lawson a.e. how do humans acquire knowledge

Science & Education9: 577–598, 2000.© 2000Kluwer Academic Publishers. Printed in the Netherlands.

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How Do Humans Acquire Knowledge? And WhatDoes That Imply About the Nature of Knowledge?

ANTON E. LAWSONDepartment of Biology, Arizona State University, Tempe, AZ 85297-1501, USA

Abstract. This paper offers a resolution to the debate between constructivists and realists regardingthe epistemological status of human knowledge. Evidence in the form of three case studies andone experimental study is presented. The conclusion drawn is that knowledge acquisition involves apattern of idea (representation) generation and test that, when cast in the form of a verbal argument,follows an If/then/Thereforepattern. Self-generated ideas/representations are tested by comparingexpected and observed outcomes. Ideas may be retained or rejected, but can not be proved ordisproved. Therefore, absolute Truth about any and all ideas, including the idea that the externalworld exists, is unattainable. Yet learning at all levels above the sensory-motor requires that oneassume the independent existence of the external world because only then can the behavior of theobjects in that world be used to test subsequent higher-order ideas. In the final analysis, ideas –including scientific hypotheses and theories – stand or fall, not due to social negotiation, but dueto their ability to predict future events. Although the knowledge acquisition process has limitations,its use nevertheless results in increasingly useful representations about an assumed to exist externalworld as evidenced by technological progress that is undeniably based on sound scientific theory.The primary instructional implication is that science instruction should remain committed to helpingstudents understand the crucial role played by hypotheses, predictions and evidence in learning.

Much recent debate has centered on the relative merits of various constructivistpositions of knowledge acquisition and epistemology. For example, Staver (1998)in staking out an extreme version of constructivism for science education wrote:“For constructivists, observations, objects, events, data, laws, and theory do notexist independent of observers. The lawful and certain nature of natural phenom-ena are properties of us, those who describe, not of nature, what is described.. . . constructivists begin this work without first assuming an independent reality”(p. 503). And Driver et al. (1994) emphasized the social aspect of constructivismwhen they stated: “. . . scientific knowledge is symbolic in nature and socially nego-tiated. The objects of science are not the phenomena of nature but constructs thatare advanced by the scientific community to interpret nature” (p. 5). And lastly,Fosnot (1996) described a theory of constructivism that “. . . describes knowledgeas temporary, developmental, nonobjective, internally constructed, and socially andculturally mediated” (p. ix).

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Realism stands in contrast to these constructivist views. Hwang (1996) defines arealist as one who believes that: “. . . .the world exists and is organized independentof us, our language, and our methods of inquiry” (p. 345). Realist critics of con-structivism, such as Matthews (1995), have argued: “For all its faults, the scientifictradition has prompted rationality, critical thinking and objectivity. It instills a con-cern for evidence, and for having ideas judged not by personal or social interest,but by how the world is” (p. 2.). In a similar vein, Osborne (1996) concluded: “This[constructivism] has led to the portrayal of science as a process of constructing andmanipulating representations which bear no necessary relation to any ontologicalreality. In so doing constructivists have forgotten that it is the world that imposesconstraints on human thought, and not human thought that imposes constraints onthe world” (pp. 76–77). More recently, Matthews (1998) summarized several keydifferences between realist and constructivist beliefs as follows:

Realists believe that science aims to tell us about reality, not about our exper-iences; that is knowledge claims are evaluated by reference to the world, notby reference to their personal, social, or national utility; that scientific meth-odology is normative, and consequently distinctions can be made betweengood and bad science; that science is objective in the sense of being differentfrom personal, inner experience; that science tries to identify and minimizethe impact of noncognitive interests (political, religious, gender, class) in itsdevelopment; that decision making in science has a central cognitive elementand is not reducible to mere sociological considerations, and so on. (p. 166)

1. Knowledge Acquisition and the Nature of Knowledge

The purpose of the present paper is to offer a theoretical resolution to the debatebetween these sorts of constructivist and realist positions. To do so, we will focuson the knowledge acquisition process in selected cases and then step back andidentify common elements including the roles played by the learner and the envir-onment. The present position is that focusing on knowledge acquisition in terms ofits underlying pattern will help resolve the debate. In other words, understandinghow humans acquire knowledge will inform us about the nature of the knowledgeacquired.

We start with a look at knowledge acquisition in a personal setting. We willthen explore learning on progressively more and less advanced levels including ascientist working at the cutting edge of human knowledge acquisition and childrenlearning that hidden objects, although no longer in sight, continue to exist. We willend with a discussion of the nature of knowledge so acquired and the extent towhich it can be said to be “constructed”.

