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The Catalyst: The Biological Basis of Thinking and Learning

Excerpts from the article by Dr. Lawrence F. Lowery,
Lawrence Hall of Science
University of California, Berkeley, CA 94720
1990 University of California

Biological Stages and Thinking

Compared to other living organisms, we enter this world empty headed. The human baby is quite helpless and must construct its knowledge of the world for itself.

From a biological perspective, the human baby's lack of prior knowledge has survival value. Humans can reproduce in virtually any environment, and the offspring will learn that environment through observations of and interactions with it. Nature has prepared us to seek patterns in what we see and do, and the patterns we discover enable us to cope with, understand, and appreciate our environment.

Discovery-learning-does not happen all at once but, rather, in stages. We develop a set of thinking capabilities at intervals, and each capability is fairly well established before the next appears. These are the capabilities that allow us to learn how to survive in a wide variety of environments.

The nature of thinking capabilities and the sequence in which they appear have been well established on two research fronts. The biological basis underlying their appearance is established by periodic increases in brain size, brain weight, cellular growth within the brain, electrical functioning with the brain, and head circumference. The psychological basis is established through evidence of the individual's increasing capa-city to deal with independent ideas and to exhibit the same kinds of behaviors as other individuals within two- to three-year ranges and, with growth, the individual's ability to replace naive with more sophisticated views.

Researchers have provided various descriptions of the unfolding of the thinking phenomenon. Here, descriptions of a child's interactions with a set of concrete objects help illustrate seven biologically based stages of cognitive development. The clinical technique described is that of sorting objects.


Stage 1: Accidental Representation -- Inability to Impose Patterns

A child's thinking capability in this first stage of cognitive development is highly sensory and characterized by sensing actions on an object. Once the child has chosen an object-only one at a time at this stage-he or she will look at it and perceive aspects of its color, size, and shape. The child will also touch the object, push, pull, or throw it, and definitely taste it, noting from these actions such information as flavor, texture, firmness, and how an object behaves. The child can be seen deliberately carrying out inquiry processes that contribute to building his or her personal repertoire. Repeated experiences of this kind are fundamental, and the child will call upon them in future stages.

In terms of accidental representation, from birth until about age 3, the child explores objects randomly and indicates no system that suggests an organized, rational plan. The final arrangement of objects might represent something to the child, but only accidentally-and only after the action. For example, if in the process of arranging objects randomly, the arrangement begins to resemble something familiar to the child, the child may name it or provide an explanation for it. The distinctiveness of this stage, however, is that in it, the child does not impose a pattern on objects in advance of an action on them.


Stage 2: Resemblance Sorting -- Pre-Patterning Abilities

This second stage of cognitive development begins to unfold at about age 3. Now when the child thinks about objects and acts on them, she produces pairing on the basis of size, shape, color, or other property. Her rationale for each pairing is derived from the repertoire acquired through previous experiences.

From her pairing actions, the child establishes additional mental constructs about the world and how the objects and events in it are related. All of her thinking is characterized by the ability to match objects in pairs on the basis of one common attribute or to link two events on the basis of one relationship. This continues to be the dominant way by which she thinks and solves problems until about age 6.

Figure 1 -- Example of What Learners Do in Stage 2

After creating a pairing, the child may sometimes consider the pair to be a single entity that will permit another single entity to be placed with it. This chunking ability is important, for later it enables the child to deal with larger and larger quantities of objects (for example, to chunk spaniels and terriers together as dogs, dogs and wolves together as canines, and so on). Chunking, or collapsing quantities into smaller numbers, enables the human brain to deal with greater quantities of objects and events within its environment.


Stage 3: Consistent and Exhaustive Sorting

The next stage of cognitive development begins at about age 6 and is established for most children by age 8.

At this stage, the child organizes in a logical way all the pieces in a set. When grouping, she has a consistent rule for all the objects in the set. She also gives a rule that is consistent for all the groupings. For example, if the child puts all the blue objects together from an array, she will then go on to sort the other colors into groups, then explain that "I've grouped all of these by their colors."

The sorting ability at this stage is characterized by the child's grouping of all objects in a set on the basis of one common attribute. If earlier experiences have been rich, the child will have a broad repertoire of possible properties to draw on, and she will be able to sort objects to the extent of that repertoire. Each sorting will always be on the basis of one property, however, because at this stage, children cannot yet mentally combine more than one property at a time.


Stage 4: Multiple Membership Classifying -- True Patterning Abilities

When children exhibit thinking that indicates they can mentally combine more than one idea at a time, they have entered this stage. For most children, this takes place at about age 8 and continues to be the dominant way they think until about age 10.

At this stage, the child can classify an object into more than one category at the same time or into one category based on two or more simultaneous properties. The child can now understand that an object can be both brown and square at the same time.

Figure 2 -- Example of What Learners Do in Stage 4

Although younger children can produce results that appear to exemplify this stage, the manner by which they get results is quite different: for example, the younger child may first sort objects by their colors, then by a desired state, whereas the older child will cognitively select the correct object by both properties before acting on it.


Stage 5: Inclusive Classifying

Thinking about the relationships among groups of objects and having a superordinate concept of them are indicators of this stage of development, which appears at about age 10. A child engaged in such thinking realizes that if one collection of objects is included in another, then all of the objects in the smaller grouping are but a part or some of the larger, and the converse. There also is recognition that the whole is equal to the sum of its parts and that an example to represent the whole does not exist.

One characteristic of this stage is the emergence of deductive reasoning, which allows students to make logical inferences between the more general and the less general: All women are mortal; all queens are women; therefore, all queens are mortal. Given the opportunity, the student can learn to recognize logical relationships between larger and smaller classes-for example, that while all whales are mammals, not all mammals are whales. It is at this stage that students understand that they live in a particular city and a particular state at the same time and that one is superordinate to the other.


Stage 6: Horizontal Repatterning -- Flexibility in Patterning Abilities

As the next stage unfolds, at about age 13, students become more flexible in their thinking. They can organize and then reorganize a collection of objects or ideas in different ways while realizing that each way is possible at the same time and that the choice for an organization depends on one's purpose. For example, if an individual is given a set of books with the identifying characteristics of size, shape, color, and content, the individual realizes that the books can be organized on the basis of size; shape; color; content; size and shape; size and color; size and content; shape and color; and so on. Given the goal of locating information, the individual selects only content as the organizing attribute because the other attributes are not useful in order to achieve the goal. Given a different goal, such as the determination of the ratio of books with fewer than 100 pages to those with more than 100 pages, the individual reclassifies the books for a different attribute to achieve that goal.


Stage 7: Hierarchical Repatterning

When Stage 7 appears at about age 16, students are able to classify and reclassify objects or ideas into hierarchies of increasingly related or inclusive classes.

It is now that the individual can develop a taxonomy based on a logical rationale concerning the relationships among the objects or ideas comprising the taxonomy while also realizing that the arrangement she has made is tentative and can be changed based on fresh insights. A content expertise is necessary. This cognitive stage exemplifies the highest order of flexible thinking.

Figure 3 -- Example of What Learners Do in Stage 7

Copyright National Academy of Sciences. All rights reserved.