A test for order relevance in a three-element serial learning task

Rats were trained in a straight runway on a simple three-element series of differing reward quantities. The first trial of the series ended with a two-pellet reward, and the second and third trials ended with a 12-pellet reward and a nonreward, respectively (2-12-0). All animals developed accurate anticipation of the terminal nonreward in the 2-12-0 series before it was rearranged for two test days during which the elements appeared in the order 12-2-0. The rats' anticipation of the terminal nonreward did not transfer to the reordered series, a result taken to mean that anticipation had been based upon interitem associations among memorial representations of the differing reward quantities. A second transfer test to 0-0-0, given after anticipation was reestablished to the 2-12-0 series, gave evidence that the ordinal position of the series elements was also a source of anticipation; the animals continued to run relatively slowly on the third trial in extinction. In neither transfer test was there evidence that the rats employed the strategy of enumerating rewarded trials, because counting is an order-irrelevant process.     

Reward schedule effects in extinction: Intertrial interval, memory, and memory retrieval

Rats were trained in a runway such that partial reward occurred on Trial 1 of the day and consistent reward on subsequent massed trials (Group PRT1), or consistent reward occurred on Trial 1 of the day and partial reward on subsequent massed trials (Group PRTM). Under spaced (24-hr) extinction, Group PRT1 was more resistant to extinction than Group PRTM and under massed (1-min) extinction, Group PRTM was more resistant to extinction than Group PRT1. These findings suggest that (a) distinctive stimuli are associated with Trial 1 of the day and with subsequent massed trials, (b) these distinctive stimuli function as retrieval cues for memories, memory retrieval being independent of intertrial interval, and (c) behavior in extinction is controlled by a stimulus compound consisting of the memory of nonreward plus stimuli which accompany the memory of nonreward on rewarded acquisition trials.     

Organized responding in instrumental learning: Chunks and superchunks

Two investigations attempted to determine if rats could learn that the second series of runway trials, the test series, was the same as the first series, the study series. Series were constructed from runway responses which terminated either in food reward (R) or nonreward (N). In the series RNR, for example, three successive responses terminated in R, N, and R, respectively. Rats manifested mastery of a series by running fast to R and slow to N. In Experiment 1 the test series (either RNR or RNN) occurred in a black runway about 15 s after the study series presented in a white runway. In Experiment 2 the test series (either RN or RRN) occurred in a gray runway about 15 min after the study series, also in a gray runway. In both experiments rats learned that the study series was the same as the test series. A hierarchical interpretation was suggested in which runway trials are organized into series, series being organized into lists.     

Schedules of reward shift in the double runway

Eighty food deprived rats received 62 trials in a double runway. On Trials 1-30, reward in the first goal box (GB1) was either always two food pellets or always zero pellets. All subjects received two pellets in the second goal box (GB2). On Trials 31-62 subjects in each preshift group (GB1 reward or GB1 nonreward) were shifted to the opposite GB1 reward level on 0, 25, 50, 75 or 100% of occasions. GB2 reward remained unaltered in all cases. For subjects experiencing reward decrease, second runway (A2) run and goal speeds after nonreward were generally enhanced, both within-group and in comparison with never rewarded controls. No such effect was evident on A2 start speed, nor was there any evidence to suggest that A2 performance after decreased reward was a function of the schedule of decrease. Increased GB1 reward resulted in general within-group impairment of A2 start and run speeds, with no effect on A2 goal performance. However, comparisons of speeds after increased reward with those of always rewarded controls revealed no difference on A2 start or run but indicated impairment of A2 goal performance. With the 50% schedule of reward increase, A2 run speeds after nonreward (the training level) exceeded those of never rewarded controls. Results are discussed with reference to McHose's contrast account of double runway phenomena and Amsel's frustration theory.     

