Showing papers in "Journal of Experimental Psychology: Animal Behavior Processes in 1997"

Language-Naive Chimpanzees (Pan troglodytes) Judge Relations Between Relations in a Conceptual Matching-to-Sample Task

Abstract: Three chimpanzees with a history of conditional and numeric token training spontaneously matched relations between relations under conditions of nondifferential reinforcement. Heretofore, this conceptual ability was demonstrated only in language-trained chimpanzees. The performance levels of the language-naive animals in this study, however, were equivalent to those of a 4th animal--Sarah--whose history included language training and analogical problem solving. There was no evidence that associative factors mediated successful performance in any of the animals. Prior claims of a profound disparity between language-trained and language-naive chimpanzees apparently can be attributed to prior experience with arbitrary tokens consistently associated with abstract relations and not language per se.

Blocking in the spatial domain.

Abstract: An initial series of experiments with rats in a swimming pool established that they could find a hidden platform the location of which was defined in terms of 3 or 4 landmarks and that, when trained with all 4, any subset of 3 (or even, after a sufficient number of swimming trials, 2) landmarks was sufficient to produce accurate performance. When only one landmark was present during testing, however, performance fell to chance. Two additional experiments demonstrated a significant blocking effect: If rats were first trained to locate the platform with 3 landmarks, they did not learn to use a 4th landmark added to their initial set of 3.

Entropy detection by pigeons: response to mixed visual displays after same-different discrimination training.

Abstract: Pigeons were trained to peck 2 different buttons in response to 16-icon Same versus Different arrays. In Same arrays, the icons were identical to one another, whereas in Different arrays, the icons were different from one another. In Experiment 1, pigeons discriminated Same from Different arrays and transferred their discriminative responding to arrays of novel icons. In Experiments 2-4, pigeons exhibited sensitivity to the degree of display variability when shown intermediate Mixture arrays. Entropy, an information theoretic measure, systematically described these results while outperforming rival accounts.

Effects of repeated disorientation on the acquisition of spatial tasks in rats: dissociation between the appetitive radial arm maze and aversive water maze.

Abstract: This study examined the effects of disorientation on the acquisition of different spatial reference memory tasks. In an appetitively motivated radial arm maze task in which 1 arm was consistently baited, rats that were disoriented before each trial were impaired in their ability to acquire the task relative to rats placed in a clear container and not disoriented. However, disoriented rats were able to learn a Morris water maze and a water version of the radial arm maze under similar training conditions, suggesting that the effects of disorientation may interact with the quality or quantity of motivation involved in a given task. These results suggest that appetitive and aversive spatial tasks are dissociable, and that any impairment that is due to disorientation is specific to the appetitive radial arm maze task.

Scalar timing in temporal generalization in humans with longer stimulus durations.

Abstract: Three experiments investigated temporal generalization performance in humans by using stimulus durations similar to those previously used with rats. In most conditions, chronometric counting was prevented by concurrent shadowing of temporally irregular numbers. Experiment 1 examined performance with visual stimuli, when the standard was 4.0 s long and nonstandard stimuli were spaced either linearly or logarithmically around the standard. Generalization gradients were asymmetrical with linear spacing but symmetrical with logarithmic spacing, a result obtained previously with humans. Experiment 2 used auditory stimuli and varied the standard across values of 2.0, 4.0, 6.0, and 8.0 s. All gradients were asymmetrical, and good superposition was obtained, indicating conformity to scalar timing. Experiment 3 prevented or encouraged chronometric counting by changing instructions, and temporal generalization gradients differed when counting was and was not used.

Judgments of ordinality and summation of number symbols by squirrel monkeys (Saimiri sciureus).

Abstract: In Experiment 1, 2 squirrel monkeys (Saimiri sciureus) were given choices between all possible pairs of the arabic numbers 0, 1, 3, 5, 7, and 9, with choice of any number yielding that number of pieces of peanut as a reward. Both monkeys learned to choose the larger number in all pairings and learned to choose the largest number within a set of 4 numbers. In Experiments 2-4, the monkeys were tested on problems in which they chose between pairs of stimuli containing 2 numbers versus 2 numbers, 1 number versus 2 numbers, and 3 numbers versus 3 numbers. Both monkeys showed a significant tendency to choose the stimulus that contained the largest sum. Various tests indicated that this effect could not be explained by choice of the stimulus with the largest single number, by avoidance of the stimulus with the smallest single number, or by experimenter cuing.

