The role of information about the response-outcome relation in instrumental discrimination learning

In 4 instrumental learning experiments, the hierarchical organization among responses (R), outcomes (O), and stimuli (S) was examined. Each experiment explored the possibility that S becomes associated with the R-O relation by providing information about that relation. In each case, an analogy was developed to a paradigm that has been important for concluding that informational relations affect Pavlovian conditioning. Experiments 1 and 2 found an effect of the information that S provides about the R-O relation, using paradigms analogous to blocking and contingency experiments. Experiments 3 and 4 demonstrated a similar result, using a paradigm like that of relative validity. In each case, the experiments pointed to the importance of the information that S gives about the R-O relation, rather than about the individual R and O elements.     

Differential outcomes effect in children: Demonstration and mechanisms

The present paper reports three experiments that examine the role of sample stimulus-outcome (S-O) and of comparison or choice response stimulus-outcome (R-O) relations in the differential outcomes discrimination learning of five-year-old children. In these experiments, S-O relations or R-O relations were maintained or removed across two different conditional discrimination tasks. The results indicated that only children who received training in either S-O or R-O relations showed positive transfer between the conditional discriminations. These data support a two-process (‘outcome expectancy’) account of differential outcomes phenomena in which each sub-problem in a discriminative conditional choice task has its own unique reinforcer, but they also indicate that both unique sample-outcome associations and unique choice-outcome associations are important contributing features to enhanced discriminative learning under differential outcomes procedures in humans. Comparison to a control in Experiments 2 and 3 indicated that merely having had previous experience with the stimuli or having previously discriminated the stimuli did not contribute to cross-discrimination transfer in the absence of prior explicit association between those stimuli and the specific differential outcomes.     

Discrimination learning during the first year: stimulus and positional cues

In four studies, 3-, 6-, and 9-month-old human infants were tested in a discrimination learning task in which visual fixation to a particular stimulus or lateral position was reinforced with an auditory stimulus. In Experiment 1, all age groups exhibited acquisition, extinction, and reinstatement of fixation to the reinforced target or position. Experiment 2 revealed that 3-month-olds retained the positional discrimination but not the stimulus discrimination after a 5-min delay between acquisition and extinction; older infants retained both types of discriminations. In Experiments 3 and 4 we investigated a possible developmental shift in the dominance of positional versus stimulus cues by training infants on displays in which stimulus and position were confounded and then by dissociating the cues on test trials. Results from both experiments indicated positional cue dominance for young infants and stimulus cue dominance for older infants. The findings are discussed in terms of differences in the attentional demands elicited by proprioceptive versus exteroceptive cues.     

The effect of deprivation level during noncontingent pairings and instrumental learning on subsequent instrumental performance

In Experiment 1, rats received either response-noncontingent pairings of a tone stimulus with food or response-contingent instrumental training during which only responses in the presence of the tone were reinforced. During this training rats were maintained at either 70 or 90% of their growth-adjusted predeprivation body weights. In a subsequent test phase, one-half of the subjects in each training condition were tested under either 70 or 90% body weight. Subjects which had received response-contingent instrumental training under 70% body weight responded significantly faster to presentations of the tone than did 90% body weight-trained subjects, regardless of test deprivation condition. There was no effect of the deprivation level in effect during response-noncontingent pairings. In Experiment 2, rats received noncontingent tone-reward pairings or nonpairings under either 70 or 90% body weight. In a later test phase under 90% body weight, instrumental responding to the tone was significantly faster for subjects which had received the tone-reward pairings. Deprivation level during the pairings again produced no effect. These results support two conclusions. First, the expectancy learning process appears to be relatively independent of deprivation conditions in effect when such learning takes place; and secondly, deprivation conditions in effect during instrumental learning affect the strength of S-R associative bonds formed.     

The Simon effect for vertical S–R relations: changing the mechanism by randomly varying the S–R mapping rule?

Recent findings indicate that the shape of the effect function of the Simon effect--derived by analysing the response time distribution for corresponding and non-corresponding trials--differs depending on the task. Specifically, decreasing effect functions have been reported for horizontal and stable rather increasing effect functions have been obtained for vertical stimulus-response (S-R) relations. Furthermore, it has been assumed that these differences reflect distinct mechanisms underlying the Simon effect. However, in two studies decreasing effect functions were reported for the vertical dimension. In order to investigate these contradictory findings four experiments were conducted. Since both studies--in which a decreasing effect function was obtained--used a modified version of the Simon task, that is, randomly varying S-R mapping rules, the Simon effect for fixed and random S-R mapping rules was investigated using vertical (Experiments 1, 2, and 4) and horizontal (Experiment 3) S-R relations. The results indicate that randomly varying S-R mapping rules affect the shape of the effect function for vertical but not for horizontal S-R relations. It was concluded that these findings indicate that the alternation of S-R mapping rules changes the information processing for the vertical dimension in a way, that the same mechanism as for horizontal S-R relations occurs.     