The effects of post-acquisition-trial sodium amylobarbitone on subsequent extinction behaviour

In a one-trial-per-day runway task, previously trained rats were injected via temporary intravenous cannulae with Sodium Amylobarbitone (SA) 15 mg/kg, or saline, immediately following each of six acquisition trials, according to one of four regimes. The animals were then extinguished with no further drug or saline treatments. Those that had been consistently reinforced (CR) and consistently treated with saline extinguished faster than those that had been partially reinforced (PR) and consistently treated with saline: the brief PR schedule thus generated a typical PR extinction effect. PR animals that had received SA treatments following nonrewarded trials and saline treatments following rewarded trials extinguished faster than those that had received the opposite treatments. Post-nonreward SA treatment during acquisition thus led to a pseudo CR extinction effect, while post-reward SA treatment in acquisition led to an undistorted PR extinction effect. The results are interpreted as showing that there is a critical period occurring between some tens of seconds and a very few minutes after frustrative nonreward which is vulnerable to SA in a non-state-dependent manner, and on which frustrative nonreward's control of subsequent behaviour depends.     

Infantile handling and the extinction of responses acquired under food reward

A comparison was made of the runway behaviour of rats which had been handled from Days 1-21 and their non-handled litter mates. The training began on Day 70 after the animals were habituated to a restricted food schedule for 10 days. The subjects were given six trials each day in the runway and were rewarded with a 0.045 g. Noyes pellet. After 10 days of rewarded training trials, subjects were given 6 extinction trials a day for 10 days. Results showed that handled rats ran faster than non-handled rats during acquisition and during the first 3 days of extinction. The extinction data suggested that the relationship between emotionality and effects of frustrative non-reward should be re-evaluated.     

Ordinal Position Learning and Remote Anticipation

Rats were runway trained on each of two 3-trial series of reward outcomes. The series are labeled XNY and ZNN, for which X represents a trial that was rewarded with Noyes pellets and N represents a trial that ended with no reward. Units of distinctively flavored breakfast cereals served as reward on trials labeled Y and Z. One group (Floor) had each series occur with a correlated runway floor, either smooth and black or rough and white. For a second group (Memory), the floor cue was uncorrelated with series. Animals in both groups learned to approach the goal rapidly on the 1st trials of the 2 series and slowly on the 2nd trials, but only Group Floor learned to differentiate the 3rd trials of the series. These results recommend a view of serial learning that emphasizes the role played by information about the ordinal position of series items.     

Ordinal position learning and remote anticipation

Rats were runway trained on each of two 3-trial series of reward outcomes. The series are labeled XNY and ZNN, for which X represents a trial that was rewarded with Noyes pellets and N represents a trial that ended with no reward. Units of distinctively flavored breakfast cereals served as reward on trials labeled Y and Z. One group (Floor) had each series occur with a correlated runway floor, either smooth and black or rough and white. For a second group (Memory), the floor cue was uncorrelated with series. Animals in both groups learned to approach the goal rapidly on the 1st trials of the 2 series and slowly on the 2nd trials, but only Group Floor learned to differentiate the 3rd trials of the series. These results recommend a view of serial learning that emphasizes the role played by information about the ordinal position of series items.     

The temporal course of the frustration effect

General activity subsequent to reward (R) and nonreward (N) was monitored at 5-sec intervals with a stabilimeter in the runway goal box. Activity of never-rewarded control Ss was also measured. In Expt 1 it was found that the frustration effect (difference between N- and R-trial activities) disappeared after about 40 sec of goal box confinement. This disappearance of the frustration effect was due to activity increase on R trials rather than activity decrease on N trials as a function of time. Comparison of N-trial activity with control group activity indicated that frustration does not dissipate within 60 sec. Expt 2 investigated activity following reward and nonreward as a function of reward magnitude. Evidence from these experiments suggests that the late R-trial activity increase results from frustration, possibly conditioned to apparatus cues on N trials.     

Sodium amylobarbitone and responses to nonreward

Three experiments are reported testing two alternative hypotheses concerning the behavioural effects of sodium amylobarbitone (SA): (1) that it blocks the after-effect of nonreward; (2) that it blocks conditioned frustration, elicited by stimuli associated with nonreward. In support of (2) Experiment I showed that SA given in acquisition abolished the partial reinforcement extinction effect (PREE) when rats were run at one trial a day in an alley for food reward on a continuous (CRF) or partial (PRF) reinforcement schedule. Experiment II showed that, in the goal section, the effect of the drug on the PREE was due to its presence during acquisition and was not due to state dependency; but the effect of the drug in the start section was consistent with state dependency of the PREE. In Experiment III, in opposition to (1) and again in support of (2), SA given to rats trained to show patterned running for water reward on a single alternation schedule blocked patterning by increasing running speeds on nonreward trials, not by decreasing running speeds on rewarded trials.     

