Self-control revisited: Some factors that affect autoshaped responding

Pigeons were exposed to autoshaping procedures under which 50% of red key illuminations were followed by 9-sec food deliveries, and 50% of blue key illuminations were followed by 3-sec food deliveries. When all key illuminations were 6 sec, pigeons preferred the red stimulus. Subsequent manipulations demonstrated that preference could be shifted to the blue stimulus by either increasing the duration of the red stimulus or imposing a delay interval between the offset of that stimulus and food delivery. A final experiment demonstrated that, in two of three subjects, preference for key illuminations associated with longer, but delayed, food deliveries generally increased as the duration of all key illuminations was lengthened. These results, obtained under conditions where keypecking had no programmed consequences, are similar to those previously observed under procedures involving a positive response-food dependency.

The schism between experimental and applied behavior analysis: Is it real and who cares?

This paper addresses the relationship between the experimental analysis of behavior and applied behavior analysis. Citation data indicate that across time the Journal of the Experimental Analysis of Behavior, and other experimental sources, have been referenced increasingly infrequently in the Journal of Applied Behavior Analysis, Behavior Therapy, and Behavior Research and Therapy. Such sources are now rarely cited in these journals, and never have been regularly referenced in Behavior Modification. Although their proper interpretation is far from certain, these data partially support recent suggestions that the experimental analysis of behavior and applied behavior analysis are largely separate, insular fields. A questionnaire, mailed to the editorial staffs of the Journal of the Experimental Analysis of Behavior and the Journal of Applied Behavior Analysis, was intended to gather further information about the alleged schism between the fields. Few respondents regularly read both journals, publish in both journals, or find both journals useful in their current research efforts. The majority of editors of both journals indicated that the fields were growing apart, although there was no consensus that this is harmful for behavior analysis. Most editors of the Journal of Applied Behavior Analysis reported that research published in the Journal of the Experimental Analysis of Behavior has decreased in value to applied researchers across time; most editors of the Journal of the Experimental Analysis of Behavior indicated that research published there has not changed in applied value. Several respondents commented at length concerning the relationship of experimental and applied behavior analysis. These comments, many of which appear in the article, reveal a marked plurality of views.

Effects of clozapine on fixed-consecutive-number responding in rats: a comparison to other neuroleptic drugs

The effects of clozapine and several other neuroleptic drugs were examined in rats responding under fixed-consecutive-number (FCN) schedules with minimum response requirements of 4 and 8. Under these schedules, rats were trained to respond either 8 or more times or 4 or more times on one lever, and then respond once on a second lever. In one component of these schedules, an external discriminative stimulus was presented following the completion of the response requirement on the first lever, whereas no stimulus change was programmed under the other. Under the FCN 8 schedule without the external discriminative stimulus, clozapine produced large dose-dependent decreases in accuracy (percent of reinforced response runs), whereas molindone produced small decreases in accuracy. Neither clozapine or molindone, however, altered accuracy under the FCN 4 without the external discriminative stimulus. Under these same schedules, loxapine, chlorpromazine, haloperidol and thioridazine produced small increases in accuracy at intermediate doses without affecting accuracy at the low and high doses. None of the neuroleptics evaluated produced accuracy-altering effects under the FCN schedules with the external discriminative stimulus. In general, all of these drugs decreased response rates in a dose-dependent fashion. The order of potency for the rate-decreasing effects of these drugs was loxapine greater than haloperidol greater than molindone greater than clozapine = chlorpromazine greater than thioridazine. Thus, the effects of clozapine on accuracy under the FCN schedules without the external discriminative stimulus differed qualitatively from those of other neuroleptic agents.

