Stimulus Array Research Articles

The effect of object-centered instructions in Cartesian and polar coordinates on saccade vector

Express saccades (ES) are the most reflexive saccadic eye movements, with very short reaction times of 70–110 ms. It is likely that ES have the shortest saccade reaction times (SRTs) possible given the known physiological and anatomical delays present in sensory and motor systems. Nevertheless, it has been demonstrated that a vector displacement of ES to spatially extended stimuli can be influenced by spatial cognition. Edelman, Kristjansson, and Nakayama (2007) found that when two horizontally separated visual stimuli appear at a random location, the spatial vector, but not the reaction time, of human ES is strongly influenced by an instruction to make a saccade to one side (either left or right) of a visual stimulus array. Presently, we attempt to extend these findings of cognitive effects on saccades in three ways: (a) determining whether ES could be affected by other types of spatial instructions: vertical, polar amplitude, and polar direction; (b) determining whether these spatial effects increased with practice; and (c) determining how these effects depended on SRTs. The results demonstrate that both types of Cartesian as well as polar amplitude instructions strongly affect ES vector, but only modestly affect SRTs. Polar direction instructions had sizable effects only on nonreflexive saccades where the visual stimuli could be viewed for several hundred milliseconds prior to saccade execution. Short- (trial order within a block) and long-term (experience across several sessions) practice had little effect, though the effect of instruction increased with SRT. Such findings suggest a generalized, innate ability of cognition to affect the most reflexive saccadic eye movements.

Peripheral target identification performance modulates eye movements

We often shift our eyes to an interesting stimulus, but it is important to inhibit that eye movement in some environments (e.g., a no-look pass in basketball). Here, we investigated participants’ ability to inhibit eye movements when they had to process a peripheral target with a requirement to maintain strict fixation. An array of eight letters composed of four characters was briefly presented and a directional cue was centrally presented to indicate the target location. The stimulus onset asynchrony (SOA) between the cue and the stimulus array was chosen from six values, consisting of pre-cue conditions (−400 and −200ms), a simultaneous cue condition (0ms), and post-cue conditions (200, 400, and 800ms). We found the following: 1) participants shifted their eyes toward the cued location even though the stimulus array was absent at the onset of eye movements, but the eye movement amplitude was smaller than the actual location of the target; 2) eye movements occurred approximately 150ms after the onset of stimulus array in the pre-cue conditions and 250ms after cue onset in the simultaneous and post-cue conditions; and 3) eye movement onsets were delayed and their amplitudes were smaller in correct trials than incorrect trials. These results indicate that the inhibitory process controlling eye movements also compete for cognitive resources like other cognitive processes.

How Configural Is the Configural Superiority Effect? A Neuroimaging Investigation of Emergent Features in Visual Cortex.

The perception of a visual stimulus is dependent not only upon local features, but also on the arrangement of those features. When stimulus features are perceptually well organized (e.g., symmetric or parallel), a global configuration with a high degree of salience emerges from the interactions between these features, often referred to as emergent features. Emergent features can be demonstrated in the Configural Superiority Effect (CSE): presenting a stimulus within an organized context relative to its presentation in a disarranged one results in better performance. Prior neuroimaging work on the perception of emergent features regards the CSE as an “all or none” phenomenon, focusing on the contrast between configural and non-configural stimuli. However, it is still not clear how emergent features are processed between these two endpoints. The current study examined the extent to which behavioral and neuroimaging markers of emergent features are responsive to the degree of configurality in visual displays. Subjects were tasked with reporting the anomalous quadrant in a visual search task while being scanned. Degree of configurality was manipulated by incrementally varying the rotational angle of low-level features within the stimulus arrays. Behaviorally, we observed faster response times with increasing levels of configurality. These behavioral changes were accompanied by increases in response magnitude across multiple visual areas in occipito-temporal cortex, primarily early visual cortex and object-selective cortex. Our findings suggest that the neural correlates of emergent features can be observed even in response to stimuli that are not fully configural, and demonstrate that configural information is already present at early stages of the visual hierarchy.

