This paper introduces a special issue of Cognitive Science initiated on the 25th anniversary of the publication of Parallel Distributed Processing (PDP), a two-volume work that introduced the use of neural network models as vehicles for understanding cognition. The collection surveys the core commitments of the PDP framework, the key issues the framework has addressed, and the debates the framework has spawned, and presents viewpoints on the current status of these issues. The articles focus on both historical roots and contemporary (...) developments in learning, optimality theory, perception, memory, language, conceptual knowledge, cognitive control, and consciousness. Here we consider the approach more generally, reviewing the original motivations, the resulting framework, and the central tenets of the underlying theory. We then evaluate the impact of PDP both on the field at large and within specific subdomains of cognitive science and consider the current role of PDP models within the broader landscape of contemporary theoretical frameworks in cognitive science. Looking to the future, we consider the implications for cognitive science of the recent success of machine learning systems called “deep networks”—systems that build on key ideas presented in the PDP volumes. (shrink)

Understanding novel phrases (e.g. upside‐down daisy) and classifying objects in categories named by phrases ought to have common properties, but you'd never know it from current theories. The best candidate for both jobs is the Theory Theory, but it faces difficulties when theories are impoverished. A potential solution is a dual approach that couples theories (representations‐about categories) with fixed mentalese expressions (representations‐of categories). Both representations combine information in parallel when understanding phrases. Although there are objections to the notion that theories (...) can combine, some of them lose their force when applied to a suitable dual model. (shrink)

The present studies tested the hypothesis that strong assumptions about within-category homogeneity impede children’s recognition of the inductive value of diverse samples of evidence. In Study 1a, children (7-year-olds) and adults were randomly assigned to receive a prime emphasizing within-category variability, a prime emphasizing within-category similarities, or to not receive a prime. Only following the variability prime, children demonstrated a reliable preference for evaluating diverse over nondiverse samples to determine whether there is support for a category-wide generalization. Adults demonstrated a (...) robust preference for diverse samples in all conditions. These effects extended beyond the specific categories included in the prime, as well as to multiple types of test questions. Study 1b demonstrated that priming variability leads children to select diverse samples only when doing so is informative for induction. Implications for conceptual development are discussed. (shrink)

A central question in cognitive research concerns how new properties are generalized to categories. This article introduces a model of how generalizations involve a process of causal inference in which people estimate the likely presence of the new property in individual category exemplars and then the prevalence of the property among all category members. Evidence in favor of this causal‐based generalization (CBG) view included effects of an existing feature’s base rate (Experiment 1), the direction of the causal relations (Experiments 2 (...) and 4), the number of those relations (Experiment 3), and the distribution of features among category members (Experiments 4 and 5). The results provided no support for an alternative view that generalizations are promoted by the centrality of the to‐be‐generalized feature. However, there was evidence that a minority of participants based their judgments on simpler associative reasoning processes. (shrink)

The distinction between rules and similarity is central to our understanding of much of cognitive psychology. Two aspects of existing research have motivated the present work. First, in different cognitive psychology areas we typically see different conceptions of rules and similarity; for example, rules in language appear to be of a different kind compared to rules in categorization. Second, rules processes are typically modeled as separate from similarity ones; for example, in a learning experiment, rules and similarity influences would be (...) described on the basis of separate models. In the present article, I assume that the rules versus similarity distinction can be understood in the same way in learning, reasoning, categorization, and language, and that a unified model for rules and similarity is appropriate. A rules process is considered to be a similarity one where only a single or a small subset of an object's properties are involved. Hence, rules and overall similarity operations are extremes in a single continuum of similarity operations. It is argued that this viewpoint allows adequate coverage of theory and empirical findings in learning, reasoning, categorization, and language, and also a reassessment of the objectives in research on rules versus similarity. Key Words: categorization; cognitive explanation; language; learning; reasoning; rules; similarity. (shrink)