Differential effects of opioid and nonopioid analgesics on conditional discriminations in pigeons

Under the fixed-consecutive-number schedule (FCN), pigeons were reinforced for responding eight or more times on one response key (work key), and then responding once on a second response key. In one component of this schedule, an external stimulus signalled the completion of the response requirement on the work key (FCN 8-SD), whereas no stimulus change was programmed under the other (FCN 8). Across a range of doses, the mu opioid agonist morphine, the kappa opioid agonist U50,488 and the opioid antagonist naloxone had no consistent effect on accuracy under either FCN schedule. Naloxone and accuracy under either FCN schedule. Naloxone and U50,488 produced a general flattening of the conditional probability functions by decreasing the conditional probability of response runs exceeding the minimum response requirement of eight consecutive responses on the work key. The sigma agonists phencyclidine and (+)N-allylnormetazocine and the nonopioid analgesics clonidine and l-nantradol produced large decreases in accuracy under the FCN 8 and small decreases under the FCN 8-SD. With the exception of (+)N-allylnormetazocine, these drugs consistently increased the conditional probability of responses runs shorter than the minimum response requirement on the work key. These findings indicate that the accuracy-altering effects of some opioid and nonopioid analgesics depend in part on the type of discrimination task.

Comparison of the discriminative stimulus properties of U50,488 and morphine in pigeons

Pigeons were trained to discriminate a dose of either 4.2 mg/kg of U50,488 or 1.0 mg/kg of morphine from water using a two-key drug discrimination procedure. In U50,488-trained pigeons, the kappa agonist bremazocine occasioned drug-appropriate responding during substitution tests, whereas ethylketocyclazocine and ketocyclazocine occasioned intermediate levels of drug-appropriate responding up to and including doses that markedly suppressed response rates. The mu agonists morphine, l-methadone and fentanyl produced responding predominantly on the water-appropriate key. In morphine-trained pigeons, l-methadone, fentanyl, ethylketocyclazocine and ketocyclazocine, but not U50,488 and bremazocine, occasioned drug-appropriate responding. Nonopioid compounds, such as d-amphetamine, pentobarbital, phencyclidine and (+)-SKF 10,047 produced responding predominantly on the water-appropriate key in both U50,488- and morphine-trained pigeons. During tests of antagonism, a 0.1 and 1.0 mg/kg dose of naloxone antagonized completely the discriminative stimulus properties of the training dose of U50,488 and morphine, respectively. In addition, morphine displayed a substantially longer duration of action than U50,488, in that intermediate levels of drug-appropriate responding were evident as long as 4 hr after the administration of morphine and only 1 hr after the administration of U50,488. Over a period of approximately 8 months, the dose-effect curves for the discriminative stimulus properties of both drugs were unchanged. The present findings illustrate further the unique behavioral response of pigeons to the discriminative stimulus properties of the kappa agonists, and establishes that pigeons can discriminate between mu and some kappa agonists.

Evaluation of the effects of opioid agonists and antagonists under a fixed-consecutive-number schedule in rats

The effects of several opioid agonists and the opioid antagonist naloxone were examined in rats responding under a fixed-consecutive-number (FCN) schedule. Under this schedule, a reinforced response run consisted of responding eight or more times on one response lever, and then responding once on a second response lever. In one component of this schedule, an external discriminative stimulus signalled the completion of the response requirement on the first lever, whereas no stimulus change was programmed in the other. Morphine, l-methadone, U50488, ketocyclazocine, phencyclidine, and (+/-)N-allylnormetazocine decreased the percent of reinforced response runs (accuracy) under the FCN schedule without the external discriminative stimulus, but had no effect under the FCN schedule with the external discriminative stimulus. Naloxone and bremazocine, in contrast, had no effect on the accuracy of the discrimination under either FCN schedule. With the exception of bremazocine and U50488, which increased rates of responding at low doses, all drugs produced comparable decreases in rates of responding under both FCN schedules. During tests of antagonism, a 0.1 mg/kg dose of naloxone reversed completely the accuracy-decreasing effects produced by U50488 and morphine. The rate-decreasing effects of morphine and U50488 were reversed completely by a 0.01 and 1.0 mg/kg dose of naloxone, respectively. These results suggest that the addition of an external discriminative stimulus can modulate the disruptive effects of opioids, and that mu, sigma and some kappa agonists produce similar effects when evaluated under the FCN schedules.