Efectos del contenido funcional de la instrucción sobre el desempeño en igualación a la muestra de segundo orden

The effect of the functional content of instructions on the acquisition, transfer and description of performance in a second order matching-to-sample task was evaluated. Twenty undergraduate students were assigned to one of four experimental groups: (a) procedural instruction at the start of the task (PStart); (b) procedural instruction in each trial (PTrial); (c) instruction referring to instances in each trial (ITrial); and (d) instruction referring to relation in each trial (RTrial). The proportion of correct attempts was analyzed, and was found to be higher in the ITrial and RTrial groups for the training phase, and for the PStart, PTrial and RTrial groups in the extra-instance and extra-modal transfer test, as well as for the ITrial group in the extra-relational test; the larger number of accurate performance descriptions was observed in the RTrial group. These results show that abstract stimulus control can be presented either by way of transfer of functions throughout instructions, or by differentiation of positive and negative cases of the contingencies, which is enhanced by the concurrent presence of the instruction and the stimulus array.

Spatio-Temporal Structure, Path Characteristics, and Perceptual Grouping in Immediate Serial Spatial Recall.

Immediate serial spatial recall measures the ability to retain sequences of locations in short-term memory and is considered the spatial equivalent of digit span. It is tested by requiring participants to reproduce sequences of movements performed by an experimenter or displayed on a monitor. Different organizational factors dramatically affect serial spatial recall but they are often confounded or underspecified. Untangling them is crucial for the characterization of working-memory models and for establishing the contribution of structure and memory capacity to spatial span. We report five experiments assessing the relative role and independence of factors that have been reported in the literature. Experiment 1 disentangled the effects of spatial clustering and path-length by manipulating the distance of items displayed on a touchscreen monitor. Long-path sequences segregated by spatial clusters were compared with short-path sequences not segregated by clusters. Recall was more accurate for sequences segregated by clusters independently from path-length. Experiment 2 featured conditions where temporal pauses were introduced between or within cluster boundaries during the presentation of sequences with the same paths. Thus, the temporal structure of the sequences was either consistent or inconsistent with a hierarchical representation based on segmentation by spatial clusters but the effect of structure could not be confounded with effects of path-characteristics. Pauses at cluster boundaries yielded more accurate recall, as predicted by a hierarchical model. In Experiment 3, the systematic manipulation of sequence structure, path-length, and presence of path-crossings of sequences showed that structure explained most of the variance, followed by the presence/absence of path-crossings, and path-length. Experiments 4 and 5 replicated the results of the previous experiments in immersive virtual reality navigation tasks where the viewpoint of the observer changed dynamically during encoding and recall. This suggested that the effects of structure in spatial span are not dependent on perceptual grouping processes induced by the aerial view of the stimulus array typically afforded by spatial recall tasks. These results demonstrate the independence of coding strategies based on structure from effects of path characteristics and perceptual grouping in immediate serial spatial recall.

A new electroretinogram function that can move the centre of the multifocal hexagonal stimulus array

PurposeWe can examine declines in visual sensitivity at arbitrary points on the retina using a precise perimetry device with a fundus camera function. However, the retinal layer causing the decline in visual sensitivity can not be identified. To investigate cryptogenic diseases, such as macular dystrophy, acute zonal occult outer retinopathy and multiple evanescent white dot syndrome, we studied a new electroretinogram function that can move the centre of the multifocal hexagonal stimulus array.MethodsAn electroretinographic optical system, specifically perimetric optical system, was added to an experimental device with the same optical system as a fundus camera. We also added an Edmund infrared camera EO‐0413, a lens with a focal length of 25 mm, a 45‐degree cold mirror, a halogen lamp and an 8‐inch monitor. Software was generated to show the multifocal hexagonal stimulus array on the monitor using C++Builder XE8 and to move the centre of the array up and down as well as back and forth. We used National Instruments’ USB‐6008 and their system design platform LabVIEW 2015 for data retrieval. The Nihon Kohden plate electrode NE‐113As were used to measure electrodermal activities around the eyes. Some contact lens electrodes were used to measure electrical potentials of retina.ResultsWe used a multifocal hexagonal stimulus array with 37 elements in the software. The centre of the multifocal hexagonal stimulus array could be adjusted to the same position as the examination target of the precise perimetry.ConclusionsWe successfully added this new electroretinogram function to the experimental ophthalmologic device.

