Memory for, and salience of, the unique features of similar stimuli in perceptual learning.

In two experiments, participants received exposure to complex checkerboards (e.g., AX and BX) that consisted of small distinctive features (A and B) superimposed on a larger common background (X). Subsequent discrimination between AX and BX, assessed by a same-different task, was facilitated when the stimuli were presented on alternate trials in preexposure—a perceptual learning effect (Experiment 1). The hypothesis that this form of exposure results in more accurate representations of the unique features was supported in Experiment 1, which showed that participants were well able to match the color of the feature with its shape. Experiment 2 showed that exposure to A and B in isolation, intermixed with presentations of AX and BX, enhanced the perceptual learning effect, which confirmed that the better encoding of the unique features during intermixed preexposure is a direct cause of the enhanced discrimination observed following preexposure on this schedule. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Inhibitory associations contribute to perceptual learning in humans.

Perceptual learning in humans was examined in 2 experiments. In Experiment 1, participants received intermixed exposure to 2 similar compounds (AX, BX, AX, BX, . . .) and blocked exposure to a 2nd pair of similar compounds (CY, CY, . . . , DY, DY, . . .). Aversions established to AX and CY generalized less to BX than to DY. In Experiment 2, 1 pair of compounds was presented in a forward order (i.e., AX3BX), whereas the 2nd pair of compounds was presented in a backward order (i.e., DY→CY). Aversions established to AX and CY generalized less to BX than to DY. These results indicate that inhibitory associations contribute to perceptual learning in humans and thereby establish a fundamental similarity between the mechanisms that underlie perceptual learning in humans and rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attention and relative novelty in human perceptual learning.

Four experiments examined the role of attention in human perceptual learning. In Experiment 1, participants were preexposed to a pair of visual (checkerboard) stimuli AX and BX, with common elements X and unique features A and B. A same-different task was then used to assess discrimination of AX and BX and a pair of control stimuli, CY and DY. In addition, participants' eye movements were recorded to assess the role of attentional processes. The results showed that preexposure enhanced discrimination between AX and BX. Furthermore, participants showed greater attention to the preexposed unique features A and B than to the novel unique features C and D, as measured by the eye gaze monitor. Experiments 2 and 3 examined the prediction that perceptual learning is due to the relative familiarity of the common and unique stimulus features. Experiment 4 replicated the intermixed-blocked effect and showed that the way in which AX and BX are presented is also important for perceptual learning. The results generally support the idea that intermixed preexposure to AX and BX increases attention to the unique stimulus features A and B. Some aspects of the results are consistent with a relative novelty account, whereas others implicate a high-level attentional process that is not driven by stimulus novelty. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Avoidance learning of perceptual defense and vigilance.

Thirty-two undergraduates were randomly assigned to defense and vigilance training groups. "This study supports the view that perceptual defense and vigilance are learned reactions to anxiety arousing stimuli." A behavior theory analysis of the learning process is proposed. "According to this analysis, perceptual defense is learned when the perceptual response to a threatening stimulus is punished and competing perceptual responses are instrumental to anxiety reduction. Competing perceptual responses when reinforced are strengthened at the expense of the critical perceptual response. Perceptual vigilance is learned when the perceptual response to a threatening stimulus is reinforced by anxiety reduction and competing perceptual responses are punished." Learning for both groups "proceeded in the absence of awareness." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Associative activation of stimulus representations restores lost salience: Implications for perceptual learning.

In 3 experiments, rats received preexposure to presentations of a compound flavor BX. The effective salience of B was then tested by assessing its ability to interfere with the aversion controlled by another flavor or the tendency to drink a saline solution after the induction of a salt need. It was found that the effective salience of B was maintained when during preexposure, presentations of BX alternated with presentations of X alone. This was true both when BX was presented as a simultaneous compound (Experiment 1) and as a serial compound (X→B; Experiments 2 and 3); salience was not maintained when the serial compound took the form B→X (Experiments 2 and 3a). It was argued that the salience of B declines during preexposure but is restored when presentations of X are able to activate the representation of B by way of the associative X-B link. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preexposure effects in the spatial domain: Dissociation between latent inhibition and perceptual learning.