Choice between sequences of fixed-ratio schedules: effects of ratio values and probability of food delivery

Pigeons were exposed to schedules of food delivery that consisted of two sequential fixed ratios. When alternative sequences provided two food deliveries per 50 responses, the schedule with the shorter initial fixed-ratio value was consistently preferred. Progressively reducing from 1.0 to .25 the probability of food delivery following completion of the second fixed ratio of the sequence with the shorter initial fixed ratio did not reduce preference for this sequence. Moreover, the sequence with the shorter initial fixed ratio also was preferred when the probability of food delivery following completion of the initial ratio in that sequence was progressively reduced from 1.0 to .5, although preference shifted to the alternative when the probability was reduced to 0. These findings suggest that the length of the initial fixed ratio was a primary determinant of choice. Subsequent manipulations demonstrated, however, that when the initial fixed ratios of the two alternatives were equal, changes in the ratio value and probability of food delivery following completion of the second fixed ratio lawfully affected choice.

Evaluation of the effects of opioid agonists and antagonists under a delayed matching-to-sample procedure in pigeons

The effects of several opioid agonists and antagonists were examined in pigeons performing under a delayed matching-to-sample procedure. The mu agonists morphine and l-methadone, the kappa agonists U 50,488 and ethylketocyclazocine, and the opioid antagonist naloxone had no effect on the accuracy of responding. These drugs were, however, behaviorally active as evidenced by the dose-dependent decreases in rates of responding associated with their administration. In contrast, the sigma agonists (+) N-allylnormetazocine and phencyclidine decreased the accuracy of responding in a dose-dependent fashion. The relative magnitude of these drug-induced decreases in accuracy were similar across the no delay (0-s), short (2-s), and long (8-s) delay intervals. For these drugs, accuracy-decreasing effects were obtained only at doses that reduced rates of responding. The results of the present investigation parallel those reported in pigeons responding under drug discrimination tasks, in which the discriminative stimulus properties produced by the mu and kappa agonists are similar to each other but distinguishable from those produced by the sigma agonists.

Effects of phenobarbital in combination with phenytoin or valproic acid on the delayed-matching-to-sample performance of pigeons

The present study examined the effects of phenobarbital (5, 10, 20, and 40 mg/kg), phenytoin (2.5, 5, 7.5, and 15 mg/kg), and valproic acid (40, 60, 80, and 120 mg/kg), and those of phenobarbital (10 and 20 mg/kg) in combination with phenytoin (2.5, 5, and 7.5 mg/kg) or valproic acid (40, 60, and 80 mg/kg), on the delayed-matching-to-sample performance of pigeons. In general, high doses of each individual drug reduced accuracy. Drug combinations also reduced accuracy relative to control values. Reductions in accuracy produced by drug combinations were very similar in magnitude to those predicted by a response-addition model of drug interaction.

Modulation of the behavioral effects of anticonvulsant drugs by an external discriminative stimulus in the pigeon

The effects of the anticonvulsant drugs valproic acid, phenytoin, phenobarbital and diazepam were examined in pigeons performing under a fixed-consecutive-number schedule with and without an added external discriminative stimulus. Under these schedules, a reinforced response run consisted of responding between eight and 12 times on one response key (work key) and then responding once on a second response key (reinforced key). For one group of pigeons, an external discriminative stimulus signaled completion of the response requirement on the work key, whereas no stimulus change was programmed for the other group. Phenobarbital (5-60 mg/kg) and diazepam (0.5-6 mg/kg) produced large decreases in reinforced response runs (accuracy) and rates of responding. The magnitude of these accuracy- and rate-decreasing effects was larger in the group without the external discriminative stimulus. Under both schedules, these drugs produced pronounced increases in the probability of switching to the reinforcement key before completion of the minimal response requirement on the work key. Valproic acid (20-160 mg/kg) and phenytoin (1.25-10 mg/kg) also decreased both accuracy and rates of responding. Although the accuracy-decreasing effects of these drugs were relatively small in magnitude, they were consistently larger in the group without the external discriminative stimulus. These data suggest that the addition of an external discriminative stimulus attenuates the disruptive behavioral effects of anticonvulsant drugs.

