Learning about environmental geometry: an associative model

K. Cheng (1986) suggested that learning the geometry of enclosing surfaces takes place in a geometric module blind to other spatial information. Failures to find blocking or overshadowing of geometry learning by features near a goal seem consistent with this view. The authors present an operant model in which learning spatial features competes with geometry learning, as in the Rescorla-Wagner model. Relative total associative strength of cues at a location determines choice of that location and thus the frequencies of reward paired with each cue. The model shows how competitive learning of local features and geometry can appear to result in potentiation, blocking, or independence, depending on enclosure shape and kind of features. The model reproduces numerous findings from dry arenas and water mazes.     

Curved saccade trajectories reveal conflicting predictions in associative learning

We report how the trajectories of saccadic eye movements are affected by memory interference acquired during associative learning. Human participants learned to perform saccadic choice responses based on the presentation of arbitrary central cues A, B, AC, BC, AX, BY, X, and Y that were trained to predict the appearance of a peripheral target stimulus at 1 of 3 possible locations, right (R), mid (M), or left (L), in the upper hemifield. We analyzed as measures of associative learning the frequency, latency, and curvature of saccades elicited by the cues and directed at the trained locations in anticipation of the targets. Participants were trained on two concurrent discrimination problems A+R, AC+R, AX+M, X+M and B+L, BC+L, BY+M, Y+M. From a connectionist perspective, cues were predicted to acquire associative links connecting the cues to the trained outcomes in memory. Model simulations based on the learning rule of the Rescorla and Wagner (1972) model revealed that for some cues, the prediction of the correct target location was challenged by the interfering prediction of an incorrect location. We observed that saccades directed at the correct location in anticipation of the target curved away from the location that was predicted by the interfering association. Furthermore, changes in curvature during training corresponded to predicted changes in associative memory. We propose that this curvature was caused by the inhibition of the incorrect prediction, as previously has been suggested with the concept of distractor inhibition (Sheliga, Riggio, & Rizzolatti, 1994; Tipper, Howard, & Houghton, 2000). The paradigm provides a new method to examine memory interference during associative learning.     

Prawn-in-a-tube procedure: habituation or associative learning in cuttlefish?

The prawn-in-a-tube procedure (J. B. Messenger, 1973a) has been used almost exclusively to study associative learning in cuttlefish. In two experiments, the authors sought to determine whether the decline in attack responses observed in this procedure was best accounted for by habituation or associative learning. Results of Experiment 1 revealed an asymmetrical stimulus-specificity effect that could be interpreted as either an instance of habituation or of associative learning. Results of Experiment 2 demonstrated that the response decline could not be reversed following the presentation of a dishabituatory stimulus. The combined results of these experiments support the conclusion that the response decline is best viewed as a resulting of associative processes. The authors considered whether the response decline represents extinction or passive avoidance.     

Association, inhibition, and object permanence in dogs' (Canis familiaris) spatial search

The relative role of associative processes and the use of explicit cues about object location in search behavior in dogs (Canis familiaris) was assessed by using a spatial binary discrimination reversal paradigm in which reversal conditions featured: (1) a previously rewarded location and a novel location, (2) a previously nonrewarded location and a novel location, or (3) a previously rewarded location and a previously nonrewarded location. Rule mediated learning predicts a similar performance in these different reversal conditions whereas associative learning predicts the worst performance in Condition 3. Evidence for an associative control of search emerged when no explicit cues about food location were provided (Experiment 1) but also when dogs witnessed the hiding of food in the reversal trials (Experiment 2) and when they did so in both the prereversal and the reversal trials (Experiment 3). Nevertheless, dogs performed better in the prereversal phase of Experiment 3 indicating that their search could be informed by the knowledge of the food location. Experiment 4 confirmed the results of Experiments 1 and 2, under a different arrangement of search locations. We conclude that knowledge about object location guides search behavior in dogs but it cannot override associative processes.     