Saccades inevitably protect visual memory traces

With each visual fixation, a vast amount of information enters the visual system, only part of which will be stored durably in visual short-term memory (VSTM). We present four experiments testing the hypothesis that saccadic eye movements decide upon the content of VSTM, and determine naturally what we remember and what we forget. We studied whether saccades, planned and executed after the disappearance of a visual stimulus array, influence memory performance even if the saccade is irrelevant to the memory task. We flashed briefly (100 ms) an array of oriented Gabor patches and—after a variable delay—prompted saccades to a random (now empty) location in the array. Subsequently, a response cue instructed observers to report the orientation of one randomly selected stimulus in the array, probing memory either at the same (congruent) or at a different location than the saccade target (incongruent). In all experiments, memory performance was markedly better when the probed location and the saccade target coincided. This effect of saccades on visual memory was time-dependent; it was strongest right after array offset, still present after 800 ms, and no longer significant after 1600 ms (Experiment 1). In contrast, the performance difference between congruent and incongruent trials remained constant across a large range of intervals between saccade cue and the onset of the response cue (Experiment 2). Masking the memory array up to 800 ms after its offset—but simultaneously with the onset of the saccade cue—reduced performance, yet a congruency effect remained (Experiment 3). Finally, we show that this impact of saccades on VSTM is inevitable even when congruent trials are far less likely than incongruent ones (Experiment 4). These results demonstrate that saccades inadvertently determine the content of VSTM, imposing a natural bottleneck on the transition of fragile sensory traces to durable memories. Meeting abstract presented at VSS 2016

Task-irrelevant contextual expectation impairs orientation discrimination performance

Expectations play a critical role in guiding vision during everyday life. In some cases, expectation is directly relevant to the currently relevant stimulus, while in other cases, expectation is not directly relevant but is instead tied to some other contextual aspect of the task (termed contextual expectation). Information about what target features are relevant (e.g., target orientation and location) has been shown to improve visual discrimination by enhancing the efficiency of sensory processing. However, less is known about how task-irrelevant contextual performance are similar to those induced by information about task relevance. Here, we presented subjects with a bilateral visual display of square-shaped and circle-shaped cues; these cues were presented 0-450ms before a bilateral stimulus array containing a horizontal (non-target) or a slightly tilted vertical grating (target). Task-irrelevant contextual expectation was manipulated by changing the relationship between the color of the left and right cues (e.g., in 70% of trials, left and right cue were presented in red and blue respectively, while in 30% of trials the left and right cue were presetned in blue and red respectively). We found that information about target location increased behavioral performance by reducing reaction times, specifically when the target array appeared 50-450ms after cue onset. In contrast, contextual expectation only had an effect on accuracy at the 0ms cue-to-target onset asynchrony such that an 'unexpected' context increased discrimination accuracy. Taken together, these results suggest that task-irrelevant contextual expectation and task-relevant information can have opposing effects on perceptual performance with distinct temporal dynamics. Meeting abstract presented at VSS 2016

The psychophysiology of approach, avoidance and conflict personality traits

Behavior analysts frequently use stimulus preference assessments to identify putative reinforcers for consumers with autism spectrum disorder. The current study evaluated the effect of video modeling with voiceover instruction and on-screen text (VMVOT) and performance feedback to train staff to implement the multiple-stimulus-without-replacement, paired-stimulus, and single-stimulus preference assessments. Generalization probes with a larger stimulus array and with an actual consumer were conducted. The results indicated that VMVOT may be a useful prelude to in-vivo training approaches, as all staff mastered the preference assessments and demonstrated high levels of generalized responding. This outcome is discussed in light of previous staff training studies and avenues for future research.

The agranular and granular insula differentially contribute to gambling-like behavior on a rat slot machine task: effects of inactivation and local infusion of a dopamine D4 agonist on reward expectancy.

Rats, like humans, are susceptible to the reinforcing effects of reward-related stimuli presented within a compound stimulus array, putatively analogous to the so-called near-miss effect. We have previously demonstrated using a rodent slot machine task (rSMT) that the reward expectancy these stimuli elicit is critically mediated by the dopamine D4 receptor. D4 receptors are principally located in prefrontal regions activated during slot machine play in humans, such as the insular cortex. The insula has recently attracted considerable interest as it appears to play a crucial role in substance and behavioral addictions. However, the insula is a heterogeneous area, and the relative contributions of subregions to addictive behaviors are unclear. Male Long Evans rats were trained to perform the rSMT, and then bilateral cannula targeting either the granular or agranular insula were implanted. The effects of inactivation and local administration of a D4 agonist were investigated. Temporary inactivation of the agranular, but not the granular insula impaired performance on the rSMT. In contrast, local infusion of the D4 agonist PD168077 into the agranular insula had no effect on task performance, but when administered into the granular insula, it improved animals' ability to differentiate winning from non-winning trials. The agranular insula may therefore modulate decision making when conflicting stimuli are present, potentially due to its role in generating a cohesive emotional percept based on both externally and internally generated signals, whereas the granular insular is not critical for this process. Nevertheless, D4 receptors within the granular insula may amplify the incentive salience of aversive environmental stimuli. These data provide insight into the neurobiological mechanism underpinning maladaptive reward expectancy during gambling and provide further evidence that D4 receptors represent a potential target for developing pharmacotherapies for problem gambling.

