Transfer of noncorresponding spatial associations to the auditory Simon task.

Four experiments examined transfer of noncorresponding spatial stimulus-response associations to an auditory Simon task for which stimulus location was irrelevant. Experiment 1 established that, for a horizontal auditory Simon task, transfer of spatial associations occurs after 300 trials of practice with an incompatible mapping of auditory stimuli to keypress responses. Experiments 2-4 examined transfer effects within the auditory modality when the stimuli and responses were varied along vertical and horizontal dimensions. Transfer occurred when the stimuli and responses were arrayed along the same dimension in practice and transfer but not when they were arrayed along orthogonal dimensions. These findings indicate that prior task-defined associations have less influence on the auditory Simon effect than on the visual Simon effect, possibly because of the stronger tendency for an auditory stimulus to activate its corresponding response. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual discrimination of orientation by the goldfish (Carassius auratus).

Trained 4 large goldfish to choose a vertically oriented grating when it appeared along with gratings of other orientations on a circular field. Ss produced psychometric functions of responses correct as a function of stimulus orientation. 2 psychophysical methods, constant stimuli and stimulus tracking, yielded similar orientation thresholds which ranged from about 14 to 30. of tilt for the 4 Ss. One of these Ss and 2 untrained Ss were subsequently trained to choose a grating tilted 45., and yielded similar thresholds, ranging from 15 to 28.. Results are discussed in relation to orientation detectors which have been investigated neurophysiologically in the visual systems of several species. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The nature and processes of preverbal learning: implications from nine-month-old infants' discrimination problem solving

Nine-month-old infants' performance on discrimination-learning problems was investigated in four experiments using the synchronous reinforcement paradigm. These experiments were organized around basic theoretical postulates concerning the relation between attention and learning. In each of the experiments, infants were trained to respond differentially to a particular stimulus feature, with the goal of establishing whether they could learn to respond to a particular stimulus feature under conditions where other stimulus dimensions were present and varying. In the first experiment, 48 infants were trained to fixate visually on a particular feature in a pair of stimuli that varied in color, form, and position dimensions. Contingencies for responding were then shifted either within a dimension (reversal shift) or across dimensions (nonreversal shift). Infants learned to respond to the reinforced feature during initial training; moreover, infants assigned to a reversal shift condition showed a higher level of transfer of learning during the test phase than those assigned to a nonreversal shift condition. The second experiment extended the results of Experiment 1 by testing 48 additional infants under conditions in which the number of varying irrelevant dimensions was increased during the shift phase. Although the difficulty added to this task by this manipulation made transfer more difficult for all infants, results again indicated that transfer of learning was more evident for infants in a reversal shift than a nonreversal shift condition. In the third experiment, 64 infants were trained in a similar manner, except that completely new values were substituted during shift phases on the color and form dimensions. This manipulation was meant to probe whether infants were formulating a dimension response from previous training and to test the predictions of such dimension processing for transfer of learning to a functionally new problem. Infants were reinforced for fixating on a new feature either within the same dimension as during training (intradimension shift) or within the dimension that was not originally trained (extradimension shift). Transfer of learning was clearly superior in the intradimension shift condition. The findings of the first three experiments suggested that, during discrimination-learning problems, infants selected and tested individual stimulus features and dimensions from an array of potential solutions to the problem until discovering the one that was consistently associated with reinforcement.(ABSTRACT TRUNCATED AT 400 WORDS)     

Directed attention prolongs the perceived duration of a brief stimulus

Stelmach, Herdman, and McNeil (1994) suggested recently that the perceived duration for attended stimuli is shorter than that for unattended ones. In contrast, the attenuation hypothesis (Thomas & Weaver, 1975) suggests the reverse relation between directed attention and perceived duration. We conducted six experiments to test the validity of the two contradictory hypotheses. In all the experiments, attention was directed to one of two possible stimulus sources. Experiments 1 and 2 employed stimulus durations from 70 to 270 msec. A stimulus appeared in either the visual or the auditory modality. Stimuli in the attended modality were rated as longer than stimuli in the unattended modality. Experiment 3 replicated this finding using a different psychophysical procedure. Experiments 4-6 showed that the finding applies not only to stimuli from different sensory modalities but also to stimuli appearing at different locations within the visual field. The results of all six experiments support the assumption that directed attention prolongs the perceived duration of a stimulus.     

