The attention-weighted sample-size model of visual short-term memory: Attention capture predicts resource allocation and memory load.

We investigated the capacity of visual short-term memory (VSTM) in a phase discrimination task that required judgments about the configural relations between pairs of black and white features. Sewell et al. (2014) previously showed that VSTM capacity in an orientation discrimination task was well described by a sample-size model, which views VSTM as a resource comprised of a finite number of noisy stimulus samples. The model predicts the invariance of [Formula: see text] , the sum of squared sensitivities across items, for displays of different sizes. For phase discrimination, the set-size effect significantly exceeded that predicted by the sample-size model for both simultaneously and sequentially presented stimuli. Instead, the set-size effect and the serial position curves with sequential presentation were predicted by an attention-weighted version of the sample-size model, which assumes that one of the items in the display captures attention and receives a disproportionate share of resources. The choice probabilities and response time distributions from the task were well described by a diffusion decision model in which the drift rates embodied the assumptions of the attention-weighted sample-size model.

Testing biased competition between attention shifts: The new multiple cue paradigm.

While the classic Posner cuing paradigm has been used to study cuing of a single endogenous shift of attention, we present a new multiple cue paradigm to study the competition between multiple endogenous shifts of attention. The new paradigm enables us to manipulate the number of competing attention shifts and their relative importance. In three experiments, we demonstrate that the process of selecting one among other relevant attention shifts is governed by limited capacity and biased competition. We show that the probability of performing the most optimal attention shift is influenced by the total number of attention shifts competing for execution and that reward is a determining factor for the selection between attention shifts. We explain our results with a recent mathematical model of biased selection of response sets (the model of intention selection [MIS]). Our new paradigm offers a critical test of MIS and is an important new tool for investigating the mechanisms underlying the retrieval of response sets from long-term memory (LTM). The model (MIS) and the new multiple cue paradigm can provide a new perspective on LTM representations of response sets for instrumental action and on habitual and goal-directed processing in action control. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Attentional dwell times for targets and masks.

Studies on the temporal dynamics of attention have shown that the report of a masked target (T2) is severely impaired when the target is presented with a delay (stimulus onset asynchrony) of less than 500 ms after a spatially separate masked target (T1). This is known as the attentional dwell time. Recently, we have proposed a computational model of this effect building on the idea that a stimulus retained in visual short-term memory (VSTM) takes up visual processing resources that otherwise could have been used to encode subsequent stimuli into VSTM. The resources are locked until the stimulus in VSTM has been recoded, which explains the long dwell time. Challenges for this model and others are findings by Moore, Egeth, Berglan, and Luck (1996) suggesting that the dwell time is substantially reduced when the mask of T1 is removed. Here we suggest that the mask of T1 modulates performance not by noticeably affecting the dwell time but instead by acting as a distractor drawing processing resources away from T2. This is consistent with our proposed model in which targets and masks compete for attentional resources and attention dwells on both. We tested the model by replicating the study by Moore et al., including a new condition in which T1 is omitted but the mask of T1 is retained. Results from this and the original study by Moore et al. are modeled with great precision.

Visual processing speed in old age.

Mental speed is a common concept in theories of cognitive aging, but it is difficult to get measures of the speed of a particular psychological process that are not confounded by the speed of other processes. We used Bundesen's (1990) Theory of Visual Attention (TVA) to obtain specific estimates of processing speed in the visual system controlled for the influence of response latency and individual variations of the perception threshold. A total of 33 non-demented old people (69-87 years) were tested for the ability to recognize briefly presented letters. Performance was analyzed by the TVA model. Visual processing speed decreased approximately linearly with age and was on average halved from 70 to 85 years. Less dramatic aging effects were found for the perception threshold and the visual apprehension span. In the visual domain, cognitive aging seems to be most clearly related to reductions in processing speed.

Attentional priorities and access to short-term memory: parietal interactions.

The intraparietal sulcus (IPS) has been implicated in selective attention as well as visual short-term memory (VSTM). To contrast mechanisms of target selection, distracter filtering, and access to VSTM, we combined behavioral testing, computational modeling and functional magnetic resonance imaging. Sixteen healthy subjects participated in a change detection task in which we manipulated both target and distracter set sizes. We directly compared the IPS response as a function of the number of targets and distracters in the display and in VSTM. When distracters were not present, the posterior and middle segments of IPS showed the predicted asymptotic activity increase with an increasing target set size. When distracters were added to a single target, activity also increased as predicted. However, the addition of distracters to multiple targets suppressed both middle and posterior IPS activities, thereby displaying a significant interaction between the two factors. The interaction between target and distracter set size in IPS could not be accounted for by a simple explanation in terms of number of items accessing VSTM. Instead, it led us to a model where items accessing VSTM receive differential weights depending on their behavioral relevance, and secondly, a suppressive effect originates during the selection phase when multiple targets and multiple distracters are simultaneously present. The reverse interaction between target and distracter set size was significant in the right temporoparietal junction (TPJ), where activity was highest for a single target compared to any other condition. Our study reconciles the role of middle IPS in attentional selection and biased competition with its role in VSTM access.