HOW DO HUMANS ACQUIRE KNOWLEDGE? 579

2. How Do People Learn? A Case of Practical Learning

Let us start in a setting in which introspection was used to identify key steps thatled to learning. Of course introspective analysis is difficult because thinking takesplace very rapidly and at least partially on a subconscious level. Also prior con-ceptions about learning may distort the process. Nevertheless, one might correctlyidentify steps in learning, particularly if consciously trying to do so and, as in thiscase, one is trying to identify the steps immediately after the fact when memoryis not clouded by intervening experiences. Further, independent methods that donot suffer from these potential pitfalls exist to test the validity of introspectively“discovered” patterns. Consequently, the following example is offered for yourconsideration.

Before I arrived home one evening, my wife had lit the gas barbecue and putsome meat on for dinner. Upon arriving, she asked me to check the meat. Whendoing so, I noticed that the barbecue was no longer lit. It was windy so I suspectedthat the wind had blown out the flames – as it had a few times before. So I triedto relight the barbecue by striking a match and inserting its flame into a small“lighting” hole just above one of the unlit burners. But the barbecue did not relight.I tried a second, and then a third match. But it still did not relight. At this point, Isuspected that the tank might be out of gas. So I lifted the tank and sure enoughit lifted easily – as though it were empty. I then checked the lever-like gas gaugeand it was pointed at empty. So it seemed that the barbecue was no longer lit, notbecause the wind had blown out its flames, but because its tank was out of gas.

2.1. THE RECONSTRUCTED PATTERN

What pattern of thinking was guiding this learning? Retrospectively, it would seemthat thinking was initiated by a causal question, i.e., Why was the barbecue nolonger lit? In response to this question, the reconstructed thinking goes like this:If . . . the wind had blown out the flames (windhypothesis),and . . . a match is used to relight the barbecue (test condition)then. . . the barbecue should relight (expected result).But. . . when the first match wastried, the barbecue did not relight (observed result).Therefore. . . either the windhypothesis is wrong or something is wrong with thetest. Perhaps the match flame went out before it could ignite the escaping gas. Thisseems plausible as the wind had blown out several matches in the past. So retainthe wind hypothesis and try again (conclusion).

Thus,If . . . the wind had blown out the flames (windhypothesis),and . . . asecond match is used to relight the barbecue (test condition)then. . . the barbecue should relight (expected result).But . . . when thesecond match was used, the barbecue still did not relight (observedresult).

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Therefore. . . once again, either the wind hypothesis is wrong or something is wrongwith the test (conclusion). Although it appeared as though the inserted match flamereached the unlit burner, perhaps it nevertheless did get blown out. So again retainthe wind hypothesis and repeat the experiment. But this time closely watch thematch flame to see if it does in fact reach its destination.

Thus,If . . . the wind had blown out the flames (windhypothesis)and . . . a third match is used to relight the barbecue while closely watching theflame (test condition)then. . . the flame should reach its destination and barbecue should relight (expectedresult).But . . . when the third match was used while closely watching the flame, the flameappeared to reach its destination, but the barbecue still did not relight (observedresult).Therefore. . . apparently there was nothing wrong with the test. Instead the windhypothesis is probably wrong and another hypothesis is needed (conclusion).

Perhaps the tank was out of gas. Thus,If . . . the tank is out of gas (empty-tankhypothesis),and . . . the tank islifted (test condition)then. . . it should feel light and should lift easily (expected result).And. . . when the tank waslifted, it did feel light and did lift easily (observed result).Therefore. . . the empty tankhypothesis is supported (conclusion).

Further,If . . . the tank is out of gas (empty-tankhypothesis),and . . . the gas gauge is checked (test condition)then. . . it should be pointed at empty (expected result).And. . . it was pointed at empty (observed result).Therefore. . . the empty-tankhypothesis is supported once again (conclusion).

2.2. THE ELEMENTS OF KNOWLEDGE ACQUISITION

The introspective analysis suggests that knowledge acquisition involves the gen-eration and test of ideas and takes the form of severalIf/and/Thereforeargumentsreminiscent of the hypothetico-deductive pattern previously identified by others(e.g., Chamberlain 1965; Cohen and Nagel 1934; Hempel 1966; Lawson 1995;Lewis 1988; Medawar 1969; Platt 1964; Popper 1959, 1965). Notice that the attain-ment of evidence contradicting the initial wind hypothesis did not immediately leadto its rejection. This is because the failure of expected results to match observedresults can arise from one of two sources – a faulty hypothesis or a faulty test.Consequently, before a plausible hypothesis is rejected, one has to be reasonablysure that its test is not faulty.

