Edward Wasserman

University of Iowa | UI · Department of Psychological and Brain Sciences

The associative learning theory of Robert Rescorla and Allan Wagner has been duly celebrated for its 50-year reign as the predominant model in learning science. One special recognition is warranted: its close correspondence with David Hume's associative theory of causality judgment. Hume's rules by which causes come to suggest effects are not only...

COVIS (COmpetition between Verbal and Implicit Systems; Ashby, Alfonso-Reese, & Waldron, 1998) is a prominent model of categorization which hypothesizes that humans have two independent categorization systems – one declarative, one associative – that can be recruited to solve category learning tasks. To date, most COVIS-related research has focused...

Pigeons readily learn and transfer same-different discriminations in a variety of experimental paradigms. However, strategically designed probe tests suggest that they might only represent sameness. Here, we provide the first direct evidence that pigeons also represent difference. We first trained pigeons on a conditional same-different discriminat...

Appreciating that varied stimuli belong to different categories requires that attention be differentially allocated to relevant and irrelevant features of those stimuli. Such selective attention ought to be definable and measurable in both humans and nonhuman animals. We first discuss the definition of attention and methods of assessing it in anima...

Research on same-different categorization has shown that mastery of tasks of this kind can be strongly affected by the number of items in the training arrays-for both humans and nonhuman animals. Evidence for two-item same-different categorization in pigeons is decidedly mixed: although some investigations have succeeded, others have failed. To dat...

Category learning groups stimuli according to similarity or function. This involves finding and attending to stimulus features that reliably inform category membership. Although many of the neural mechanisms underlying categorization remain elusive, models of human category learning posit that prefrontal cortex plays a substantial role. Here, we in...

This special issue originally placed a Call for Papers that emphasized the importance of "Conceptual and Methodological" advances in the field of Comparative Cognition. Represented here is a collection of 14 papers that helps to display some of the diversity of ideas and approaches within this flourishing research area. The first paper in this issu...

Adaptively and flexibly modifying one's behavior depending on the current demands of the situation is a hallmark of executive function. Here, we examined whether pigeons could flexibly shift their attention from one set of features that were relevant in one categorization task to another set of features that were relevant in a second categorization...

Learning of exceptions – those items that violate a known regularity – takes longer than learning of rule-following items. Studies reporting this disparity have used exceptions that share most of their features with members of the opposite category (crossover exceptions). Yet, exceptions can be distinctly different from members of their own categor...

Both humans and pigeons are highly adept at task switching. However, unlike humans, pigeons do not show measurable switch costs: decreased accuracy and/or increased response times when required to switch tasks on successive trials. This striking disparity suggests that humans and pigeons may succeed at task switching via different means: humans may...

Can nonhuman animals learn abstract concepts? This intriguing question has been extensively studied over the past several decades with many different species and experimental methods. Here, we review evidence showing that pigeons can acquire a same–different concept: they readily learn to discriminate between arrays of same and different items as w...

Can nonhuman animals use an abstract sense of sameness to perceive relations-between-relations? This question has been studied over the last 40 years; yet, the extent to which nonhuman species can do so is still debated. Here, we review evidence suggesting that crows and parrots can acquire an abstract sameness rule after mastering a series of high...

Optimal foraging theory suggests that animals have evolved to maximize their net rate of energy intake; all things being equal, they should leave a current depleting patch when an alternative patch would provide either more or sooner food. In nature, however, typically all things are not equal. For example, uncertainty about the value of alternativ...

Attention to relevant stimulus features in a categorization task helps to optimize performance. However, the relationship between attention and categorization is not fully understood. For example, even when human adults and young children exhibit comparable categorization behavior, adults tend to attend selectively during learning, whereas young ch...

The study of bidirectional conditioning began more than a century ago, yet it has failed to take strong root in psychology and neuroscience. We revisit this topic by exploiting E. A. Asratyan’s alternating procedure of stimulus presentation, in which both forward (e.g., A→B) and backward (e.g., B→A) training trials are concurrently given, in order...

In two experiments, we trained pigeons (Columba livia) to sort visual images (obtained by clinical myocardial perfusion imaging techniques) depicting different degrees of human cardiac disfunction (myocardial hypoperfusion of the left ventricle) into normal and abnormal categories by providing food reward only after correct choice responses. Pigeon...

A prominent model of categorization (Ashby, Alfonso-Reese, Turken, & Waldron, 1998) posits that 2 separate mechanisms-one declarative, one associative-can be recruited in category learning. These 2 systems can effectively be distinguished by 2 task structures: rule-based (RB) tasks are unidimensional and encourage analytic processing, whereas infor...