A new cognitive model of long-term memory for intentions.

In this paper, we propose a new mathematical model of retrieval of intentions from long-term memory. We model retrieval as a stochastic race between a plurality of potentially relevant intentions stored in long-term memory. Psychological theories are dominated by two opposing conceptions of the role of memory in temporally extended agency - as when a person has to remember to make a phone call in the afternoon because, in the morning, she promised she would do so. According to the Working Memory conception, remembering to make the phone call is explained in terms of the construction and maintenance of intentions in working-memory. According to the Long-Term Memory conception, we should explain the episode in terms of an ability to store intentions in long-term memory. The two conceptions predict different processing profiles. The aim of this paper is to present a new mathematical model of the type of memory mechanism that could realise the long-term memory representations of intentions necessary for the Long-Term Memory conception. We present and illustrate the formal model and propose a new type of experimental paradigm that could allow us to test which of the two conceptions provides the best explanation of the role of memory in temporally extended agency.

A Poisson random walk model of response times.

Based on the simple what first comes to mind rule, the theory of visual attention (TVA; Bundesen, 1990) provides a comprehensive account of visual attention that has been successful in explaining performance in visual categorization for a variety of attention tasks. If the stimuli to be categorized are mutually confusable, a response rule based on the amount of evidence collected over a longer time seems more appropriate. In this paper, we extend the idea of a simple race to continuous sampling of evidence in favor of a certain response category. The resulting Poisson random walk model is a TVA-based response time model in which categories are reported based on the amount of evidence obtained. We demonstrate that the model provides an excellent account for response time distributions obtained in speeded visual categorization tasks. The model is mathematically tractable, and its parameters are well founded and easily interpretable. We also provide an extension of the Poisson random walk to any number of response alternatives. We tested the model in experiments with speeded and nonspeeded binary responses and a speeded response task with multiple report categories. The Poisson random walk model agreed very well with the data. A thorough investigation of processing rates revealed that the perceptual categorizations described by the Poisson random walk were the same as those obtained from TVA. The Poisson random walk model could therefore provide a unifying account of attention and response times. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

A physiologically based nonhomogeneous Poisson counter model of visual identification.

A physiologically based nonhomogeneous Poisson counter model of visual identification is presented. The model was developed in the framework of a Theory of Visual Attention (Bundesen, 1990; Kyllingsbæk, Markussen, & Bundesen, 2012) and meant for modeling visual identification of objects that are mutually confusable and hard to see. The model assumes that the visual system's initial sensory response consists in tentative visual categorizations, which are accumulated by leaky integration of both transient and sustained components comparable with those found in spike density patterns of early sensory neurons. The sensory response (tentative categorizations) feeds independent Poisson counters, each of which accumulates tentative object categorizations of a particular type to guide overt identification performance. We tested the model's ability to predict the effect of stimulus duration on observed distributions of responses in a nonspeeded (pure accuracy) identification task with eight response alternatives. The time courses of correct and erroneous categorizations were well accounted for when the event-rates of competing Poisson counters were allowed to vary independently over time in a way that mimicked the dynamics of receptive field selectivity as found in neurophysiological studies. Furthermore, the initial sensory response yielded theoretical hazard rate functions that closely resembled empirically estimated ones. Finally, supplied with a Naka-Rushton type contrast gain control, the model provided an explanation for Bloch's law. (PsycINFO Database Record

The power law of visual working memory characterizes attention engagement.

The quality or precision of stimulus representations in visual working memory can be characterized by a power law, which states that precision decreases as a power of the number of items in memory, with an exponent whose magnitude typically varies in the range 0.5 to 0.75. The authors show that the magnitude of the exponent is an index of the attentional demands of memory formation. They report 5 visual working memory experiments with tasks using noisy, backward-masked stimuli that varied in their attentional demands and show that the magnitude of the exponent increases systematically with the attentional demands of the task. Recall accuracy in the experiments was well described by an attention-weighted sample-size model that views visual working memory as a resource comprised of noisy evidence samples that are recruited during stimulus exposure and which can be allocated flexibly under attentional control. The magnitude of the exponent indexes the degree to which attention allocates resources to items in memory unequally rather than equally. (PsycINFO Database Record

Parallel processing in a multifeature whole-report paradigm.