In short, this knowledge acquisition seems to have involved the followingelements:


1. Making an initial observation: The barbecue is no longer lit.2. Raising a causal question: Why is the barbecue no longer lit?3. Generating an initial possible cause (a hypothesis): In this case the initial hy-

pothesis was that the barbecue was no longer lit because the wind had blownout its flames. The process of hypothesis generation is seen as one involvinganalogies, analogical transfer, analogical reasoning, i.e., borrowing ideas thathave been found to “work” in one or more past related contexts and usingthem as possible solutions/hypotheses in the present context (cf. Biela 1993;Bruner 1962; Dreistad 1968; Finke et al. 1992; Gentner 1989; Hestenes 1992;Hoffman 1980; Hofstadter 1981; Holland et al. 1986; Johnson 1987; Koestler1964; Wong 1993). Presumably the wind hypothesis was based on one or moreprevious experiences in which the wind had blown out flames of one sort or an-other including the barbecue’s flames. Presumably the empty-tank hypothesiswas similarly generated. In other words, a similar experience was recalled (e.g.,a car’s gas empty tank led to a failure of its engine to start) and used this as thesource of the empty-tank hypothesis used in the present context.

4. Assuming that the hypothesis under consideration is correct: This assumptionis necessary so that the hypothesis can be tested and perhaps be found incorrect.A test requires imagining relevant condition(s) that along with the assumedhypothesis allows the generation of an expected result (a prediction).

5. Carrying out the imagined test: The imagined test must be carried out so thatits expected result (the prediction) can be compared with the observed resultof the actual test.

6. Comparing expected and observed results: This comparison allows one to drawa conclusion. A good match means that the hypothesis is supported, but notproven. While a poor match means that something is wrong with the hypo-thesis, the test, or with both. In the case of a good match, the hypothesis hasnot been “proven” correct with certainty because one or more unstated and per-haps un-imagined alternative hypotheses may give rise to the same predictionunder this test condition (e.g., Hempel 1966; Salmon 1995). Similarly, a poormatch cannot “disprove” or falsify a hypothesis in any ultimate sense. A poormatch cannot be said to falsify with certainty because the failure to achieve agood match may be the fault of the test condition(s) rather than the fault of thehypothesis (e.g., Hempel 1966; Salmon 1995).

7. Recycling the procedure: The procedure must be recycled until a hypothesis isgenerated, which when tested, is supported on one or more occasions. In thepresent example, the initial conclusion was that the test of the wind hypothesiswas faulty. Yet on repeated attempts and a closer inspection of the test, thewind hypothesis was rejected, which allowed the generation, test, and supportof the empty-tank hypothesis.

In this case at least, learning required feedback from the external world (albeitfiltered through sense receptors). In other words, the learning was accomplishedalone and the fact that the barbecue would not relight, in spite of repeated at-

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tempts, was the key sensory evidence that eventually led to rejection of the windhypothesis. And only after the wind hypothesis was rejected, was the alternativeempty-tank hypothesis generated and tested.

3. How Do Scientists Acquire Knowledge?

If the above knowledge acquisition pattern is basic, then we should find it else-where. For example, we should find it in the work of scientists. Let us examine aresearch paper of a currently active scientist to see if the pattern can be identified.Admittedly many scientific papers are not written in a way that reveals the thinkingpatterns the author(s) may have employed (e.g., Medawar 1990). But several recentpapers inBehavioral Ecology and Sociobiologyreveal thinking that appears veryclose to the identified pattern (e.g., Alcock 1996; Lambin 1997; Muehter et al.1997). Let us consider the Alcock paper entitled “Provisional rejection of three al-ternative hypotheses on the maintenance of a size dichotomy in males of Dawson’sburrowing bee,Amegilla dawsoni”.

3.1. ALCOCK’ S CAUSAL QUESTION

Alcock’s paper suggests that his key causal question is: Why do (i.e., what causes)male Dawson’s bees to exist in two distinctly different size groups? Althoughthis question is not explicitly stated, the introduction does state: “The presence ofboth major and minor males in Dawson’s burrowing bees is a special evolutionarypuzzle . . . ” (p.182) This wording seems to adequately covey the key issue, i.e., thekey causal question.

3.2. GENERATING ALTERNATIVE HYPOTHESES

Here Alcock is very explicit. Not only does the paper’s title mention alternativehypotheses, but so does its introduction. In Alcock’s words:

. . . it is possible that females produce minor sons as part of an adaptive strategyof selectively allocating brood provisions among male offspring.