The Effect of Background Context on the Size–Time Illusion

Previous studies suggest that time perception may be altered by nontemporal stimulus properties, such as size and numerosity, where increases lead to a longer perception of time. These studies have led to the suggestion of a generalized magnitude system that processes abstract quantities. However, the majority of studies on this phenomenon have used simple stimuli, varying along one or two dimensions, and occurring in the same location. Here, we sought to explore the influence of the size–time illusion amongst complex visual scenes. Across five experiments, human participants judged the duration of two visual stimuli, of different sizes, appearing at different spatial locations for a range of sub-second durations. In half of the trials, these stimuli were overlaid on an image of a city street, with one stimulus presented farther away than the other. We found that larger stimuli were judged to be longer, but only when the larger stimulus was presented on the left side of space, and not when presented on the right or when the entire stimulus array was on the left. This effect extended to a marginal bias for left-sided stimuli to be judged as longer. However, we found that the size–time illusion for right-sided stimuli was reinstated when a background city context was presented, which may have been driven by an imposed effect of perceived distance. These results suggest that the size–time illusion is affected by the background context and location against which stimuli are presented, and provide important qualifications to theories of a common magnitude system.

Individual differences in the components of children’s and adults’ information processing for simple symbolic and non-symbolic numeric decisions

How do speed and accuracy trade off, and what components of information processing develop as children and adults make simple numeric comparisons? Data from symbolic and non-symbolic number tasks were collected from 19 first graders (Mage=7.12 years), 26 second/third graders (Mage=8.20 years), 27 fourth/fifth graders (Mage=10.46 years), and 19 seventh/eighth graders (Mage=13.22 years). The non-symbolic task asked children to decide whether an array of asterisks had a larger or smaller number than 50, and the symbolic task asked whether a two-digit number was greater than or less than 50. We used a diffusion model analysis to estimate components of processing in tasks from accuracy, correct and error response times, and response time (RT) distributions. Participants who were accurate on one task were accurate on the other task, and participants who made fast decisions on one task made fast decisions on the other task. Older participants extracted a higher quality of information from the stimulus arrays, were more willing to make a decision, and were faster at encoding, transforming the stimulus representation, and executing their responses. Individual participants’ accuracy and RTs were uncorrelated. Drift rate and boundary settings were significantly related across tasks, but they were unrelated to each other. Accuracy was mainly determined by drift rate, and RT was mainly determined by boundary separation. We concluded that RT and accuracy operate largely independently.

Movement Sonification: Effects on Motor Learning beyond Rhythmic Adjustments.

Motor learning is based on motor perception and emergent perceptual-motor representations. A lot of behavioral research is related to single perceptual modalities but during last two decades the contribution of multimodal perception on motor behavior was discovered more and more. A growing number of studies indicates an enhanced impact of multimodal stimuli on motor perception, motor control and motor learning in terms of better precision and higher reliability of the related actions. Behavioral research is supported by neurophysiological data, revealing that multisensory integration supports motor control and learning. But the overwhelming part of both research lines is dedicated to basic research. Besides research in the domains of music, dance and motor rehabilitation, there is almost no evidence for enhanced effectiveness of multisensory information on learning of gross motor skills. To reduce this gap, movement sonification is used here in applied research on motor learning in sports. Based on the current knowledge on the multimodal organization of the perceptual system, we generate additional real-time movement information being suitable for integration with perceptual feedback streams of visual and proprioceptive modality. With ongoing training, synchronously processed auditory information should be initially integrated into the emerging internal models, enhancing the efficacy of motor learning. This is achieved by a direct mapping of kinematic and dynamic motion parameters to electronic sounds, resulting in continuous auditory and convergent audiovisual or audio-proprioceptive stimulus arrays. In sharp contrast to other approaches using acoustic information as error-feedback in motor learning settings, we try to generate additional movement information suitable for acceleration and enhancement of adequate sensorimotor representations and processible below the level of consciousness. In the experimental setting, participants were asked to learn a closed motor skill (technique acquisition of indoor rowing). One group was treated with visual information and two groups with audiovisual information (sonification vs. natural sounds). For all three groups learning became evident and remained stable. Participants treated with additional movement sonification showed better performance compared to both other groups. Results indicate that movement sonification enhances motor learning of a complex gross motor skill—even exceeding usually expected acoustic rhythmic effects on motor learning.

