to S^L (S+ cue), and showed a negative contrast effect, running slower to S- than a small-reward control group. Discrimination was somewhat faster at massed than at spaced trials. The within-groups manipulation of ITI suggested that the effects of ITI were mediated by time-dependent changes in internal cues produced by reward events and by the instrumental response. The control exercised by internal cues was shown to be associative rather than nonassociative, e.g., motivational. Similarities with, and implications for, conventional brightness differential conditioning were discussed.     

Duration discrimination: effects of probability of stimulus presentation

Monkeys initiated a stimulus by pressing on the center of three levers and the stimulus terminated independently of behavior 60, 80, 90, or 100 sec later. Presses on the right lever were reinforced with food following the three briefer durations, and presses on the left lever, following the 100-sec duration. Incorrect responses produced a 10-sec timeout. Probability of presenting the 100-sec duration was manipulated in the range from 0.25 to 0.75, with the probabilities of the briefer durations remaining equal and summing to one minus the probability of the 100-sec duration. Percentage of responses on either side lever was functionally related to both the probability of presenting the 100-sec stimulus and to stimulus duration. An analysis of the data based on the theory of signal detection resulted in operating characteristics that were linear when plotted on normal-normal coordinates. The percentage of responses on either lever approximated the optimal values for maximizing reinforcement probability in each condition of the experiment.     

Right-left discrimination: effects of handedness and educational background

The present study investigated right left discrimination, with a paper-and-pen test with cartoon figures. The test consisted of line drawings of a person with no, one, or both arms crossing the vertical axis of the body in the figure. The subjects' task was to mark with a pencil, as fast as possible, which was the right or left hand in the figure. The line drawings were viewed from the back, from the front, or randomly alternating between the back and front views. Two studies were conducted. The first consisted of 393 adults: 153 males and 240 females; 338 right-handers and 55 left-handers. The results showed that the males performed better than the females. The left-handers and the right-handers performed equally well. However, the left-handed males performed better than the right-handed males. There was no difference in performance between the right-handed and the left-handed females. The second study consisted of 175 right-handed college students: 63 psychology students. 54 medical students, and 58 law students. The main finding was that the medical students performed better than the psychology students for all figure orientation subtests and for all arm positions. In comparison with the law students, the medical students performed at the same level on the back view subtest, but they performed better on the front view subtest and on two out of three arm positions on the alternating view subtest.     

Fixed-ratio punishment by timeout of concurrent variable-interval behavior

Pigeons' responding was maintained by two concurrently available variable-interval reinforcement schedules. A fixed-ratio punishment schedule of timeout periods from the concurrent reinforcement schedules was arranged for responding during one of the variable-interval schedules. The greater the probability of a timeout after a response on the punished variable-interval schedule (the smaller the fixed ratio that produced timeout), the greater the decline in the relative punished response rates. Relative reinforcement rates remained invariant when relative response rates declined. Both behavioral contrast and induction effects were observed on the unpunished variable-interval schedule as a function of timeout punishment of the other schedule.     

Auditory discrimination: a three-variable analysis of intensity effects

The acquisition of auditory intensity discriminations in rats trained on multiple variable-interval extinction schedules was studied as a function of some of the variables that contribute to the speed of development of differential responding and the final level attained. The effects of three variables were isolated and studied in detail: (1) the decibel difference between the discriminative stimuli (intensity difference); (2) the intensity relationship between the stimuli (relative intensity); and (3) the position of the stimuli on the intensity continuum (absolute intensity). Each of the three variables generated orderly relationships and interacted with one another to produce complex effects upon differential responding.     

Sequential effects on discrimination reversal

In Experiment 1 the sequence of trials to the positive (S+) and negative (S?) discriminanda was varied between groups during acquisition and reversal of a successive brightness discrimination. In Experiments 2 and 3, groups received different reward sequences in Phase 1 within S+. In general, groups given transitions from nonrewarded trials to rewarded trials (N-R transitions) in Phase 1 learned both the original discrimination and its reversal more slowly than groups given schedules devoid of N-R transitions. The results were discussed in relation to previously reported effects of partial reinforcement on acquisition and reversal of a discrimination and the role of sequential variables and internal, reward-produced cues in discrimination learning, reversal learning, and nonreversal shifts.