Extradimensional transfer in the discriminative learning of goldfish

In Experiment I, one group of goldfish (TD) was trained to discriminate blue and green while a second group (PD) was exposed to the same colors in a “pseudodiscrimination,” after which both groups were reinforced for response to a tone. The TD group subsequently showed a sharper auditory discrimination gradient than the PD group and performed better in a differentially reinforced tone discrimination. The former PD animals then were given true discrimination training and the former TD animals pseudodiscrimination training with the colors, after which the first group showed better tone discrimination than the second. These results are analogous to those found in pigeons and rats. In Experiment II, goldfish which were trained in an easy color discrimination and shifted to a more difficult tone discrimination performed better than a control group trained from the outset with the tones. This result suggests that the dimensional specificity of the processes responsible for “transfer along a continuum” cannot safely be assumed in the absence of appropriate controls.     

Observational learning of discriminative avoidance in hooded rats

To determine the aspects of an observational situation facilitating subsequent acquisition of an observed task, two experimental groups of rats were exposed to a model’s performance of a two-way discriminative shuttlebox avoidance task with a tone as the discriminative stimulus. One experimental group (OND) observed the performance of a naive demonstrator; the other experimental group (OSD) observed a skilled demonstrator. A stimulus control group (SC) was exposed to the tone with no model present; a response control group (RC) observed demonstrator running with no tone present. A naive control group (NC) received no observational experience. All groups were subsequently tested on acquisition of the task. An analysis of variance on avoidance scores and Newman-Keuls tests for differences between means revealed that OND and OSD groups performed significantly more avoidances than the control groups. Exposure to the total tone-running sequence was found to be necessary for observational learning. The results were interpreted in terms of a sensory-sensory conditioning model.

     

A differential-outcome effect in pigeons using spatial hedonically nondifferential outcomes

We examined the extent to which nonhedonically different differential outcomes involving feeder location control pigeons’ comparison choices in matching to sample. In Experiment 1, we showed that differential feeder location outcomes associated with each of two samples can facilitate delayed-matching accuracy. In Experiment 2, we found positive transfer following training on two matching tasks with differential feeder location outcomes when samples from one task were replaced by samples from the other task. In Experiment 3, we found that when differential-outcome expectations could no longer serve as the cues for comparison choice, sample stimuli continued to exert some control over choice of comparisons. The results indicate that differential outcomes (involving feeder location) that presumably do not differ in hedonic value are sufficient to control comparison choice. Thus, the differential hedonic value of the outcome elicited by the sample does not appear to be a requirement of the differential-outcome effect. Furthermore, these differential outcomes appear to augment matching accuracy, but they do not eliminate control by the samples.     

Stimulus selection in discriminative taste-aversion learning in the rat

In three experiments, rats were presented compound solutions consisting of a common element, saccharin, mixed with one of two different flavor elements, cinnamon and wintergreen. Rats in the experimental groups consistently received a toxicosis-inducing injection following one compound solution but not following the other compound solution. Rats in the control groups received toxicosis-inducing injections half the time following each of the compound solutions. After training in each experiment, there were tests for conditioning to the saccharin alone. The experimental groups drank significantly more than the control groups, indicating that the aversion to the partially reinforced saccharin in isolation was less when the different flavor cues were more highly correlated with reinforcement. In Experiment III, there was also a test for conditioning to the cinnamon or wintergreen flavor alone. The experimental group drank significantly less of the continuously reinforced flavor than the control group did of the partially reinforced flavor. These results are similar to those reported within more traditional conditioning paradigms.     

Facilitating stimulus effects of reward and punishment in discrimination learning

To demonstrate a facilitating stimulus effect, as opposed to an incentive effect, of food reward, rats were trained on an easy, light-dark discrimination with different amounts of reward for correct and incorrect responses (1-0, 2-0, 3-1, and 5-1 pellets, respectively), and with shock or no shock administered in the correct goalbox. Both errors and trials to criterion were fewer with a large reward differential (LRD: 2-0 and 5-1), as compared with a small reward differential (SRD: 1-0 and 3-1), but were not affected by the “base” reinforcement condition of either 1 or 0 pellets for the incorrect response. In addition, choice and arm speeds during early training were positively related to the combined, or average, number of pellets contingent upon both correct and incorrect responses, indicating a generalization of reward expectancies. Although shock uniformly suppressed arm speeds under all reward conditions, it facilitated discrimination learning in the SRD conditions. That such facilitation occurred only when the conditions of reward for correct and incorrect responses were relatively similar indicates that not only shock, but also food can function as a distinctive cue: As a stimulus selectively applied to one response, it can decrease the similarity of the alternatives, and, in this manner, it can faciltate performance.     

