Scientific Concepts Development Research Paper

1. Initial Understanding Of Scientific Concepts

A large amount of recently obtained evidence indicates that infants’ conceptual understanding is considerably more sophisticated than previously assumed. Traditionally, researchers relied on children’s verbal explanations and/or their actions as measures of their conceptual understanding. These methods often underestimated infants’ and very young children’s understanding, owing to their inarticulateness and poor motor coordination. However, a new method, the violation-of-expectation paradigm, has made it possible to assess infants’ physical knowledge by examining how long they look at ‘possible’ and ‘impossible’ events. A typical experiment involves habituating the child to a series of physically possible events and then presenting either a different possible event or an impossible event. The assumption is that children who understand the impossibility of the one event will look longer at it, because they are surprised to see the violation of the principle.

Studies using this violation of expectation paradigm have revealed impressive initial understanding of physical concepts. Even infants possess certain core concepts and understand several principles that govern the mechanical movement of objects (Spelke and Newport 1998). For example, 4-month-olds have a notion that one solid object cannot move through the space occupied by another solid object. In the studies that demonstrated this phenomenon, infants were first habituated to a display in which a ball was dropped behind a screen, which was then removed to reveal the ball on the floor. They then saw two events. In the consistent condition, the ball was again dropped, and when the screen was removed, infants saw the ball resting on a platform above the stage floor. In the inconsistent event, the ball was resting on the stage floor under the platform. Infants looked longer at the inconsistent event than at the consistent one, as if they were surprised to see the violation of the object–solidity principle. Other studies with a similar approach have also revealed infants’ understanding of gravity and other physical regularities. Infants appear to understand that an unsupported object should move downward and that objects do not ordinarily move without any external force being applied.

Infants’ knowledge of physical regularities is gradually refined over the first year, as demonstrated by their understanding of collisions. Most 3-month-olds appear surprised to see a stationary object move when not hit by another object. Six-month-olds can appreciate how the features of objects affect a collision. They appeared to be surprised when an object moves further following a collision with a small moving object than it does after colliding with a larger moving object. Later during the first year, infants responded differently to events in which the object that was struck moved at an angle perpendicular to the motion of the object that struck it than when it moved in a more standard path.

Other researchers, however, raise concerns about the use of such paradigms to draw inferences about infants’ conceptual knowledge (e.g., Haith and Benson 1998). They argue that differential looking only indicates that infants discriminate between two events and that perceptual rather than conceptual features might drive this discrimination. Thus, infants’ visual preference or looking time might have been incorrectly interpreted as evidence of an appreciation of physical principles.

Early conceptual understanding is not limited to understanding of physics principles. By age 3 years, children can distinguish living from nonliving things. They recognize that self-produced movement is unique to animals. In one study that made this point, preschoolers were shown brief videotapes in which animals or inanimate artifacts moved across the screen. Then the children were asked to make judgments about internal causes (does something inside this object make it move) and external causes (did a person make this move). Children typically attributed the cause of the animate object’s motion to internal features (‘it moves itself;’ ‘something inside makes it move’). In contrast, they were more likely to attribute the motion of an artifact to an external agent (Gelman 1990).

Preschoolers are also sensitive to differences in the ‘types of stuff’ inside animate and inanimate objects. They draw inferences about identity and capacity to function based on internal parts, associating, for example, internal organs, bones, and blood with animals and ‘hard stuff’ or ‘nothing’ with inanimate objects. After hearing a story about a skunk that was surgically altered so that it looked like a raccoon, young children reported that the animal was still a skunk, despite its altered appearance. However, children did not reason in the same way when they heard similar stories about artifacts; a key that was melted down and stamped into pennies was no longer a key (Keil 1989).

2. Developing Understanding Of Physical Concepts

Rudimentary understanding of basic concepts does not imply full-blown appreciation of physical principles. Even older children’s concepts and theories often involve substantial misconceptions. Understanding of physical concepts undergoes substantial change with age and experience. One good example involves physical causality and mechanical movement. When Event A precedes Event B, many 3and 4-yearolds fail to choose A consistently as the cause, whereas 5- and 6-year-olds are considerably more likely to choose A. Children also hold intuitive theories of motion that are inconsistent with fundamental mechanical principles. For example, when asked to predict how a ball would travel after rolling through a spiral tube, only one-fourth of 9-year-olds and less than half of 11-year-olds correctly predicted the ball’s trajectory.

Misconceptions also occur with other concepts. For example, children’s conceptions of matter, weight, volume, and density undergo substantial change with age. Most 3-year-olds have undifferentiated notions of the roles of density, weight, and volume in producing buoyancy of objects placed in liquids. Most 4and 5year-olds have some conception of density, although their judgments are also affected by other features of the objects (i.e., weight and volume). Eight and 9year-olds, in contrast, rely consistently on density in judging whether objects will sink or float.