Human Performance on a Signal Detection Task: Discriminability and Sensitivity to Reinforcement

Ten human participants worked on a computer-based discrete-trials signal detection task in which stimulus disparity and the ratio of reinforcers for correct responses were manipulated. During each trial, a 12 × 12 stimulus array consisting of an unequal number of randomly arranged circles and squares was presented. Participants responded by indicating whether the stimulus contained more circles or more squares. Two levels of stimulus disparity, high and low, were arranged by changing the numbers of circles and squares in the stimulus. At both levels of disparity, the ratio of reinforcers for correct circle and square responses was varied across 5 different levels ranging from 1:9 to 9:1. Reinforcers were assigned using a controlled reinforcer procedure that held obtained reinforcer ratios close to the programmed ratios. For all participants, discriminability was higher when the stimulus disparity was high but was not affected by changes in the reinforcer ratio. Response bias varied as a function of the reinforcer ratio. Estimates of the sensitivity of bias to changes in the reinforcer ratio varied with changes in disparity; however, the variations were typically small and their direction differed across participants. These findings are consistent with previous human research (Gallagher & Alsop, Journal of the Experimental Analysis of Behavior, 75(2), 183–203, 2001; Johnstone & Alsop, Journal of the Experimental Analysis of Behavior, 73, 275–290, 2000; Lie & Alsop, Journal of the Experimental Analysis of Behavior, 93(2), 185-201, 2010) showing that when a controlled reinforcer procedure is used, bias and sensitivity are independent of discriminability.

Activation of dopamine D4 receptors within the anterior cingulate cortex enhances the erroneous expectation of reward on a rat slot machine task

Using a rodent slot machine task (rSMT), we have previously shown that rats, like humans, are susceptible to the reinforcing effects of winning signals presented within a compound stimulus array, even when the pattern generated predicts a negative rather than a positive outcome such as during a “near-miss”. The dopamine D4 receptor critically mediates the erroneous reward expectancy generated on such trials. D4 receptors are particularly enriched within frontal and limbic areas activated during slot machine play, such as the anterior cingulate cortex (ACC). We therefore selectively inactivated the ACC to confirm involvement of this region in rSMT performance, and subsequently examined the specific contribution of local D4 receptors. ACC inactivations generally impaired animals' ability to optimally differentiate winning from losing outcomes. Local administration of the D4 agonist PD168077 had a qualitatively similar effect, but increased reward expectancy was only evident on archetypal “near-miss” trials i.e. when the first two of three stimuli in the array were concordant with a rewarding outcome, and only the last stimulus critically signalled a non-win. These data indicate that the ACC is critically involved in parsing the appropriate response when competing stimulus–outcome associations are activated, and that signalling via D4 receptors may play a particularly important role in gating the temporal and spatial summation of salient events. Such findings provide novel insights into the mechanism underlying the erroneous expectations of reward generated when playing slot machines, and suggest a mechanism by which D4 receptor antagonists may be effective in treating gambling disorder.

Executive control and task switching in pigeons

Flexibly adjusting one’s behavior depending on the task at hand is a hallmark of executive function. In two experiments, we explored pigeons’ cognitive flexibility to concurrently perform two complex categorization tasks: a numerosity discrimination (where number was the relevant dimension and variability was the irrelevant dimension) and a variability discrimination (where variability was the relevant dimension and number was the irrelevant dimension). The flexibility of pigeons’ behavior was evidenced by their rapid, on-demand switching between tasks within training sessions. In addition, in Experiment 1, pigeons more accurately performed the numerosity task with arrays of different stimuli than with arrays of same stimuli and they more accurately performed the variability task with arrays of 16 stimuli than with arrays of 6 stimuli. In Experiment 2, when the magnitudes of the relevant and irrelevant dimensions were congruent, pigeons’ accuracy was higher than when the magnitudes were incongruent. Thus, the irrelevant dimension facilitated target discrimination performance when its magnitude matched the magnitude of the correct choice. These cross-task interactions suggest that a common computational mechanism underlies both discriminations. Pigeons’ cognitive complexity and flexibility—even in the absence of a prefrontal cortex—indicates that other avian brain areas can support behaviors emblematic of executive functioning.

