Timothy F Brady

Harvard University | Harvard · Department of Psychology

Traditional memory research has focused on identifying separate memory systems and exploring different stages of memory processing. This approach has been valuable for establishing a taxonomy of memory systems and characterizing their function but has been less informative about the nature of stored memory representations. Recent research on visual...

Influential models of visual working memory treat each item to be stored as an independent unit and assume that there are no interactions between items. However, real-world displays have structure that provides higher-order constraints on the items to be remembered. Even in the case of a display of simple colored circles, observers can compute stat...

One of the major lessons of memory research has been that human memory is fallible, imprecise, and subject to interference. Thus, although observers can remember thousands of images, it is widely assumed that these memories lack detail. Contrary to this assumption, here we show that long-term memory is capable of storing a massive number of objects...

Working memory is a reconstructive process that requires integrating multiple hierarchical representations of objects. This hierarchical reconstruction allows us to overcome perceptual uncertainty and limited cognitive capacity but yields systematic biases in working memory as individual items are influenced by the ensemble statistics of the scene,...

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...

We argue that critical areas of memory research rely on problematic measurement practices and provide concrete suggestions to improve the situation. In particular, we highlight the prevalence of memory studies that use tasks (like the "old/new" task: "have you seen this item before? yes/no") where quantifying performance is deeply dependent on coun...

Visual working memory is highly limited, and its capacity is tied to many indices of cognitive function. For this reason, there is much interest in understanding its architecture and the sources of its limited capacity. As part of this research effort, researchers often attempt to decompose visual working memory errors into different kinds of error...

In response to the reported replication crisis in psychology, much recent work focused on increasing the rigor of theory assessment in the social sciences. This research highlights that testing theories is challenging because they inherit a new set of auxiliary assumptions as soon as they are linked to a specific methodology. In this article, we in...

In many decision tasks, we have a set of alternative choices and are faced with the problem of how to use our latent beliefs and preferences about each alternative to make a single choice. Cognitive and decision models typically presume that beliefs and preferences are distilled to a scalar latent strength for each alternative, but it is also criti...

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...

Working memory is a reconstructive process that requires integrating multiple hierarchical representations of objects. This hierarchical reconstruction allows us to overcome perceptual uncertainty and limited cognitive capacity, but yields systematic biases in working memory as individual items are influenced by the ensemble statistics of the scene...

Working memory is thought to have a highly limited storage capacity, which constrains many cognitive abilities including fluid intelligence. Here we show that working memory is limited not only by storage capacity but also by failures to retrieve or make decisions about items that were successfully maintained. Participants memorized an array of cir...

Social interactions are dynamic and unfold over time. To make sense of social interactions, people must aggregate sequential information into summary, global evaluations. But how do people do this? Here, to address this question, we conducted nine studies (N = 1,583) using a diverse set of stimuli. Our focus was a central aspect of social interacti...

Network-based approaches are a popular representational scheme of semantic units and the relations about them. Recent network-based approaches use graph theoretic analyses to examine individual differences in semantic networks and how they relate to other higher-level cognitive processes. However, it remains ambiguous whether individual differences...

Prominent theories of visual working memory postulate that the capacity to maintain a particular visual feature is fixed. In contrast to these theories, recent studies have demonstrated that meaningful objects are better remembered than simple, non-meaningful stimuli. Here, we test whether this is solely because meaningful stimuli can recruit addit...

When holding multiple items in visual working memory, representations of individual items are often attracted to, or repelled from, each other. While this is empirically well-established, existing frameworks do not account for both types of distortions, which appear to be in opposition. Here, we demonstrate that both types of memory distortion may...

Items that are held in visual working memory can guide attention toward matching features in the environment. Predominant theories propose that to guide attention, a memory item must be internally prioritized and given a special template status, which builds on the assumption that there are qualitatively distinct states in working memory. Here, we...

Visual working memory is highly limited, and its capacity is tied to many indices of cognitive function. For this reason, there is much interest in understanding its architecture and the sources of its limited capacity. As part of this research effort, researchers often attempt to decompose visual working memory errors into different kinds of error...

Ensemble perception is a process by which we extract and consolidate redundancies in the environment, getting the ‘gist’ of a set of objects. This ability to summarize complex scenes is thought to underlie our ability to construct robust memory representations, guide attention and classify features or objects when many objects are present. Despite...

Change detection tasks are commonly used to measure and understand the nature of visual working memory capacity. Across two experiments, we examine whether the nature of the latent 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 f...

People can rapidly and efficiently categorize the animacy of natural objects. Does this imply that the visual system has an unlimited capacity for processing animacy across the entire visual field? To test this, we generated a set of morphed “animacy continua” between animate and inanimate silhouettes. Observers were shown different ratios of these...

