Showing papers in "Animal Learning & Behavior in 1994"
TL;DR: The control of goal-directed, instrumental actions by primary motivational states, such as hunger and thirst, is mediated by two processes: the Pavlovian association between contextual or discriminative stimuli and the outcome or reinforcer presented during instrumental training and knowledge of the contingency between the action and its outcome and the value assigned to this outcome.
Abstract: The control of goal-directed, instrumental actions by primary motivational states, such as hunger and thirst, is mediated by two processes. The first is engaged by the Pavlovian association between contextual or discriminative stimuli and the outcome or reinforcer presented during instrumental training. Such stimuli exert a motivational influence on instrumental performance that depends upon the relevance of the associated outcome to the current motivational state of the agent. Moreover, the motivational effects of these stimuli operate in the absence of prior experience with the outcome under the relevant motivational state. The second, instrumental, process is mediated by knowledge of the contingency between the action and its outcome and controls the value assigned to this outcome. In contrast to the Pavlovian process, motivational states do not influence the instrumental process directly; rather, the agent has to learn about the value of an outcome in a given motivational state by exposure to it while in that state. This incentive learning is similar in certain respects to the acquisition of “cathexes” envisaged by Tolman (1949a, 1949b).
886 citations
TL;DR: It is demonstrated that a conditioned response that is learned and extinguished in one context and renewed when the conditioned stimulus is tested in a second context, consistent with the view that retrieval of extinction depends more on the context than does retrieval of conditioning.
Abstract: In three experiments with rats, we demonstrated that a conditioned response that is learned and extinguished in one context (Context A) can be renewed when the conditioned stimulus (CS) is tested in a second context (Context B). In Experiments 1 and 3, the effect was observed in conditioned suppression; in Experiment 2, it was produced in appetitive conditioning. The result occurs when Contexts A and B are equally familiar, equally associated with reinforcement, or equally associated with both reinforcement and nonreinforcement. The results extend the range of conditions known to produce the renewal effect, and they are consistent with the view that retrieval of extinction depends more on the context than does retrieval of conditioning.
305 citations
TL;DR: The results suggest that, in addition to using egocentric strategies, goldfish are able to solve spatial tasks on the basis of allocentric frames of reference and to build complex spatial cognitive representations of their environment.
Abstract: Goldfish were trained to obtain food in a four-arm maze placed in a room with relevant spatial cues. Four experimental conditions were run: allocentric, egocentric, egocentric + allocentric, and control. Relative to controls, all groups were able to solve the different tasks with high accuracy after 1 week of training. Subsequent transfer tests revealed place and response strategies for allocentric and egocentric groups, respectively, and both types of strategies for the ego-allocentric group. Moreover, the allocentric group showed the capacity to choose the appropriate trajectory toward the goal, even from novel starting points, presumably by using the distal cues as a whole. The results suggest that, in addition to using egocentric strategies, goldfish are able to solve spatial tasks on the basis of allocentric frames of reference and to build complex spatial cognitive representations of their environment.
139 citations
TL;DR: In this paper, rat subjects were used to explore transfer of an instrumental discriminative stimulus to a new response, and the stimulus increased the likelihood of that response to the degree that the stimulus and response had a history of association with the same outcome.
Abstract: In three instrumental learning experiments, rat subjects were used to explore transfer of an instrumental discriminative stimulus to a new response. The stimulus increased the likelihood of that response to the degree that the stimulus and response had a history of association with the same outcome. Moreover, devaluation of the outcome by pairing with lithium chloride had no detrimental effects on its ability to mediate transfer to a new response. This result helps one choose among various accounts of transfer.
128 citations
TL;DR: Three experiments, using rats, demonstrated the encoding of a food unconditioned stimulus (US) in a simple Pavlovian conditioning paradigm and indicate that a detailed representation of the outcome is encoded in the normal course of Pavlovians conditioning.
Abstract: Three experiments, using rats, demonstrated the encoding of a food unconditioned stimulus (US) in a simple Pavlovian conditioning paradigm. In all three studies, one stimulus was used to signal the delivery of pellets and a different stimulus was used to signal the delivery of sucrose. In Experiment 1, postconditioning devaluation of one of the food USs selectively reduced the frequency of conditioned magazine-directed behavior during the stimulus trained with that US. In Experiment 2, transfer of the stimuli to instrumental responses resulted in selective depression of the response trained with a different outcome. In Experiment 3, acquisition of stimulus-outcome learning was impaired by unsignaled intertrial presentations of the same outcome but not of a different outcome. These results indicate that a detailed representation of the outcome is encoded in the normal course of Pavlovian conditioning.