Effects of number of items on the pigeon's discrimination of same from different visual displays.

Abstract: Three experiments explored the baboon’s discrimination of visual displays that comprised 2 to 24 black-and-white computer icons; the displayed icons were either the same as (same) or different from one another (different). The baboons’ discrimination of same from different displays was a positive function of the number of icons. When the number of icons was decreased to 2 or 4, the baboons responded indiscriminately to the same and different displays, exhibiting strong position preferences. These results are both similar to and different from those of pigeons that were trained and tested under comparable conditions.

Pigeon same-different concept learning with multiple stimulus classes.

Abstract: Two experiments examined the acquisition and transfer of a complex same-different discrimination by pigeons. With the use of a 2-alternative choice task, 5 pigeons were reinforced for discriminating odd-item Different displays in which a contrasting target ws present, from Same displays, in which all elements were identical. Four different types of same-different displays were concurrently tested. The display types differed in their configuration (texture vs. visual search organization), the nature of their elements (small and large colored shapes; pictures of birds, flowers, fish, and humans), and the processing demands required by their global-local element arrangement. Despite these differences, the pigeons learned to discriminate all 4 display types at the same rate and showed positive discrimination transfer to novel examples of each type, suggesting that a single generalized rule was used to discriminate all display types. These results provide some of the strongest evidence yet that pigeons, like many primates, can learn an abstract, visually mediated same-different concept.

Additivity of the effects of retention interval and context change on latent inhibition: toward resolution of the context forgetting paradox.

Abstract: Three experiments with rats examined retention interval and context switch effects factorially in the latent inhibition paradigm. In Experiment 1, a 28-day retention interval abolished a context switch effect on latent inhibition. In Experiment 2, re-exposure to the contexts before conditioning re-established the context switch effect at the 28-day interval. In this case, the retention interval and context switch effects were additive: Latent inhibition was weakest when the retention interval and context switch were combined. Experiment 3 replicated the context switch effect at the 28-day interval. The results suggest that context switch and retention interval effects may be based on the same process. Context switch effects may weaken over time because physical contexts are embedded in superordinate temporal contexts; animals fail to retrieve physical context when the temporal context changes. This view helps resolve a paradox that has been noted for contextual change theories of forgetting.

Spatial disorientation blocks reliable goal location on a plus maze but does not prevent goal location in the Morris maze.

Abstract: Cue control in spatial learning was investigated in a plus maze and a Morris maze. Rats transported in opaque containers with prior rotation to a plus maze, but not a Morris maze, could not find a goal defined by external cues. Rats transported in clear containers without rotation found the goal in both mazes. In the Morris maze, goal location was readily relearned following cue removal by rats in clear containers but not by rats in the opaque/rotation group. B. L. McNaughton et al.'s (1996) theory that during spatial learning sensory information is bound to preconfigured internal maps in the hippocampus, whose metric is self-motion and whose orientation depends on input from an inertial based head direction system, may explain this study's findings.

Interaction between piloting and beacon homing by rats in a swimming pool

Abstract: In three experiments, rats in a swimming pool were trained to find a submerged platform with a beacon attached to it. For some rats this beacon unambiguously identified the location of the platform; for others the beacon was made ambiguous by placement of an identical beacon in a different part of the pool. Test trials, in the absence of the platform and the beacons, revealed more persistent searching near the original location of the platform if the beacon attached to the platform had been ambiguous. These results show that learning about the location of the platform, with regard to cues that lie beyond the pool, is influenced by the extent to which an animal can find the platform by relying on other cues. The final experiment shows that this interaction between cues is influenced by an animal's prior experience.

Rats use an ordinal timer in a daily time-place learning task.

Abstract: Rats received 2 daily sessions in a large clear chamber. A lever was mounted on each of the 4 chamber walls. For each rat, a different lever provided food during 0930 and 1530 sessions. The rats learned which lever would provide food at 0930 and 1530. Probe tests suggested that the rats learned to press 1 lever during their 1st session of each day and to then press a 2nd lever during their 2nd session of each day. We propose that this knowledge of the order of a set of events within a period of time constitutes ordinal timing. We contrast the temporal information provided by ordinal, phase, and interval timing and consider why multiple timing systems have evolved in animals.