Effects of exemplar training in exclusion responding on auditory-visual discrimination tasks with children with autism

In Experiment 1 with 7 autistic children (3 to 6 years old), auditory-visual exclusion was tested with four unknown word-item pairs for each child. One child demonstrated exclusion and positive learning outcomes unequivocally with the four auditory-visual relations. Three children demonstrated exclusion, though inconsistently, and failed to demonstrate positive learning outcomes. The remaining 3 children failed to demonstrate exclusion; therefore, the learning outcome test was omitted. The 6 children who failed to demonstrate exclusion or positive learning outcomes participated in the second experiment. In Experiment 2, nonreinforced exclusion trials with four new unknown word-item pairs were included in trial blocks that also contained reinforced exclusion trials with the unknown exemplars from Experiment 1. Five children demonstrated exclusion with the new word-item pairs, and 4 of these demonstrated positive learning outcomes in further tests. One child demonstrated some limited but inconsistent improvement in exclusion and was not tested for learning outcomes. The data suggest that contemporaneous presentation of multiple examples of reinforced exclusion facilitated nonreinforced exclusion performances and that the resulting reduction in errors was critical in producing accurate learning outcomes with the new word-item discriminations.     

From conditioning to category learning: an adaptive network model

We used adaptive network theory to extend the Rescorla-Wagner (1972) least mean squares (LMS) model of associative learning to phenomena of human learning and judgment. In three experiments subjects learned to categorize hypothetical patients with particular symptom patterns as having certain diseases. When one disease is far more likely than another, the model predicts that subjects will substantially overestimate the diagnosticity of the more valid symptom for the rare disease. The results of Experiments 1 and 2 provide clear support for this prediction in contradistinction to predictions from probability matching, exemplar retrieval, or simple prototype learning models. Experiment 3 contrasted the adaptive network model with one predicting pattern-probability matching when patients always had four symptoms (chosen from four opponent pairs) rather than the presence or absence of each of four symptoms, as in Experiment 1. The results again support the Rescorla-Wagner LMS learning rule as embedded within an adaptive network model.     

The role of anticipation and intention in the learning of effects of self-performed actions

The anticipative learning model for acquiring action-effect relations states that the acquisition of action-effect relations depends on processes that are part of action planning, in particular the anticipation of possible effects. Experiment 1 shows that response planning is indeed crucial for the learning of response effects. In this experiment distractors (tones) were presented either during response preparation or in the time interval between response execution and the presentation of a response effect. Response-effect learning was impaired when the distractors were presented during response preparation. The finding is consistent with the assumption that the distractors impaired the anticipation of potential effects and therefore reduced effect learning. In Experiment 2 all responses had two effects. Participants were instructed to produce one of the effects. Under this condition, response-effect learning was only found for the instructed effect, not for the non-instructed effect. The two experiments thus support the view that response-effect learning is selective and depends on the anticipation of potential effects during response planning. The results are discussed in terms of a model that explains both the learning of response-effect relations and the use of these effects for action control within the same theoretical framework.     

Anticipatory response control in motor sequence learning: evidence from stimulus-response compatibility

Three experiments using a serial four-choice reaction-time (RT) task explored the interaction of sequence learning and stimulus-based response conflict. In Experiment 1, the spatial stimulus-response (S-R) mapping was manipulated between participants. Incompatible S-R mappings produced much higher RTs than the compatible mapping, but sequence learning decreased this S-R compatibility effect. In Experiment 2, the spatial stimulus feature was made task-irrelevant by assigning responses to symbols that were presented at unpredictable locations. The data indicated a Simon effect (i.e., increased RT when irrelevant stimulus location is spatially incompatible with response location) that was reduced by sequence learning. However, this effect was observed only in participants who developed an explicit sequence representation. Experiment 3 replicated this learning-based modulation of the Simon effect using explicit sequence-learning instructions. Taken together, the data support the notion that explicit sequence learning can lead to motor 'chunking', so that pre-planned response sequences are shielded from conflicting stimulus information.     

Discrimination of structure: I. Implications for connectionist theories of discrimination learning

In each of 4 experiments animals were given a structural discrimination task that involved visual patterns composed of identical features, but the spatial relations among the features were different for reinforced and nonreinforced trials. In Experiment 1 the stimuli were pairs of colored circles, and pigeons were required to discriminate between patterns that were the mirror image of each other. A related task was given to rats in Experiment 2. Subjects solved these discriminations. For Experiment 3, some pigeons were given a discrimination similar to that used in Experiment 1, which they solved, whereas others received a comparable task but with 3 colored circles present on every trial, which they failed to solve. The findings from Experiment 3 were replicated in Experiment 4 using different patterns. The results are difficult to explain by certain connectionist theories of discrimination learning, unless they are modified to take account of the way in which compound stimuli are structured.     