On some physical tasks, children’s increasing understanding can be characterized as a series of increasingly adequate rules. One such task is Siegler’s (1976) balance scale task. On each side of the scale’s fulcrum were four pegs on which metal weights could be placed. In each trial, children were shown a configuration of weights on pegs and were asked to predict whether the scale would balance or whether one side would go down after release of a lever that held the scale motionless. Most children based their predictions on one of four rules. The large majority of 5-year-olds relied solely on weight (Rule I). This involved predicting that the scale would balance if both sides had the same amount of weight and that the side with more weight would go down if the two sides had different amounts of weight. Nine-year-olds often used Rule II. This involved predicting that the side with more weight would go down when one side had more weight, but predicting that the side with its weight further from the fulcrum would go down when weights on the two sides were equal. Some 9-year-olds and most 13–17-yearolds used Rule III. They considered both weight and distance on all problems, and predicted correctly when weights, distances, or both were equal for the two sides. However, when one side had more weight and the other side’s weights were further from the fulcrum, children muddled through, not relying consistently on any identifiable approach. Rule IV allowed children to solve all balance scale problems. It involved choosing the side with greater torque (W_LD_L vs. W_RD_R) when one side had more weight (W) and the other had its weight further from the fulcrum (D). Few children or adults used Rule IV. Similar sequences of rules have been shown to characterize the development of a variety of tasks, including projection of shadow, probability, water displacement, conservation of liquid and solid quantity, and time, speed, and distance.

A related way of conceptualizing the development of scientific understanding is as a succession of increasingly adequate mental models. One good example of such a succession involves understanding of the Earth as an astronomical object (Vosniadou and Brewer 1992). Some children, particularly young ones, conceive of the Earth as a flat, solid, rectangular shape. A slightly more sophisticated mental model is to think of the Earth as a disk. Three yet more advanced incorrect approaches are the ‘dual Earth model,’ which includes a flat, disk-like Earth where people live and a spherical Earth up in the sky; the ‘hollow sphere model,’ in which people live on flat ground inside a hollow sphere; and the ‘flat sphere model,’ in which, people live on flat ground on top of a hollow sphere. All three of these models allow children to reconcile their perception that the Earth looks flat with their teachers’ and textbooks’ insistence that the Earth is round. The proportion of children who possess the correct ‘spherical model’ of the Earth increases from 15 percent to 40 percent to 60 percent from first to third to fifth grade.

3. Developing Understanding Of Biological Concepts

Young children have a concept of living things, but it does not perfectly match the concept of older children and adults. Until about age 7 years, most children do not view plants as living things. In addition, 3-yearolds fairly often attribute life to powerful, complex, or moving inanimate objects, such as robots and the Sun. A similar mix of understandings and misunderstandings is evident in preschoolers’ views regarding internal parts of living things. They know that animals have bones and hearts, but have little idea of their functions.

Children’s understanding of other uniquely biological concepts, such as growth, inheritance, and illness, also undergoes substantial change with age and experience. Preschool children have some appreciation of biological growth. They expect animals to grow, appreciate that growth can only occur in living things, and understand that growth is directional (small to big). However, preschoolers also believe that living things may or may not grow, and have difficulty accepting that even small things, such as a worm or butterfly, grow. Not until age 5 or 6 years do children realize the inevitability of growth; one cannot keep a baby pet small and cute just because one wants to do so.

Children’s understanding of inheritance, another uniquely biological process, also develops with age and experience. Preschoolers understand that like begets like: Dogs have baby dogs, rabbits have baby rabbits, and offspring generally share biological properties with parents (Wellman and Gelman 1998). They also believe that animals of the same family share physical features even when they are raised in different environments. For example, preschoolers believe that a rabbit raised by monkeys would still prefer carrots to bananas. However, other studies suggest that not until 7 years of age do children understand birth as part of a process mediating the acquisition of physical traits and nurturance as mediating the acquisition of beliefs. Only older children clearly distinguish between properties likely to be affected by heredity and properties likely to be affected by environment. For example, not until school age do children expect a boy to resemble his biological father in appearance but to resemble his adoptive father in beliefs. Thus, younger children seem to have different intuitions about the mechanisms of inheritance than do older children and adults.

Even preschoolers show some understanding of illness, yet another biological process. For example, preschoolers have a notion that an entity can induce illness or be contaminated and that contamination may occur through the workings of invisible, physical particles. Four- and 5-year-olds have some understanding of contagion; they believe that a child is more likely to get sick from exposure to another person who caught the symptom by playing with a sick friend than from another person who developed the symptom through other means. Although preschoolers may have a general idea that germs can cause symptoms, they do not differentiate the effects of symptoms caused by germs from those caused by poison, for example. The mature concept of illness, which is characterized as uniting various components such as its acquisition, symptoms, treatment, and transmission, is not mastered until much later (Solomon and Cassimatis 1999).

As with physical concepts, children’s understanding of biological concepts involves substantial developmental change. For some concepts, changes involve enrichment, as children learn more and more details and phenomena relevant to the concepts. For others, developmental changes involve radical conceptual reorganization. There are some interesting parallels between the redefining and restructuring involved in the history of scientific understanding and the changes that occur within an individual lifetime (Carey 1985).