Disruption of overlearned discriminative behavior in monkeys (Cebus paella) by delay of reward

Previous work has shown that when a delay of reward (DOR) is introduced into a well-learned discrimination, even gradually, discriminative performance deteriorates and, with moderately long DORs, does not recover with practice. The present experiment assessed whether the decrement in performance was due to an associative loss or to a decline in the incentive value of the reward object caused by the DOR. Cebus monkeys were trained on a simple visual discrimination and tested with either a DOR or an identical delay period which preceded the appearance of S+ and S? (“predelay” trials); reinforcement on predelay trials was immediate. On half of the daily trials, the animals were given the option of choosing either the DOR or the predelay trial. The duration of the delay was increased gradually until terminal delays of 32 to 128 sec were reached. All four animals maintained almost errorless performance on predelay trials; in contrast, their error rate reached 36% on DOR trials. Surprisingly, none of the animals learned to choose predelay over DOR trials. Both results were interpreted in terms of the incentive loss hypothesis.     

Time-of-day discriminative learning in homing pigeons,Columba livia

Pigeons were trained on an operant procedure to discriminate between morning and afternoon when location did not vary (Experiment 1). The pigeons were placed on a fixed interval (FI) schedule in the morning and on a different FI schedule in the afternoon. Probe trials that occurred at the beginning of the training sessions were examined. The pigeons responded differently, depending on the time of day, reflecting the learning of a stable 24-h memory representation of the association between the FI schedules and the time of day. The pigeons from Experiment 1 were then clock shifted and tested twice, to determine whether they were relying on an endogenous circadian oscillator, an hourglass mechanism influenced by the photoperiod, or environmental noise to make the time-of-day discrimination (Experiment 2). The results of the second experiment indicated a circadian mechanism was most important for the observed time-of-day learning.     

Partial reinforcement effect: The expectancy of reward on nonreward trials

In order to determine the importance of the development of expectancy of reward prior to partial reward trials; rats were given 20 continuously reinforced trials prior to 20 partially reinforced trials (CRF-PRF) and compared to Ss given only 20 partially reinforced trials (PRF). Control groups received 20 or 40 continuously reinforced trials (CRF-20, CRF-40) to determine the effect of differing numbers of acquisition trials. Results showed that terminal acquisition differences were minimal in the run segment of the alley and that Group CRF-PRF was more resistant to extinction than Group PRF, and both were more resistant to extinction than the CRF-20 and CRF-40 groups, which did not differ from each other. These results were interpreted as supporting the notion that the expectancy of reward on nonreward trials during partial reinforcement acquisition is a determiner of the magnitude of the partial reinforcement extinction effect.     

Effects of external reward on paired associate learning in a group setting

A study was conducted to determine the effects of external reward in the form of prizes on the performance of college students in a paired-associate learning task in which subjects were asked to recall a real word associated with a nonsense word. Two groups, one of whom was offered a prize, received the S-R pairs with no aid (no mediators); and two groups, one of whom was offered a prize, received the S-R pairs with a sentence-pictorial aid mediator. Results of two-way ANOVA supported the hypothesis that the No Prize/Aided and No Prize/NonAided groups would exhibit performance of higher quality than the groups offered prizes. The dependent measure was number of correct responses over six trials.     

Intradimensional vs. extradimensional transfer in the discriminative learning of goldfish and pigeons

Evidence of better intradimensional than extradimensional transfer was sought in naive goldfish trained under free-operant single-stimulus conditions (Experiment I), sophisticated pigeons trained under free-operant single-stimulus conditions (Experiment II), sophisticated pigeons trained under discrete-trials choice conditions (Experiment III), and naive pigeons trained under discrete-trials choice conditions (Experiment IV). The results provide no support for attention theory.