Extinction of a running response as a function of reinforcement magnitude

Four groups of rats were trained on different sucrose solutions in a straight runway. Terminal running speed was a monotonic function of reinforcement magnitude. After training each group was subdivided, one subgroup being extinguished under spaced, the other under massed conditions. In spaced extinction the animals trained on non extreme reward magnitudes showed most resistance to extinction. It was concluded that resistance to extinction is an inverted U-shaped function of reinforcement magnitude found in training. The massed extinction trials were conducted with a very short inter-trial interval. The animals showed an immediate drop in running speed followed by a gradual recovery and a subsequent decline. The number of trials taken to reach the peak recovery speed was a function of reinforcement magnitude found in training. Results on both massed and spaced extinction trials were interpreted in terms of the facilitatory and inhibitory effects of momentary and conditioned frustration.     

Number tags applied by rats to reinforcers are general and exert powerful control over responding

Rats are capable of employing the number of successively presented food reinforcers in a runway as a discriminative cue. Trained, for example, under a series in which three food-reinforced trials precede a non-reinforced trial (RRRN), rats have run fast to R, R, and R, slowly to N. Such numerical discriminations have been shown to be general to some extent, being maintained in connection with either novel reinforcers suddenly introduced, or various alterations of the old series of reinforcers. In the two investigations reported here, the four-event series R'RRN was employed, R' and R being qualitatively different reinforcers. On being shifted to more severe alterations of this series than heretofore, the previously established numerical discrimination was maintained, indicating that the number tags rats apply to reinforcing events are to a considerable extent general. In Experiment 1 rats trained under the two series R'RRN and RRN maintained the numerical discrimination when shifted to the series R'RN and NR'RN, despite the fact that the specific events R'R that signalled R in original training (R'RRN series) now signalled N in the shift or transfer phase. In Experiment 2 rats trained under R'RRN and RRN maintained the numerical discrimination on being shifted to the series NRRRN and RRRN (count to three), despite the fact that they had previously received the RRN series (count to two). Various other findings obtained here are consistent with the view that the rat's number tags are to a considerable extent general.     

Frustation and learned helplessness.

This article reports the transfer of learned helplessness from one aversive motivator, shock to another, frustration. In experiment 1, animals were trained to approach food in a runway and concomitantly exposed to either escapable, inescapable, or no shock in a different situation. Extinction was conducted in the runway, and subsequently the animals were tested for hurdle-jump escape from the frustrating goal box. Inescapably shocked rats failed to learn to hurdle-jump, whereas escapably or nonshocked animals learned the frustration escape response. Experiment 2 replicated the basic finidngs of Experiment 1 and showed transfer of learned helplessness from shock to frustration when no running response had been first acquired in the runway.     

Position reversal training in the virginia opossum: Evidence for the acquisition of a learning set

To obtain an estimate of the learning ability of opossums, five tame ones were trained on a series of position reversals to a criterion. With 4 trials per day there was no consistent improvement over a series of 15 reversals. When each daily session was increased to as many trials as needed to reach criterion, errors dropped sharply, indicating the formation of a position learning set. Upon return to 4 trials per day, 3 of 4 animals continued to perform with few errors, showing transfer of learning set. Opossums do more poorly than rats on this task, which is in agreement with the relative phyletic level of the two species.     

Learning about water by hungry rats

In Experiments 1 and 2 hungry rats were trained in a straight alley with consistent food reward (FF), food and nonreward trials intermixed (FN), or food and water trials intermixed (FW). In Experiment 1 rats were tested with nonrewarded trials (extinction) and Groups FN and FW did not differ, both running faster then Group FF. In Experiment 2 rats were tested with consistent water reward, and Group FW ran faster then Group FN, which was superior to Group FF. In Experiment 3, one group of hungry rats was trained on a single alternating schedule of food and water in Phase 1 and was shifted to a single alternating schedule of food and nonreward in Phase 2 (Group FW); the second group (Group FN) received a single alternating schedule of food and nonreward in both phases. When Group FW was shifted to nonreward from water, performance to nonreward was temporarily disrupted. These results indicate that, contrary to previous conclusions, hungry rats can learn about water when drive is strong and food is received in the situation.     