4. Learning Processes

Acquisition of scientific understanding involves the discovery of new rules and concepts through direct experience, as well as through instruction. Children’s misconceptions can be overcome through experience that contradicts them. Only recently, however, have researchers directly examined the learning processes involved in the acquisition of scientific concepts. One approach that has proved particularly useful for learning about changing understanding of scientific concepts is the microgenetic method. This approach involves observing changing performance on a trialby-trial basis, usually as children gain experience that promotes rapid change. Thus, the approach yields the type of high-density data needed to understand change processes (Siegler and Crowley 1991).

One example of the usefulness of the approach is provided by Siegler and Chen’s (1998) study of preschoolers’ learning about balance scales. The children were presented problems in which the two sides of the scale had the same amount of weight, but one side’s weight was further from the fulcrum. The goal was to see if children acquired Rule II, which correctly solves such problems, as well as problems on which weight on the two sides varies but distance does not. Children’s rules were assessed in a pretest and posttest in which children were asked to predict which side of the scale would go down or whether it would remain balanced. In the feedback phase between the pretest and post-test, children were repeatedly asked to predict which side of the balance, if either, would go down if a lever that held the arm motionless was released; then the lever was released and the child observed the scale’s movement; and then the child was asked to explain the outcome they had observed. The trial-by-trial analysis of changes in children’s predictions and explanations allowed the examination of the learning processes involved in rule acquisition. Four learning processes were identified. The first component of learning involves noticing potential explanatory variables (e.g., the role of distance) which previously had been ignored. The second step involves formulating a rule that incorporated distance as well as weight. To be classified as formulating a rule, children needed to explain the scale’s action in one trial by stating that a given side went down because its disks were further from the fulcrum, and then in the next trial to predict that the side with its disks further from the fulcrum would go down. The third component involves generalizing the rule to novel problems by using it in most trials after it was formulated. Finally, the last component involves maintaining the new rule under less facilitative circumstances, by using the new rule in the posttest, where no feedback was given.

The componential analysis proved useful for understanding learning in general and also developmental differences in learning. The key variable for learning of both older and younger children, and the largest source of developmental differences in learning, involved the first component, noticing the potential explanatory role of distance from the fulcrum. Most 5year-olds noticed the potential role of distance during learning, whereas most 4-year-olds did not. Children of both ages who noticed the role of distance showed high degrees of learning; those of both ages who did not, did not. The same componential analysis of children’s learning of scientific concepts has proved useful in examining children’s learning about water displacement and seems applicable to many other concepts also.

Although children often discover new rules, modify their mental models, or acquire new concepts through direct experience both in physical and biological domains, direct observation of the natural world is often inadequate for learning new concepts. Indeed, daily experience sometimes hinders children’s understanding. For example, children’s misconceptions about the shape and motion of the Earth might result from the fact that the world looks flat. Well planned instruction is essential for helping children to overcome these misconceptions and to gain more advanced understanding.

The effects of instruction on children’s scientific understanding can be illustrated by a study of the acquisition of the variable control principle (Chen and Klahr 1999). The variable control principle involves manipulating only one variable at a time so that an unconfounded experiment can be conducted and valid inferences can be made about the results. Most early elementary school children do not discover the variable control concept on their own. This observation led Chen and Klahr (1999) to test whether second, third and fourth graders could learn the concept through carefully planned instruction. Children were asked to design experiments to test the possible effects of different variables (whether the diameter of a spring affects how far it stretches, whether the shape of an object affects the speed with which it sinks in water, etc.). An unconfounded design would contrast springs that differed only in diameter but not in length, for example. Providing direct instruction proved to be effective in acquiring the control of variables concept. Both older and younger children who received instruction in designing tests in a specific task were able to understand the rationale and to apply the principle to other tasks. However, the older children were more able to extend the principle to novel contexts. When receiving training in designing tests involving the diameter of a spring, for example, second graders were able to apply the concept only to testing other variables involving springs (e.g., wire size). Third graders used the principle in designing experiments involving other mechanical tasks, such the speed with which objects sank in water. Only fourth graders, however, were able to apply the principle to remote contexts, such as experiments on the causes of plant growth.

In summary, recent research has revealed that infants, toddlers, and preschoolers have considerably greater scientific knowledge than previously recognized. However, their knowledge is far from complete, though. Developmental changes in children’s scientific understanding involve both enrichment and structural reorganization. Older children possess more accurate and coherent rules and mental models. These understandings arise, at least in part, from their richer experience, their more advanced abilities to encode and interpret that experience, and their superior ability to separate their theories from the data (Kuhn et al. 1995). Older children also generalize the lessons from instruction more effectively than do younger children.

Although there is general agreement that early understanding of scientific concepts is surprisingly strong, there are disagreements about exactly what knowledge or concepts to attribute to infants, toddlers, and preschoolers. Even less is known about how children progress from their initial understanding of scientific concepts to more advanced understanding. Addressing the issue of how change occurs remains a major challenge, as well as a fruitful direction for future research.

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