Dual learning processes in interactive skill acquisition

Acquisition of interactive skills involves the use of internal and external cues. Experiment 1 showed that when actions were interdependent, learning was effective with and without external cues in the single-task condition but was effective only with the presence of external cues in the dual-task condition. In the dual-task condition, actions closer to the feedback were learned faster than actions farther away but this difference was reversed in the single-task condition. Experiment 2 tested how knowledge acquired in single and dual-task conditions would transfer to a new reward structure. Results confirmed the two forms of learning mediated by the secondary task: A declarative memory encoding process that simultaneously assigned credits to actions and a reinforcement-learning process that slowly propagated credits backward from the feedback. The results showed that both forms of learning were engaged during training, but only at the response selection stage, one form of knowledge may dominate over the other depending on the availability of attentional resources.     

Time and order effects on causal learning

Five experiments were conducted to explore trial order and retention interval effects upon causal predictive judgments. Experiment 1 found that participants show a strong effect of trial order when a stimulus was sequentially paired with two different outcomes compared to a condition where both outcomes were presented intermixed. Experiment 2 found that a 48-h retention interval eliminates the trial order effect, so that participants gave a global judgment about the relationship between the stimulus and the two outcomes equivalent to the one given by participants that received the two phases intermixed. This result was replicated in Experiment 3 in a situation in which the probability of the outcome in the presence of the cue was changed from .5 for both outcomes (Experiments 1, 2, 4, and 5) to .75 and .25 for outcomes 1 and 2, respectively. Experiment 4 found that retention intervals ranging from 45 min to 48 h eliminated the trial order effect similarly. Experiment 5 found that a 10-min retention interval replicated the effect of time upon sequential training found in precedent experiments, regardless of whether participants remained within the laboratory during the retention interval or spent it outside. The combined results of this experimental series suggest that retention intervals reduce retroactive interference in causal learning by allowing participants to use all the information presented across phases, rather than differentially increasing or decreasing retrieval of information about each of them.     

Action-effect binding by observational learning

The acquisition of bidirectional action–effect associations plays a central role in the ability to intentionally control actions. Humans learn about actions not only through active experience, but also through observing the actions of others. In Experiment 1, we examined whether action–effect associations can be acquired by observational learning. To this end, participants observed how a model repeatedly pressed two buttons during an observation phase. Each of the buttonpresses led to a specific tone (action effect). In a subsequent test phase, the tones served as target stimuli to which the participants had to respond with buttonpresses. Reaction times were shorter if the stimulus–response mapping in the test phase was compatible with the action–effect association in the observation phase. Experiment 2 excluded the possibility that the impact of perceived action effects on own actions was driven merely by an association of spatial features with the particular tones. Furthermore, we demonstrated that the presence of an agent is necessary to acquire novel action–effect associations through observation. Altogether, the study provides evidence for the claim that bidirectional action–effect associations can be acquired by observational learning. Our findings are discussed in the context of the idea that the acquisition of action–effect associations through observation is an important cognitive mechanism subserving the human ability for social learning.     

Modes of knowledge acquisition and retrieval in artificial grammar learning

The aim of this study was to conceptualize artificial grammar learning (AGL) in terms of two orthogonal dimensions—the mode of knowledge acquisition and the mode of knowledge retrieval—as was done by Perlman and Tzelgov (2006) for sequence learning. Experiment 1 was carried out to validate our experimental task; Experiments 2–4 tested, respectively, performance in the intentional, incidental, and automatic retrieval modes, for each of the three modes of acquisition. Furthermore, signal detection theory (SDT) was used as an analytic tool, consistent with our assumption that the processing of legality-relevant information involves decisions along a continuous dimension of fluency. The results presented support the analysis of AGL in terms of the proposed dimensions. They also indicate that knowledge acquired during training may include many aspects of the presented stimuli (whole strings, relations among elements, etc.). The contribution of the various components to performance depends on both the specific instruction in the acquisition phase and the requirements of the retrieval task.     

