Multi-modal discrimination learning in humans: evidence for configural theory

Human contingency learning was used to compare the predictions of configural and elemental theories. In three experiments, participants were required to learn which indicators were associated with an increase in core temperature of a fictitious nuclear plant. Experiments 1 and 2 investigated the rate at which a triple-element stimulus (ABC) could be discriminated from either single-element stimuli (A, B, and C) or double-element stimuli (AB, BC, and AC). Experiment 1 used visual stimuli, whilst Experiment 2 used visual, auditory, and tactile stimuli. In both experiments the participants took longer to discriminate the triple-element stimulus from the more similar double-element stimuli than from the less similar single-element stimuli. Experiment 3 tested for summation with stimuli from either single or multiple modalities and summation was found only in the latter. Thus the pattern of results seen in Experiments 1 and 2 was not dependent on whether the stimuli were single- or multi-modal nor was it dependent on whether the stimuli could elicit summation. This pattern of results is consistent with the predictions of Pearce’s (1987) configural theory

A new protocol for investigating visual two‑choice discrimination learning in lizards

One of the most widely studied abilities in lizards is discrimination learning. The protocols used to test lizards are often novel or adapted from other taxa without proper validation. We need to ensure that tests of discrimination learning are appropriate and properly applied in lizards so that robust inferences can be made about cognitive ability. Here, we present a new protocol for testing lizard discrimination learning that incorporates a target training procedure, uses many daily trials for efficiency and reinforcement, and has a robust, validated, learning criterion. We trained lizards to touch a cue card using operant conditioning and tested lizards separately on a colour, and pattern discrimination test. Lizards successfully learnt to touch a cue card and to discriminate between light and dark blue but had issues discriminating the patterns. After modifying the test procedure, some lizards reached criterion, revealing possible issues with stimulus processing and interference of generalisation. Here, we describe a protocol for operant conditioning and two-choice discrimination learning in lizards with a robust learning criterion that can help researcher better design future studies on discrimination learning in lizards

Facial Emotions Improve Face Discrimination Learning

How visual experience modulates the ability to discriminate faces from one another is still poorly understood. The aim of this study is to investigate whether emotions may favor face discrimination learning. To this purpose, we measured face discrimination thresholds before and after a training phase, where participants are exposed to (task-irrelevant) subtle variations in face images from trial to trial. A task-irrelevant perceptual learning paradigm was used because it closely mimics the learning processes that daily occur, without a conscious intention to learn and without a focused attention on specific facial features. During the four sessions of training, participants performed a contrast-discrimination task on face images. The task-irrelevant features were face images variations along the morphing continuum of facial identity (Identity group) or face images variations along the morphing continuum of emotional expressions (Emotion group). A group of participants (Control group) did not perform the contrast training, but their face discrimination thresholds were measured with the same temporal gap between them as the other two groups. Results indicate a face discrimination improvement only for the Emotion group. Participants in the Emotion Group showed a discrimination improvement when tested with variations along the dimension of identity and with variations along the dimension of expression, even if identity variations were not used during training. The present results suggest a role of emotions in face discrimination learning and show that faces, differently from the other classes of stimuli, may manifest a higher degree of learning transfer

Stimulus similarity affects patterning discrimination learning.

© 2018 American Psychological Association. In four experiments, participants' performance on a variety of nonlinear patterning discriminations was assessed using a predictive learning task and visual patterns. Between groups, the similarity of the stimuli that composed these visual patterns was manipulated. When the stimuli were of low similarity, participants' performance was consistent with the predictions of one version of Pearce's (1987, 1994, 2002) configural theory of learning (Kinder & Lachnit, 2003); they were better able to discriminate between different patterns when they shared few, rather than many, stimuli. This effect was not observed when the similarity of the stimuli was high. Under these conditions, the results were more consistent with predictions of elemental theories of learning (e.g., Rescorla & Wagner, 1972; Wagner, 2003). This is the first time that these different patterns of performance on complex patterning discriminations have been shown within a single stimulus modality in the same experiment. The overall pattern of results is difficult to reconcile with either elemental or configural models of associative learning

Preexposure along a continuum: Differentiation and association.