119 citations
TL;DR: In this paper, two California sea lions were trained with a two-choice visual matching-to-sample task, where one passed on the first task and the other failed on the second task.
Abstract: In order to assess the abilities of two California sea lions to generalize an identity concept, both animals were taught a two-choice, visual matching-to-sample task. We hypothesized that initial identity-matching problems would be learned as conditional (if...then) discriminations but that an identity concept would emerge after training numerous exemplars of identity matching. After training with 15 two-stimulus identity matching-to-sample problems, transfer tests consisting of 15 novel problems were given to the animals. Pass-fail criteria were defined in terms of performance on Trial 1 of each test problem, performance on test trials compared with baseline trials, and performance on four-trial problem blocks. One sea lion passed on the second transfer test and the other passed on the third; both demonstrated successful generalization of an identity concept by all criteria used. A second experiment consisted of presentation of stimuli previously learned in a different context (arbitrary matching-to-sample). Both subjects immediately applied an identity concept to accurately solve these new problems. These tests conclusively demonstrate transfer of an identity matching rule in California sea lions.
95 citations
TL;DR: Atomic processes appear to predominate in cross-modal compounding within the auditory modality, but atomistic alternatives—namely, common elements and selective attention hypotheses—may be able to explain the results.
Abstract: Three experiments examined “atomistic” and “configurai” processes in stimulus compounding using the rabbit’s conditioned nictitating membrane response. Two conditioned stimuli (CSs) were trained separately and then tested together in a compound. Animals trained with CSs from different modalities—namely, tone and light—showed summation in both acquisition and extinction. That is, the probability of a response to the compound could be predicted by the statistical sum of responding to the CSs. In contrast, animals trained with CSs from the auditory modality, tone and noise, showed a level of responding to the tone + noise compound that was the same as that of the CSs, well under the level predicted by the statistical sum of responding to the CSs. In conclusion, atomistic processes appear to predominate in cross-modal compounding. Configurai processes may occur during compounding within the auditory modality, but atomistic alternatives—namely, common elements and selective attention hypotheses—may be able to explain the results.
93 citations
TL;DR: Support for a circadian type of timing mechanism with a self-sustaining oscillator mediates time-place learning over a period of 24 h was found in a fifth experiment, in which the subjects were tested in constant dim light.
Abstract: Pigeons were trained to discriminate between four keys. One provided food in the mornings, another provided food in the afternoons, and two never provided food. Three experiments were performed to determine whether pigeons could track food availability over a 24-h period. All the subjects appeared to demonstrate time-place associative learning. A fourth experiment was designed to investigate the mechanisms underlying the timing behavior. Lights-on time was shifted back by 6 h, and no decrease in performance was found during the first session following the phase shift. This suggests that a circadian type of timing mechanism with a self-sustaining oscillator mediates time-place learning over a period of 24 h. Further support for this notion was found in a fifth experiment, in which the subjects were tested in constant dim light. In that experiment, the subjects’ continued correct responding provides additional support for a self-sustaining circadian timer.
78 citations
TL;DR: In a one-trial associative memory task, Birds obtained a reward by returning to the site where they had eaten part of the reward 30 min earlier, and storers preferentially returned to sites that had been visited in Phase 1, irrespective of whether or not they contained a reward.
Abstract: Experiment 1 compared food-storing marsh tits and nonstoring blue tits, and Experiment 2 compared food-storing jays and nonstoring jackdaws, in a one-trial associative memory task, Birds obtained a reward by returning to the site where they had eaten part of the reward 30 min earlier. In “visible” versions, the reward was visible in Phase 1 but hidden in Phase 2 so that the bird had to search for it; in “hidden” versions, the reward was hidden in both phases. No species differences were found in performance in the visible version. However, in the hidden version, the 2 storers preferentially returned to rewarded sites, whereas nonstorers preferentially returned to sites that had been visited in Phase 1, irrespective of whether or not they contained a reward. This suggests that storers differ from nonstorers in the way they discriminate between remembered events.