Observers given brief exposures of pairs of colored bars and asked to report both the color and the orientation of each bar showed evidence of stochastic independence between reports of the 4 features (2 colors and 2 orientations). The authors also found virtually perfect stochastic independence between reports of colors and directions of motion of pairwise presented circular disks at each of 3 levels of exposure duration that varied unpredictably from trial to trial. Stimulus triples, rather than pairs, yielded more complex results. However, the findings provide strong evidence that the relevant features of the 2-3 stimuli were identified and localized in parallel across the display.

Out with the old? The role of selective attention in retaining targets in partial report.

In the partial-report task, subjects are asked to report only a portion of the items presented. Selective attention chooses which objects to represent in short-term memory (STM) on the basis of their relevance. Because STM is limited in capacity, one must sometimes choose which objects are removed from memory in light of new relevant information. We tested the hypothesis that the choices among newly presented information and old information in STM involve the same process-that both are acts of selective attention. We tested this hypothesis using a two-display partial-report procedure. In this procedure, subjects had to select and retain relevant letters (targets) from two sequentially presented displays. If selection in perception and retention in STM are the same process, then irrelevant letters (distractors) in the second display, which demanded attention because of their similarity to the targets, should have decreased target report from the first display. This effect was not obtained in any of four experiments. Thus, choosing objects to keep in STM is not the same process as choosing new objects to bring into STM.

Neurons in Primate Visual Cortex Alternate between Responses to Multiple Stimuli in Their Receptive Field.

A fundamental question concerning representation of the visual world in our brain is how a cortical cell responds when presented with more than a single stimulus. We find supportive evidence that most cells presented with a pair of stimuli respond predominantly to one stimulus at a time, rather than a weighted average response. Traditionally, the firing rate is assumed to be a weighted average of the firing rates to the individual stimuli (response-averaging model) (Bundesen et al., 2005). Here, we also evaluate a probability-mixing model (Bundesen et al., 2005), where neurons temporally multiplex the responses to the individual stimuli. This provides a mechanism by which the representational identity of multiple stimuli in complex visual scenes can be maintained despite the large receptive fields in higher extrastriate visual cortex in primates. We compare the two models through analysis of data from single cells in the middle temporal visual area (MT) of rhesus monkeys when presented with two separate stimuli inside their receptive field with attention directed to one of the two stimuli or outside the receptive field. The spike trains were modeled by stochastic point processes, including memory effects of past spikes and attentional effects, and statistical model selection between the two models was performed by information theoretic measures as well as the predictive accuracy of the models. As an auxiliary measure, we also tested for uni- or multimodality in interspike interval distributions, and performed a correlation analysis of simultaneously recorded pairs of neurons, to evaluate population behavior.

Activation in the MT-complex during visual perception of apparent motion and temporal succession.

Previous studies have shown that MT (i.e., the MT-complex) is activated during visual perception of apparent motion. To further explore the function of MT, we measured activation in MT by positron emission tomography (PET) using a broad range of stroboscopic stimulus events in which (a) the frame rate was so fast that observers perceived stimulus frames as simultaneous, (b) the frame rate was slower and generated compelling impressions of apparent motion, or (c) the frame rate was so slow that observers perceived temporal succession (successive views of the same objects at different locations) instead of motion. As expected, the simultaneity condition showed no activation (reliable increase in regional cerebral blood flow, rCBF) in MT whereas the motion condition showed activation in both left and right MT. However, the succession condition showed even stronger activation in left and right MT than did the motion condition. MT seems implicated in perception of retinal stimuli as successive views of the same object at different locations whether or not the views are connected by apparent motion.

A neural theory of visual attention: bridging cognition and neurophysiology.

A neural theory of visual attention (NTVA) is presented. NTVA is a neural interpretation of C. Bundesen's (1990) theory of visual attention (TVA). In NTVA, visual processing capacity is distributed across stimuli by dynamic remapping of receptive fields of cortical cells such that more processing resources (cells) are devoted to behaviorally important objects than to less important ones. By use of the same basic equations used in TVA, NTVA accounts for a wide range of known attentional effects in human performance (reaction times and error rates) and a wide range of effects observed in firing rates of single cells in the primate visual system. NTVA provides a mathematical framework to unify the 2 fields of research--formulas bridging cognition and neurophysiology.