Chronic effects of clonazepam, phenytoin, ethosuximide, and valproic acid on learning in pigeons as assayed by a repeated acquisition procedure

The acute and chronic effects of the antiepileptic drugs clonazepam (0.06, 0.13, and 0.25 mg/kg), phenytoin (2.5, 5, and 7.5 mg/kg), ethosuximide (40, 80, and 120 mg/kg), and valproic acid (40, 80, and 120 mg/kg) were evaluated in pigeons responding under a repeated acquisition procedure. At certain doses, acute administrations of all drugs impaired learning (i.e., increased errors) and reduced rate of responding. Appreciable tolerance developed to these effects with chronic exposure, although the physiological mechanism responsible for this outcome is unknown.

Effects of anticonvulsant drugs under automaintenance and negative automaintenance procedures

The behavioral effects of phenytoin, phenobarbital, clonazepam, valproic acid, and ethosuximide were evaluated in food-deprived pigeons performing under automaintenance and negative automaintenance procedures. Under the automaintenance procedure, brief periods of key illumination were followed by food delivery without regard to the subject's behavior. In most instances, when drugs were not given this procedure engendered high rates of keypecking during almost all key illuminations (trials). Acute administrations of phenytoin (10-20 mg/kg), valproic acid (40-120 mg/kg), and ethosuximide (40-120 mg/kg) produced generally dose-dependent decreases in percent trials with a response and rate of responding. Although phenobarbital (30-60 mg/kg) and clonazepam (2.5-7.5 mg/kg) produced little obvious effect on percent trials with a response, these drugs generally increased rate of responding. Under the negative automaintenance procedure, food delivery followed only key illuminations during which keypecking did not occur. Keypecking occurred at a low rate under this procedure, with no responses occurring during the majority of key illuminations. Thus, this procedure appeared to involve responding elicited by respondent conditioning but suppressed by the response-dependent omission of food. Across the same dose ranges evaluated under the automaintenance procedure, clonazepam and phenobarbital generally increased percent trials with a response and rate of responding in dose-dependent fashion. Phenytoin similarly increased percent trials with a response but had little consistent effect on rate of responding. Ethosuximide and valproic acid failed to affect responding under this procedure.

Chronic effects of ethosuximide, phenytoin, clonazepam, and valproic acid on the delayed-matching-to-sample performance of pigeons

Acute and chronic effects of ethosuximide (40, 80, and 120 mg/kg), phenytoin (2.5, 5, and 7.5 mg/kg), clonazepam (0.25, 0.5, and 0.75 mg/kg), and valproic acid (40, 80, and 120 mg/kg) were examined in pigeons performing under a delayed-matching-to-sample procedure. Acute administration of clonazepam or valproic acid produced generally dose-dependent decreases in accuracy; over 50 sessions of daily exposure, complete or nearly complete tolerance developed to the accuracy-reducing effects of these drugs. Whether administered acutely or chronically, ethosuximide and phenytoin failed to affect accuracy. When given acutely, all drugs typically reduced rate of responding to the sample stimulus. A degree of tolerance appeared to develop to the rate-decreasing effects of all of the drugs tested.