Establishing healthy dietary habits in childhood is crucial in preventing long-term repercussions, as a lack of dietary variety in childhood leads to enduring impacts on both physical and cognitive health. Poor conceptual knowledge about food has recently been shown to be a driving factor of food rejection. The majority of studies that have investigated the development of food knowledge along with food rejection have mainly focused on one subtype of conceptual knowledge about food, namely taxonomic categories. However, taxonomic categorization is (...) not the only way to understand the food domain. We also heavily rely on other conceptual structures, namely thematic associations, in which objects are grouped because they share spatial-temporal properties or exhibit a complementary relationship. We rely on such thematic associations between food items, which may not fall into the same taxon, to determine the acceptability of food combinations. However, the development of children's ability to master these relations has not been systematically investigated, nor alongside the phenomenon of food rejection. The present research aims to fill this gap by investigating the development of conceptual food knowledge and the putative relationship between children's food rejection and both thematic and taxonomic food knowledge. A proportional analogy task, with a choice between taxonomic and thematic food associates, was conducted on children between 3 and 7-years-old. The children were systematically presented with either a thematic or taxonomic food base pair and then asked to extend the example type of relation to select the respective thematic or taxonomic match to the target. Our results revealed, for the first time, that increased levels of food rejection were significantly predictive of poorer food identification and decreased thematic understanding. These findings entitle us to hypothesize that knowledge-based food education programs to foster dietary variety in young children, should not only aim to improve taxonomic understanding of food, but also thematic relations. (shrink)

Each of our theories of mental representation provides some insight into how the mind works. However, these insights often seem incompatible, as the debates between symbolic, dynamical, emergentist, sub-symbolic, and grounded approaches to cognition attest. Mental representations—whatever they are—must share many features with each of our theories of representation, and yet there are few hypotheses about how a synthesis could be possible. Here, I develop a theory of the underpinnings of symbolic cognition that shows how sub-symbolic dynamics may give rise (...) to higher-level cognitive representations of structures, systems of knowledge, and algorithmic processes. This theory implements a version of conceptual role semantics by positing an internal universal representation language in which learners may create mental models to capture dynamics they observe in the world. The theory formalizes one account of how truly novel conceptual content may arise, allowing us to explain how even elementary logical and computational operations may be learned from a more primitive basis. I provide an implementation that learns to represent a variety of structures, including logic, number, kinship trees, regular languages, context-free languages, domains of theories like magnetism, dominance hierarchies, list structures, quantification, and computational primitives like repetition, reversal, and recursion. This account is based on simple discrete dynamical processes that could be implemented in a variety of different physical or biological systems. In particular, I describe how the required dynamics can be directly implemented in a connectionist framework. The resulting theory provides an “assembly language” for cognition, where high-level theories of symbolic computation can be implemented in simple dynamics that themselves could be encoded in biologically plausible systems. (shrink)

This study investigates the trajectories of intended critical thinking in a social context present in the K-5 social studies content standards of six states. It considers how the nature of context-based critical thinking present in the standards’ benchmarks is represented. The findings reveal a complex dynamic in K-5 social studies content standards, which fundamentally expect young learners to advance their critical thinking in social context. But the content standards promote inconsistent critical thinking in a social context across grade levels. The (...) sophistication of context-based critical thinking decreases within the standards as students advance through the grades. As such, implications for elementary social studies education in terms of how standards reflect official stances from the state on the nature of social studies in elementary education are discussed. (shrink)

Three experiments, adopting an evolutionary biology perspective, investigated subjects’ inferences about living things. Subjects were told that different enzymes help regulate cell function in two taxa and asked which enzyme a third taxon most likely uses. Experiment 1 and its follow-up, with college students, used triads involving amphibians, reptiles, and mammals (reptiles and mammals are most closely related evolutionarily) and plants, fungi, and animals (fungi are more closely related to animals than to plants). Experiment 2, with 10th graders, also included (...) triads involving mammals, birds, and snakes/crocodilians (birds and snakes/crocodilians are most closely related). Some subjects received cladograms (hierarchical diagrams) depicting the evolutionary relationships among the taxa. The effect of providing cladograms depended on students’ background in biology. The results illuminate students’ misconceptions concerning common taxa and constraints on their willingness to override faulty knowledge when given appropriate evolutionary evidence. Implications for introducing tree thinking into biology curricula are discussed. (shrink)

The concept of authenticity is central to how people value many different types of objects and yet there is considerable disagreement about how individuals evaluate authenticity or how the concept itself should be defined. This paper attempts to reconcile previous approaches by proposing a novel view of authenticity. Specifically, I draw upon past research on psychological essentialism and propose that when people evaluate the authenticity of objects, they do so by evaluating the extent to which the object embodies or reflects (...) a valued essence. I suggest that this explanation of authenticity provides an overarching framework that describes how people evaluate object authenticity across a variety of contexts and I report the results of three experiments that directly test the predictions made by this explanation. (shrink)