Previous work has shown that semantically meaningful properties of visually presented real-world objects, such as their color, their state/configuration of their parts/pose, or the features that differentiate them from other exemplars of the same category category, are stored with a high degree of independence in long-term memory (e.g., are frequen...

Extant research has shown that previously acquired categorical knowledge affects recognition memory, and that differences in category learning strategies impact classification accuracy. However, it is unknown whether different learning strategies also have downstream effects on subsequent recognition memory. The present study investigates the effec...

Social interactions are dynamic, and unfold over time. To make sense of social interactions, people must aggregate sequential information into summary, global evaluations. But how do people do this? To address this question, we conducted 9 studies (N= 1,583), using a diverse set of stimuli. Our focus was a central aspect of social interaction, name...

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

“Similarity” is often thought to dictate memory errors. For example, in visual memory, memory judgements of lures are related to their psychophysical similarity to targets: an approximately exponential function in stimulus space (Schurgin et al. 2020). However, similarity is ill-defined for more complex stimuli, and memory errors seem to depend on...

We argue there is a ‘crisis of measurement’ in critical areas of memory research and provide concrete suggestions to improve the situation. In particular, we highlight the prevalence of memory studies that use tasks (like the “old/new” task: “have you seen this item before? yes/no”) where quantifying performance is deeply dependent on counterfactua...

Chunks allow us to use long-term knowledge to efficiently represent the world in working memory. Most views of chunking assume that when we use chunks, this results in the loss of specific perceptual details, since it is presumed the contents of chunks are decoded from long-term memory rather than reflecting the exact details of the item that was p...

Memories are encoded in a manner that depends on our knowledge and expectations (“schemas”). Consistent with this, expertise tends to improve memory: Experts have elaborated schemas in their domains of expertise, allowing them to efficiently represent information in this domain (e.g., chess experts have enhanced memory for realistic chess layouts)....

Visual working memory is a capacity-limited cognitive system used to actively store and manipulate visual information. Visual working memory capacity is not fixed, but varies by stimulus type: Stimuli that are more meaningful are better remembered. In the current work, we investigate what conditions lead to the strongest benefits for meaningful sti...

When storing multiple objects in visual working memory, observers sometimes misattribute perceived features to incorrect locations or objects. These misattributions are called binding errors (or swaps) and have been previously demonstrated mostly in simple objects whose features are easy to encode independently and arbitrarily chosen, like colors a...

Almost all models of visual working memory—the cognitive system that holds visual information in an active state—assume it has a fixed capacity: Some models propose a limit of three to four objects, where others propose there is a fixed pool of resources for each basic visual feature. Recent findings, however, suggest that memory performance is imp...

When you search repeatedly for a set of items among very similar distractors, does that make you more efficient in locating the targets? To address this, we had observers search for two categories of targets among the same set of distractors across trials. Visual and conceptual similarity of the stimuli were validated with a multidimensional scalin...

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....

When we ask people to hold a color in working memory, what do they store? Do they remember colors as point estimates (e.g. a particular shade of red) or are memory representations richer, such as uncertainty distributions over feature space? We developed a novel paradigm (a betting game) to measure the nature of working memory representations. Part...

A single working memory item automatically guides attention towards matching features in the environment. However, results on multiple items guiding attention are mixed, which has led to a major debate about the architecture of working memory and the relat ionship between attention and memory. Specifically, theories that propose only a single it...

When objects move, their motion is governed by the laws of physics. We investigated whether multiple objects that move while correctly obeying aspects of Newtonian physics are easier to track than those that do not accurately obey the laws of physics. Participants were asked to track multiple objects that either did or did not take on the correct a...

Visual working memory is the cognitive system that holds visual information active to make it resistant to interference from new perceptual input. Information about simple stimuli – colors, orientations – is encoded into working memory rapidly: in under 100ms, working memory ‘fills up’, revealing a stark capacity limit. However, for real-world obje...

Existing knowledge shapes and distorts our memories, serving as a prior for newly encoded information. Here, we investigate the role of stable long-term priors (e.g. categorical knowledge) in conjunction with priors arising from recently encountered information (e.g. 'serial dependence') in visual working memory for color. We use an iterated reprod...

The capacity of visual working memory has been subject to considerable debate: whether there is a relatively fixed item limit, regardless of what these items are; or a fixed resource limit; or whether capacity limits vary depending on the complexity or familiarity of items. Here, we argue that before asking the question of how capacity varies acros...

Visual working memory is a capacity-limited cognitive system used to actively store and manipulate visual information. Visual working memory capacity is not fixed, but varies by stimulus type: stimuli that are more meaningful are better remembered. In the current work, we investigate what conditions lead to the strongest benefits for meaningful sti...