P300 from a single-stimulus paradigm: auditory intensity and tone frequency effects

The P300 component of the event-related brain potential (ERP) was elicited with auditory stimuli in two different tasks. The oddball paradigm presented both target and standard stimuli; the single-stimulus paradigm presented a target but no standard tone stimulus, with the inter-target interval the same as that for the oddball condition. Experiment 1 manipulated stimulus intensity and Experiment 2 manipulated tone stimulus frequency, with the relative target probability maintained 0.20 for both tasks. P300 amplitude and latency were highly similar for the oddball and single-stimulus procedures in both experiments across independent variables. The findings suggest that the single-stimulus paradigm may prove useful in experimental and applied contexts that require very simple ERP task conditions.     

Cytogenetic and molecular analysis of dynamic mutation associated with fragile X syndrome

The gate control theory of pain (Melzack and Wall, 1965) suggests that tactile stimuli can decrease the perception of pain. We have found the reverse effect: Heat at levels that induce pain can substantially suppress tactile sensitivity, independently of shifts in attention or arousal. Ten human observers were stimulated by a tonic, pain-producing heat stimulus and vibrotactile stimuli (1, 10, and 100 Hz) coincidentally presented to the right thenar eminence. Vibrotactile thresholds were assessed with the skin at a normative temperature of 31 degrees C and at higher temperatures producing pain. Increases in vibrotactile thresholds (mean change = 7.3 dB) occurred at skin temperatures just below and above those that induced pain. Furthermore, absolute-magnitude estimates of suprathreshold vibrotactile stimuli determined during the same experiments showed decreased sensitivity and psychophysical recruitment. The changes are not attributable to attentional or arousal shifts, since they were not associated with changes in auditory thresholds. Furthermore, the changes occurred just below the subjects' pain thresholds (where nociceptors are presumably activated). This over-twofold diminution of vibrotactile sensitivity suggests that heat stimuli capable of inducing pain can significantly diminish taction, perhaps through a "touch gate" in a manner similar to the gate control theory proposed for pain.     

Learning mode and exemplar sequencing in unsupervised category learning.

Exemplar sequencing effects in incidental and intentional unsupervised category learning were investigated to illuminate how people form categories without an external teacher. Stimuli were perfectly separable into 2 categories based on 1 of 2 dimensions of variation. Sequencing of the first 20 training stimuli was manipulated. In the blocked condition, 10 Category A stimuli were followed by 10 Category B stimuli. In the intermixed condition, these 20 stimuli were ordered randomly. Experiment 1 revealed an interaction between learning mode and sequence, with better intentional learning for intermixed sequences but better incidental learning for blocked sequences. Experiment 2 showed that manipulating trial-to-trial variability along each dimension can impact intentional learning. Training sequences that emphasized variation along the category-relevant dimension resulted in better performance than sequences that emphasized variation along the category-irrelevant dimension. The results suggest that unsupervised category learning is influenced by the mode of learning and the order and nature of encountered exemplars. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of stimulus modality and task condition on blink startle modification and on electrodermal responses

Participants in Experiments 1 and 2 performed a discrimination and counting task to assess the effect of lead stimulus modality on attentional modification of the acoustic startle reflex. Modality of the discrimination stimuli was changed across subjects. Electrodermal responses were larger during task-relevant stimuli than during task-irrelevant stimuli in all conditions. Larger blink magnitude facilitation was found during auditory and visual task-relevant stimuli, but not for tactile stimuli. Experiment 3 used acoustic, visual, and tactile conditioned stimuli (CSs) in differential conditioning with an aversive unconditioned stimulus (US). Startle magnitude facilitation and electrodermal responses were larger during a CS that preceded the US than during a CS that was presented alone regardless of lead stimulus modality. Although not unequivocal, the present data pose problems for attentional accounts of blink modification that emphasize the importance of lead stimulus modality.     