77 citations
TL;DR: Results support the direction-averaging model and suggest that distance and direction are independently computed in landmark-based search.
Abstract: In four experiments, pigeons were trained to find hidden food at a constant location with respect to one or two arrays of landmarks. On crucial tests, the birds were presented with conflicting cues associated with two different directions, which were 90° apart from the center of the search space at the same radial distance. The direction-averaging model predicts that the radial distance of search should not change on these tests, compared with radial distance of search on control tests without conflicting cues. The vector-averaging (vector sum) model predicts that when pigeons average the two conflicting cues, the radial distance of search should be shorter. Results support the direction-averaging model and suggest that distance and direction are independently computed in landmark-based search. Multiple sources are averaged by pigeons in determining direction.
71 citations
TL;DR: In this paper, the authors examined the role of CS-context associations and context-US associations in attenuating Latent Inhibition (LI) using conditioned suppression in rats and concluded that LI is a performance deficit mediated by unusually strong CS-Context associations.
Abstract: Treatments that attenuate latent inhibition (LI) were examined using conditioned suppression in rats. In Experiment 1, retarded conditioned responding was produced by nonreinforced exposure to the CS prior to the CS-US pairings used to assess retardation (i.e., conventional LI). In Experiment la, retarded conditioned responding was induced by preexposure to pairings of the CS and a weak US prior to retardation-test pairings of the CS with a strong US (i.e., Hall-Pearce [1979] LI). Both types of LI were attenuated by extensive exposure to the training context (i.e., context extinction) following the CS-US pairings of the retardation test. Experiment 2 examined the specificity of the attenuated LI effect observed in Experiment 1. After preexposure to two different CSs in two different contexts, each CS was paired with a US in its respective preexposure context. One of the two contexts was then extinguished. This attenuated LI to a greater degree for the CS that had been trained in the extinguished context. Experiment 3 differentiated the roles in LI of CS-context associations and context-US associations. Following preexposure to the CS in the training context, LI was reduced by further exposure to the CS outside the training context. This observation was interpreted as implicating the CS-context association as a factor in LI. Thus, the results of these experiments suggest that LI is a performance deficit mediated by unusually strong CS-context associations. Implications for Wagner’s (1981) SOP model and Miller and Matzel’s (1988) comparator hypothesis are discussed.
TL;DR: In this paper, the authors investigated quantitative features of responding maintained by running and found that response rate was a negatively accelerated function of reinforcement rate, and the relationship between these two variables was described well by the equation for a rectangular hyperbola.
Abstract: Previous research has demonstrated that running in a rotating wheel functions as a reinforcer for leverpressing in rats. In these studies, the pattern of responding was similar to the pattern of responding maintained by consummatory reinforcers, such as food and water. The present study investigated quantitative features of responding maintained by running. In previous experiments in which responses were reinforced according to variable-interval (VI) schedules and food and water served as the reinforcer, the equation for a rectangular hyperbola described the relationship between response rate and reinforcement rate. This experiment tested whether this quantitative regularity also applies to leverpressing maintained by the opportunity to run in a wheel. Fourteen male Wistar rats responded on levers for the opportunity to run. In each session, subjects were exposed to a series of VI schedules. An opportunity to run for 60 sec was the reinforcing consequence. Results showed that response rate was a negatively accelerated function of reinforcement rate, and the relationship between these two variables was described well by the equation for a rectangular hyperbola. To further test the similarity between running and consummatory reinforcers, the response requirement and access were manipulated. In previous experiments with food and water, these types of manipulations differentially changed the two parameters of the hyperbola. A similar pattern of results was obtained with wheel running. Thus, the equation appears to apply to running about as well as it does to consummatory reinforcers.
TL;DR: In this paper, the effects of intertrial-interval duration and length of the terminal-link delays on choice of the 50% alternative were investigated in four experiments, and the results are discussed in terms of conditioned-reinforcement effects, Mazur's hyperbolic-decay model, and delay reduction.
