مدل های ذهنی و دیگر تصورات غلط در درک کودکان از زمین

This study investigated the claim (e.g., Vosniadou & Brewer’s, 1992) that children have naive “mental models” of the earth and believe, for example, that the earth is flat or hollow. It tested the proposal that children appear to have these misconceptions because they find the researchers’ tasks and questions to be confusing and ambiguous. Participants were 6- and 7-year-olds (N = 127) who were given either the mental model theorists’ original drawing task or a new version in which the same instructions and questions were rephrased to minimize ambiguity and, thus, possible misinterpretation. In response to the new version, children gave substantially more indication of having scientific understanding and less of having naive mental models, suggesting that the misconceptions reported by the mental model theorists are largely methodological artifacts. There were also differences between the responses to the original version and those reported by Vosniadou and Brewer, indicating that other factors, such as cohort and cultural effects, are also likely to help explain the discrepant findings of previous research.

The study of children’s conceptual development in the domain of observational astronomy focuses on the origins, content, and structure of children’s concepts of the shape of the earth, gravity, and the day–night cycle. Vosniadou and Brewer, 1992 and Vosniadou and Brewer, 1994 tested the earth knowledge of 6- to 11-year-old Americans with interviews that included drawing instructions (e.g., “Can you draw a picture of the earth?”, “Show me where the people live”) and factual questions (e.g., “What is the shape of the earth?”, “Which way do we look to see the earth?”). In these interviews, children were also asked “generative” questions (e.g., “If you walked for many days in a straight line, where would you end up?”, “Would you ever reach the edge of the earth?”). Vosniadou and Brewer (1992) argued that generative questions have a greater potential to reveal underlying conceptual structures than do factual questions because the former require an inference from a knowledge base rather than repetition of what children have been taught. Analysis of children’s drawings and answers has led to the claim that the majority of children have a small number of well-defined “mental models” of the earth (Vosniadou & Brewer, 1992): the “flat earth” with the people and the sky on top and an edge from which one can fall; the “hollow sphere” with the sky located inside the Northern Hemisphere and the people situated inside at the bottom of the earth; the “dual earth” consisting of a flat earth where people live and a round earth that is up in the sky; and the “spherical earth” that is round with the people and sky around it. Similar studies conducted in different cultures (e.g., Brewer et al., 1987, Diakidoy et al., 1997, Hayes et al., 2003 and Vosniadou and Brewer, 1990), and using clay model-making instead of drawings (Samarapungavan et al., 1996 and Vosniadou et al., 2004), have supported these findings and led these researchers to claim that, notwithstanding some differences in the types of mental models due to specific cultural influences, young children’s emerging concepts of the earth are largely universal. This mental model view proposes that, before children acquire the scientific view, they form naive, theory-like mental models of the earth. These are (a) coherent, (b) constructed under the influence of flatness and support constraints that lead to the belief that the ground extends on a flat plane and all unsupported things fall, (c) reinforced by children’s observations of their local environment, and (d) used in a systematic way to explain phenomena such as whether it is possible to fall off the edge of the world (Vosniadou and Brewer, 1992, Vosniadou and Brewer, 1994 and Vosniadou and Ioannides, 1998). Before any exposure to instruction, children form an “initial” mental model of a flat earth that is gradually replaced by “synthetic” models such as hollow and dual earths. Synthetic models result from the combination of children’s intuitive beliefs (e.g., the earth is flat and supported) and counterintuitive scientific facts transmitted by the culture (e.g., the earth is spherical and unsupported). Only during late childhood are synthetic models superseded by the scientific view of the spherical earth. The development of children’s knowledge of the earth from initial, through synthetic, to scientific is said to resemble the historical shifts from the ancient flat earth view, through Ptolemy’s geocentric theory, to the Copernican revolution. Vosniadou, 1994a and Vosniadou, 1994b described knowledge acquisition in this domain as a gradual and slow process that requires radical restructuring and theory change. Consistent with the “theory theory” (Gopnik, 2005 and Wellman and Gelman, 1998) that is also applied in domains such as biology (e.g., Inagaki and Hatano, 2002, Jaakkola and Slaughter, 2003 and Keil, 1989), psychology (Johnson and Wellman, 1982 and Wellman and Estes, 1986), and physics (e.g., Spelke & Kinzler, 2007), children construct naive theories that enable them to explain and predict phenomena in the physical and psychological worlds. During conceptual development, they encounter new evidence that contradicts their initial conceptions and presents them with theoretical anomalies. Conceptual change, therefore, involves the gradual revision, restructuring, and replacement of these naive theories with new explanatory structures that are consistent with culturally transmitted scientific information. A different view concerning the nature of children’s conceptions of the earth is based on studies that, instead of drawings and open questions, have used three-dimensional (3D) model selection tasks and forced-choice questions (Martin, 2006, Nobes et al., 2003, Panagiotaki, 2003, Panagiotaki et al., 2006b and Siegal et al., 2004), picture selection tasks (Nobes et al., 2005 and Straatemeier et al., 2008), and interviews in which reference is made to a globe (Schoultz, Säljö, & Wyndhamn, 2001). In these studies, children between 4 and 11 years of age were interviewed about the earth’s shape, the location of the people and sky, gravity, and the day–night cycle with questions such as “Is the earth flat or round?,” “Which of these models [sphere, disk, or hollow sphere] looks more like the earth?”, and “Some children think that people live all around the earth and other children think that people live only on top of the earth—what do you think?” Findings from these studies