Landmark Stability: Further Studies Pointing to a Role in Spatial Learning

Two experiments were conducted to investigate the possible role of landmark stability in spatial learning. Rats were trained to search in a large arena for food hidden at a consistent distance and direction from either a single radially symmetric landmark or an array of two landmarks. We varied the relative degree to which the landmark array and/or the cues of the training context predicted the location of food, without varying the conditional probability of food being available given either cue. Experiment 1 used vestibular disorientation to ensure control of search location by experimenter-controlled cues. The results showed that making either a single landmark or a cluster of two adjacent landmarks the sole spatial predictor of reward location reduced the accuracy of search compared to a condition where both the landmark array and context cues were reliable spatial predictors. Varying global landmark stability had no effect when training was conducted using an array of two landmarks located some distance from each other. Context cues, when tested alone, triggered very little searching in appropriate locations, and the absolute magnitude of control over search was insufficient to account for the superiority of stable landmarks. The better learning with a stable landmark, and the dependence of this effect on the geometrical arrangement of landmarks, points to the conditions of spatial learning involving additional principles to those of simple associative conditioning. Experiment 2 examined landmark stability using a single landmark and fixed directional cues in the absence of vestibular disorientation. This also revealed a relative advantage of landmark stability, but animals with a landmark that moved from trial to trial did show some evidence of learning. Context cues when tested alone had minimal influence. Parametric manipulation of landmark stability offers a novel way of influencing spatial learning and thus understanding better the process through which egocentric representations of perceived space are transformed into allocentric representations of the real world. The purpose of this paper is to describe two experiments concerned with identifying the psychological processes of allocentric spatial learning. The results point to the idea that landmark stability is an important factor in spatial learning. Specifically, they reveal that whether or not a landmark will be used for the purpose of representing the location of another object (including hidden objects) is influenced by whether it is perceived as geometrically stable with respect to at least one other landmark and/or certain geometric features of the environment. This phenomenon is relevant to the application of associative learning principles to the spatial domain.     

Developmental differences in memory for cross‐modal associations

Associative learning is critical to normal cognitive development in children. However, young adults typically outperform children on paired‐associate tasks involving visual, verbal and spatial location stimuli. The present experiment investigated cross‐modal odour–place associative memory in children (7–10 years) and young adults (18–24 years). During the study phase, six odours were individually presented and paired with one of 12 spatial locations on a board. During the test phase, participants were presented with the six stimuli individually and were asked to place each stimulus on the correct spatial location. Children committed significantly more errors on the odour–place task than did young adults. However, item recognition memory for the odours or spatial locations involved in the odour–place associative memory task was similar between children and young adults. Therefore, poor odour–place associative memory in children did not result from impaired memory for the individual odours or spatial locations involved in the associations. The results suggest that cross‐modal associative memory is not fully developed in children.     

Stimulus generalization in two associative learning processes

Recent studies involving nonlinear discrimination problems suggest that stimuli in human associative learning are represented configurally with narrow generalization, such that presentation of stimuli that are even slightly dissimilar to stored configurations weakly activate these configurations. The authors note that another well-known set of findings in human associative learning, cue-interaction phenomena, suggest relatively broad generalization. Three experiments show that current models of human associative learning, which try to model both nonlinear discrimination and cue interaction as the result of 1 process, fail because they cannot simultaneously account for narrow and broad generalization. Results suggest that human associative learning involves (a) an exemplar-based process with configural stimulus representation and narrow generalization and (b) an adaptive learning process characterized by broad generalization and cue interaction.     

The effects of study order and backward associative strength on illusory recollection: A source-strength effect does not always occur

We investigated illusory recollection by dividing lists of associated words into three subsets (high, medium and low) based on their backward associative strength (BAS) to an unstudied theme. Participants studied these subsets at different visual locations on a computer screen and afterwards were given a source memory test. In Experiment 1, we varied the order in which high- and medium-BAS subsets were studied. In Experiment 2, we again manipulated study order as well as the associative strength of the medium-BAS subsets (strong or weak). Across both experiments, illusory recollection was constrained by both study order and BAS. Source attributions to the high-BAS location were more likely (a source-strength effect) when high-BAS items were studied first or studied following items of relatively low associative strength. However, attributions to the strong medium-BAS studied location were more likely when these items were studied before high-BAS items. These findings are interpreted as resulting from misbinding of source details at encoding which can be explained by the activation-monitoring theory of illusory recollection.     