In 4 experiments, rats were given intermixed or blocked preexposure to an array of landmarks that subsequently defined the location of a hidden goal in a Morris pool task. Previous research has shown that intermixed preexposure to pairs of adjacent landmarks retards learning whereas preexposure to individual landmarks facilitates subsequent learning (J. Prados, V. D. Chamizo, & N. J. Mackintosh, 1999). Accordingly, in Experiment 1, intermixed and blocked preexposure to pairs of adjacent landmarks was found to retard learning. In Experiment 2, however, a scheduling effect was found: Rats given intermixed preexposure to the individual landmarks learned faster than rats given blocked or no preexposure. Experiment 3 showed that intermixed (but not blocked) preexposure to pairs of landmarks resulted in a facilitatory effect when preexposure and test were carried out in different contexts. Experiment 4 replicated within a single experiment the main results observed in Experiments 1 and 3. This pattern of results suggests that intermixed preexposure engages learning processes other than latent inhibition that facilitate subsequent learning of the navigation task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of punishment (electric shock) on perceptual learning.

3 experiments were conducted to explore the consequences of the association of punishment with percepts and to trace its residual effects. Electric shock was associated with tactual profiles of faces. Voltage, temporal contiguity, and ability to escape shock were varied. The results showed that there was more reporting of the non-shocked profile as intensity of shock increased, that escape conditions lead to more reporting of the shocked profiles, the shocked profile is recalled more vividly, and as the delay between exposure and recall increases there is more reporting of the nonshocked profile. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The intermixed-blocked effect in human perceptual learning is not the consequence of trial spacing.

A robust finding in humans and animals is that intermixed exposure to 2 similar stimuli (AX/BX) results in better discriminability of those stimuli on test than does exposure to 2 equally similar stimuli in 2 separate blocks (CX_DX)--the intermixed-blocked effect. This intermixed-blocked effect may be an example of the superiority of spaced over massed practice; in the intermixed, but not the blocked exposure regime, each presentation of a given stimulus (e.g., AX) is separated from the next by the presentation of its partner (BX). Two experiments with human participants replicated the intermixed-blocked effect and showed that the effect was not due to the spacing of exposure trials. A mechanism for the intermixed-blocked effect is proposed, which combines theories from associative learning and memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Involvement of the retrosplenial cortex in processing multiple conditioned stimuli.

Lesions of retrosplenial cortex (RSP) disrupt spatial and contextual learning, suggesting that RSP may have a fundamental role in processing overlapping, or simultaneously presented stimuli. If so, then RSP lesions might also be expected to disrupt learning that requires the concurrent processing of phasic conditioned stimuli. In Experiment 1, rats were trained in a compound feature negative discrimination task in which a tone was presented and immediately followed by food on some trials, while on other trials a visual stimulus was simultaneously presented along with the tone and not reinforced. Normal rats learned to discriminate between the trials but RSP-lesioned rats exhibited low levels of conditioning on both types of trials. Experiment 2 demonstrated that this effect was not simply due to a general inability to form associations, since RSP-lesioned rats exhibited normal responding when the visual stimulus was presented alone and paired with food. These findings support the view that RSP has an important role in learning that involves the processing of simultaneously presented stimuli and have implications for understanding the functional relationship between the hippocampus and RSP. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contributions of procedure and stimulus learning to early, rapid perceptual improvements.

Improvements in performance on many perceptual skills can occur with only a single training session. Of interest here is what aspects of the training experience are being learned during this brief exposure. Although there is considerable evidence that learning associated with specific feature values of the stimulus used in training (stimulus learning) contributes to these rapid improvements, there has been little direct investigation of the possibility that other types of learning do so as well. Here the authors show that not only stimulus learning but also learning of more general aspects of the training experience (procedure learning) contributed to rapid improvements in performance on interaural time difference discrimination. However, practice on the type of judgment to be made did not appear to aid performance (no task learning). These results are consistent with physiological reports that different neural mechanisms are engaged at different time points during even a brief training session, and imply that the circuits that are engaged and likely modified vary in the degree of their selectivity to the target condition. Such changes presumably enable further learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of similarity in human associative learning.