Hoerl & McCormack propose that animals learn sequences through an entrainment-like process, rather than tracking the temporal addresses of each event in a given sequence. However, past research suggests that animals form “temporal maps” of sequential events and also comprehend the concept of ordinal position. These findings suggest that a clarifica...

Putting things off as long as possible (procrastination) is a well-known tendency. Less well known is the tendency to attempt to get things done as soon as possible, even if that involves extra effort (precrastination). Since its discovery in 2014, precrastination has been demonstrated in humans and animals and has recently been revealed in an anal...

In a seminal study, Shepard, Hovland, and Jenkins (1961; henceforth SHJ) assessed potential mechanisms involved in categorization learning. To do so, they sequentially trained human participants with 6 different visual categorization tasks that varied in structural complexity. Humans' exceptionally strong performance on 1 of these tasks (Type 2, or...

A prominent theory of category learning, COVIS, posits that new categories are learned with either a declarative or procedural system, depending on the task. The declarative system uses the prefrontal cortex (PFC) to learn rule-based (RB) category tasks in which there is one relevant sensory dimension that can be used to establish a rule for solvin...

Prior categorization studies have shown that pigeons reliably track features that are relevant to category discrimination. In these studies, category exemplars contained two relevant and two irrelevant features; therefore, category density (specifically, the relevant to irrelevant information ratio) was relatively high. Here, we manipulated categor...

We explored the pigeon's representation of the shape of simple three-dimensional objects (geons) rotated in depth (four views each of four geons). Pigeons assigned to the Categorization group had to respond differentially to images of four different geons—termed arch, barrel, brick, and wedge—based on their 3D shape, regardless of the orientation o...

Procrastination is a familiar and widely discussed proclivity: postponing tasks that can be done earlier. Precrastination is a lesser known and explored tendency: completing tasks quickly just to get them done sooner. Recent research suggests that precrastination may represent an important penchant that can be observed in both people and animals. T...

We trained 8 pigeons (Columba livia) on a stagewise go/no-go visual discrimination task of increasing complexity, to document the dynamics of selective attention. We constructed negative compound stimuli (S-s) on the basis of their overall similarity to a positive compound stimulus (S+) along 4 binary-valued dimensions: shape (circle/square), size...

The hippocampus may play a role in categorization because of the need to differentiate stimulus categories (pattern separation) and to recognize category membership of stimuli from partial information (pattern completion). We hypothesized that the hippocampus would be more crucial for categorization of low-density (few relevant features) stimuli–du...

Are there minding machines? In this paper, I consult historical, philosophical, and empirical sources in trying to answer this intriguing question. My historical and philosophical discussions focus on five famous Frenchmen (Michele de Montaigne, René Descartes, Salomon de Caus, Julien Offray de La Mettrie, and Jacques Vaucanson) and one famous Amer...

Are concepts and categories unique to the human brain? In this chapter, we review extensive empirical evidence on nonhuman animals' ability to form three broad types of concepts: (1) perceptual concepts, in which members of a class are perceptually similar to each other; (2) nonsimilarity-based concepts, in which members of a class are united by a...

Whether nonhuman animals—even those phylogenetically distant from humans, such as pigeons—can learn categories and to what extent the involved learning mechanisms are perceptually or conceptually based have been extensively researched over the past few decades. In this chapter, we will discuss similarity-based or perceptual category learning, which...

Supervised learning results from explicit corrective feedback, whereas unsupervised learning results from statistical co-occurrence. In an initial training phase, we gave pigeons an unsupervised learning task to see if mere pairing could establish associations between multiple pairs of visual images. To assess learning, we administered occasional t...

Considerable research in cognitive science, neuroscience, and developmental science has revealed that the temporal, spatial, and numerical features of a stimulus can interact with one another [1,2, as when larger stimuli are perceived as lasting longer than smaller stimuli. These findings have inspired the prominent hypothesis that time, space, and...

Prior categorization studies have shown that pigeons reliably track features that are perfect predictors of category membership (Castro & Wasserman, 2014, 2016a). One might further ask whether pigeons would also track features that are relevant, but imperfect predictors of category membership. In our present project, pigeons had to categorize multi...

We report a novel method for investigating the acquisition of anticipatory responding in the pigeon. Four pigeons (Columba livia) received food for pecking a starburst target stimulus displayed in the bottom-left or bottom-right portion of a computer screen. The target stimulus was preceded by 1 of 3 fractal images displayed in either the upper-lef...

Scientists hoping to elucidate the origin of human stone tool manufacture and use have looked to extant primate species for possible clues. Although some skepticism has been raised, there is clear evidence that today’s capuchin monkeys can make and use stone tools.