Comparing elemental and configural associative theories in human causal learning: a case for attention

In two causal learning experiments with human participants, the authors compared various associative theories that assumed either elemental (unique cue, modified unique cue, replaced elements model, and Harris' model) or configural processing of stimuli (Pearce's theory and a modification of it). The authors used modified patterning problems initially suggested by Redhead and Pearce (1995). Predictions for all theories were generated by computer simulations. Both configural theories and the unique cue approach failed to account for the observations. The replaced elements model was able to account for part of the data, but only if the replacement parameters could vary across discrimination problems. The Harris model and the modified unique cue approach, assuming that the salience of stimuli decreases with an increasing number of stimuli in a compound, successfully accounted for all of our data. This success implies that attentional factors should be explicitly taken into account in associative learning theory.     

Perceptual learning in the rat: stimulus differentiation or latent inhibition of common elements?

Preexposure to an unreinforced stimulus facilitates learning (perceptual learning) under some conditions, but it can have the opposite effect (latent inhibition) under other conditions. Researchers have suggested that perceptual learning depends on a change of context, whereas latent inhibition is usually context specific. The associative theory explains both phenomena within a single framework. The authors report 4 experiments that show that perceptual learning does not depend on a context change. The experiments suggest that latent inhibition, unlike perceptual learning, depends on passive exposure. Thus the results do not support the associative theory. They are more consistent with Gibson's stimulus-differentiation theory.     

Perceptual Learning in the Rat: Stimulus Differentiation or Latent Inhibition of Common Elements?

Preexposure to an unreinforced stimulus facilitates learning (perceptual learning) under some conditions, but it can have the opposite effect (latent inhibition) under other conditions. Researchers have suggested that perceptual learning depends on a change of context, whereas latent inhibition is usually context specific. The associative theory explains both phenomena within a single framework. The authors report 4 experiments that show that perceptual learning does not depend on a context change. The experiments suggest that latent inhibition, unlike perceptual learning, depends on passive exposure. Thus the results do not support the associative theory. They are more consistent with Gibson's stimulus-differentiation theory.     

Associative symmetry versus independent associations in the memory for object-location associations

The formation of associations between objects and locations is a vital aspect of episodic memory. More specifically, remembering the location where one experienced an object and, vice versa, the object one encountered at a specific location are both important elements for the memory of an event. Whether episodic associations are holistic representations of individual components or whether there are unidirectional, separately modifiable connections between them has been investigated nearly exclusively using verbal stimuli. A preliminary conclusion concerning this controversy is that verbal associations are, at least, highly correlated (M. J. Kahana, 2002). This theoretical debate, which in the past has undergone a major empirical effort, is still of relevance for the concurrent global matching models of associative memory (S. E. Clark & S. D. Gronlund, 1996). The authors used variations of a novel object-location learning paradigm to complement the accumulated evidence regarding the nature of episodic associations.     

Feature binding in children and young adults

The authors measured memory for individual features (objects only or locations only) and the combination of those features (objects and locations) in 9-, 12-, and 21-year-old students with a yes or no recognition task. Analysis of recognition memory performance (d' scores) revealed that although age differences existed in memory for individual features, age differences were greater in the tasks that required memory for combined features (objects and locations). Hierarchical multiple regression analyses indicated that age remained a significant predictor of memory performance in the combination condition even after the authors statistically removed memory performance in object and location conditions and the interaction effects of object and location. These results provide evidence for developmental differences in the binding of features in memory.     

Associative sequence learning in humans

In a series of experiments using the serial reaction time paradigm, the authors compared the predictions of a powerful associative model of sequence learning (the simple recurrent network; J. L. Elman, 1990) with human performance on the problem devised by A. Maskara and W. Noetzel (1993). Even though the predictions made by the simple recurrent network for variants of this problem are often counterintuitive, they matched human performance closely, suggesting that performance was associatively based rather than rule based. Simple associative chaining models of sequence learning, however, have difficulty in accommodating these results. The authors' conclusion is that, under the conditions of the experiments, human sequence learning is associatively driven, as long as this is understood to mean that a sufficiently powerful means of extracting the statistical regularities in the sequences is in play.     

Word learning as Bayesian inference

The authors present a Bayesian framework for understanding how adults and children learn the meanings of words. The theory explains how learners can generalize meaningfully from just one or a few positive examples of a novel word's referents, by making rational inductive inferences that integrate prior knowledge about plausible word meanings with the statistical structure of the observed examples. The theory addresses shortcomings of the two best known approaches to modeling word learning, based on deductive hypothesis elimination and associative learning. Three experiments with adults and children test the Bayesian account's predictions in the context of learning words for object categories at multiple levels of a taxonomic hierarchy. Results provide strong support for the Bayesian account over competing accounts, in terms of both quantitative model fits and the ability to explain important qualitative phenomena. Several extensions of the basic theory are discussed, illustrating the broader potential for Bayesian models of word learning.     