Abstract: Pigeons chose between 50% and 100% reinforcement on a discrete-trials concurrent-chains procedure with fixed-ratio 1 initial links and fixed-time terminal links. The 100% alternative always provided food after a terminal-link delay, whereas the 50% alternative provided food or blackout equally often after a delay. Additionally, the terminal-link stimuli on the 50% alternative were correlated with the outcomes in signaled, but not in unsignaled, conditions. The effects of intertrial-interval duration and length of the terminal-link delays on choice of the 50% alternative were investigated in four experiments. Preference for the 50% alternative varied with signal condition and duration of the terminal link leading to food, but not with duration of either intertrial interval or the terminal link leading to a blackout. The results are discussed in terms of conditioned-reinforcement effects, Mazur’s hyperbolic-decay model, and delay reduction. This research was supported by a Natural Sciences and Engineering Research Council of Canada research grant awarded to the first author.
TL;DR: It is suggested that deprivation may enhance the reinforcing value of sweetness only when calories increase along with sweetness, and that deprivation can enhance flavor preference learning by increasing consumption and thereby increasing exposure to the flavored solutions.
Abstract: In four experiments, food deprivation was varied during conditioning and testing of conditioning of flavor preferences by sweeteners. Conditioned preferences for a flavor associated with a more concentrated solution were enhanced by increased deprivation in training whether sucrose or saccharin was used when rats consumed solutions freely during training. When consumption of solutions was controlled and higher deprivation levels were used, preference for the higher concentration of sucrose was still enhanced by increased deprivation in training, but this did not occur with saccharin. We suggest that deprivation may enhance the reinforcing value of sweetness only when calories increase along with sweetness. We also suggest that deprivation can enhance flavor preference learning by increasing consumption and thereby increasing exposure to the flavored solutions.
TL;DR: The similarities between the results for rats and for pigeons when session length varied suggest that at least one of the factors that produces the within-session changes in responding is shared by the present species, responses, and reinforcers.
Abstract: Rats and pigeons responded for food delivered according to multiple schedules. The session length varied from 10 to 120 min, and the programmed rate of reinforcement varied from 15 to 240 reinforcers per hour. Response rates usually changed systematically within experimental sessions. For both rats and pigeons, responding reached a peak after an approximately constant amount of time since the beginning of the session, regardless of session length. When rats, but not pigeons, served as subjects, the peak rates of responding occurred later in the session and the within-session changes were smaller for lower than for higher rates of reinforcement. The similarities between the results for rats and for pigeons when session length varied suggest that at least one of the factors that produces the within-session changes in responding is shared by the present species, responses, and reinforcers. The differences in results when rate of reinforcement varied are more difficult to interpret.
TL;DR: The results indicate that the blocking effect occurs in sexual conditioning even with stimulus objects that can support copulation, but the addition of species-typical head cues to an object makes that object such a powerful stimulus that conditioned approach responding to it cannot be blocked by a previously conditioned arbitrary audiovisual cue.
Abstract: The blocking phenomenon was investigated in the sexual response system of male Japanese quail. Access to a live female quail served as the unconditioned stimulus (US). The same audiovisual cue served as the pretrained stimulus in all of the experiments. Following asymptotic conditioning of the audiovisual cue, a second conditioned stimulus (CS2) was added. In Experiment 1, CS2 was a rectangular wood block that had little or no resemblance to a female quail and could not support copulatory behavior. In Experiment 2, CS2 was a terrycloth object that had no quail parts but could support copulatory behavior, and, in Experiment 3, CS2 was a terrycloth object that had a taxidermically prepared head of a female quail added. The terrycloth-only object supported more rapid conditioning than did the wood block, but the blocking effect was obtained with both kinds of stimuli. Approach responding to the terrycloth + head object required pairing it with copulatory opportunity, and the terrycloth + head object supported at least as rapid conditioning as did the terrycloth-only object. However, responding to the terrycloth + head object was not blocked by the pretrained audiovisual cue. These results indicate that the blocking effect occurs in sexual conditioning even with stimulus objects that can support copulation. However, the addition of species-typical head cues to an object makes that object such a powerful stimulus that conditioned approach responding to it cannot be blocked by a previously conditioned arbitrary audiovisual cue.
TL;DR: Pigeon subjects received training of a diffuse stimulus as either a conditioned inhibitor or a conditioned facilitator of a keylight signal for food, and the ability of these diffuse stimuli to modulate responding was assessed with two other keylights that were undergoing discrimination reversal.