suggest that young children know considerably more about the earth than the mental model theorists have proposed, and that this knowledge is fragmented rather than theory-like. According to the “fragmentation” view, young children have neither conceptions nor misconceptions of the earth, but rather are theory free. Their knowledge consists of fragments that in some ways resemble diSessa’s (1988) “pieces of knowledge” (“p-prims”). Both are small, self-explanatory, and loosely connected “rather than one or even any small number of integrated structures one might call theories” (p. 52). However, in contrast to p-prims fragments of knowledge about properties of the earth, such as its shape and the fact that people can live “down under”, must be acquired from the culture (e.g., parents, school, media). Scientific information is communicated piecemeal and stored fragment by fragment until the coherent cultural theory is acquired (Nobes et al., 2003 and Nobes et al., 2005). As with metaphysical issues, such as what happens to people after they die (Harris, 2000, Harris, 2007 and Harris and Koenig, 2006), knowledge of the earth cannot be derived from intuition or direct observation. The debate between the mental model and fragmentation accounts has important implications, first, for how we can best characterize the processes of conceptual development and second, for how we should teach children scientific ideas and concepts. If, as the mental model theorists suggest, children’s strong intuitions of flatness and support render them resistant to instruction in this domain, the principal role of teachers is to challenge these constraints. On the other hand, if the fragmentation account is correct and constraints are weak or nonexistent, children can be taught and can acquire the scientific model of the earth relatively easily from an early age. The discrepant findings of the mental model theorists and their critics are accounted for largely by their use of different methods. Four studies (Frède et al., 2008, Panagiotaki et al., 2006a, Siegal et al., 2004 and Vosniadou et al., 2004) show that children appear to have naive mental models when they are asked to draw or make models of the earth and to answer open and repeated questions (the mental model theorists’ method), but not when they are asked to choose from a set of 3D models or pictures and to answer forced-choice questions. The latter method has repeatedly elicited earth representations that are either scientific or inconsistent (Nobes et al., 2003, Nobes et al., 2005, Panagiotaki et al., 2006a, Siegal et al., 2004 and Straatemeier et al., 2008). To explain the differences in these findings, Vosniadou and colleagues (2004) suggested that the use of a limited set of 3D models restricts children’s choices and does not allow them to express any alternative ideas they might have. Thus, very few children appear to have flat or synthetic earth mental models. Furthermore, Vosniadou and colleagues proposed that the different methods elicit different “modes of knowing”; “recognition” methods, such as forced-choice questions and picture or model selection tasks, lead children to simply repeat or recognize scientific facts without necessarily understanding them. This, they suggested, is an easier task that fails to measure children’s “generative use of scientific concepts” (p. 221). In contrast, critics of the mental model account suggest that naive mental models are methodological artifacts that result from (a) problems with the drawing and model-making tasks (Nobes et al., 2003, Nobes et al., 2005 and Siegal et al., 2004) and (b) participants’ misinterpretation of the interview instructions and questions (Siegal, 1997, Siegal and Surian, 2004 and Siegal et al., 2004). For example, because children tend to be poor artists and have difficulty in representing 3D objects on the picture plane (e.g., Blades & Spencer, 1994), they might draw a flat, hollow, or dual earth because these are more easily represented on paper than is a sphere. Moreover, it is possible that, in the unfamiliar context of a research interview, children misunderstand the meaning of apparently simple instructions such as “draw the earth”. Therefore, they draw or make nonscientific pictures or clay models not because they lack knowledge of the earth but rather because they misinterpret the point of the task (Nobes and Panagiotaki, 2007 and Siegal, 2008). Choosing from 3D models or pictures and answering forced-choice questions reduce the ambiguity of researchers’ instructions and clarify the meaning of questions, allowing children to represent their knowledge more accurately. To test the claim that only children appear to have naive earth mental models because they have problems with the mental model theorists’ methods, Nobes and Panagiotaki (2007) gave Vosniadou and Brewer’s (1992) drawing instructions and questions to adults. Many gave the same nonscientific responses as did children; they drew flat, hollow, or dual earths and said that the sky and people are located on top of or inside the earth. The adults’ feedback on the task revealed that the main explanation for their nonscientific answers lies in the difficulty of interpreting instructions and questions that they considered ambiguous and confusing. For example, many found the instructions “draw the earth” and/or “draw some people to show where people live” to be ambiguous because there was no indication of which perspective they should take or to what scale the pictures should be drawn. Thus, participants who took a (literally) global perspective drew scientific pictures, whereas those who took a local perspective drew flat earths. Adults who drew hollow and dual earths reported that they did so in an attempt to include both perspectives in the same pictures. None of the participants believed the earth to be flat, dual, or hollow. In a follow-up study, Nobes and Panagiotaki (in press) constructed a new questionnaire that minimized the ambiguity of the original task by, for example, specifying the perspective to be taken and using symbols to avoid the problem of scale. Adults’ responses to this new version were compared with those of adults who were tested with the original task. The changes in phrasing of the instructions and questions resulted in substantial increases in proportions of scientific drawings and answers as well as substantial decreases in all types of naive (flat, hollow, and dual) responses. These findings confirm that adults do not have naive mental models of the earth and that the principal reasons for their nonscientific responses are methodological.