Effect Of Set Size Research Articles

Perceiving Spatial Relations via Attentional Tracking and Shifting

Perceiving which of a scene's objects are adjacent may require selecting them with a limited-capacity attentional process. Previous results support this notion [1-3] but leave open whether the process operates simultaneously on several objects or proceeds one by one. With arrays of colored discs moving together, we first tested the effect of moving the discs faster than the speed limit for following them with attentional selection [4]. At these high speeds, participants could identify which colors were present and determine whether identical arrays were aligned or offset by one disc. They could not, however, apprehend which colors in the arrays were adjacent, indicating that attentional selection is required for this judgment. If selection operates serially to determine which colors are neighbors, then after the color of one disc is identified, attention must shift to the adjacent disc. As a result of the motion, attention might occasionally miss its target and land on the trailing disc. We cued attention to first select one or the other of a pair of discs and found the pattern of errors predicted. Perceiving these spatial relationships evidently requires selecting and processing objects one by one and is only possible at low object speeds.

The search for the neural mechanisms of the set size effect

The set size effect in visual search refers to the linear increase in response time (RT) or decrease in accuracy as the number of distractors increases. Previous human and monkey studies have reported a correlation between set size and neural activity in the frontal eye field (FEF) and intraparietal sulcus (IPS). In a recent functional magnetic resonance imaging study, we did not observe a set size effect in the superior precentral sulcus (sPCS, thought to be the human homolog of the FEF) and IPS in an oculomotor visual search task (Ikkai et al., 2011). Our task used placeholders in the search array, along with the target and distractors, in order to equate the amount of retinal stimulation for each set size. We here attempted to reconcile these differences with the results from a follow-up experiment in which the same oculomotor visual search task was used, but without placeholders. A strong behavioral set size effect was observed in both studies, with very similar saccadic RTs and slopes between RT and set size. However, a set size effect was now observed in the sPCS and IPS. We comment on this finding and discuss the role of these neural areas in visual search.

"Measuring search efficiency in complex visual search tasks: Global and local clutter": Correction to Beck et al. (2010).

Reports an error in Measuring search efficiency in complex visual search tasks: Global and local by Melissa R. Beck, Maura C. Lohrenz and J. Gregory Trafton (Journal of Experimental Psychology: Applied, 2010[Sep], Vol 16[3], 238-250). The copyright for the article was incorrectly listed. The correct copyright information is provided in the erratum. (The following abstract of the original article appeared in record 2010-19027-002.) Set size and crowding affect search efficiency by limiting attention for recognition and attention against competition; however, these factors can be difficult to quantify in complex search tasks. The current experiments use a quantitative measure of the amount and variability of visual information (i.e., clutter) in highly complex stimuli (i.e., digital aeronautical charts) to examine limits of attention in visual search. Undergraduates at a large southern university searched for a target among 4, 8, or 16 distractors in charts with high, medium, or low global clutter. The target was in a high or low local-clutter region of the chart. In Experiment 1, reaction time increased as global clutter increased, particularly when the target was in a high local-clutter region. However, there was no effect of distractor set size, supporting the notion that global clutter is a better measure of attention against competition in complex visual search tasks. As a control, Experiment 2 demonstrated that increasing the number of distractors leads to a typical set size effect when there is no additional clutter (i.e., no chart). In Experiment 3, the effects of global and local clutter were minimized when the target was highly salient. When the target was nonsalient, more fixations were observed in high global clutter charts, indicating that the number of elements competing with the target for attention was also high. The results suggest design techniques that could improve pilots' search performance in aeronautical charts. (PsycINFO Database Record (c) 2011 APA, all rights reserved). Language: en

Linear and nonlinear prefrontal and parietal activity during multiple-item working memory

Most parts of the prefrontal and posterior parietal cortices show sustained activity during short-term maintenance of visual information and their activity increases with increasing memory set size. To investigate the interplay of feature selectivity, memory load and inter-item interaction (or interference) on sustained activity, we compared and contrasted fMRI signal during the retention of two items from the same or different visual feature categories (e.g., two line orientations versus a line and a color) relative to the retention of single items. Data from 16 young adults revealed three types of activation patterns in the prefrontal and posterior parietal cortices. First, among the prefrontal and posterior parietal areas that showed preferential responses to line orientations, some exhibited linear increases in sustained activity whereas others exhibited nonlinear increases in correspondence to the number of lines in the memory set. Second, the right lateral prefrontal and ventral posterior parietal areas, albeit not showing differential sustained activity relative to lines or colors, were disproportionately more active during holding two lines in comparison to holding a line and a color. Third, the left posterior intraparietal sulcus showed a weak effect of memory set size regardless of the items' visual features. These observations suggest that rather than number of items, a combination of factors such as visual feature and memory-set homogeneity may have the greater influence on prefrontal and parietal activity during multiple-item working memory. This is consistent with the view that working memory capacity is influenced by the level of interaction or interference between visual stimuli, which is stronger between items from the same feature category.