Abstract: Pigeon subjects received training of a diffuse stimulus as either a conditioned inhibitor or a conditioned facilitator of a keylight signal for food. The ability of these diffuse stimuli to modulate responding was then assessed with two other keylights that were undergoing discrimination reversal. At a point where responding was equivalent for the two targets, the modulators had a greater impact on the target undergoing extinction than on the target undergoing acquisition. These results have implications for the nature of modulation and extinction.
TL;DR: It was found that mild footshocks elicited initial exploration followed by an increased tendency to escape from the compartment in which the shocks were administered, which led to a considerable increase in latency to enter the shocked compartment.
Abstract: The effects of footshock and various light-spot models on the shuttling activity of mice were examined in a passive avoidance situation. It was found that mild footshocks elicited initial exploration followed by an increased tendency to escape from the compartment in which the shocks were administered. An encounter with models, consisting of various numbers of small yellow lights, without footshock did not cause significant differences in shuttling activity. But if the models were paired with footshock, a tendency to explore during the first trial, high readiness to escape, and avoidance learning were found. These were characterized by a temporary increase in number of gate crossings, a decrease in the time spent in the shocked compartment, and a considerable increase in latency to enter the shocked compartment. The most effective model had two horizontally arranged yellow lights, which may share some characteristics with eye-like patterns.
TL;DR: Black-capped chickadees (Parus atricapillus), a food-storing bird, were presented with three-item lists of unique spatial configurations and memory for the location of the hidden bait in each configuration was tested.
Abstract: Black-capped chickadees (Parus atricapillus), a food-storing bird, were presented with three-item lists of unique spatial configurations. Each item consisted of one baited and three nonbaited feeders. Memory for the location of the hidden bait in each configuration was tested. Both primacy and recency effects were observed. The results from this use of a new species and procedure provide further evidence for the generality of serial position effects in animals.
TL;DR: The immediate-shock deficit, previously reported for freezing and defecation, also occurs for analgesia, suggesting that shock levels sufficient to condition analgesia are not necessarily sufficient to produce analgesia as an unconditional response.
Abstract: Rats received a 3-sec, 1-mA footshock either immediately or 3 min after placement in a chamber. Postshock pain sensitivity was assessed with the formalin test. The animals that received the 3-min delay between placement and shock showed an analgesic response compared with noshock controls. The immediate-shock animals did not. Thus the immediate-shock deficit, previously reported for freezing and defecation, also occurs for analgesia. This suggests that shock levels sufficient to condition analgesia are not necessarily sufficient to produce analgesia as an unconditional response. As with freezing, there is a dissociation between conditional and unconditional responses in the fear-conditioning system. Increasing immediate-shock levels to 6 sec, 2 mA produced a transient unconditional analgesia. For analgesia, a conditional response is more readily produced than an unconditional response.
TL;DR: It is shown that fear-potentiated startle can be produced with three discriminable conditioned stimulus modalities, allowing the future use of fear- Potentiate startle in the investigation of higher order conditioning phenomena.
Abstract: The capacities of three different conditioned stimulus modalities (light, noise, and airflow produced by a fan) to produce fear-potentiated startle were evaluated. Previous experiments have shown that following either light-shock or noise-shock pairings, both the light and noise conditioned stimuli acquire the ability to potentiate the acoustically elicited startle response in rats (the so-calledfear-potentiated startle effect). In Experiment 1, the ability of airflow produced by a fan to act as a conditioned stimulus was investigated. Rats were given either paired or impaired fan-shock training followed by a test for fear-potentiated startle. The fan conditioned stimulus potentiated startle only in the group given explicit fan-shock pairings. In Experiment 2, we evaluated the discriminability of the three conditioned stimulus modalities. Rats were given light, noise, or fan-shock pairings and were subsequently tested for fear-potentiated startle with the trained conditioned stimulus as well as the two remaining novel conditioned stimuli. Only the trained conditioned stimulus potentiated startle. These results show that fear-potentiated startle can be produced with three discriminable conditioned stimulus modalities, allowing the future use of fear-potentiated startle in the investigation of higher order conditioning phenomena.
TL;DR: Findings indicate that intertriai proactive interference (PI) occurred only with massed trials and was weakened by changing intra- and extramaze cues between such trials.