Spatial peak shift and generalization in pigeons.

Abstract: How pigeons generalize across spatial locations was examined in the 4 experiments reported in this article. During training, a square was presented at a fixed height at 1 of 2 horizontal locations on a monitor screen. One location (S +) signaled reward, whereas the other one (S -) signaled no reward. The birds were then tested occasionally with a range of locations. After training with S+ only, the generalization gradient peaked at S + and was approximately Gaussian in shape. After training with equal numbers of S + and S- trials, response rates were higher on the S + side of the distribution. This asymmetry diminished over testing. When the S + and S- were close together, the peak of responding was shifted on initial generalization tests. Generalization gradients along the orthogonal vertical dimension were approximately exponential in shape. This is the first demonstration of generalization and peak shift in the spatial domain. An important task for the experimental analysis of behavior has been to understand how stimuli present when behavior is reinforced to gain control over the behavior. Stimulus generalization--cesponding in a similar fashion despite changes in properties of a stimulus--and discriminationmresponding differently when a stimulus property is changed--are opposite ends of a continuum of stimulus control. Stimulus control typically is indexed by decremental stimulus generalization gradients, in which increasing changes in a stimulus value lead to increasing changes in responding. Guttman and Kalish (1956) conducted a now-classic study of stimulus generalization in pigeons. They reinforced pigeons on an intermittent schedule for pecking a key in the presence of a monochromatic light source. Different groups of pigeons were trained with different spectral stimuli. After a steady rate of responding emerged, the pigeons were tested in extinction with a range of spectral wavelengths on either side of, and including, the training value. Plots of responses as a function of spectral wavelength showed orderly generalization gradients, with the highest rate of responding at the

Models of Ratio Schedule Performance

Abstract: Predictions of P. R. Killeen's (1994) mathematical principles of reinforcement were tested for responding on ratio reinforcement schedules. The type of response key, the number of sessions per condition, and first vs. second half of a session had negligible effects on responding. Longer reinforcer durations and larger grain types engendered more responding, affecting primarily the parameter alpha (specific activation). Key pecking was faster than treadle pressing, affecting primarily the parameter delta (response time). Longer intertrial intervals led to higher overall response rates and shorter postreinforcement pauses and higher running rates, and ruled out some competing explanations. The treadle data required a distinction between the energetic requirements and rate-limiting properties of extended responses. The theory was extended to predict pause durations and run rates on ratio schedules.

Adjusting to changes in the time of reinforcement: peak-interval transitions in rats.

Abstract: Thirty rats received training on a peak-interval procedure, where a baseline with a 20-s time of reinforcement was interspersed among cyclic transitions to other reinforcement time values (10, 20, 30, or 40 s), each of which was either in force for only a single session or for 3 sessions. Peak times were close to the time of reinforcement on the 20-s baseline and tracked the new reinforcement times both closely (but not exactly) and very rapidly. Peak time during transitions was affected by the criterion value in force on the previous session, exhibiting a proactive interference effect. Analysis of individual peak times during a session showed that transitions from lower to higher reinforcement time values were usually characterized by abrupt jumps in peak time, whereas descending transitions were mostly smooth but rapid.

Configural analysis of summation in autoshaping

Abstract: In 4 experiments, pigeons received autoshaping with various combinations of three stimuli, A, B, and C, before test trials in which responding during all three stimuli, ABC, was compared with that during a three-element control compound, DEF, which had been consistently paired with food. Pairing A, B, and C individually with food resulted in similar rates of responding during ABC and DEF (Experiments 1 and 2). Responding was faster, however, during ABC than during DEF after training in which food was signaled by the pairs of stimuli (AB, AC, and BC; Experiment 1). Responding was also faster during ABC than during DEF after training involving reinforced ( +) and nonreinforced (°) trials of the form ABC + A° BC°, followed by A + BC + (Experiment 2), or AB + BC + B° (Experiments 3 and 4). The results are consistent with those of a configural analysis of summation.

Context dependency of conditioned aversions to water and sweet tastes.