In five experiments, we assessed the effects of pre-exposure to simple auditory stimuli on subsequent conditioning and discrimination learning. Experiment 1 showed that pre-exposure to a single stimulus retarded acquisition of conditioned responding to that stimulus. The same pre-exposure regimen facilitated the subsequent acquisition of a discrimination between two stimuli that flanked the pre-exposed stimulus along the frequency dimension. Experiment 2 replicated this midpoint pre-exposure effect on discrimination learning but also found that alternating pre-exposure to the discriminative stimuli retarded discrimination learning. Experiments 3 to 5 explored the causes of these effects. These experiments are the first to examine perceptual learning in animals using simple auditory stimuli and their results suggest that in at least some circumstances alternating pre-exposure to auditory stimuli results in an increase in generalization between them

Discrimination learning with variable stimulus 'salience'.

BACKGROUND: In nature, sensory stimuli are organized in heterogeneous combinations. Salient items from these combinations 'stand-out' from their surroundings and determine what and how we learn. Yet, the relationship between varying stimulus salience and discrimination learning remains unclear. PRESENTATION OF THE HYPOTHESIS: A rigorous formulation of the problem of discrimination learning should account for varying salience effects. We hypothesize that structural variations in the environment where the conditioned stimulus (CS) is embedded will be a significant determinant of learning rate and retention level. TESTING THE HYPOTHESIS: Using numerical simulations, we show how a modified version of the Rescorla-Wagner model, an influential theory of associative learning, predicts relevant interactions between varying salience and discrimination learning. IMPLICATIONS OF THE HYPOTHESIS: If supported by empirical data, our model will help to interpret critical experiments addressing the relations between attention, discrimination and learning

Neuron analysis of visual perception

The receptive fields of single cells in the visual system of cat and squirrel monkey were studied investigating the vestibular input affecting the cells, and the cell's responses during visual discrimination learning process. The receptive field characteristics of the rabbit visual system, its normal development, its abnormal development following visual deprivation, and on the structural and functional re-organization of the visual system following neo-natal and prenatal surgery were also studied. The results of each individual part of each investigation are detailed

Medial prefrontal cortex circuit function during retrieval and extinction of associative learning under anesthesia

Associative learning is encoded under anesthesia and involves the medial prefrontal cortex (mPFC). Neuronal activity in mPFC increases in response to a conditioned stimulus (CS+) previously paired with an unconditioned stimulus (US) but not during presentation of an unpaired stimulus (CS-) in anesthetized animals. Studies in conscious animals have shown dissociable roles for different mPFC subregions in mediating various memory processes, with the prelimbic (PL) and infralimbic (IL) cortex involved in the retrieval and extinction of conditioned responding, respectively. Therefore PL and IL may also play different roles in mediating the retrieval and extinction of discrimination learning under anesthesia. Here we used in vivo electrophysiology to examine unit and local field potential (LFP) activity in PL and IL before and after auditory discrimination learning and during later retrieval and extinction testing in anesthetized rats. Animals received repeated presentations of two distinct sounds, one of which was paired with footshock (US). In separate control experiments animals received footshocks without sounds. After discrimination learning the paired (CS+) and unpaired (CS-) sounds were repeatedly presented alone. We found increased unit firing and LFP power in PL and, to a lesser extent, IL after discrimination learning but not after footshocks alone. After discrimination learning, unit firing and LFP power increased in PL and IL in response to presentation of the first CS+, compared to the first CS-. However, PL and IL activity increased during the last CS- presentation, such that activity during presentation of the last CS+ and CS- did not differ. These results confirm previous findings and extend them by showing that increased PL and IL activity result from encoding of the CS+/US association rather than US presentation. They also suggest that extinction may occur under anesthesia and might be represented at the neural level in PL and IL