Abstract: Rats are typically less accurate in their arm selections in the radial maze over successive trials in a session (Roberts & Dale, 1981). In the present study, rats’ choice accuracy declined when such trials were separated by 2-min (massed) but not by 2-h (spaced) intertriai intervals. Changing intramaze visual/tactile arm stimuli (Experiments 1 and 3) or extramaze landmark stimuli (Experiment 4) between trials weakened the massed-trials effect, but changing the number of food pellets per arm, either alone or in conjunction with changes in intramaze cues (Experiments 2 and 3), did not. The rats also tended to avoid the spatial locations of their last four choices on a previous trial during their first four choices on a current trial, and more so with massed than with spaced trials. These findings indicate that intertriai proactive interference (PI) occurred only with massed trials and was weakened by changing intra- and extramaze cues between such trials.
TL;DR: There is growing evidence that animal memory is similar to, at least, the nonverbal part of human memory, and conditions conducive for obtaining primacy effects are discussed.
Abstract: Evidence for primacy effects in animals’ list memory is accumulating, despite assertions that these primacy effects may be list-initiation-response artifacts (D. Gaffan, 1983; E. Gaffan, 1992). This evidence comes from list-memory experiments with pigeons and monkeys in which primacy changed with retention interval, experiments with monkeys in which primacy correlated with list length, and experiments with monkeys in which there were no list-initiation responses. Furthermore, there is growing evidence that animal memory is similar to, at least, the nonverbal part of human memory. This evidence comes from human nonverbal-memory experiments in which primacy changed with retention interval (similar to animals) when using kaleidoscope or snowflake stimuli, and similar experiments in which the verbal/nonverbal component was manipulated. Conditions conducive for obtaining primacy effects are discussed.
TL;DR: In this article, a discrete-trials procedure was used to determine whether pigeons match when the overall reinforcement probabilities for two responses depend inversely on their recent frequency, and how pigeons meet the schedule constraint in terms of local responding, i.e., do they respond quasi-randomly (Bernoulli mode), or do they learn the stable pattern of the schedule (stable-pattern mode).
Abstract: In a discrete-trials procedure, a frequency-dependent schedule shaped left-right choice proportion toward various equilibrium values between 0 and 1. At issue was (1) whether pigeons match when the overall reinforcement probabilities for two responses depend inversely on their recent frequency, and (2) how pigeons meet the schedule constraint in terms of local responding. That is, do they respond quasi-randomly (Bernoulli mode), or do they learn the stable pattern of the schedule (stable-pattern mode)? Molar choice behavior always tracked the equilibrium solution of the schedule, but the molecular response patterns varied substantially. Markov chains applied to the data revealed that responding was generally intermediate between the memoryless Bernoulli mode, and the perfect memory stable-pattern mode. The polymorphism of molecular patterns, despite molar regularities in behavior, suggests that (1) in order to engender the Bernoulli or stable-pattern modes, the reinforcement rule must strongly discourage competing response patterns (e.g., perseveration), and (2) under frequency-dependent schedules, molar matching is apparently not the outcome of momentary maximizing.
TL;DR: It is suggested that a taste/extract compound produces a configural stimulus that is more characteristic of the extract than the taste, and that extracts do not interfere with sensing the tastes.
Abstract: Almond and peppermint extracts were combined with salt and citric acid as cues in conditioned flavor preference conditioning. In Experiment 1, extracts overshadowed tastes, although tastes and extracts conditioned equally well when presented in isolation. In Experiments 2 and 3, tastes and extracts were conditioned in isolation prior to conditioning of a taste/extract compound. The conditioning history of the tastes and extracts did not affect the overshadowing of taste by extract. The results of Experiment 4 showed that rats could learn to discriminate between a taste and extract presented in isolation vs. the taste/extract compound. Thus, extracts do not interfere with sensing the tastes. We suggest that a taste/extract compound produces a configural stimulus that is more characteristic of the extract than the taste.
TL;DR: In this paper, a three-phase transfer design was used to determine whether pigeons use a single, common code to represent line and duration samples that are associated with the same comparison stimulus.
Abstract: A three-phase transfer design was used to determine whether pigeons use a single, common code to represent line and duration samples that are associated with the same comparison stimulus. In Phase 1, two sets of samples (two lines and two durations) were associated with either a single set of comparisons (Group MTO, many-to-one) or with different sets of comparisons (Group OTO, one-to-one). In Phase 2, one set of samples was associated with a new set of comparisons. In Phase 3 (transfer test), the alternate set of samples was substituted for the Phase 2 samples. Group MTO, but not Group OTO, demonstrated immediate transfer. It was concluded that associating a line and a duration sample with the same comparison stimulus results in representation of those samples by a single code.