Effector-dependent learning by observation of a finger movement sequence

Can observational learning be effector dependent? In 3 experiments, observers watched a model respond to a 6-item unique sequence in a serial reaction time task. Their sequence knowledge was then compared with that of controls who had performed an unrelated task or observed a model responding to random targets. Observational learning was indicated when the introduction of a new sequence was associated with more reaction time elevation in observers than in controls. The authors found evidence of observational learning only when observers used the finger movement sequence that they observed during training, not when they responded at the same sequence of locations using different digits. Free generation and recognition tests also detected observational learning. These results imply that observational learning can be both explicit and effector dependent.     

Break expectancy in duration discrimination

Effects of break expectancy, observed previously in time production, were examined in 3 experiments using a discrimination paradigm. Participants classified a tone as being short or long. Location and duration of breaks in tone presentation were varied. Proportion of short responses increased as the break occurred later in the duration to be estimated in all experiments. With a higher number of break locations covering a wider range of location values, functions relating proportion of short responses to location were sigmoid and tended to flatten at extreme values of location. The authors conclude that attentional time-sharing elicited by break expectancy induces loss in accumulation of temporal information, but its effect on discrimination depends on the accumulation outcome relative to a decisional criterion.     

Blocking in category learning

Many theories of category learning assume that learning is driven by a need to minimize classification error. When there is no classification error, therefore, learning of individual features should be negligible. The authors tested this hypothesis by conducting three category-learning experiments adapted from an associative learning blocking paradigm. Contrary to an error-driven account of learning, participants learned a wide range of information when they learned about categories, and blocking effects were difficult to obtain. Conversely, when participants learned to predict an outcome in a task with the same formal structure and materials, blocking effects were robust and followed the predictions of error-driven learning. The authors discuss their findings in relation to models of category learning and the usefulness of category knowledge in the environment.     

Learning the association between a context and a target location in infancy

Extracting the statistical regularities present in the environment is a central learning mechanism in infancy. For instance, infants are able to learn the associations between simultaneously or successively presented visual objects (Fiser & Aslin, 2002 ; Kirkham, Slemmer & Johnson, 2002 ). The present study extends these results by investigating whether infants can learn the association between a target location and the context in which it is presented. With this aim, we used a visual associative learning procedure inspired by the contextual cuing paradigm, with infants from 8 to 12 months of age. In two experiments, in which we varied the complexity of the stimuli, we first habituated infants to several scenes where the location of a target (a cartoon character) was consistently associated with a context, namely a specific configuration of geometrical shapes. Second, we examined whether infants learned the covariation between the target location and the context by measuring looking times at scenes that either respected or violated the association. In both experiments, results showed that infants learned the target–context associations, as they looked longer at the familiar scenes than at the novel ones. In particular, infants selected clusters of co‐occurring contextual shapes and learned the covariation between the target location and this subset. These results support the existence of a powerful and versatile statistical learning mechanism that may influence the orientation of infants’ visual attention toward areas of interest in their environment during early developmental stages. A video abstract of this article can be viewed at: https://www.youtube.com/watch?v=9Hm1unyLBn0     

Reversal learning as a function of changed reward location or changed drive

In two experiments, rats were trained with food in one location (e.g., black alley) and water in another location (white alley) under hunger or thirst. Subsequently, either the locations of the rewards were reversed, or the drive was changed (from hunger to thirst or thirst to hunger). Reversal of instrumental responses took considerably longer when drive was changed and rewards remained in the same locations than when reward locations were reversed. These results were interpreted as indicating that the animal's internal representations of the rewards received in each location transfer when drive is changed. These internal-reward representations interfere with reversal learning by eliciting the responses which were conditioned to them in Phase 1. Because the values of food and water reverse when drive is changed from hunger to thirst or vice versa, it was suggested that the reward representations surviving the drive shift are cognitive representations of the specific events received (food or water), independent of the value of the rewards under either hunger or thirst.