Shared learning shapes human performance: Transfer effects in task sharing

We investigated whether performing a task with a co-actor shapes the way a subsequent task is performed. In four experiments participants were administered a Simon task after practicing a spatial compatibility task with an incompatible S-R mapping. In Experiment 1 they performed both tasks alongside another person; in Experiment 2 they performed the spatial compatibility task alone, responding to only one stimulus position, and the Simon task with another person; in Experiment 3, they performed the spatial compatibility task with another person and the Simon task alone; finally, in Experiment 4, they performed the spatial compatibility task alone and the Simon task with another person. The incompatible practice eliminated the Simon effect in Experiments 1 and 4. These results indicate that when a task is distributed between two participants with each one performing a different part of it, they tend to represent the whole task rather than their own part of it. This experience can influence the way a subsequent task is performed, as long as this latter occurs in a social context.     

Contrast effects in flavour preference learning

In four experiments the role of contrast effects in producing learned flavour preferences was examined. The experiments showed that contrast effects are pervasive in flavour preference learning, producing results that are often paradoxical from a traditional reinforcement point of view. In Experiment 1, rats preferred a reinforced flavour over a nonreinforced flavour more if the reinforcer was 1% sucrose than if the reinforcer was 8% sucrose. Because the cue flavour was dissolved in 8% sucrose, this represents an anticipatory positive contrast effect. In Experiment 2, the relationship between cue and consequence was shown to be important in flavour preference learning, as expected if contrast effects are involved. In Experiment 3, rats preferred a flavour that was reinforced 4 times, and they preferred this flavour more than one reinforced 8 times, presumably because the greater the expectancy of the consequence, the greater the anticipatory negative contrast. In Experiment 4, rats consumed less of 0.15% saccharin if they received 32% sucrose randomly 90 min either before or after the 0.15% saccharin than if they received only 0.15% saccharin, a simultaneous negative contrast effect.     

Element pretraining influences the content of appetitive serial compound conditioning in rats

Four experiments with rat subjects in a Pavlovian appetitive conditioning procedure examined the effects of prior pairings of S2 with the unconditioned stimulus (US) on the nature of the associations formed in S1----S2----US serial compound conditioning. Experiments 1 and 2 showed that prior training of S2 prevented the acquisition of stimulus-stimulus (S-S) associations between S1 and stimulus features of S2, but enhanced the acquisition of stimulus-response (S-R) associations between S1 and the emotional conditioned response (CR) evoked by S2. Experiments 3 and 4 showed that the effects of S2 pretraining were not due to S2 training itself, but rather to its endowing S2 with the ability to evoke a strong CR during the early stages of serial compound conditioning. In Experiment 3, suppression of the CR to a pretrained S2 during serial compound conditioning permitted the establishment of S-S associations. In Experiment 4, the induction of a CR in the presence of an untrained S2 during serial compound conditioning prevented the acquisition of S-S associations. Implications of these data for our understanding of compound conditioning are discussed.     

Effects of learning contexts on implicit and explicit learning

Two parallel tasks involving rule learning were identified in Experiment 1A and were used to assess implicit and explicit learning. In both tasks, subjects had to input numbers in order to reach the target values of outputs. The relationship between inputs and outputs was either simple (in the simple task) or complex (in the complex task), and the way in which target values were presented could be in the form of either numbers (in the simple task) or lines (in the complex task). Experiment 1B examined the validity of the explicit measure in the complex task. Experiments 2–4 investigated the interaction between learning contexts and the simple/complex learning tasks. Verbalization and instructions to search for the rules facilitated the simple-task learning and hurt or have no effect on the complex-task learning. In the observational-learning condition, no learning occurred for the simple task, and the complex task learning was impaired. These results suggest that the complex task and simple task involve two distinct learning systems. Other implications are also discussed.     

Investigating the role of response in spatial context learning

Recent research has shown that simple motor actions, such as pointing or grasping, can modulate the way we perceive and attend to our visual environment. Here we examine the role of action in spatial context learning. Previous studies using keyboard responses have revealed that people are faster locating a target on repeated visual search displays (“contextual cueing”). However, this learning appears to depend on the task and response requirements. In Experiment 1, participants searched for a T-target among L-distractors and responded either by pressing a key or by touching the screen. Comparable contextual cueing was found in both response modes. Moreover, learning transferred between keyboard and touch screen responses. Experiment 2 showed that learning occurred even for repeated displays that required no response, and this learning was as strong as learning for displays that required a response. Learning on no-response trials cannot be accounted for by oculomotor responses, as learning was observed when eye movements were discouraged (Experiment 3). We suggest that spatial context learning is abstracted from motor actions.     

Associative relations in instrumental learning: The eighteenth Bartlett memorial lecture

Instrumental learning involves three primary events: a stimulus (S), a response (R), and an outcome (O). Evidence is reviewed indicating the presence of binary associations among those events, as well as a hierarchical structure of the form S-(R-O). Experiments examining the conditions that produce learning, the content of the learning once it has occurred, and the way learning maps into performance all suggest the presence of such a hierarchical structure.