Abstract: Three experiments exposed rats (Rattus norvegicus) to a discriminative conditioning procedure whereby a specific fluid was followed by lithium in one environment but not in another. This produced context-specific aversion to water, as detected by 2-bottle tests in Experiment 1, and a context-dependent saccharin aversion, which was unaffected by context extinction, in Experiment 2. Experiment 3 found that sucrose preexposure increased contextual control over the aversion established by sucrose-lithium pairings but had no effect on the target context. By contrast, target context exposure during conditioning reduced aversion to this context but did not affect contextual control of the sucrose aversion. In conclusion, depending on the conditioning procedures, contextual control of a taste aversion can be independent of the context's Pavlovian properties.

Converging evidence for one-trial context fear conditioning with an immediate shock: importance of shock potency.

Abstract: In a sample of 208 Holtzman-descended albino rats, we found evidence with 4 measures of conditioning (freezing, defecation, side crossing, and nose crossing) that a single 2-s, 1.0-mA immediate shock could condition fear to a context (Experiments 1, 2, and 4). When we reduced the shock intensity to 0.5 mA, we obtained a complete immediate-shock conditioning deficit according to all measures in Experiment 3 and to all but the defecation measure in Experiment 4. Results suggest two conclusions: (a) Differences in shock potency between laboratories may help explain discrepant findings about whether immediate shock supports contextual conditioning; (b) theories of contextual conditioning need a mechanism that permits that conditioning to result from immediate shock.

Quantitative models of animal learning and cognition.

Abstract: This article reviews the prerequisites for quantitative models of animal learning and cognition, describes the types of models, provides a rationale for the development of such quantitative models, describes criteria for their evaluation, and makes recommendations for the next generation of quantitative models. A modular approach to the development of models is described in which a procedure is considered as a generator of stimuli and a model is considered as a generator of responses. The goal is to develop models that, in combination with many different procedures, produce sequences of times of occurrence of events (stimuli and responses) that are indistinguishable from those produced by the animal under many experimental procedures and data analysis techniques.

Blocking of subsequent and antecedent events.

Abstract: Stimulus competition (e.g., blocking) has been observed between antecedent events (i.e., conditioned stimuli or potential causes), but recent evidence within the human causal learning literature suggests that it could also be obtained between subsequent events (i.e., unconditioned stimuli or potential effects). The present research tested this hypothesis with rat subjects. To avoid confounding the antecedent versus subsequent variable with the affective value of the events involved (i.e., unconditioned stimuli are ordinarily of greater affective value than conditioned stimuli), a preparation was used in which antecedent and subsequent events all lacked affective value during the blocking phases of the study. This was achieved through the use of sensory preconditioning. Blocking of subsequent events as well as antecedent events was observed. The challenge to most associative theories that is provided by blocking of subsequent events is discussed. Copyright 1997 by the American Psychological Association, Inc.

Temporal specificity in serial feature-positive discrimination learning

Abstract: Two experiments examined the temporal specificity of learning in operant serial feature-positive discriminations (feature-->target+/target-). Test performance was better when the target cues were presented at their customary times after the features than when they were presented at earlier or later times. When features trained with one feature-target interval were combined with targets trained with another interval, performance was best when the test interval was the same as the interval associated with the feature, suggesting that the temporal information was coded with the feature cue. Finally, the temporal specificity of the responding controlled by occasion setters was unaffected by feature extinction. Implications for the nature of learning in occasion setting are discussed.

Same-different texture discrimination in pigeons: testing competing models of discrimination and stimulus integration.

Abstract: The choice behavior of 6 pigeons performing a mulltidimensional same-different texture discrimination was examined. On each trial, they had to choose among 2 choice hoppers depending on whether a color, shape, or redundant (color and shape) target signal was present or not in a textured stimulus. Receiver operating characteristic (ROC) curves were produced by variations in the priori signal presentation probabilities across conditions. Quantitative analyses of these ROC curves were used to evaluate different competing theories of discrimination (signal detection vs. high-threshold-default response models) and information integration (independent observations, additive integration, unidimensional models). The results suggested the structure of the pigeons' choice behavior in this same-different discrimination was best described by an unequal variance signal detection model involving a unidimensional evidence variable (e.g., degree of difference).

Systematic nonlinearities in the memory representation of time.

