Absence of differential protection from extinction in human causal learning.

Elemental models of associative learning typically employ a common prediction-error term. Following a conditioning trial, they predict that the change in the strength of an association between a cue and an outcome is dependent upon how well the outcome was predicted. When multiple cues are present, they each contribute to that prediction. The same rule applies both to increases in associative strength during excitatory conditioning and the loss of associative strength during extinction. In five experiments using an allergy prediction task, we tested the involvement of a common error term in the extinction of causal learning. Two target cues were each paired with an outcome prior to undergoing extinction in compound either with a second excitatory cue or with a cue that had previously undergone extinction in isolation. At test, there was no difference in the causal ratings of the two target cues. Manipulations designed to bias participants toward elemental processing of cue compounds, to promote the acquisition of inhibitory associations, or to reduce generalization decrement between training and test were each without effect. These results are not consistent with common error term models of associative learning. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Attentional bias in psoriasis: The role of processing time and emotional valence.

PURPOSE: The present study explored whether people with psoriasis display an attentional bias towards disease-related threat words and whether this bias occurs relatively early during the phase of stimulus disengagement, or during a later maintained attention phase dominated by controlled strategic processes. We also explored the degree to which attentional bias is dependent on the emotional valence of control words. METHODS: Individuals with psoriasis and matched controls took part in 4 online experiments. Participants completed a spatial cueing paradigm using disease-related threat words and control words as cues, in order to obtain reaction time estimates of attentional bias. RESULTS: We did not observe evidence for attentional bias when control words were matched with threat words for emotional valence, regardless of whether processing time for the cues was limited (Experiment 1: SOA = 250 ms) or extended (Experiment 2: SOA = 1050 ms). We also did not observe evidence for attentional bias when control words of positive valence were used, but processing time was limited (Experiment 3). An attentional bias was only observed (p = .012, Cohen's d = .37) when sufficient processing time was available and positively-valanced control words were used (Experiment 4). CONCLUSION: Rather than showing large and generalized AB effects as predicted by previous accounts, our results tentatively suggest that AB in psoriasis is restricted to situations where participants have ample processing time and threat words are easily distinguishable from control words on the basis of emotional valence. The pattern of results suggests that attentional bias in psoriasis is best characterized as a relatively slow strategic process.

Competing contextual processes rely on the infralimbic and prelimbic medial prefrontal cortices in the rat.

Ambiguous relationships between events may be established using interference procedures such as latent inhibition, extinction or counterconditioning. Under these conditions, the retrieval of individual associations between a stimulus and outcome is affected by contextual cues. To examine the roles of the dorsal (prelimbic) and ventral (infralimbic) medial prefrontal cortex in the contextual modulation of such associations, we investigated the context specificity of latent inhibition. Male Lister hooded rats were pre-exposed to two separate stimuli, one in each of two distinct contexts. Both stimuli were then paired with the delivery of mild foot-shock in the same one of these contexts. Finally, the strength of the resultant conditioned emotional response (CER) to each stimulus was assessed in each context. For the sham-operated control rats, the CER was attenuated for each stimulus when it was tested in the context in which it had been pre-exposed. Rats who had received lesions to the infralimbic cortex showed this effect only in the conditioning context, whereas rats with lesions to the prelimbic cortex showed the effect only in the context in which conditioning had not taken place. These findings indicate that infralimbic and prelimbic cortices play distinct, and competing, roles in the contextual modulation of initial and later learning.

Acute Itch Induces Attentional Avoidance of Itch-related Information.

Attention is known to modulate itch intensity. In contrast, the reverse relationship, i.e. the degree to which the presence of an acute itch affects attention, is currently not well understood. The aims of this study were to investigate whether acute itch induces an attentional bias towards or away from visual itch-related stimuli, and if so, whether it occurs in the early or later stages of processing. A volunteer sample of 60 healthy individuals were subjected to a skin prick (either histamine or placebo), followed by completion of a spatial cueing paradigm using itch-related and neutral words as cues, in order to obtain reaction time estimates of attentional bias. The results suggest that experience of acute itch induces attentional avoidance of visual itch threats. This attentional avoidance occurs at a later processing stage in the form of facilitated disengagement of attention from itch and/or delayed disengagement from neutral information.

