The role of motion in visual working memory for dynamic stimuli: More lagged but more precise representations of moving objects.

While most visual working memory studies use static stimuli with unchanging features, objects in the real world are often dynamic, introducing significant differences in the surface feature information hitting the retina from the same object over time (e.g., changes in orientation, lighting, shadows). Previous research on dynamic stimuli has shown that change detection is improved if objects obey rules of physical motion, but it is unclear how memory for visual features interacts with object motion. In the current study, we investigated whether object motion facilitates greater temporal integration of continuously changing surface feature information. In a series of experiments, participants were asked to report the final color of continuously changing colored dots that were either moving or stationary on the screen. We found that the reported colors "lagged behind" the physical states of the dots when they were in motion. We also observed that the precision of memory responses was significantly higher for stimuli in the moving condition compared to the stationary condition. Together, these findings suggest that memory representation is improved - but lagged - for moving objects, consistent with the idea that object motion may facilitate integration of object information over longer intervals.

You cannot "count" how many items people remember in visual working memory: The importance of signal detection-based measures for understanding change detection performance.

Change detection tasks are commonly used to measure and understand the nature of visual working memory capacity. Across three experiments, we examine whether the nature of the memory signals used to perform change detection are continuous or all-or-none and consider the implications for proper measurement of performance. In Experiment 1, we find evidence from confidence reports that visual working memory is continuous in strength, with strong support for an equal variance signal detection model with no guesses or lapses. Experiments 2 and 3 test an implication of this, which is that K should confound response criteria and memory. We found K values increased by roughly 30% when criteria are shifted despite no change in the underlying memory signals. Overall, our data call into question a large body of work using threshold measures, like K, to analyze change detection data. This metric confounds response bias with memory performance and is inconsistent with the vast majority of visual working memory models, which propose variations in precision or strength are present in working memory. Instead, our data indicate an equal variance signal detection model (and thus, d')-without need for lapses or guesses-is sufficient to explain change detection performance. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Psychophysical scaling reveals a unified theory of visual memory strength.

Almost all models of visual memory implicitly assume that errors in mnemonic representations are linearly related to distance in stimulus space. Here we show that neither memory nor perception are appropriately scaled in stimulus space; instead, they are based on a transformed similarity representation that is nonlinearly related to stimulus space. This result calls into question a foundational assumption of extant models of visual working memory. Once psychophysical similarity is taken into account, aspects of memory that have been thought to demonstrate a fixed working memory capacity of around three or four items and to require fundamentally different representations-across different stimuli, tasks and types of memory-can be parsimoniously explained with a unitary signal detection framework. These results have substantial implications for the study of visual memory and lead to a substantial reinterpretation of the relationship between perception, working memory and long-term memory.

Is working memory inherently more "precise" than long-term memory? Extremely high fidelity visual long-term memories for frequently encountered objects.

Long-term memory is often considered easily corruptible, imprecise, and inaccurate, especially in comparison to working memory. However, most research used to support these findings relies on weak long-term memories: those where people have had only one brief exposure to an item. Here we investigated the fidelity of visual long-term memory in more naturalistic setting, with repeated exposures, and ask how it compares to visual working memory fidelity. Using psychophysical methods designed to precisely measure the fidelity of visual memory, we demonstrate that long-term memory for the color of frequently seen objects is as accurate as working memory for the color of a single item seen 1 s ago. In particular, we show that repetition greatly improves long-term memory, including the ability to discriminate an item from a very similar item (fidelity), in both a lab setting (Experiments 1-3) and a naturalistic setting (brand logos, Experiment 4). Overall, our results demonstrate the impressive nature of visual long-term memory fidelity, which we find is even higher fidelity than previously indicated in situations involving repetitions. Furthermore, our results suggest that there is no distinction between the fidelity of visual working memory and visual long-term memory, but instead both memory systems are capable of storing similar incredibly high-fidelity memories under the right circumstances. Our results also provide further evidence that there is no fundamental distinction between the "precision" of memory and the "likelihood of retrieving a memory," instead suggesting a single continuous measure of memory strength best accounts for working and long-term memory. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

When "capacity" changes with set size: Ensemble representations support the detection of across-category changes in visual working memory.

Is there a fixed limit on how many objects we can hold actively in mind? Generally, researchers have found participants are worse at remembering a small number of objects if those objects are more complex, suggesting a limited resource rather than a fixed number of objects best explains working memory performance. However, some evidence has suggested that stimulus similarity better accounts for these effects and that, after accounting for such similarity, the data support a slot-based fixed item limit for working memory. Much of the evidence used to support the latter claim relies on working memory displays containing different categories of items. It has been found that, for large, across-category changes, performance does not differ for different kinds of complex stimuli. However, many of these studies fail to adequately control for the potential use of ensemble information in discriminating such large changes. Here, we sought to identify how much ensemble representations may explain performance across these tasks. In Experiment 1, we observed that, as set size increased from four to 12 items, capacity estimates for across-category changes increased linearly as well, providing evidence against the claim of a fixed capacity. In Experiment 2, we controlled for stimulus complexity and similarity but varied the utility of ensemble representations for the change-detection task. We observed significantly greater capacity when ensemble information could be used. Altogether, these results are contrary to a slot-like, fixed-object constraint on working memory capacity and consistent with object complexity and ensemble representations strongly affecting working memory performance.