A developmental ecological study of novel metaphoric language use

From the perspective of the ecological direct realist approach to perceiving-acting-knowing, we argue that linguistic metaphor involves understanding one kind of thing by means of a different kind of thing. This understanding is based on invariants in an ambient stimulus array that specify objects and events over time, and, therefore, the metaphoric process is rooted in perception. The present research investigated children's and adults' knowledge of ordinary kinds of objects and events, the development of their ability to detect metaphoric resemblances across these real kinds, and their abilities to respond to discourse contexts that supported metaphor use. We used pairs of photographs depicting objects and events from verbal metaphors earlier produced by other children. Thirty participants at each age group (4, 6, 8, 10, adults) first said what they knew of each depicted object or event. Then half of the participants in each age group chose depictions from the whole set of photographs that were “like” the given standards; the other half chose those that were “of the same kind”. Finally, the experimenter encouraged metaphor use by showing pictures from metaphoric pairs to all the participants and asking questions about the pictures. Participants at all ages described the objects and events predominantly in terms of functions, physical properties, and dynamic properties. Whereas metaphoric matches in the “kind” condition were rare at all ages, they were frequent in the “like” condition, and increased with age. Metaphor use also increased with age and participants did not use metaphors about objects or events that they had said were of the same kind. Thus, children know that metaphors are about different real kind things and, therefore, their utterances are truly metaphoric. Even though these abilities begin at early ages, they continue to develop in facility and frequency at least to adulthood. Future studies will investigate developments in the forms of metaphoric utterances, and in the links between visual and verbal metaphors.

Spatial attention facilitates assembly of the briefest percepts: Electrophysiological evidence from color fusion.

When two different color stimuli are presented in rapid succession, the resulting percept is sometimes that of a mixture of both colors, due to a perceptual process called color fusion. Although color fusion might seem to occur very early in the visual pathway, and only happens across the briefest of stimulus presentation intervals (< 50 ms), the present study showed that spatial attention can alter the fusion process. In a series of experiments, spatial cues were presented that either validly indicated the location of a pair of (different) color stimuli in successive stimulus arrays, or did not, pointing toward isoluminant gray distractors in the other visual hemifield. Increased color fusion was observed for valid cues across a range of stimulus durations, at the expense of individual color reports. By contrast, perception of repeated, same-color stimulus pairs did not change, suggesting that the enhancement was specific to fusion, not color discrimination per se. Electrophysiological measures furthermore showed that the amplitude of the N1, N2pc, and P3 components of the ERP were differentially modulated during the perception of individual and fused colors, as a function of cueing and stimulus duration. Fusion itself, collapsed across cueing conditions, was reflected uniquely in N1 amplitude. Overall, the results suggest that spatial attention enhances color fusion and decreases competition between stimuli, constituting an adaptive slowdown in service of temporal integration.

Evidence against continuous variables driving numerical discrimination in infancy

Over the past decades, abundant evidence has amassed that demonstrates infants’ sensitivity to changes in number. Nonetheless, a prevalent view is that infants are more sensitive to continuous properties of stimulus arrays such as surface area and contour length than they are to numerosity. Very little research, however, has directly addressed infants’ sensitivity to contour. Here we used a change detection paradigm to assess infants’ acuity for the cumulative contour length of an array when the array’s surface area and number were held constant. Seven-month-old infants detected a threefold change in contour length but failed to detect a twofold change. These results, in conjunction with previously published data on numerosity discrimination using the same experimental paradigm, suggest that infants are not more sensitive to changes in contour length compared to changes in numerosity. Consequently, these findings undermine the claim that attention toward contour length is a primary driver of numerical discrimination in infancy.

Allocation of cognitive resources in comparative visual search – Individual and task dependent effects

Behaviors recruit multiple, mutually substitutable types of cognitive resources (e.g., data acquisition and memorization in comparative visual search), and the allocation of resources is performed in a cost-optimizing way. If costs associated with each type of resource are manipulated, e.g., by varying the complexity of the items studied or the visual separation of the arrays to be compared, according adjustments of resource allocation (“trade-offs”) have been demonstrated. Using between-subject designs, previous studies showed overall trade-off behavior but neglected inter-individual variability of trade-off behavior. Here, we present a simplified paradigm for comparative visual search in which gaze-measurements are replaced by switching of a visual mask covering one stimulus array at a time. This paradigm allows for a full within-subject design. While overall trade-off curves could be reproduced, we found that each subject used a specific trade-off strategy which differ substantially between subjects. Still, task-dependent adjustment of resource allocation can be demonstrated but accounts only for a minor part of the overall trade-off range. In addition, we show that the individual trade-offs were adjusted in an unconscious and rather intuitive way, enabling a robust manifestation of the selected strategy space.