Domestic dogs (Canis lupus familiaris) are sensitive to the correlation between pitch and timbre in human speech.

The perceived pitch of human voices is highly correlated with the fundamental frequency (f0) of the laryngeal source, which is determined largely by the length and mass of the vocal folds. The vocal folds are larger in adult males than in adult females, and men's voices consequently have a lower pitch than women's. The length of the supralaryngeal vocal tract (vocal-tract length; VTL) affects the resonant frequencies (formants) of speech which characterize the timbre of the voice. Men's longer vocal tracts produce lower frequency, and less dispersed, formants than women's shorter vocal tracts. Pitch and timbre combine to influence the perception of speaker characteristics such as size and age. Together, they can be used to categorize speaker sex with almost perfect accuracy. While it is known that domestic dogs can match a voice to a person of the same sex, there has been no investigation into whether dogs are sensitive to the correlation between pitch and timbre. We recorded a female voice giving three commands ('Sit', 'Lay down', 'Come here'), and manipulated the recordings to lower the fundamental frequency (thus lowering pitch), increase simulated VTL (hence affecting timbre), or both (synthesized adult male voice). Dogs responded to the original adult female and synthesized adult male voices equivalently. Their tendency to obey the commands was, however, reduced when either pitch or timbre was manipulated alone. These results suggest that dogs are sensitive to both the pitch and timbre of human voices, and that they learn about the natural covariation of these perceptual attributes.

Preexposure along a continuum: Differentiation and association.

In 5 experiments, we assessed the effects of preexposure to simple auditory stimuli on subsequent conditioning and discrimination learning. Experiment 1 showed that preexposure to a single stimulus retarded acquisition of conditioned responding to that stimulus. The same preexposure regimen facilitated the subsequent acquisition of a discrimination between 2 stimuli that flanked the preexposed stimulus along the frequency dimension. Experiment 2 replicated this midpoint preexposure effect on discrimination learning but also found that alternating preexposure 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 preexposure to auditory stimuli results in an increase in generalization between them. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

The representation of stimulus conjunction in theories of associative learning: A context-dependent added-elements model.

This article briefly reviews 3 theories concerning elemental and configural approaches to stimulus representation in associative learning and presents a new context-dependent added-elements model (C-AEM). This model takes an elemental approach to stimulus representation where individual stimuli are represented by single units and stimulus compounds activate both those units and configurational units corresponding to each conjunction of 2 or more stimuli. Activity across these units is scaled such that each stimulus always contributes the same amount of activity to the system whether it is presented in isolation or in compound; the configurational units "borrow" activity from representational units for individual stimuli (and from each other). This scaling is affected by the extent to which stimuli interact with each other perceptually. Hence, the model is conceptually similar to Wagner's (2003) replaced elements model but lacks features that explicitly code for the absence of stimuli (i.e., inhibited elements). Simulations of the model are reported for a range of generalization and discrimination learning tasks, conflicting results from which have previously been taken to provide support for either configural or elemental theories of learning. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Disentangling the effects of attentional weighting and associative mediation in perceptual learning reveals no evidence for associative mediation.

Learning to categorize perceptually similar stimuli can result in people becoming more sensitive to differences along perceptual dimensions that are relevant to category membership and/or less sensitive to equivalent differences along irrelevant perceptual dimensions. These effects of acquired distinctiveness and acquired equivalence may be caused by changes in the representations of stimuli which come about through adjustment to the relative attentional weighting of perceptual features or dimensions. Alternatively, the development of associations between individual stimuli and category labels could result in those labels being incorporated into the stimulus representation, hence increasing or decreasing generalization between the stimuli. For many categorization tasks, the expected effects of attentional weighting and associative mediation on stimulus similarity are the same. We report 3 experiments using complex category structures, which allowed us to assess the independent influence of each mechanism on stimulus similarity. The results suggest that, in these categorization tasks, attentional weighting affects perceptual similarity but associative mediation does not. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

A computational implementation of a Hebbian learning network and its application to configural forms of acquired equivalence.