Properties of visual episodic memory following repeated encounters with objects.

A person sees an object once, and then seconds, minutes, hours, days, or weeks later, she sees it again. How is the person's visual memory for that object changed, improved, or degraded by the second encounter, compared to a situation in which she will have only seen the object once? The answer is unknown, a glaring lacuna in the current understanding of visual episodic memory. The overwhelming majority of research considers recognition following a single exposure to a set of objects, whereas objects reoccur regularly in lived experience. We therefore sought to address some of the more basic and salient questions that are unanswered with respect to how repetition affects visual episodic memory. In particular, we investigated how spacing between repeated encounters affects memory, as well as variable input quality across encounters and changes in viewed orientation. Memory was better when the spacing between encounters was larger, and when a first encounter with an object supplied high quality input (compared to low quality input first, followed later by higher quality input). These experiments lay a foundation for further understanding how memory changes, improves, and degrades over the course of experience.

Visual working memory is more tolerant than visual long-term memory.

Human visual memory is tolerant, meaning that it supports object recognition despite variability across encounters at the image level. Tolerant object recognition remains one capacity in which artificial intelligence trails humans. Typically, tolerance is described as a property of human visual long-term memory (VLTM). In contrast, visual working memory (VWM) is not usually ascribed a role in tolerant recognition, with tests of that system usually demanding discriminatory power-identifying changes, not sameness. There are good reasons to expect that VLTM is more tolerant; functionally, recognition over the long-term must accommodate the fact that objects will not be viewed under identical conditions; and practically, the passive and massive nature of VLTM may impose relatively permissive criteria for thinking that two inputs are the same. But empirically, tolerance has never been compared across working and long-term visual memory. We therefore developed a novel paradigm for equating encoding and test across different memory types. In each experiment trial, participants saw two objects, memory for one tested immediately (VWM) and later for the other (VLTM). VWM performance was better than VLTM and remained robust despite the introduction of image and object variability. In contrast, VLTM performance suffered linearly as more variability was introduced into test stimuli. Additional experiments excluded interference effects as causes for the observed differences. These results suggest the possibility of a previously unidentified role for VWM in the acquisition of tolerant representations for object recognition. (PsycINFO Database Record

Visual memory, the long and the short of it: A review of visual working memory and long-term memory.

The majority of research on visual memory has taken a compartmentalized approach, focusing exclusively on memory over shorter or longer durations, that is, visual working memory (VWM) or visual episodic long-term memory (VLTM), respectively. This tutorial provides a review spanning the two areas, with readers in mind who may only be familiar with one or the other. The review is divided into six sections. It starts by distinguishing VWM and VLTM from one another, in terms of how they are generally defined and their relative functions. This is followed by a review of the major theories and methods guiding VLTM and VWM research. The final section is devoted toward identifying points of overlap and distinction across the two literatures to provide a synthesis that will inform future research in both fields. By more intimately relating methods and theories from VWM and VLTM to one another, new advances can be made that may shed light on the kinds of representational content and structure supporting human visual memory.

Exploiting core knowledge for visual object recognition.

Humans recognize thousands of objects, and with relative tolerance to variable retinal inputs. The acquisition of this ability is not fully understood, and it remains an area in which artificial systems have yet to surpass people. We sought to investigate the memory process that supports object recognition. Specifically, we investigated the association of inputs that co-occur over short periods of time. We tested the hypothesis that human perception exploits expectations about object kinematics to limit the scope of association to inputs that are likely to have the same token as a source. In several experiments we exposed participants to images of objects, and we then tested recognition sensitivity. Using motion, we manipulated whether successive encounters with an image took place through kinematics that implied the same or a different token as the source of those encounters. Images were injected with noise, or shown at varying orientations, and we included 2 manipulations of motion kinematics. Across all experiments, memory performance was better for images that had been previously encountered with kinematics that implied a single token. A model-based analysis similarly showed greater memory strength when images were shown via kinematics that implied a single token. These results suggest that constraints from physics are built into the mechanisms that support memory about objects. Such constraints-often characterized as 'Core Knowledge'-are known to support perception and cognition broadly, even in young infants. But they have never been considered as a mechanism for memory with respect to recognition. (PsycINFO Database Record

How undistorted spatial memories can produce distorted responses.

Reproducing the location of an object from the contents of spatial working memory requires the translation of a noisy representation into an action at a single location-for instance, a mouse click or a mark with a writing utensil. In many studies, these kinds of actions result in biased responses that suggest distortions in spatial working memory. We sought to investigate the possibility of one mechanism by which distortions could arise, involving an interaction between undistorted memories and nonuniformities in attention. Specifically, the resolution of attention is finer below than above fixation, which led us to predict that bias could arise if participants tend to respond in locations below as opposed to above fixation. In Experiment 1 we found such a bias to respond below the true position of an object. Experiment 2 demonstrated with eye-tracking that fixations during response were unbiased and centered on the remembered object's true position. Experiment 3 further evidenced a dependency on attention relative to fixation, by shifting the effect horizontally when participants were required to tilt their heads. Together, these results highlight the complex pathway involved in translating probabilistic memories into discrete actions, and they present a new attentional mechanism by which undistorted spatial memories can lead to distorted reproduction responses.