In 2 experiments, humans received sequences of patterns that were similar (AX→BX, AY→BY, AZ→BZ) or dissimilar (CX→DY, CY→DZ, CZ→DX). The patterns were portrayed as bugs that could be eliminated with 2 insecticide sprays (red or blue). Either spray eliminated bugs with Features A and C, and participants learned by trial and error to use one spray (e.g., red) to eliminate bugs with Feature B and the other spray (e.g., blue) to eliminate those with Feature D. In Experiment 1, participants' spray choice for bugs with Feature A came to match that used to eliminate bugs with Feature B, but there was no such associative transfer between Features C and D. That is, similarity promoted associative transfer of responding between paired patterns when the features used to manipulate similarity (i.e., X, Y, and Z) were irrelevant. In Experiment 2, in which X, Y, and Z were relevant to the solution of configural discrimination, similarity hindered such associative transfer. These results complement those found in pigeons (R. A. Rescorla & D. J. Gillan, 1980) and indicate that similarity should not be accorded independent status as a principle of associative learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of fractality in perceptual learning: Exploration in dynamic touch.

Perceptual systems must learn to explore and to use the resulting information to hone performance. Optimal performance depends on using information available at many time scales, from the near instantaneous values of variables underlying perception (i.e., detection), to longer term information about appropriate scaling (i.e., calibration), to yet longer term information guiding variable use (i.e., attunement). Fractal fluctuations in explorations would entail fluctuation at all time scales, allowing perceptual systems a flexible way to detect information at all time scales. We tested whether perceptual learning in dynamic touch is related to the fractality of wielding behaviors. A reanalysis of wielding behaviors from Arzamarski, Isenhower, Kay, Turvey, and Michaels (2010) revealed that exploratory movements were fractal and that a fractal-scaling exponent predicts individual differences in haptic judgments. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fuzzy picture processing: Effects of size reduction and blurring on emotional processing.

Previous studies have suggested that picture size reduction affects emotional reactions, possibly because scenes subtending a small visual angle are perceived as being more distant and less relevant compared to larger stimuli. However, pictures that subtend a small visual angle also contain few fine-grained details, which may determine less vivid representations and responses compared to larger and more detailed images. Critically, the present study compared two different types of manipulations, namely size reduction and low-pass spatial filtering, which determined similar detail loss but affected visual angles differently. Affective modulation was assessed using an evaluative task and a behavioral interference task. Results showed that the availability of fine-grained details, independently of visual angle, modulated emotional evaluation. Moreover, interference in an unrelated task was unaffected by either size reduction or low-pass spatial filtering. These findings suggest that high spatial frequencies affect subjective emotional response whereas attentional capture by affective stimuli seems to rely on information that is sufficient to allow a categorization of picture content. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Analysis of the role of associative inhibition in perceptual learning by means of the same-different task.

In Experiment 1a, participants were exposed, over a series of trials, to separate presentations of 2 similar checkerboard stimuli, AX and BX (where X represents a common background). In one group, AX and BX were presented on alternating trials (intermixed), in another, they were presented in separate blocks of trials (blocked). The intermixed group performed to a higher standard than the blocked group on a same-different test. A superiority of intermixed over blocked exposure was also evident in a within-subject design (Experiment 1b) and when the test required discrimination between a preexposed stimulus and the background (e.g., AX vs. X), even if the background changed between preexposure and test (AY vs. Y) (Experiment 2). In Experiment 3, the intermixed/blocked effect was observed when, in preexposure, stimulus presentations were alternated with the background alone (e.g., AX/X). This suggests that the perceptual learning effect is not the consequence of inhibitory associations between unique features but to increased salience of those features. Experiment 4 confirmed this finding and also ruled out an account of the effect in terms of trial spacing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sequence effects in categorization of simple perceptual stimuli.