We describe and report the results of computer simulations of the three-layer Hebbian network informally described by Honey, Close, and Lin (2010): A general account of discrimination that has been shaped by data from configural acquired equivalence experiments that are beyond the scope of alternative models. Simulations implemented a conditional principle-components analysis Hebbian learning algorithm and were of four published experimental demonstrations of configural acquired equivalence. Experiments involved training rats on appetitive biconditional discriminations in which discrete cues (w and x) signaled food delivery (+) or its absence (-) in 4 different contexts (A, B, C, and D): Aw+ Bw- Cw+ Dw- Ax- Bx+ Cx- Dx+. Contexts A and C acquired equivalence. In 3 of the experiments acquired equivalence was evident from subsequent revaluation, from compound testing or from whole-/part-reversal training. The fourth experiment added concurrent biconditional discriminations with the same contexts but a pair of additional discrete cues (y and z). The congruent form of the discrimination, in which A and C provided the same information about y and z, was solved relatively readily. Parametric variation allowed the network to successfully simulate the results of each of the 4 experiments. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Effects of Short-term Temperature Change in the Innocuous Range on Histaminergic and Non-histaminergic Acute Itch.

While temperatures in the noxious range are well-known to inhibit acute itch, the impact of temperature in the innocuous temperature range is less well understood. We investigated the effect of alternating short-term temperature changes in the innocuous range on histamine and cowhage-induced acute itch, taking into account individual differences in baseline skin temperature and sensory thresholds. Results indicate that cooling the skin to the cold threshold causes a temporary increase in the intensity of histamine-induced itch, in line with previous findings. Skin warming increased cowhage-induced itch intensity. Potential mecha-nisms of this interaction between thermosensation and pruritoception could involve cold-sensitive channels such as TRPM8, TREK-1 or TRPC5 in the case of histamine. The rapid modulation of cowhage induced itch - but not histamine-induced itch - by transient skin warming could be related to the lower temperature threshold of pruriceptive polymodal C-fibres (cowhage) as compared to the higher temperature threshold of the mechanoinsensitive C-fibres conveying histaminergic itch.

More evidence that less is better: Sub-optimal choice in dogs.

The less-is-better effect is a preference for the lesser of two alternatives sometimes observed when they are evaluated separately. For example, a dinner service of 24 intact pieces might be judged to be more valuable than a 40-piece dinner service containing nine broken pieces. Pattison and Zentall (Animal Cognition, 17: 1019-1022, 2014) reported similar sub-optimal choice behavior in dogs using a simultaneous choice procedure. Given a choice between a single high-value food item (cheese) or an equivalent high-value item plus a lower-value food item (carrot), their dogs chose the individual item. In a subsequent test, the dogs preferred two high-value items to a single high-value item, suggesting that avoidance of multiple items did not cause the sub-optimal choice behavior. In two experiments, we replicated Pattison and Zentall's procedure while including additional controls. In Experiment 1, habituation of neophobia for multiple items was controlled for by intermixing the two types of test trial within a single experimental session. In Experiment 2, we controlled for avoidance of heterogeneous rewards by including test trials in which a choice was offered between the combination of items and a single low-value item. In both experiments we observed sub-optimal choice behavior which could not be explained by either of these putative mechanisms. Our results, as well as those of Pattison and Zentall, are consistent with the suggestion that dogs' assessment of the total value of multiple items is based, at least partly, on their average quality.

Stimulus similarity affects patterning discrimination learning.

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. (PsycINFO Database Record

Placebo Analgesia From a Rubber Hand.