A Componential Analysis of Visual Attention in Children With ADHD.

OBJECTIVE: Inattentive behaviour is a defining characteristic of ADHD. Researchers have wondered about the nature of the attentional deficit underlying these symptoms. The primary purpose of the current study was to examine this attentional deficit using a novel paradigm based upon the Theory of Visual Attention (TVA). METHOD: The TVA paradigm enabled a componential analysis of visual attention through the use of a mathematical model to estimate parameters relating to attentional selectivity and capacity. Children's ability to sustain attention was also assessed using the Sustained Attention to Response Task. The sample included a comparison between 25 children with ADHD and 25 control children aged 9-13. RESULTS: Children with ADHD had significantly impaired sustained attention and visual processing speed but intact attentional selectivity, perceptual threshold and visual short-term memory capacity. CONCLUSION: The results of this study lend support to the notion of differential impairment of attentional functions in children with ADHD.

Independent encoding of colors and shapes from two stimuli.

Observers were presented with brief exposures of pairs of colored objects (letters) and asked to report both the color and the shape of each object. Several observers showed strikingly clear evidence of nearly perfect stochastic independence between reports of the four features (two colors and two shapes). For instance, the probability that the shape of a given object could be reported seemed independent of (a) whether the color of the object could be reported and (b) whether features of the other object could be reported. Such stochastic independence is predicted by many parallel-processing models (e.g., Bundesen, 1990). However, the results are difficult to reconcile with simple serial models in which the encoding of one object is completed before the encoding of another object is begun.

[The working brain--how does it look like?]. / Den arbejdende hjerne--hvordan kan den se ud?

Numerous brain functions, such as awareness of surroundings, control of movements, thoughts, and memory have always been a kind of mystery, which has provoked human curiosity and thus inspired research in many areas. The present paper gives an overview on imaging research of the human brain's functions. The historical progress is briefly reviewed with the emphasis on major Danish contributions. The major methods of mapping brain functions and their biological basis are mentioned. These methods are positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). They are highly technological and generate enormous amounts of data. Thus, data analysis will per se be a research area in brain imaging. Finally, several examples of the authors' results on functional activation are dealt with. These examples aim to illustrate the research area and its contribution to our increased knowledge of the working brain.

A new perspective on the perceptual selectivity of attention under load.

The human attention system helps us cope with a complex environment by supporting the selective processing of information relevant to our current goals. Understanding the perceptual, cognitive, and neural mechanisms that mediate selective attention is a core issue in cognitive neuroscience. One prominent model of selective attention, known as load theory, offers an account of how task demands determine when information is selected and an account of the efficiency of the selection process. However, load theory has several critical weaknesses that suggest that it is time for a new perspective. Here we review the strengths and weaknesses of load theory and offer an alternative biologically plausible computational account that is based on the neural theory of visual attention. We argue that this new perspective provides a detailed computational account of how bottom-up and top-down information is integrated to provide efficient attentional selection and allocation of perceptual processing resources.

Automatic attraction of visual attention by supraletter features of former target strings.

Observers were trained to search for a particular horizontal string of three capital letters presented among similar strings consisting of exactly the same letters in different orders. The training was followed by a test in which the observers searched for a new target that was identical to one of the former distractors. The new distractor set consisted of the remaining former distractors plus the former target. On each trial, three letter strings were displayed, which included the target string with a probability of 0.5. In Experiment 1, the strings were centered at different locations on the circumference of an imaginary circle around the fixation point. The training phase of Experiment 2 was similar, but in the test phase of the experiment, the strings were located in a vertical array centered on fixation, and in target-present arrays, the target always appeared at fixation. In both experiments, performance (d') degraded on trials in which former targets were present, suggesting that the former targets automatically drew processing resources away from the current targets. Apparently, the two experiments showed automatic attraction of visual attention by supraletter features of former target strings.

A common representation of spatial features drives action and perception: grasping and judging object features within trials.

Spatial features of an object can be specified using two different response types: either by use of symbols or motorically by directly acting upon the object. Is this response dichotomy reflected in a dual representation of the visual world: one for perception and one for action? Previously, symbolic and motoric responses, specifying location, has been shown to rely on a common representation. What about more elaborate features such as length and orientation? Here we show that when motoric and symbolic responses are made within the same trial, the probability of making the same symbolic and motoric response is well above chance for both length and orientation. This suggests that motoric and symbolic responses to length and orientation are driven by a common representation. We also show that, for both response types, the spatial features of an object are processed independently. This finding of matching object-processing characteristics is also in agreement with the idea of a common representation driving both response types.