world must be caused by intentional agents who “designed” those living things.

The study of children’s intuitive biology has also revealed strong cross-cultural variations that seem to be closely related to cultural practices and traditions. Thus, children in non-Western traditional cultures often seem to have more sophisticated notions about taxonomies, ecology, and what properties are likely to be shared among various groups of animals and plants (Atran et al., 2001; Atran, Medin, and Ross, 2004; Ross et al., 2003; Waxman and Medin, in press). The simple act of raising a goldfish can help a child move to more sophisticated forms of biological thought (Inagaki and Hatano, 2001). One intriguing interpretation of cultural differences has emerged from a comparison between cross-cultural studies and changes in beliefs about biology through the course of history. It appears that with respect to an understanding of the taxonomies of genera, species, and subspecies, there has been a gradual devolution of biological knowledge in Western urbanized cultures over the past 400 years (Wolff, Medin, and Pankratz, 1999; Atran, Medin, and Ross, 2004).

Expanding Understandings of Matter and Its Transformation

We discussed how preschool conceptions of matter and its transformation continue to change in the elementary school years. In addition, we treat this topic in depth in Chapter 8 where we discuss how a learning progression can be developed for teaching about matter and the atomic-molecular theory. We therefore provide only a brief overview here to illustrate the complexity of the terrain children will have to cover, some of the shifts in conceptualization that can occur along the way, and how different ideas interact with each other and with forms of teaching.

There is now an extensive literature of misconceptions in the area broadly known as chemistry. Misconceptions have been documented in concepts of burning (Boujaoude, 1991), the nature of gases (Benson, Wittrock, and Baur, 1993), the particulate nature of matter (De Vos and Verdonk, 1996), and many other areas (Abraham et al., 1992; Andersson, 1990). One major area of difficulty involves coming to conceptualize gases as material bodies. Students tend to think of gases as immaterial and ethereal—belonging to an ontologically different category than solids and liquids.

Another major difficulty involves developing a macroscopic conception of chemical substances (as characterized by its properties such as boiling and melting points, different spectra, etc.) that allows them to identify substances and track the ways substances can go in and out of existence in chemical change (Johnson, 2000, 2002). Although very young children tend to identify material kinds by their perceptual properties, during elementary



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