Naturalistic psychophysics: Thresholds of ducklings (Anas platyrynchos) and chicks (Gallus gallus) to tones that resemble mallard calls.

Six neonatal ducklings and 6 chickens were tested for responsiveness to a pulsing pure tone that was as similar as possible to the mallard maternal alarm call. It is known that ducklings momentarily cease vocalizing when they hear the alarm call and that chicks do the same when they hear pure tones. The duration of peep suppression could thus be used as a measure of whether Ss of either species heard the stimulus. Chicks might not be as sensitive as ducklings to a mallard alarm call because the signal is less significant to them. An adaptive, or staircase, procedure was used to estimate absolute thresholds, and group psychometric functions were reconstructed for each species from the trial-by-trial data. Ducklings had lower thresholds and steeper psychometric functions to this stimulus than did chicks. Results suggest that more sensitive and consistent behavioral responses can be elicited by naturalistic sounds than by more arbitrary acoustic stimuli. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceiving affordances for fitting through apertures.

Affordances--possibilities for action--are constrained by the match between actors and their environments. For motor decisions to be adaptive, affordances must be detected accurately. Three experiments examined the correspondence between motor decisions and affordances as participants reached through apertures of varying size. A psychophysical procedure was used to estimate an affordance threshold for each participant (smallest aperture they could fit their hand through on 50% of trials), and motor decisions were assessed relative to affordance thresholds. Experiment 1 showed that participants scale motor decisions to hand size, and motor decisions and affordance thresholds are reliable over two blocked protocols. Experiment 2 examined the effects of habitual practice: Motor decisions were equally accurate when reaching with the more practiced dominant hand and less practiced nondominant hand. Experiment 3 showed that participants recalibrate motor decisions to take changing body dimensions into account: Motor decisions while wearing a hand-enlarging prosthesis were similar to motor decisions without the prosthesis when data were normalized to affordance thresholds. Across experiments, errors in decisions to reach through too-small apertures were likely due to low penalty for error. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Identification and Bisection of Temporal Durations and Tone Frequencies: Common Models for Temporal and Nontemporal Stimuli.

Two experiments examined identification and bisection of tones varying in temporal duration (Experiment 1) or frequency (Experiment 2). Absolute identification of both durations and frequencies was influenced by prior stimuli and by stimulus distribution. Stimulus distribution influenced bisection for both stimulus types consistently, with more positively skewed distributions producing lower bisection points. The effect of distribution was greater when the ratio of the largest to smallest stimulus magnitude was greater. A simple mathematical model, temporal range frequency theory, was applied. It is concluded that (a) similar principles describe identification of temporal durations and other stimulus dimensions and (b) temporal bisection point shifts can be understood in terms of psychophysical principles independently developed in nontemporal domains, such as A. Parducci's (1965) range frequency theory. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Within- and between-dimensional processing in the auditory modality.

Participants made speeded target-nontarget responses to singly presented auditory stimuli in 2 tasks. In within-dimension conditions, participants listened for either of 2 target features taken from the same dimension; in between-dimensions conditions, the target features were taken from different dimensions. Judgments were based on the presence or absence of either target feature. Speech sounds, defined relative to sound identity and locale, were used in Experiment 1, whereas tones, comprising pitch and locale components, were used in Experiments 2 and 3. In all cases, participants performed better when the target features were taken from the same dimension than when they were taken from different dimensions. Data suggest that the auditory and visual systems exhibit the same higher level processing constraints. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A confluence of contexts: Asymmetric versus global failures of selective attention to Stroop dimensions.