Both visual attention and visual working memory tend to be studied with very simple stimuli and low-level paradigms, designed to allow us to understand the representations and processes in detail, or with fully realistic stimuli that make such precise understanding difficult but are more representative of the real world. In this chapter we argue fo...

Traditionally, recognizing the objects within a scene has been treated as a prerequisite to recognizing the scene itself. However, research now suggests that the ability to rapidly recognize visual scenes could be supported by global properties of the scene itself rather than the objects within the scene. Here, we argue for a particular instantiati...

Commentary on: An Integrative Memory model of recollection and familiarity to understand memory deficits by Bastin, Besson, Simon, Delhaye, Geurten, Willems, & Salmon. Behavioral and Brain Sciences. Abstract: Although Bastin et al. propose a useful model for thinking about the structure of memory and memory deficits, their distinction between entit...

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...

Prevailing theories of visual working memory assume that each encoded item is stored or forgotten as a separate unit independent from other items. Here, we show that items are not independent and that the recalled orientation of an individual item is strongly influenced by the summary statistical representation of all items (ensemble representation...

Many studies have shown that people can rapidly and efficiently categorize the animacy of individual objects and scenes, even with few visual features available. Does this necessarily mean that the visual system has an unlimited capacity to process animacy across the entire visual field? We tested this in an ensemble task requiring observers to jud...

Understanding how people rate their confidence is critical for the characterization of a wide range of perceptual, memory, motor and cognitive processes. To enable the continued exploration of these processes, we created a large database of confidence studies spanning a broad set of paradigms, participant populations and fields of study. The data f...

Working memory is a core cognitive system that actively maintains information in an accessible state to support a variety of everyday tasks. Crucially, working memory performance has frequently been shown to strongly correlate with fluid intelligence. Traditionally when these correlations have been observed, the working memory tasks involved requir...

When storing multiple objects in visual working memory, observers sometimes misattribute perceived features to incorrect locations or objects. These misattributions are called binding errors (or swaps) and have been previously demonstrated mostly in simple objects whose features are easy to encode independently and arbitrarily chosen, like colors a...

Memory capacity depends on prior knowledge, both in working memory and in long-term memory. For example, radiologists have improved long-term memory for medical images compared to novices. Furthermore, people tend to remember abnormal or surprising items best. This is often claimed to arise primarily because such items attract additional attention...

People can store thousands of real-world objects in visual long-term memory with high precision. But are these objects stored as unitary, bound entities, as often assumed, or as bundles of separable features? We tested this in several experiments. In the first series of studies, participants were instructed to remember specific exemplars of real-wo...

Understanding how people rate their confidence is critical for characterizing a wide range of perceptual, memory, motor, and cognitive processes. However, progress has been slowed by the difficulty of collecting new data and the unavailability of existing data. To address this issue, we created a large database of confidence studies spanning a broa...

How do people use human-made objects (artifacts) to learn about the people and actions that created them? We test the richness of people’s reasoning in this domain, focusing on the task of judging whether social transmission has occurred (i.e. whether one person copied another). We develop a formal model of this reasoning process as a form of ratio...

When you search repeatedly for a set of items among very similar distractors, how does this impact the way you perform search? To address this, we ask in the context of a real-world object visual search task how people’s visual search performance improves over time when distractors are repeated across trials, and then what happens to search perform...

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 suggest...

Prevailing theories of visual working memory assume that each encoded item is stored or forgotten as a separate unit independent from other items. Here, we show that items are not independent, and that the recalled orientation of an individual item is strongly influenced by the summary statistical representation of all items (ensemble representatio...

Visual working memory - the cognitive system that holds visual information in an active state - has often been described as having a fixed capacity of 3 or 4 objects. Such fixed-capacity models have recently been challenged by studies showing that when people are asked to remember real-world objects (e.g., an umbrella, a chair) instead of simple is...

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 extremely weak long-term memories, in particular those where people have had only one brief exposure to an item. Here we investigated the fidelity of long-term...

When holding many things in mind, the memory of each item often becomes more similar (attraction) or more different (repulsion). There is no existing framework that explains these distortions, and here we propose and show that these opposite systematic biases reflect different behavioral goals. When remembering only a few items that are confusable,...

The ability to perceive and remember the spatial layout of a scene is critical to understanding the visual world, both for navigation and for other complex tasks that depend upon the structure of the current environment. However, surprisingly little work has investigated how and when scene layout information is maintained in memory. One prominent l...

Visual working memory is the mechanism supporting the continued maintenance of information after sensory inputs are removed. Although the capacity of visual working memory is limited, memoranda that are spaced farther apart on a 2-D display are easier to remember, potentially because neural representations are more distinct within retinotopically o...