Effects of clonazepam and ethosuximide on the responding of pigeons under a fixed-consecutive-number schedule with and without an external discriminative stimulus

The effects of the anticonvulsant drugs clonazepam and ethosuximide were examined in pigeons performing under a fixed-consecutive-number schedule with and without an added external discriminative stimulus. Under these schedules, food was delivered whenever subjects responded between and 8 and 12 times on one response key (work key), and then responded once on a second response key (reinforcement key). For one group, an external discriminative stimulus signalled completion of the response requirement on the work key, while no stimulus change was programmed for the other group. Clonazepam (0.06-0.75 mg/kg) produced dose-dependent decreases in percentage of reinforced runs and rate of responding for both groups. The magnitude of the accuracy-decreasing effect was generally greater in the group without the external discriminative stimulus. For this group, the higher doses of clonazepam produced pronounced increases in switching to the reinforcement key before completing the minimum requirement of eight consecutive responses on the work key. No consistent patterns of errors were evident for the subjects with the added external discriminative stimulus. Although ethosuximide (20-160 mg/kg) produced dose-dependent decreases in rate of responding, it had little effect on the percentage of reinforced runs or the run length distributions. These findings are consistent with previous reports indicating that clonazepam, but not ethosuximide, substantially disrupts performance under operant tasks requiring conditional discriminations. These data also suggest that the addition of an external discrimination stimulus attenuates the disruptive behavioral effects of clonazepam.

Effects of valproic acid and ethosuximide on the responding of pigeons maintained under a multiple fixed-ratio fixed-interval schedule of food delivery

The effects of valproic acid and ethosuximide were examined in pigeons responding under a multiple Fixed-Ratio 50 Fixed-Interval 90-sec schedule of food delivery. When given acutely 30 min prior to behavioral testing, both valproic acid (40, 60, 80, 100, and 120 mg/kg) and ethosuximide (40, 60, 80, 100, and 120 mg/kg) produced generally dose-dependent decreases in responding under both the Fixed-Ratio and Fixed-Interval components. Detailed analysis of drug effects on the temporal distribution of responding under the Fixed-Interval failed to reveal rate-dependent effects for either drug. Varying the presession injection interval from 15 to 120 min indicated that both valproic acid and ethosuximide reduced responding to the greatest extent when given 30 or 60 min before behavioral testing. These results indicate that the anticonvulsants valproic acid and ethosuximide similarly affect schedule-controlled responding, although previous studies have revealed the drugs to have different effects under other procedures.

Effects of phenytoin, phenobarbital, and valproic acid, alone and in selected combinations, on schedule-controlled behavior of rats

The present study examined the effects of phenytoin (20, 30, 40, and 50 mg/kg), phenobarbital (10, 20, 30, and 40 mg/kg), and valproic acid (80, 120, 160, and 240 mg/kg), and those of phenobarbital (10 and 30 mg/kg) combined with phenytoin (20, 30, and 40 mg/kg) or valproic acid (80, 120, and 160 mg/kg), on the lever pressing of rats maintained under fixed-ratio and interresponse-time-greater-than-t schedules of food delivery. High doses of each individual drug significantly decreased mean group response (and reinforcement) rate under the fixed-ratio schedule. No dose of an individual agent significantly affected mean group response rate under the interresponse-time-greater-than-t schedule, although high doses of phenobarbital and valproic acid significantly reduced the mean group reinforcement rate under this schedule. When given in combination, phenobarbital and phenytoin and phenobarbital and valproic acid significantly reduced response (and reinforcement) rate under the fixed-ratio schedule and reinforcement rate under the interresponse-time-greater-than-t schedule. These reductions did not significantly differ in magnitude from those predicted by an additive model of drug interaction.

Effects of phenobarbital, clonazepam, valproic acid, ethosuximide, and phenytoin on the delayed matching-to-sample performance of pigeons

The effects of phenobarbital, clonazepam, valproic acid, ethosuximide, and phenytoin were examined in pigeons performing under a delayed matching-to-sample procedure. Clonazepam, valproic acid, ethosuximide, and phenytoin typically reduced the rate of responding to the sample stimulus, whereas phenobarbital usually increased response rates at high doses. Phenobarbital, clonazepam, and valproic acid produced generally dose-dependent decreases in accuracy; ethosuximide and phenytoin failed to do so. These results suggest that there are qualitative as well as quantitative differences in the effects of anticonvulsant drugs under the delayed matching-to-sample procedure.