Retention interval and intertrial interval in a serial learning or delayed discrimination task

In each of four experiments, rats were provided with the same three-event decreasing series (18-1-0) of 0.045-g food pellets in a runway. Tracking, running fast to 18 pellets and running slow to 1 and 0 pellets, was investigated as a function of the temporal interval elapsing between the events of the series (the retention interval), shifts in retention interval, and number of trials each day (or the intertrial interval), a trial being defined as presentation of each of the three events of the series. Neither retention interval, which varied from 15 s to 30 min in various investigations, nor shifts in retention interval affected tracking when only one trial was given each day. But when more than one daily trial was given, tracking was acquired more slowly and was disrupted by a shift in retention interval from 15 s to 5 min. Tracking was also disrupted by a shift from one to two trials each day. These results indicate that when given one 18-1-0 trial each day, the rat partitions events on a first-event/subsequent-event basis; that little forgetting occurs even at long retention intervals; that somewhat different memories signal events when one or more than one 18-1-0 trial occurs each day; and that retention interval deficits can arise owing to the same or similar memories' signaling different events. The results described limit the generality of three hypotheses suggested in two recent investigations: that as retention interval increases, rats find it increasingly difficult to remember and utilize serial position cues; that tracking in serial tasks is not influenced by number of trials each day; and that there are specific stimuli associated with each retention interval which, when changed, necessarily disrupt performance.     

Effects of sucrose concentrations on single alternation runway responding in rats

Rats received runway training under alternating reward and nonreward in which rewarded (R) trials provided 32 or 4% sucrose concentration from a drinking tube and nonrewarded (N) trials provided a dry tube or, for half of the rats in the 32% condition, plain water. Both 32 and 4% concentrations yielded faster running on R trials than on N trials; but this effect was reliable only for the 32% condition. Compared to 4% sucrose, 32% sucrose yielded reliably slower running on N trials and unreliably faster running on R trials.     

The partial punishment effect following minimal acquisition training: Sodium amobarbital and the stimulus properties of early punished trials

In a runway investigation, six groups of rats received limited runway training such that partial punishment, partial reinforcement, or continuous reinforcement was accompanied by sodium amobarbital or saline. Following an interpolated phase of continuous reinforcement without injections, all groups were given punished extinction. The entire experiment was conducted under widely spaced conditions (ITI = 24 hr). It was found that partial punishment increased resistance to punished extinction relative to partially and continuously reinforced controls when acquisition was given under saline. When partial punishment training was accompanied by amobarbital this effect was eliminated. The drug was observed to have no effect on the punished extinction performance of the partial reinforcement and continuous groups, respectively. Moreover, the partial reinforcement effect (PRE) did not generalize to punished extinction. These data provide information concerning the difference between the stimuli associated with the early trials of punishment and nonreward and indicate that the former but not the latter contain emotional elements.     

Grouping, chunking, memory, and learning

An example of grouping is dividing a long series of digits into two or more smaller units by, for example, pausing for a short time between items within groups but for a longer time between groups. Grouping, virtually neglected in animal learning, was examined in each of five rat investigations reported here in which a series of two or more runway trials was either grouped together with or apart from a terminal large reward trial. It was found that running speed on early small reward trials in the series was greater when prior trials were grouped together with rather than apart from the terminal large reward trial and this when the intertrial interval was short, 20 sec, or long, 20 to 40 min. Three possible explanations of the present findings were examined: a reward schedule view, a rule-learning view, and an anticipation view based on memory. The most feasible of these explanations, it was suggested, was the anticipation view. According to this view, when prior trials are grouped together with a terminal large reward, there is a tendency for the rat to anticipate the terminal large reward well before its scheduled occurrence, elevating running speed on earlier small reward trials. Such anticipation occurs, it was suggested, because when trials are grouped together the memory of each reward event in the series is retrieved on each subsequent trial, including the remote terminal large reward trial, where it becomes a signal for large reward. Thus the present results implicate not merely adjacent associations—associations between adjacent events—but also the highly controversial remote associations—associations between two events separated not only in time but by one or more intervening events as well.     

A runway for the fish

A runway and a training procedure arc described. Acquisition and extinction curves for a sample of 12 goldfish trained in spaced trials are plotted in terms of three measures.