Placebo analgesia, reductions in pain after administration of an inert treatment, is a well documented phenomenon. We report, to our knowledge, the first demonstration that placebo analgesia can be experienced when a sham analgesic is applied onto a rubber hand. The effect was obtained by exploiting the rubber hand illusion, in which ownership is felt over a rubber arm that is unattached to the body. Under conditions of synchronous as well as asynchronous visuotactile stimulation, a thermal pain stimulus was delivered on the real arm of 20 participants and seemingly also on the rubber arm, before and after applying a sham analgesic and a control cream only to the rubber arm. During synchronous visuotactile stimulation, pain was experienced on the rubber arm, and the application of the sham analgesic to the rubber arm significantly decreased the severity of reported pain. This shows that experience of the body can modulate expectations and the induction of placebo analgesia. PERSPECTIVE: This article presents an experiment suggesting that a placebo treatment applied to a rubber hand during the rubber hand illusion can produce placebo analgesia. This finding indicates that embodiment may influence the placebo effect, a previously unexamined factor in the treatment process with potential applications to treatment administration.

Attention and associative learning in humans: An integrative review.

This article presents a comprehensive survey of research concerning interactions between associative learning and attention in humans. Four main findings are described. First, attention is biased toward stimuli that predict their consequences reliably (learned predictiveness). This finding is consistent with the approach taken by Mackintosh (1975) in his attentional model of associative learning in nonhuman animals. Second, the strength of this attentional bias is modulated by the value of the outcome (learned value). That is, predictors of high-value outcomes receive especially high levels of attention. Third, the related but opposing idea that uncertainty may result in increased attention to stimuli (Pearce & Hall, 1980), receives less support. This suggests that hybrid models of associative learning, incorporating the mechanisms of both the Mackintosh and Pearce-Hall theories, may not be required to explain data from human participants. Rather, a simpler model, in which attention to stimuli is determined by how strongly they are associated with significant outcomes, goes a long way to account for the data on human attentional learning. The last main finding, and an exciting area for future research and theorizing, is that learned predictiveness and learned value modulate both deliberate attentional focus, and more automatic attentional capture. The automatic influence of learning on attention does not appear to fit the traditional view of attention as being either goal-directed or stimulus-driven. Rather, it suggests a new kind of "derived" attention.

Extreme elemental processing in a high schizotypy population: relation to cognitive deficits.

The cognitive deficits observed in schizophrenia have been characterized as a failure to utilize task-setting information to guide behaviour, especially in situations in which there is response conflict. Recently, we have provided support for this account; high schizotypy individuals demonstrated inferior biconditional discrimination performance compared to low scorers, but were not impaired on a simple discrimination that did not require the use of task-setting cues. These results may, however, also be explained by the way in which individuals with high schizotypy process stimulus compounds. Here, we examine the initial approaches to solving biconditional and control discrimination tasks of participants with high and low schizotypy scores. In particular, we focus on performance during the first block of training trials to capture processing style before the acquisition of the discrimination tasks. Participants scoring highly on the introvertive anhedonia subscale (which has been allied to the negative and cognitive symptoms of schizophrenia) demonstrated better biconditional performance during the first block of training trials than did low-schizotypy individuals, consistent with a highly elemental approach to stimulus processing. Subsequent recognition tests confirmed this analysis demonstrating that the pattern of performance observed in participants with high schizotypy was associated with a failure to discriminate conjunctions of items that had been seen before from those that had not. These results suggest that the negative/cognitive symptoms of schizophrenia may reflect an extreme bias towards elemental, as opposed to configural, processing of stimulus conjunctions.

Pavlovian-to-instrumental transfer: paradoxical effects of the Pavlovian relationship explained.

Four experiments with rats examined the origin of outcome-selective Pavlovian-to-instrumental transfer (PIT). Experiment 1 used a standard procedure, where outcomes were embedded within extended conditioned stimuli (CSs), to demonstrate the basic effect: Pavlovian stimuli augmented instrumental lever presses that had been paired with the same outcomes. Experiments 2 and 3 showed that after instrumental conditioning, whereas a conditioned stimulus (CS) trained using a backward conditioning procedure produced outcome-selective PIT, forward conditioning with a CS did not. These results are consistent with the idea that backward conditioning results in the outcome provoking its associated instrumental response during the CS and thereby allows a stimulus-response association to be acquired that directly generates outcome-selective PIT at test. Experiment 4 provided direct support for the assumptions that underlie this stimulus-response analysis. These results, and other paradoxical effects of the Pavlovian relationship, are incongruent with accounts of outcome-selective PIT that rely on a stimulus-outcome-response chain.