Discriminative stimulus properties of tripelennamine in the pigeon

Pigeons trained under a two-key drug discrimination procedure eventually learned to discriminate the antihistaminic tripelennamine (5 mg/kg) from saline. When 0.63-7.5 mg/kg doses of tripelennamine were administered in generalization test sessions, the percentage of responses directed to the tripelennamine-appropriate key varied directly with dose. At certain doses, the discriminative stimulus properties of the antihistaminics, diphenhydramine and pyrilamine, clearly generalized to tripelennamine, whereas intermediate generalization was evident with the antihistaminics, chlorpheniramine and promethazine. Chlorpromazine, cimetidine, d-amphetamine, diazepam, morphine, pentazocine, phenobarbital, and sodium valproate failed to produce tripelennamine-like patterns of responding.

Discriminative stimulus properties of valproic acid in the pigeon

Pigeons were successfully trained to discriminate 60 mg/kg valproic acid from saline using a two-key drug discrimination procedure. When 5-80 mg/kg doses of valproic acid were administered during generalization tests the percentage of responses directed to the valproic acid-appropriate key varied directly with dose. The effects of administering the training dose of valproic acid at presession injection intervals ranging from 15 to 120 min were described by an inverted U-shaped function; the 30-min interval used during discrimination training engendered the largest percentage of valproic acid-appropriate responses. The discriminative stimulus properties of valproic acid failed to generalize to the anticonvulsant compounds phenobarbital (10, 20 mg/kg), phenytoin (2.5, 5 mg/kg), and ethosuximide (40, 80 mg/kg), indicating that not all anticonvulsant compounds share similar discriminative properties. Clonazepam (0.25, 0.50 mg/kg) and diazepam (1, 2 mg/kg), two benzodiazepines with anticonvulsant properties, produced quite different effects. The stimulus properties of valproic acid generalized to all doses of clonazepam, whereas intermediate generalization was evident with diazepam. Pentylenetetrazol (10, 20 mg/kg), chlorpromazine (5, 10 mg/kg), tripelennamine (2.5, 5.0 mg/kg), d-amphetamine (0.5, 1.0 mg/kg), morphine (1.25, 2.50 mg/kg), and imipramine (2.5, 5.0 mg/kg) induced only saline-like patterns of responding. The concomitant administration of pentylenetetrazol failed to antagonize the discriminative stimulus properties exerted by the training dose of valproic acid.

Effects of chlorprothixene, haloperidol, and trifluoperazine on the delayed-matching-to-sample performance of pigeons

The effects of chlorprothixene (4,6,8, and 10 mg/kg), haloperidol (0.13, 0.25, 0.38, and 0.5 mg/kg), and trifluoperazine (0.5, 1,2, and 3 mg/kg) were examined in pigeons responding under a delayed-matching-to-sample procedure in which delays of 0.5-, 1-, 2-, 4-, and 8-sec duration were arranged during each experimental session. Both chlorprothixene and trifluoperazine typically reduced accuracy (percent correct responses); the magnitude of this effect was generally largest at the longest delay values. Chlorprothixene was associated with an increased rate of responding to the sample stimulus in two of three subjects, whereas trifluoperazine almost always decreased response rate. Haloperidol at high doses decreased response rate, but failed to consistently impair accuracy at any dose or delay value.