The Effect of Set Size on the Dynamics of Binocular Rivalry

During binocular rivalry, the percept alternates between dissimilar images presented dichoptically. A central question in studies on binocular rivalry is whether its dynamics are affected by attention. Here we approach this question by studying how set size affects the number of alternations reported from a rivalry-inducing display. The results show that the number of alternations reported increased only slightly with increasing set size. In follow-up experiments we show that neither (1) limitations in response speed nor (2) grouping cues are responsible for this result, and that (3) increasing set size decreases the number of alternations reported per rivalry-inducing element. Our results show that the spatial distribution of attention affects the number of alternations reported in a rivalry-inducing display.

Set-size effects demonstrate a role of parietal and frontal theta oscillations in movement target selection

Set-size effects demonstrate a role of parietal and frontal theta oscillations in movement target selection

A memory-based model of Hick’s law

We propose and evaluate a memory-based model of Hick’s law, the approximately linear increase in choice reaction time with the logarithm of set size (the number of stimulus–response alternatives). According to the model, Hick’s law reflects a combination of associative interference during retrieval from declarative memory and occasional savings for stimulus–response repetitions due to non-retrieval. Fits to existing data sets show that the model accounts for the basic set-size effect, changes in the set-size effect with practice, and stimulus–response-repetition effects that challenge the information-theoretic view of Hick’s law. We derive the model’s prediction of an interaction between set size, stimulus fan (the number of responses associated with a particular stimulus), and stimulus–response transition, which is subsequently tested and confirmed in two experiments. Collectively, the results support the core structure of the model and its explanation of Hick’s law in terms of basic memory effects.

Dilution: A theoretical burden or just load? A reply to Tsal and Benoni (2010).

Load theory of attention proposes that distractor processing is reduced in tasks with high perceptual load that exhaust attentional capacity within task-relevant processing. In contrast, tasks of low perceptual load leave spare capacity that spills over, resulting in the perception of task-irrelevant, potentially distracting stimuli. Tsal and Benoni (2010) find that distractor response competition effects can be reduced under conditions with a high search set size but low perceptual load (due to a singleton color target). They claim that the usual effect of search set size on distractor processing is not due to attentional load but instead attribute this to lower level visual interference. Here, we propose an account for their findings within load theory. We argue that in tasks of low perceptual load but high set size, an irrelevant distractor competes with the search nontargets for remaining capacity. Thus, distractor processing is reduced under conditions in which the search nontargets receive the spillover of capacity instead of the irrelevant distractor. We report a new experiment testing this prediction. Our new results demonstrate that, when peripheral distractor processing is reduced, it is the search nontargets nearest to the target that are perceived instead. Our findings provide new evidence for the spare capacity spillover hypothesis made by load theory and rule out accounts in terms of lower level visual interference (or mere “dilution”) for cases of reduced distractor processing under low load in displays of high set size. We also discuss additional evidence that discounts the viability of Tsal and Benoni's dilution account as an alternative to perceptual load.

The effect of training set size for the performance of neural networks of classification

Even though multilayer perceptrons and radial basis function networks belong to the class of artificial neural networks and they are used for similar tasks, they have very different structures and ...

Effects of set size and heterogeneity in set representation by statistical properties

Effects of set size and heterogeneity in set representation by statistical properties

The effect of author set size and data size in authorship attribution

Applications of authorship attribution 'in the wild' (Koppel, M., Schler, J., and Argamon, S. (2010). Authorship attribution in the wild. Language Resources and Evaluation. Advanced Access published January 12, 2010:10.1007/ s10579-009-9111-2), for instance in social networks, will likely involve large sets of candidate authors and only limited data per author. In this article, we present the results of a systematic study of two important parameters in super- vised machine learning that significantly affect performance in computational authorship attribution: (1) the number of candidate authors (i.e. the number of classes to be learned), and (2) the amount of training data available per can- didate author (i.e. the size of the training data). We also investigate the robust- ness of different types of lexical and linguistic features to the effects of author set size and data size. The approach we take is an operationalization of the standard text categorization model, using memory-based learning for discriminating be- tween the candidate authors. We performed authorship attribution experiments on a set of three benchmark corpora in which the influence of topic could be controlled. The short text fragments of e-mail length present the approach with a true challenge. Results show that, as expected, authorship attribution accuracy deteriorates as the number of candidate authors increases and size of training data decreases, although the machine learning approach continues performing significantly above chance. Some feature types (most notably character n-grams) are robust to changes in author set size and data size, but no robust individual features emerge.