A configural theory of attention and associative learning.

A formal account of the relationship between attention and associative learning is presented within the framework of a configural theory of discrimination learning. The account is based on a connectionist network in which the entire pattern of stimulation presented on a trial activates a configural unit that then enters into an association with the trial outcome. Attention is assumed to have two roles within this network. First, the salience of the stimuli at the input to the network can be increased if they are relevant to the occurrence of reinforcement and decreased if they are irrelevant. Second, the associability of configural units can increase on trials when the outcome is surprising and decrease when the outcome is not surprising.

Contextual modulation of attention in human category learning.

In a category-learning experiment, we assessed whether participants were able to selectively attend to different components of a compound stimulus in two distinct contexts. The participants were presented with stimulus compounds for which they had to learn categorical labels. Each compound comprised one feature from each of two dimensions, and on different trials the compound was presented in two contexts, X and Y. In Context X, Dimension A was relevant to the solution of the categorization task and Dimension B was irrelevant, whereas in Context Y, Dimension A was irrelevant and Dimension B was relevant. The results of transfer tests to novel stimuli suggested that people learned to attend selectively to Dimension A in Context X and Dimension B in Context Y. These findings contribute to the growing body of evidence that people can learn to selectively attend to particular dimensions of stimuli dependent on the context in which the stimuli are presented. Furthermore, the findings demonstrate that context-dependent changes in attention transfer to other categorization tasks involving novel stimuli.

Dissociation of prefrontal cortex and nucleus accumbens dopaminergic systems in conditional learning in rats.

There is converging evidence that the prefrontal and mesolimbic dopaminergic (DAergic) systems are involved in the performance of a variety of tasks that require the use of contextual, or task-setting, information to select an appropriate response from a number of candidate responses. Performance on tasks of this nature are impaired in schizophrenia and in rats exposed to psychotomimetics; impairments that are often attenuated by administration of dopamine (DA) antagonists. Rats were trained on either a complex instrumental discrimination task, that required the use of task-setting cues, or a simple discrimination task that did not. Following training, microdialysis probes were implanted unilaterally in either the medial prefrontal cortex (mPFC) or nucleus accumbens (NAc) and samples were collected in freely moving animals during a behavioural test session. In Experiment 1, we found no difference in levels of DA in the mPFC of rats while they were performing the two discrimination tasks. Rats that performed the complex task did, however, show significantly higher mPFC DA levels relative to rats in the simple discrimination condition following the end of the behavioural test session. In Experiment 2, rats performing the conditional discrimination showed lower levels of DA in the NAc compared to the simple discrimination group both during the test session and after it. These results provide direct evidence that conditional discrimination tasks engage frontal and mesolimbic DAergic systems and are consistent with the proposal that regulation of fronto-striatal DA is involved in aspects of cognitive control that are known to be impaired in individuals with schizophrenia.

Impaired conditional task performance in a high schizotypy population: relation to cognitive deficits.

Cognitive impairments in schizophrenia have been characterized as reflecting a core deficit in the maintenance or use of task-setting cues to mediate appropriate ongoing behaviour. This analysis suggests that cognitive deficits in schizophrenia will be particularly evident when different task-setting cues dictate when different responses are required by the same stimuli. One simple task in which task-setting cues are required is a biconditional discrimination. Here we examined the performance of participants with high and low schizotypy scores (Mason, Claridge, & Jackson, 1995) on a biconditional discrimination and an otherwise equivalent, control discrimination that did not require the use of task-setting cues. Participants scoring highly on the Introvertive Anhedonia subscale (which has been allied to the negative and cognitive symptoms of schizophrenia) performed poorly on the biconditional, but not on the control, discrimination. No other subscales demonstrated a significant influence on either biconditional or control performance.