The Shape Bias Shapes More Than Just Attention: Relationships Between Categorical Biases & Object Recognition Memory

The Shape Bias Shapes More Than Just Attention: Relationships Between Categorical Biases & Object Recognition Memory Haley A. Vlach (hvlach@wisc.edu) Department of Educational Psychology, 1025 W. Johnson Street Madison, WI 53706 USA Abstract The “shape bias” describes the finding that, starting around 24 months of age, children generalize object categories based upon shape to a greater degree than other perceptual features. To date, research on the shape bias has consisted of debates about how attentional mechanisms engender the development of the shape bias. The current work moves beyond theoretical explanations grounded in attention processes and examines potential consequences of the shape bias in memory processes. In this experiment, children and adults’ memory performance for features of objects was examined in relation to their categorical biases. The results of the experiment demonstrated that, across the lifespan, learners with a shape bias were more likely to remember the shape of objects than they were the color and size. Taken together, this work suggests the development of a shape bias may lead to more than just differences in attention to features of objects, but a memory bias for shape information. Keywords: shape bias; object recognition memory; word learning; categorization; language and cognitive development Introduction Categorization is a central process in human cognition and development. As a result, much research has examined the developing ability to categorize the world. In particular, research has examined the children’s ability to categorize objects and generalize this information to novel objects. Children’s categorization of objects has been described as particularly impressive because there are a seemingly infinite number of ways that objects in the world can be partitioned and generalized. One explanation for how children develop the ability to categorize objects is that they acquire categorical biases, which are used to narrow the possible ways in which objects can be categorized. An example of one of these biases is the “shape bias”, which describes the finding that, starting around 24 months of age, learners generalize object categories based upon shape to a greater degree than other perceptual features (Baldwin, 1992; Colunga & Smith, 2008; Gershkoff-Stowe & Smith, 2004; Landau, Smith, & Jones, 1988; Samuelson, 2002; Perry & Samuelson, 2011). In a typical paradigm (e.g., Landau et al., 1988), participants are presented with a novel object and a novel linguistic label (e.g., “toma”). Participants are then presented with three additional objects, one that matches the target object’s shape and two additional objects that match one of the target object’s other dimensions, such as color, size, or texture. The experimenter then prompts participants to pick which one of the three objects is also a “toma”. The majority of children and adults will pick the shape match over the color, size, or texture match, suggesting that learners assume shape is a more defining feature of object categories than other perceptual features. To date, the shape bias literature largely consists of arguments regarding the types of information children attend to during categorization and generalization, such as perceptual, linguistic, or conceptual information (for an overview of extant theories, see Samuelson & Bloom, 2008). As an example, according to the Attentional Learning Account (ALA) of the shape bias (e.g., Colunga & Smith, 2008), attention is shifted to properties of objects that have historically been relevant for the task context. The relevant properties of objects are likely to be determined by statistical regularities amongst perceptual features of objects. That is, children’s early experiences learning words and categories leads them to notice statistical regularities amongst objects (e.g., shape), enabling children to shift attention to these regularities and make generalizations from the categories they know to novel categories. Given the focus on attentional processes, the shape bias literature has a striking limitation: this work has focused on the information that children attend to when comparing multiple objects in one moment in time. In real-world learning situations, there are likely to be frequent temporal gaps between encountering a new object and subsequently generalizing to a second object of the same category. However, little research has examined how learners access their learning history (i.e., when the first object is no longer in the learner’s view) and how this ability relates to categorization and generalization. Indeed, a central tenant of all theoretical accounts of the shape bias is that learners access and use their learning history to guide generalization across time (for a discussion, see Keil, 2008). Consequently, it is essential to understand how learners remember and retrieve information about objects across time. Rather than argue for one theory over the other, this work moves beyond arguments of what is attended to in-the- moment, but what is retained across time. The current work builds upon the existing literature by examining categorical biases in relationship to learners’ memory for perceptual features of objects. As proposed by extant theories, such as the ALA account, the shape bias creates enhanced attention to shape (e.g., Colunga & Smith, 2008). The hypothesis is this work is that enhanced attention to shape has consequences beyond in-the-moment processing of objects. In particular, it is predicted that enhanced attention leads to the ability to remember shape to a greater degree than other perceptual features of objects.