Lumping and Splitting: Age-related and Experience-driven Differentiation of Children’s Semantic Networks

• In Event: 2-028 - The Organization of Knowledge: Development and Modeling of Early Semantic Networks

Integrative Statement

The organization of knowledge in semantic memory, reflecting meaningful relations among words and the entities they denote, has long been considered a central aspect of cognition. Yet, we still know fairly little about how the organization of semantic knowledge changes over development and how learning and experience shape semantic networks. Prior computational work (Hills et al., 2009; Kemp & Tenenbaum, 2008; McClelland & Rogers, 2003) suggests that children’s semantic networks become progressively differentiated as a result of experience with entities in the world. Whereas some empirical evidence is broadly consistent with this account (Carey, 1985; Keil, 1979; Mandler, 2000), few studies tested this possibility directly by examining changes in the organization of semantic networks (cf. Unger et al., 2016). Across two studies, we directly examined age-related (Study 1) and experience-driven (Study 2) changes in children’s semantic networks.

We asked children to organize cards depicting individual word referents such that related things were placed close together; we then used the physical distance between pairs of items to measure their semantic relatedness (Goldstone, 1994; Fisher et al., 2015). In Study 1, children arranged familiar items belonging to various domains (e.g., clothes, food, animals…), with some items sharing an additional relation (e.g., associated with summertime; Figure 1A). As shown in Figure 1B, both younger (4-5 year-olds) and older (7-8 year-old) children placed items belonging to the same domain closer together relative to items belonging to different domains (e.g., placed "shorts" closer to "pajamas" than to "cat"). However, only the older children placed items that belonged to the same domain and shared an additional relation (e.g., "shorts" and "sandals"; both worn in warm weather) closer together relative to items that only belong to the same domain (e.g., "shorts" and "pajamas"). A follow-up study provided converging evidence for increased within-domain differentiation with age. In Study 2, we recruited children enrolled in one of two week-long informal learning programs at a local botanical garden, and examined changes in their organization of the two biological domains targeted by each program: bugs and plants (Figure 2A). All children showed increased across-domain differentiation, such that items belonging to different domains were placed farther apart from before to after completing the program. Children also showed increased within-domain differentiation for the domain experienced during the program activities by placing: (1) same-category items (e.g., "butterfly" and "ladybug") closer together and (2) different category items (e.g., "butterfly" and "spider") farther apart. Importantly, these within-domain changes were specific to the domain children experienced in the program – no such changes were seen for the other, non-experienced domain (see Figure 2B).

Consistent with prior computational accounts, these results reveal progressive differentiation of semantic knowledge in childhood. Specifically, these results show that, over developmental time and as result of experience, lumping of items into different domains is accompanied by splitting of items within a domain according to meaningful relations. These results also suggest that the time-scales of these changes may be distinct, with early lumping preceding later splitting as children accrue knowledge about entities.

Authors

• Catarina Vales, Carnegie Mellon University
  Presenting Author

• Anna Fisher, Carnegie Mellon University
  Non-Presenting Author