In 6 experiments probing selective attention through Stroop classification, 4 factors of context were manipulated: (a) psychophysical context, the distinctiveness of values along the color and word dimensions; (b) set size context, the number of stimulus values tested; (c) production context the mode used to respond; and (d) covariate context, the correlation between the dimensions. The psychophysical and production contexts mainly caused an asymmetry in selective attention failure between colors and words, whereas the set size and covariate contexts contributed primarily to the average or global magnitudes of attentional disruption across dimensions. The results suggest that (a) Stroop dimensions are perceptually separable, (b) J. R. Stroop's (1935) classic findings arose from his particular combination of contexts, and (c) stimulus uncertainty and dimensional imbalance are the primary sources of task and congruity effects in the Stroop paradigm. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interaction between drug discriminative stimuli and exteroceptive, sensory signals.

Interactions between drug discriminative stimuli based on 5.6 and 10 mg/kg sodium pentobarbital (ip) and exteroceptive stimuli (visual and auditory) were studied in 27 male Sprague-Dawley rats in a T-maze. In 3 groups, visual stimuli (light vs dark) were differentially paired with drug stimuli; the 4th group discriminated combinations of tonal frequencies (1 kHz or 10 kHz) and the presence or absence of pentobarbital (10 mg/kg). In general, visual stimuli controlled choice behavior (left or right turn) to a greater extent than did the drug training stimuli, whereas the auditory stimuli exerted no apparent control over the pentobarbital stimulus in Group 4. Tests with higher doses (13.75 and 17.5 mg/kg) indicated augmented stimulus control by the drug dimension in 2 groups (Group 1, 10 mg/kg pentobarbital vs saline; Group 2, 5.6 mg/kg vs 10 mg/kg pentobarbital) but not in the 3rd group (5.6 mg/kg pentobarbital vs saline) in the "conflict" situation, in which the exteroceptive conditions signaled one response whereas the drug stimulus signaled the opposite response. Discrimination training with only one of the stimulus dimensions resulted in stimulus control in the following order: 10 mg/kg vs saline?>?5.6 mg/kg vs saline?>?1 kHz vs 10 kHz. This indicates that the auditory stimuli were of marginal significance. It is concluded drugs can compete with exteroceptive, visual stimuli for associative strength. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Invariance of perceptual spaces and perceptual separability of stimulus dimensions

This article reports an extension of a paradigm for studying processing of perceptual dimensions. The paradigm is the complete identification task with a feature-complete factorial design (FCFD) of stimuli providing data for multidimensional signal detection analyses. The extension uses blocks of trials with subsets of the FCFD stimulus set, allowing estimation of various d's for inferring perceptual separability (PS) of dimensions and for disambiguating stimulus configurations when PS fails. Results of 4 experiments found the following: PS of arc curvature and line orientation in a discrimination task (Experiment 1), increasing PS failure in detection of horizontal and vertical lines (Experiment 2a), 45 degrees and 135 degrees (Experiment 2b), and 50 degrees and 60 degrees oblique lines (Experiment 2c). In each experiment, corresponding d's remained equivalent across blocks with different stimulus subsets.     

Pitfalls in estimating motion detector receptive field geometry

A number of psychophysical investigations have used spatial-summation methods to estimate the receptive field (RF) geometry of motion detectors by exploring how psychophysical thresholds change with stimulus height and/or width. This approach is based on the idea that an observer's ability to detect motion direction is strongly determined by the relationship between the stimulus geometry (height and width) and the RF of the activated motion detectors. Our results show that previous estimates of RF geometry can depend significantly on stimulus position in the visual field as well as on the stimulus height-to-width ratio. The data further show that RF estimates depend on the stimulus in a manner that is inconsistent with basic predictions derived from current motion detector models. Hence previous estimates of height, width, and height-to-width ratios of motion detector RFs are inaccurate and unreliable. This inaccuracy/unreliability is attributed to a number of sources. These include incorrect fixed-parameter values in model fits, as well as the confounding of physiological spatial summation area through combined use of contrast thresholds and Gaussian-windowed stimuli. A third source of error is an asymmetric variation of spatiotemporal correlation in the stimulus as either its height or width is varied (and the other dimension held constant). Most importantly, a fourth source of unreliability is attributed to the existence of a nonlinear, nonmonotonic distribution of motion detectors in the visual field that has been previously described and is a natural result of visual anatomy.     