Effects of visual field, exposure time, and set size on icon search with varied delays using an LCD monitor

Abstract— This study investigated the effects of visual field (left or right), exposure time, and set size on icon search with varied delay times. Nineteen women and 17 men, who were Taiwanese graduate students aged 24–40 years, participated. Participants were told to search for a target icon in a circular stimulus array, which had a diameter of 7 cm and included five, seven, or nine items. The results indicated that set size significantly affected search time. Search time was significantly longer for a nine‐icon set than for five and seven icons. Search times were significantly longer for 5‐sec delays than for 3‐and 1 ‐sec delays. However, exposure time and visual field did not significantly affect search time. Results showed that set size significantly affected accuracy. The accuracy for the five‐icon condition was greater than that for the seven‐ and nine‐icon conditions. Moreover, accuracy was greater for 1 ‐ than for 3‐ and 5‐sec‐delay conditions. However, no significant effect on accuracy was found for visual field or exposure time. Finally, search times for correct and incorrect responses were analyzed separately. The results are applicable to graphics‐based interface design.

Theoretical Simulation of n-Alkane Cracking on Zeolites

The kinetics of alkane cracking in zeolites MFI and FAU have been simulated theoretically from first principles. The apparent rate coefficient for alkane cracking was described as the product of the number of alkane molecules per unit mass of zeolite that are close enough to a Bronsted-acid site to be in the reactant state for the cleavage of a specific C-C bond and the intrinsic rate coefficient for the cleavage of that bond. Adsorption thermodynamics were calculated by Monte Carlo simulation and the intrinsic rate coefficient for alkane cracking was determined from density functional theory calculations combined with absolute rate theory. The effects of functional, basis set, and cluster size on the intrinsic activation energy for alkane cracking were investigated. The dependence of the apparent rate coefficient on the carbon number for the cracking of C3-C6 alkanes on MFI and FAU determined by simulation agrees well with experimental observation, but the absolute values of the apparent rate coefficients are a factor of 10 to 100 smaller than those observed. This discrepancy is attributed to the use of a small T5 cluster representation of the Bronsted-acid site. Limited calculations for propane and butane cracking on MFI reveal that significantly better agreement between prediction and observation is achieved using a T23 cluster for both the apparent rate coefficient and the apparent activation energy. The apparent rate coefficients for alkane cracking are noticeably larger for MFI than FAU, in agreement with recent findings reported in the experimental literature.

Effects of set-size on scene recognition following locomotion

Effects of set-size on scene recognition following locomotion

Exploring set size effects in realistic scenes

Exploring set size effects in realistic scenes

Visual pop-out in infancy: Effects of set-size on the latency of their eye movements

Visual pop-out in infancy: Effects of set-size on the latency of their eye movements

An ideal observer approach to unifying set size and cueing effects for perceptual and saccadic decisions

An ideal observer approach to unifying set size and cueing effects for perceptual and saccadic decisions

Effects of set-size and lateral masking in visual search

The roles of peripheral (local) and central (global) processing limitations in visual search are still not well understood. In the present study, the number of displayed stimuli (set-size) and the distance between neighbouring stimuli were varied as independently as possible in order to measure the effect of both. Stimuli were presented briefly and observers had to indicate the presence or absence of the target stimulus. Percentage correct was used as a measure of performance. Symmetrically and asymmetrically bisected squares were used as stimuli. There were two experimental conditions: target differed from distractors either by presence/absence of a simple feature (1) or it differed by relative position of the same components only (2). The effect of distance between stimuli (lateral masking) was found to be similar in the both conditions. The effect of set-size (with lateral masking effect eliminated) was much larger for relative position stimuli. The results support the view that perception of relative position of stimulus components is limited mainly by the capacity of central processing.

Spatial resolution underlies the set size effect in conjunction search

Distractors: vertical low-frequency (2-cpd) and tilted high-frequency (10-cpd) Gabor patches. Display: 6 x 6 matrix, stimuli centered at 2.8 to 14 from fixation. Standard display: size: 3.3cm diameter; orientation: 25 tilt; frequency: 2cpd (low freq.) or 10cpd (high freq.). Magnified display: size from 1.1 to 13.9cm;spatial frequency from 1.8 to .56 (low freq.) and 9.1 to 2.8 (high freq.) Target: tilted low-frequency grating (2 cpd)

Choice Set Size and Decision Making: The Case of Medicare Part D Prescription Drug Plans

The impact of choice on consumer decision making is controversial in US health policy. The authors' objective was to determine how choice set size influences decision making among Medicare beneficiaries choosing prescription drug plans. The authors randomly assigned members of an Internet-enabled panel age 65 and older to sets of prescription drug plans of varying sizes (2, 5, 10, and 16) and asked them to choose a plan. Respondents answered questions about the plan they chose, the choice set, and the decision process. The authors used ordered probit models to estimate the effect of choice set size on the study outcomes. Both the benefits of choice, measured by whether the chosen plan is close to the ideal plan, and the costs, measured by whether the respondent found decision making difficult, increased with choice set size. Choice set size was not associated with the probability of enrolling in any plan. Medicare beneficiaries face a tension between not wanting to choose from too many options and feeling happier with an outcome when they have more alternatives. Interventions that reduce cognitive costs when choice sets are large may make this program more attractive to beneficiaries.