Anja Lotz

Extinction of conditioned inhibition: Effects of different outcome continua

For some decades, failures to find extinction of inhibition through unpaired presentations of the inhibitor were taken as evidence against conceptualizing inhibition as the symmetrical counterpart of excitation. Recently, however, our group has demonstrated successful extinction of inhibition in human causal learning. In two experiments, we replicated and strengthened this finding by using an outcome continuum that could take on negative, neutral, or positive values. In contrast, the use of a dichotomous outcome continuum (either neutral or positive) resulted in the well-known nonoccurrence of extinction. Extinction of inhibition through the pairing of inhibitors with neutral outcomes was assessed by (1) comparing the (presumably) extinguished inhibitor with a second inhibitor that had not been presented with a neutral outcome in the extinction stage, and (2) demonstrating the course of extinction in participants’ predictions.

Connectionist models of artificial grammar learning: what type of knowledge is acquired?

Two experiments are presented that test the predictions of two associative learning models of Artificial Grammar Learning. The two models are the simple recurrent network (SRN) and the competitive chunking (CC) model. The two experiments investigate acquisition of different types of knowledge in this task: knowledge of frequency and novelty of stimulus fragments (Experiment 1) and knowledge of letter positions, of small fragments, and of large fragments up to entire strings (Experiment 2). The results show that participants acquired all types of knowledge. Simulation studies demonstrate that the CC model explains the acquisition of all types of fragment knowledge but fails to account for the acquisition of positional knowledge. The SRN model, by contrast, accounts for the entire pattern of results found in the two experiments.

Blocking of conditioned inhibition in human causal learning: no learning about the absence of outcomes

Compared to blocking of conditioned excitation, which is one of the most investigated cue competition phenomena, blocking of conditioned inhibition has more or less been neglected in conditioning research. We conducted a human causal learning study and found evidence for blocking of conditioned inhibition. The results favor the view that inhibition is the symmetrical opposite of excitation, underlying the same general principles.

Classification and recognition in artificial grammar learning : Analysis of receiver operating characteristics

In two experiments we investigated recognition and classification judgements using an artificial grammar learning paradigm. In Experiment 1, when only new test items had to be judged, analysis of z-transformed receiver operating characteristics (z-ROCs) revealed no differences between classification and recognition. In Experiment 2, where we included old test items, z-ROCs in the two tasks differed, suggesting that judgements relied on different types of information. The results are interpreted in terms of heuristics that people use when making classification and recognition judgements.

An exploration of the feature-positive effect in adult humans

Experiment 1 compared the acquisition of a feature-positive and a feature-negative discrimination in humans. In the former, an outcome was signaled by two stimuli together, but not by one of these stimuli alone. In the latter, the outcome was signaled by one stimulus alone, but not by two stimuli together. Using a within-group design, the experiment revealed that the feature-positive discrimination was acquired more readily than the feature-negative discrimination. Experiment 2 tested an explanation for these results, based on the Rescorla–Wagner theory, by examining how novel discriminations, based on a combination of a feature-positive and a feature-negative discrimination, were solved. The results did not accord with predictions from the theory. Alternative explanations for the results are considered.

Multiple regression analyses in artificial-grammar learning: The importance of control groups

In artificial-grammar learning, it is crucial to ensure that above-chance performance in the test stage is due to learning in the training stage but not due to judgemental biases. Here we argue that multiple regression analysis can be successfully combined with the use of control groups to assess whether participants were able to transfer knowledge acquired during training when making judgements about test stimuli. We compared the regression weights of judgements in a transfer condition (training and test strings were constructed by the same grammar but with different letters) with those in a control condition. Predictors were identical in both conditions—judgements of control participants were treated as if they were based on knowledge gained in a standard training stage. The results of this experiment as well as reanalyses of a former study support the usefulness of our approach.

The fate of redundant cues in human predictive learning.

In each of three experiments, a single group of participants received a sequence of trials involving pictures of a variety of foods presented individually or in pairs. Participants were required to predict in which trials the food would lead to a hypothetical allergic reaction. The different trials involved blocking, A+ AX+, and a simple discrimination, BY- CY+, in which each letter stands for a different food. Training trials were followed by a test in which participants were asked to predict how likely each kind of food would be followed by the allergic reaction. The principal purpose of the experiments was to determine how the redundant cue from blocking, X, would be judged relative to the redundant cue from the simple discrimination, Y. In contrast to predictions from currently influential theories of associative learning, X was regarded as a better predictor for the allergic reaction than Y.

Rapid communication: Sex differences in artificial grammar learning: Evidence for different strategies in men and women

In this article we report an experiment that investigated differences in classification performance of women and men in artificial grammar learning (AGL). Womens and mens responses correspond to a large extent. Consistent differences, however, were found in a variable that codes overlaps between training and test items in terms of string fragments. The results are best explained by the assumption that women and men apply different cognitive strategies at test.

Indicators of early and late processing reveal the importance of within-trial-time for theories of associative learning.

In four human learning experiments (Pavlovian skin conductance, causal learning, speeded classification task), we evaluated several associative learning theories that assume either an elemental (modified unique cue model and Harris’ model) or a configural (Pearce’s configural theory and an extension of it) form of stimulus processing. The experiments used two modified patterning problems (A/B/C+, AB/BC/AC+ vs. ABC-; A+, BC+ vs. ABC-). Pearce’s configural theory successfully predicted all of our data reflecting early stimulus processing, while the predictions of the elemental theories were in accord with all of our data reflecting later stages of stimulus processing. Our results suggest that the form of stimulus representation depends on the amount of time available for stimulus processing. Our findings highlight the necessity to investigate stimulus processing during conditioning on a finer time scale than usually done in contemporary research.

Contextual control of attentional allocation in human discrimination learning.

In 3 human predictive learning experiments, we investigated whether the allocation of attention can come under the control of contextual stimuli. In each experiment, participants initially received a conditional discrimination for which one set of cues was trained as relevant in Context 1 and irrelevant in Context 2, and another set was relevant in Context 2 and irrelevant in Context 1. For Experiments 1 and 2, we observed that a second discrimination based on cues that had previously been trained as relevant in Context 1 during the conditional discrimination was acquired more rapidly in Context 1 than in Context 2. Experiment 3 revealed a similar outcome when new stimuli from the original dimensions were used in the test stage. Our results support the view that the associability of a stimulus can be controlled by the stimuli that accompany it.