To document the dynamics of discrimination learning involving increasingly complex visual stimuli, we trained six pigeons in a stagewise Multiple Necessary Cues (MNC) go/no-go task. The compound stimuli were composed from 4 dimensions, each of which could assume either of two extreme values or the intermediate value between them. Starting with a st...

Humans are commonly believed to have evolved specially adapted neural systems for processing the rich and complex content of faces. However, nonhuman animals—including fish—have also shown a well-developed capacity for discriminating human faces, raising important questions concerning the uniqueness and mechanisms of human face perception.

We trained six pigeons in a stagewise Multiple Necessary Cues (MNC) go/no-go task to document the dynamics of discrimination learning involving increasingly complex visual stimuli. The compound stimuli were composed from four dimensions, each of which could assume either of two extreme values or their intermediate value: Shape, Size, Line Orientati...

Adaptive behaviors are believed to be shaped by both positive (the strengthening of correct associations) and negative (the pruning of incorrect associations or the building of inhibitory associations) forms of associative learning. However, there has been little direct documentation of how these basic processes participate in the learning of rich...

Assessment of medical image quality and how changes in image appearance impact performance are critical but assessment can be expensive and time-consuming. Could an animal (pigeon) observer with well-known visual skills and documented ability to distinguish complex visual stimuli serve as a surrogate for the human observer? Using sets of whole slid...

How supervision is arranged can affect the way that humans learn concepts. Yet very little is known about the role that supervision plays in nonhuman concept learning. Prior research in pigeon concept learning has commonly used differential response–reinforcer procedures (involving high-level supervision) to support reliable discrimination and gene...

We trained pigeons to respond to one key when two consecutive displays were the same as one another (no-change trial) and to respond to another key when the two displays were different from one another (change trial; change detection task). Change-trial displays were distinguished by a change in all three features (color, orientation, and location)...

Previous studies showed that the anterior cingulate cortex (ACC) plays a role in selective visual attention. The current study further examined the role of the ACC in attention using a visual cuing task with task-relevant and task-irrelevant stimuli. On every trial, 2 stimuli were presented on the touchscreen; 1 was task-relevant and the other was...

As is true for most other human inventions, the origin of the violin is unknown. What is known is that this popular and versatile instrument has notably changed over the course of several hundred years. At issue is whether those evolutionary changes in the construction of the violin are the result of premeditated, intelligent design or whether they...

Once a categorization task has been mastered, if features that once were relevant become irrelevant and features that once were irrelevant become relevant, a decrement in performance-a shift cost-is typically observed. This shift cost may reflect the involvement of two distinguishable factors: the inability to release attention from a previously re...

Pathologists and radiologists spend years acquiring and refining their medically essential visual skills, so it is of considerable interest to understand how this process actually unfolds and what image features and properties are critical for accurate diagnostic performance. Key insights into human behavioral tasks can often be obtained by using a...

We explored the relation between concept learning and the number of training exemplars, programmed in a stepwise fashion. Eight pigeons (Columba livia) were trained via differential food reinforcement to peck 1 of 2 simultaneously displayed color images: benign or malignant human breast tissue samples. In each session, only 1 exemplar from each cat...

Two juvenile orange-winged amazons (Amazona amazonica) were initially trained to match visual stimuli by color, shape, and number of items, but not by size. After learning these three identity matching-to-sample tasks, the parrots transferred discriminative responding to new stimuli from the same categories that had been used in training (other col...

In four experiments, we evaluated Lea's (1984) reassignment procedure for studying object representation in pigeons (Experiments 1-3) and humans (Experiment 4). In the initial phase of Experiment 1, pigeons were taught to make discriminative button responses to five views of each of four objects. Using the same set of buttons in the second phase, o...

Analogical reasoning is vital to advanced cognition and behavioral adaptation. Many theorists deem analogical thinking to be uniquely human and to be foundational to categorization, creative problem solving, and scientific discovery [1]. Comparative psychologists have long been interested in the species generality of analogical reasoning, but they...

Procrastination is the tendency to delay initiating or completing tasks. Rosenbaum et al. (Psychological Science, May 8, 2014) recently documented the opposite of procrastination: pre-crastination, the tendency to begin or to finish tasks as soon as possible. We devised a simple two-alternative forced-choice task, in which pigeons could choose to s...

Behavioral studies of object recognition in pigeons have been conducted for 50 years, yielding a large body of data. Recent work has been directed toward synthesizing this evidence and understanding the visual, associative, and cognitive mechanisms that are involved. The outcome is that pigeons are likely to be the non-primate species for which the...

Repeated pairings of a particular visual context with a specific location of a target stimulus facilitate target search in humans. We explored an animal model of such contextual cueing. Pigeons had to peck a target, which could appear in 1 of 4 locations on color photographs of real-world scenes. On half of the trials, each of 4 scenes was consiste...