TL;DR: The degree of response suppression caused by thefree reinforcer was greater when the free reinforcers were the same as the response-contingent rein forcers than when they were different.
Abstract: Rats were trained on a discriminated operant barpressing task according to a standard blocking design. In some conditions, the reinforcer was changed between the pretraining and compound conditioning phases; for other conditions, the reinforcer remained the same across phases. In three separate experiments using both between- and within-subject designs, strong blocking effects occurred regardless of the change in the reinforcer. In a fourth experiment, a multiple schedule of reinforcement was used in which response-independent reinforcers were superimposed on the schedule of response-contingent reinforcers. The degree of response suppression caused by the free reinforcer was greater when the free reinforcers were the same as the response-contingent reinforcers than when they were different. The role played by the reinforcer identity in contingency experiments thus appears to be different from the role it plays in blocking experiments.
TL;DR: This work addressed the relative contributions of stimulus-driven factors and learned expectancies to sequential priming in pigeons and revealed significant reductions in reaction time during predictable target or location sequences compared with unpredictable repetitions within random contexts.
Abstract: Sequential priming refers to speeded visual search when target identity or location is repeated within a trial sequence. In two experiments with pigeons, we addressed the relative contributions of stimulus-driven factors and learned expectancies to this effect. Pigeons pecked at targets during trialwise presentations of visual-search displays. Random-sequence conditions minimized the role of expectancy by introducing same-target or same-location trial sequences unpredictably. Blocked-sequence conditions added predictability by regular repetition of target and/or location over trials. Intertrial interval varied from 0.5 to 3 sec. The findings revealed significant reductions in reaction time during predictable target or location sequences compared with unpredictable repetitions within random contexts. Stimulus-driven factors do not seem to have an important role in many instances of sequential priming. Expectancy-based priming of target and location followed similar patterns.
TL;DR: It is suggested that the presentation of a surprising US can interfere with the retrieval of the taste-illness association for a short period after conditioning, and that this contributes to the retention interval effect.
Abstract: Retention interval effects are seen in taste-aversion learning when single-element aversions are significantly weaker 24 h after conditioning compared with tests at later intervals This report contains three experiments which suggest that the source of the increased drinking at the 1-day interval is nonassociative interference produced by the novel conditioning episode In Experiment 1, a parametric analysis demonstrated that aversion strength increased monotonically over a 30-h period following conditioning, and that by 48 h after conditioning it was stabilized In Experiment 2, a single US preexposure was used to reduce the novelty of the US prior to conditioning As a result, animals preexposed to the US had stronger taste aversions than did non-preexposed controls at a 1-day retention interval; however, no differences were seen at a 5-day interval Experiment 3 investigated whether the counterintuitive outcome of Experiment 2 was due to the summation of environment-illness and taste-illness associations at the 1-day test The results ruled out the summation argument; the US preexposure did not need to be presented in the conditioning context to strengthen the aversion at the 1-day interval Collectively, these results suggest that the presentation of a surprising US can interfere with the retrieval of the taste-illness association for a short period after conditioning, and that this contributes to the retention interval effect
TL;DR: It is proposed that the flavor of starch, independent of its calories, is reinforcing to rats, even though these substances contain the same amount of calories.
Abstract: Rats were trained to associate artificial cherry or grape flavors with 1% starch suspensions. Conditioning was assessed by offering the rats a choice of the cherry versus grape flavors without starch. Conditioned preferences were moderately strong and persistent; 3 days of conditioning produced a preference that did not fully extinguish within 18 days. Food deprivation substantially increased intake of 1% starch suspension, However, the degree of preference conditioned was not influenced by the availability of food during the conditioning period; the rats that had been food deprived during training acquired as strong a preference as did those fed freely during training. The degree of preference obtained was similar in the rats given reinforcing and nonreinforcing fluids simultaneously or sequentially. Starch conditioned a slightly stronger preference than did the same concentration of glucose, even though these substances contain the same amount of calories. A statistically significant, but weak, preference was conditioned by 0.5%, but not by 0.25%, starch. It is proposed that the flavor of starch, independent of its calories, is reinforcing to rats.