Categorization research typically assumes that the cognitive system has access to a (more or less noisy) representation of the absolute magnitudes of the properties of stimuli and that this information is used in reaching a categorization decision. However, research on identification of simple perceptual stimuli suggests that people have very poor representations of absolute magnitude information and that judgments about absolute magnitude are strongly influenced by preceding material. The experiments presented here investigate such sequence effects in categorization tasks. Strong sequence effects were found. Classification of a borderline stimulus was more accurate when preceded by a distant member of the opposite category than by a distant member of the same category. It is argued that this category contrast effect cannot be accounted for by extant exemplar or decision-bound models of categorization. The effect suggests the use of relative magnitude information in categorization. A memory and contrast model illustrates how relative magnitude information may be used in categorization. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus-outcome interactions during instrumental discrimination learning by rats and humans.

The associative structure mediating goal-directed action was investigated using congruent and incongruent conditional discriminations. The stimulus was the same as the outcome in each component of the congruent discriminations, whereas the stimulus of one component of the incongruent discriminations was the same as the outcome of the other component. Humans, but not rats, learned the congruent discrimination more rapidly than the incongruent discrimination, a difference that the authors attribute to the fact that outcome-response associations caused response conflict in the incongruent discrimination. Moreover, responding was resistant to outcome devaluation following incongruent, but not congruent, training, suggesting that both humans and rats adopted a stimulus-response strategy to resolve the incongruent discrimination. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Absence of perceptual processing during reconfiguration of task set.

The authors manipulated stimulus contrast and response-stimulus interval in the alternating runs paradigm to investigate whether early processing could be carried out during a task switch. Subjects alternated between judging the magnitude and the parity of a digit. The results suggested that early processing was not carried out during the task switch (Experiment 1), even in the absence of potentially confounding auditory or visual warning signals (Experiment 2). This processing was, however, carried out in parallel with a demanding operation in a 2nd task (Experiment 3), using the display parameters of Experiments 1 and 2 in the psychological refractory period paradigm. It is concluded that, functionally, task switching may impose a hard bottleneck even for very early stimulus processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Temporal processing of emotional stimuli: The capture and release of attention by angry faces.

Neuroimaging data suggest that emotional information, especially threatening faces, automatically captures attention and receives rapid processing. While this is consistent with the majority of behavioral data, behavioral studies of the attentional blink (AB) additionally reveal that aversive emotional first target (T1) stimuli are associated with prolonged attentional engagement or “dwell” time. One explanation for this difference is that few AB studies have utilized manipulations of facial emotion as the T1. To address this, schematic faces varying in expression (neutral, angry, happy) served as the T1 in the current research. Results revealed that the blink associated with an angry T1 face was, primarily, of greater magnitude than that associated with either a neutral or happy T1 face, and also that initial recovery from this processing bias was faster following angry, compared with happy, T1 faces. The current data therefore provide important information regarding the time-course of attentional capture by angry faces: Angry faces are associated with both the rapid capture and rapid release of attention. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Prenatally elevated physiological arousal interferes with perceptual learning in bobwhite quail (Colinus virginianus) embryos.

Neonatal studies suggest elevated arousal can negatively influence perceptual and cognitive processes during early development. The authors explored this issue during the prenatal period by pharmacologically elevating physiological arousal in bobwhite quail (Colinus virginianus) embryos during exposure to a maternal call, then assessing preference for the familiar call following hatching. Embryos receiving norepinephrine showed a prenatal elevation in heart rate and failed to demonstrate a preference for the familiar call following hatching. Embryos not receiving norepinephrine showed no elevation in heart rate and demonstrated a preference for the familiar call. These results indicate elevated arousal can interfere with perceptual learning during the prenatal period and provide additional evidence for an optimal window of arousal necessary to foster species-typical perceptual functioning during early development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Feature-specific perceptual processing dissociates action from recognition.

Does visual processing differ for action and recognition? To address this question, the authors capitalized on research showing that color is preferred over binocular disparity in the ventral (recognition) stream, whereas disparity is preferred over color in the dorsal (action) stream. Participants searched for oblique targets among vertical distractors in displays defined only by color or disparity. Action-task participants stamped the target with a handheld block, whereas recognition-task participants lifted the block through a target-compatible gap. Analyses of reaction time and time-varying hand orientation showed that disparity and color displays were processed equally efficiently during action, but disparity was processed less efficiently than color during recognition. The results suggest that visual processing differs for action and recognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)