Scalar timing in temporal generalization in humans with longer stimulus durations

Three experiments investigated temporal generalization performance in humans by using stimulus durations similar to those previously used with rats. In most conditions, chronometric counting was prevented by concurrent shadowing of temporally irregular numbers. Experiment 1 examined performance with visual stimuli, when the standard was 4.0 s long and nonstandard stimuli were spaced either linearly or logarithmically around the standard. Generalization gradients were asymmetrical with linear spacing but symmetrical with logarithmic spacing, a result obtained previously with humans. Experiment 2 used auditory stimuli and varied the standard across values of 2.0, 4.0, 6.0, and 8.0 s. All gradients were asymmetrical, and good superposition was obtained, indicating conformity to scalar timing. Experiment 3 prevented or encouraged chronometric counting by changing instructions, and temporal generalization gradients differed when counting was and was not used.     

Contrast discrimination, non-uniform patterns and change blindness

Change blindness--our inability to detect large changes in natural scenes when saccades, blinks and other transients interrupt visual input--seems to contradict psychophysical evidence for our exquisite sensitivity to contrast changes. Can the type of effects described as 'change blindness' be observed with simple, multi-element stimuli, amenable to psychophysical analysis? Such stimuli, composed of five mixed contrast elements, elicited a striking increase in contrast increment thresholds compared to those for an isolated element. Cue presentation prior to the stimulus substantially reduced thresholds, as for change blindness with natural scenes. On one hand, explanations for change blindness based on abstract and sketchy representations in short-term visual memory seem inappropriate for this low-level image property of contrast where there is ample evidence for exquisite performance on memory tasks. On the other hand, the highly increased thresholds for mixed contrast elements, and the decreased thresholds when a cue is present, argue against any simple early attentional or sensory explanation for change blindness. Thus, psychophysical results for very simple patterns cannot straightforwardly predict results even for the slightly more complicated patterns studied here.     

Multidimensional scaling reveals two dimensions of thermal pain.

Used the individual differences scaling model of multidimensional scaling to explore the dimensions of thermal pain. 20 male undergraduates made 66 similarity judgments to all pairs of 12 different thermal stimulus intensities ranging from zero to noxious. Results reveal a 2-dimensional group stimulus space. The major dimension ordered the stimuli with respect to their intensity. This quantitative, strength-of-sensation dimension may be interpreted as indicating how weak or strong a stimulus feels, apart from any secondary qualities of warmth or pain. The 2nd dimension was related to the qualitative aspects of the stimuli and contained 2 attributes: (1) a pain attribute ranging from just detectable warmth to painful and (2) a warm–hot attribute running from just detectable warmth to hot. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus intensity modulates associative and nonassociative responding in preweanling rats

The purpose of the present study was to determine whether preweanling rats respond differentially to the intensity and energy source of a stimulus. Previous studies have suggested that infants process compound stimuli based on net stimulus intensity regardless of the energy source of the compound's elements, but more direct tests have been needed of the infant's response to the stimulus attributes of intensity and energy source. This response was tested for auditory and visual stimuli that had been equated (Experiment 1) in terms of perceived intensity (low and high). Intensity level and energy source of the stimuli were varied independently within nonassociative (Experiment 2) and associative (Experiment 3) procedures. The overall results indicate that stimuli of a low-perceived intensity were processed in terms of their intensity, whereas high-intensity stimuli were processed on the basis of energy source. These results are relevant to contemporary issues of cognitive development in humans and animals.