Generalizing from Simple Instances: An Uncomplicated Lesson from Kids Learning Object Categories

Generalizing from Simple Instances: An Uncomplicated Lesson from Kids Learning Object Categories Ji Y. Son (jys@indiana.edu) Linda B. Smith (smith4@indiana.edu) Robert L. Goldstone (rgoldsto@indiana.edu) Department of Psychological and Brain Sciences, 1101 E. 10 th Street Bloomington, IN 47401 Abstract Development of Shape-based Noun Categories Abstraction is the process of stripping away irrelevant information so that learners can generalize on relevant similarities. Can we shortcut this process by directly teaching abstractions in the form of simplified instances? We tested this prediction in the domain of shape-based generalization and found that young children were able to generalize better when taught with simplified shapes rather than complex detailed ones. Simplicity during training allowed shape novices to generalize like shape experts. Keywords: category generalization, shape, word learning. Early word learning is defined by proper generalization. Children comprehend that certain nouns go with particular categories of objects at about 9 months of age (Huttenlocher, 1974). Paul Bloom (2000) summarizes how extremely early words are learned and extended to new instances slowly but soon the pace of both learning and generalization accelerates such that shortly after 24 months, children add words to their vocabulary at a staggering rate and also generalize a newly learned name broadly and correctly to category members after experiencing just one instance (Markman, 1989). These young word learners do not need to experience a whole variety of elephants or staplers to know the range of things that are elephants or staplers. One example will do; apparently these children know the right similarity to generalize over. The relevant similarity, at least for concrete noun categories, often involves shape (e.g., Clark, 1973; Imai, Gentner & Uchida, 1994). The key experimental results documenting the importance of shape to children’s noun generalizations derive from a task in which children are taught a name with a single never-before-seen exemplar then asked to generalize that name to new also never-before- seen instances. In these tasks, 18 month olds show a limited bias to extend object names by shape whereas 30 month olds systematically extend the category name to new instances by shape, ignoring a variety of other properties including color, size, material, and fine-grained details. At the same time children also become able to recognize common object categories from highly minimalist representations of their 3-dimensional shapes. Figure 1 shows an example of a minimalist shape which leaves out finer grained details, coloring, and texture information in contrast to the richly detailed and lifelike versions presented to 18 to 24 month olds in an experiment by Smith (2003). Although to adults these objects seem very similar, younger children with more limited word knowledge did not recognize the simplified forms but did recognize (nearly perfectly) the richly detailed versions when asked, “Where is the ice cream?” In contrast, slightly older children with more advanced word knowledge recognized the simplified shapes just as well as they recognized the richly detailed shapes. Smith proposes that the process of category learning was abstracting shape descriptions. Introduction Applying past learning to new circumstances requires the recognition of similarities between those past experiences and the present. The relevant similarities are often embedded with many task-irrelevant similarities and differences. Thus, processes of abstraction – of finding the right similarities – are crucial to theories of generalization (see Harnad, 2005 for a defense of this assumption). Abstraction and generalization are also crucial to understanding the differences between immature and mature learners and between novices and experts, as mature learners generally, and experts more specifically (e.g., Chi, Bassok, Lewis, Reimann & Glaser, 1989; Gick & Holyoak, 1983), seem able to abstract the right similarities over which to generalize past experiences. Such abstracted understandings may be responsible for experts’ ability to transfer their learning to highly dissimilar situations (Holyoak, 1984). The experiments reported here explore the relationship between abstraction and generalization. If the key to generalization is the formation of a sufficiently minimal description of the relevant properties, then one should be able to directly teach that abstraction and, as a consequence, get broad and appropriate transfer. Some studies with adults learning difficult domains such as chicken sexing (Biederman & Shiffrar, 1987) or scientific principles (Goldstone & Sakamoto, 2003; Sloutsky, Kaminski & Heckler, 2005) have shown generalization benefits when information is presented with more perceptually abstract forms that leave out irrelevant details. In this paper, we ask whether training with abstractions increases transfer in a specific domain: the development of 3-dimensional object recognition in toddlers. Around 2 years of age, when young children become experts in generalizing names for things to new instances, is this an expertise based on abstraction?