Effects of anticonvulsants on learning: performance of pigeons under a repeated acquisition procedure when exposed to phenobarbital, clonazepam, valproic acid, ethosuximide and phenytoin

The effects of phenobarbital, clonazepam, valproic acid, ethosuximide and phenytoin were examined in pigeons performing under a repeated acquisition procedure. Clonazepam (0.06-0.75 mg/kg), valproic acid (40-120 mg/kg), ethosuximide (40-160 mg/kg) and phenytoin (2.5-15 mg/kg) produced generally dose-dependent decreases in rate of responding, whereas phenobarbital (5-50 mg/kg) had little consistent effect on response rate across the dose range studied. Phenobarbital and clonazepam produced dose-dependent increases in error rates. Although valproic acid and phenytoin generally increased errors relative to control values, this effect was not directly dose-dependent or consistent across subjects. A within-session analysis of the distribution of drug-induced increases in errors revealed that the main effect of phenobarbital, clonazepam, valproic acid and phenytoin was to increase errors during early acquisition (i.e., before the procurement of 15 or fewer reinforcers). Later in the session, a similar number of errors per reinforcer was made during drug and control sessions. In contrast to the other anticonvulsants examined, ethosuximide had little effect on error rates. These results suggest that there are qualitative as well as quantitative differences in the effects of anticonvulsant drugs under the repeated acquisition procedure.

Tripelennamine and pentazocine alone and in combination: effects on interresponse-time-greater-than-t responding of rats

The effects of tripelennamine (3, 6, 12, 18, and 24 mg/kg) and pentazocine (5, 10, 20, 30, and 40 mg/kg), given alone and in selected combinations, were determined in rats performing under an interresponse-time-greater-than-15-sec schedule of food delivery. Each drug alone produced statistically insignificant increases in response rates and statistically significant decreases in reinforcement rates. Combinations produced effects identical in direction to, and significantly greater than, those predicted by a simple additive model.

Effects of pentazocine and tripelennamine on analgesia

The analgesic effects of pentazocine and tripelennamine, alone and in combination, were assessed in rats with a hot plate apparatus. In Experiment 1, the combination of tripelennamine with chronic pentazocine produced analgesia at doses which were not analgesic when the drugs were given alone. This combination also reestablished analgesia in subjects made tolerant to pentazocine's effects. In Experiment 2, development of tolerance to the analgesic effects of pentazocine was delayed by addition of tripelennamine. These data may contribute to a rationale for the current popularity of combined pentazocine and tripelennamine abuse.

Effects of food deprivation on water intake induced by intermittent delivery of salted liquid food

The water intake of rats maintained through food deprivation at 70, 80, 90, and 100% of free-feeding body weights was examined under conditions where a small amount of sweetened condensed milk containing 8% sodium chloride was presented at one-minute intervals. For each of two subjects, number of licks and milliliters of water consumed varied inversely with body weight. This finding agrees with earlier reports concerning the effects of food deprivation on adjunctive behaviors induced by intermittent delivery of dry food.

Choice as a dependent measure in autoshaping: sensitivity to frequency and duration of food presentation

Previous investigations have shown that rate, latency, and percentage of trials with at least one response are somewhat insensitive measures of the strength of autoshaped responding. In the present studies, these measures were contrasted with the allocation of responding during simultaneous choice tests, a measure of response strength frequently used in operant paradigms. In two experiments, nine pigeons were exposed to a forward pairing autoshaping procedure. Training sessions consisted of the successive presentation of three stimuli, each followed by food on either 100%, 50%, or 0% of the trials. Choice testing involved the simultaneous presentation of the three stimuli. In Experiment I, all pigeons consistently directed their initial choice responses and the majority of subsequent responses to the stimulus always followed by food, despite the fact that during training sessions the response rates of most birds were highest in the presence of the stimulus followed by food on 50% of the trials. In Experiment II, rate, latency, and percentage of trials with at least one response did not change appreciably as a function of duration of feeder presentations. However, choice responding was lawfully affected by duration of feeder presentations. These data suggest that choice is perhaps a more sensitive measure of the strength of autoshaped responding than other, more commonly employed, indices.