Abstract: The representation of time was investigated by testing rats with intervals that changed by 2 s across trials. In Experiment 1, 2 ranges (20-150 s, 30-160 s; n = 10 rats per group) were examined. The times at which response bursts occurred (start time) were approximately proportional to interval durations. However, systematic departures from linearity were observed. Nonlinearities were related to the absolute duration of intervals, rather than to durations relative to the range. In Experiment 2, 660-s trials were inserted into the sequence of intervals (10-140 s, n = 20). Start and end times of response bursts were approximately proportional to intervals, but nonlinearities in start and end times were correlated, indicating that the source of nonlinearity was in the memory representation of time rather than in a decision process. These results indicate that the representation of time is nonlinearly related to physical time.

Mnemonics for variability: remembering food delay.

Abstract: Three experiments with White Carneaux pigeons (Columba livia) investigated memory and decision processes under fixed and variable reinforcement intervals. Response rate was measured during the unreinforced trials in the discrete-trial peak procedure in which reinforced trials were mixed with long unreinforced trials. Two decision models differing in assumptions about memory constraints are reviewed. In the complete-memory model (J. Gibbon, R.M. Church, S. Fairhurst, & A. Kacelnik, 1988), all interreinforcement intervals were remembered, whereas in the minimax model (D. Brunner, A. Kacelnik, & J. Gibbon, 1996), only estimates of the shortest and longest possible reinforcement times were remembered. Both models accommodated some features of response rate as a function of trial time, but only the second was compatible with the observed cessation of responding.

Pigeon perception and discrimination of rapidly changing texture stimuli.

Abstract: The perception and discrimination of rapidly changing texture stimuli by pigeons was examined in a target localization task. Five experienced pigeons were rewarded for finding and pecking at a randomly placed odd target block of small repeated elements embedded in a larger rectangular array of contrasting distractor elements. On dynamic color test trials, the color of the target, distractor, or both of these regions changed at rates of 100, 250, 500, or 1000 ms per frame. The number of colors appearing within such trials also varied. Pigeons performed well above chance in all test conditions, with target-associated changes producing the best discrimination. The results suggest: (a) global relational information can exclusively guide target localization behavior, (b) pigeons can perceptually group and segregate colored textured differences quite rapidly (< or = 100 ms), and (c) pigeons may possess automatic search control processes that can be captured by stimulus-driven changes in the display.

Inhibition of fear-potentiated startle can be detected after the offset of a feature trained in a serial feature-negative discrimination.

Abstract: Using the fear-potentiated startle paradigm in rats, 4 experiments examined whether the inhibitory effect of a feature is evident after its offset following serial feature-negative discrimination training (A+ and X-->A-). When startle probes were presented shortly after the offset of X on X-->A test trials, the inhibitory properties of X were observed immediately after its offset. Furthermore, trace reinforcement of X (X-->+), but not delay reinforcement (X+), disrupted the ability of X to inhibit fear-potentiated startle on X-->A trials. Trace conditioning to X was also retarded after A+ and X-->A- training. These results suggest that the inhibitory properties of the serially trained feature are present after its offset and raise the possibility that either temporal information regarding nonreinforcement or poststimulus attributes of X acquire inhibitory properties.

CSs and USs: what's the difference?

Abstract: Differences in processing representations of conditioned and unconditioned stimuli (CSs and USs) may result from either their temporal order in training (i.e., CSs precede USs) or the greater biological significance of USs. The CS- and US-preexposure effects were used to probe this question. These effects are similar except that context extinction between preexposure and training more readily attenuates the US- than the CS-preexposure effect. In Experiments 1, 2, and 5, context extinction following preexposure to the stimulus that later served as Event 1 in Event 1-->Event 2 pairings alleviated the response deficit due to Event 1 preexposure if Event 1 was biologically significant. In Experiments 3 and 4, context extinction alleviated the response deficit due to Event 2 preexposure if Event 2 was biologically significant. Thus, biological significance and not temporal order determines how a representation will be processed.

The science of animal cognition: past, present, and future.

Abstract: The field of animal cognition is strongly rooted in the philosophy of mind and in the theory of evolution. Despite these strong roots, work during the most famous and active period in the history of our science-the 1930s, 1940s, and 1950s-may have diverted us from the very questions that were of greatest initial interest to the comparative analysis of learning and behavior. Subsequently, the field has been in steady decline despite its increasing breadth and sophistication. Renewal of the field of animal cognition may require a return to the original questions of animal communication and intelligence using the most advanced tools of modern psychological science. Reclaiming center stage in contemporary psychology will be difficult; planning that effort with a host of strategies should enhance the chances of success.