Psychological essentialism is the hypothesis that humans represent some categories as having an underlying essence that unifies members of a category and is causally responsible for their typical attributes and behaviors. Throughout the past several decades, psychological essentialism has emerged as an extremely active area of research in cognitive science. More recently, it has also attracted attention from philosophers, who put the empirical results to use in many different philosophical areas, ranging from philosophy of mind and cognitive science to social (...) philosophy. This article aims to give philosophers who are new to the topic an overview of the key empirical findings surrounding psychological essentialism, and some of the ways the hypothesis and its related findings have been discussed, extended, and applied in philosophical research. (shrink)

Judging similarities among objects, events, and experiences is one of the most basic cognitive abilities, allowing us to make predictions and generalizations. The main assumption in similarity judgment is that people selectively attend to salient features of stimuli and judge their similarities on the basis of the common and distinct features of the stimuli. However, it is unclear how people select features from stimuli and how they weigh features. Here, we present a computational method that helps address these questions. Our (...) procedure combines image-processing techniques with a machine-learning algorithm and assesses feature weights that can account for both similarity and categorization judgment data. Our analysis suggests that a small number of local features are particularly important to explain our behavioral data. (shrink)

Psychological essentialism is a folk theory characterized by the belief that a causal internal essence or force gives rise to the common outward behaviors or attributes of a category's members. In two studies, we investigated whether 4- to 7-year-old children evidenced essentialist reasoning about heart transplants by asking them to predict whether trading hearts with an individual would cause them to take on the donor's attributes. Control conditions asked children to consider the effects of trading money with an individual. Results (...) indicated that children reasoned according to essentialism, predicting more transfer of attributes in the transplant condition versus the non-bodily money control. Children also endorsed essentialist transfer of attributes even when they did not believe that a transplant would change the recipient's category membership. This finding runs counter to predictions from a strong interpretation of the “minimalist” position, an alternative to essentialism. (shrink)

Psychological essentialism is the belief that some internal, unseen essence or force determines the common outward appearances and behaviors of category members. We investigated whether reasoning about transplants of bodily elements showed evidence of essentialist thinking. Both Americans and Indians endorsed the possibility of transplants conferring donors' personality, behavior, and luck on recipients, consistent with essentialism. Respondents also endorsed essentialist effects even when denying that transplants would change a recipient's category membership (e.g., predicting that a recipient of a pig's heart (...) would act more pig-like but denying that the recipient would become a pig). This finding runs counter to predictions from the strongest version of the “minimalist” position (Strevens,2000), an alternative to essentialism. Finally, studies asking about a broader range of donor-to-recipient transfers indicated that Indians essentialized more types of transfers than Americans, but neither sample essentialized monetary transfer. This suggests that results from bodily transplant conditions reflect genuine essentialism rather than broader magical thinking. (shrink)

Are concepts stable entities, unchanged from context to context? Or rather are they context-dependent structures, created on the fly? We argue that this does not constitute a genuine dilemma. Our main thesis is that the more a pattern of features is general and shared, the more it qualifies as a concept. Contextualists have not shown that conceptual structures lack a stable, general core, acting as an attractor on idiosyncratic information. What they have done instead is to give a contribution to (...) the comprehension of how conceptual structure organized around such a stable core can produce contextually appropriate representations on demand. (shrink)

In this paper, I develop a novel account of concept acquisition for an atomistic theory of concepts. Conceptual atomism is rarely explored in cognitive science because of the feeling that atomistic treatments of concepts are inherently nativistic. My model illustrates, on the contrary, that atomism does not preclude the learning of a concept.

The idea that genuinely racial thinking is a modern invention is widespread in the humanities and social sciences. However, it is not always clear exactly what the content of such a conceptual break is supposed to be. One suggestion is that with the scientific revolution emerged a conception of human groups that possessed essences that were thought to explain group-typical features of individuals as well the accumulated products of cultures or civilizations. However, recent work by cognitive and evolutionary psychologists suggests (...) that such essentialism is a product of culturally canalized, domain-specific, and species-typical features of human psychology. This suggests that one common explanation of the content of a break in racial thinking is wrong, and casts some doubt on the thesis that genuinely racial thinking is a culturally and historically local invention. (shrink)

Although cognitive scientists have learned a lot about concepts, their findings have yet to be organized in a coherent theoretical framework. In addition, after twenty years of controversy, there is little sign that philosophers and psychologists are converging toward an agreement about the very nature of concepts. Doing without Concepts (Machery 2009) attempts to remedy this state of affairs. In this article, I review the main points and arguments developed at greater length in Doing without Concepts.