There are, however, other possible explanations . . .1. The first hypothesis argues that minor males. . . are the incidental

byproduct of external environmental factors . . .2. The second hypothesis states that females possess a conditional brood

allocation strategy that enables competitively disadvantaged individuals(i.e., low body weight or congenitally impaired females) to salvage somereproductive success by producing low-cost, low-payoff sons . . .

3. The third hypothesis is that females divide the resources they have avail-able for making sons in such a way that they receive the same fitnesspayoff for a unit of brood provisions whether they invest it in a minor ora major son. (p. 182)


Based on these statements, it seems clear that Alcock has generated hypothesesthat he wishes to test. According to the proposed learning process, these hypothesescame from Alcock’s, and others’, prior experiences. Once Alcock has generatedseveral hypotheses, does he plan tests that result in expected/predicted outcomes?

3.3. GENERATING PREDICTIONS

Alcock is very explicit about stating predictions. Again in his words:

The three hypotheses yield different predictions that I shall examine in light ofevidence collected from observations of Dawson’s burrowing bees over threeflight seasons. (p. 182)

A prediction based on this hypothesis (hypothesis 1) is that there shouldbe substantial geographic and temporal variation in the size distribution ofboth males and females . . . Thehypothesis that small females or congenitallyhandicapped foragers salvage fitness by producing small sons that require lessbrood provision leads to the prediction that smaller or weaker females shouldspecialize in the production of minors. . . The thirdhypothesis is that minormales enjoy sufficient mating success. . . Here the key prediction is that thefitness benefit to fitness cost ratios (B/C) for the two types of males should onaverage be equal. (pp. 183–184)

These statements indicate that Alcock is using hypotheses and planned tests togenerate predictions. Presumably the next step is to compare predicted results withobserved results. Once again Alcock is explicit. The following remarks regardinghypothesis 1 should suffice to substantiate this point:

A prediction based on this hypothesis is that there should be substantialgeographic and temporal variation in the size distribution of both males andfemales . . . This prediction is not inaccord with the observations. First, no onehas ever observed a size dichotomy among females in any population studiedto date (female head-widths are normally distributed with 90% falling in the6.8–7.2 mm range, based on a sample of 81 specimens – see Fig. 6 in Houston1991). Yet a pronounced male size dichotomy appeared in all 13 populationsI examined in 1993, 1994, and 1995 as well as in those examined by Houston(1991). (p. 183)

3.4. DRAWING CONCLUSIONS BASED ON THE DEGREE OF MATCH

Presumably the final step is to draw a conclusion about the extent to which eachhypothesis was supported, or not-supported, based on the degree of match betweenexpected and observed results. Although on this point Alcock is less explicit, thefollowing remarks seem to indicate that this is how he arrived at his conclusions:

This hypothesis (hypothesis 1) is not supported by the finding that males ofintermediate sizes are consistently rare . . . asecond possibility (hypothesis 2)

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is that minors represent ‘the best of a bad job’ response of those females thatare small or otherwise disadvantaged. However, presumptive male siblingssometimes include both majors and minors, a result not predicted from thishypothesis (p. 181)

And after briefly stating the third hypothesis and summarizing its predicted res-ults (i.e., reproductive benefits/costs from major and minor sons should be equal)and observed results (i.e., the net gain to females from producing a minor son isunlikely to equal that derived from a major son), Alcock concludes: “Therefore thethird hypothesis must also be tentatively rejected. . . ” (p. 181)

3.5. A SUMMARY ARGUMENT FOR TESTING ALCOCK’ S FIRST HYPOTHESIS

In summary, the following If/then/Therefore argument can be constructed tosummarize the fate of Alcock’s first hypothesis:If . . . the male size dichotomy in male Dawson’s burrowing bees is caused byexternal environmental factors (environmental factors hypothesis)and. . . the sizes of both male and female bees are sampled frompopulations over awide geographic and temporal range with a wide range of climatic/environmentalconditions (test conditions)then. . . both male and female sizes should vary from geographic location to anotherand from season to season (expected result).But . . . male and females sizes are very consistent from one geographic location toanother and from season to season (observed result).Therefore. . . the environmental factorshypothesis is not supported (conclusion).

3.6. WHAT DOES ALCOCK THINK ABOUT HIS THINKING?

Thus, it seems safe to conclude that on the surface at least, Alcock is usingIf/then/Thereforethinking to guide and report his research. But what does Alcockthink about his thinking? The following remarks made by Alcock in an interviewsuggest that he was well aware of the thinking pattern and was very consciouslytrying to use it to guide his research. Alcock’s remarks appear in italics.

How do you do science? In other words, do you have a general plan of attack,a general set of strategies, a general method, that you use from one study to thenext?Yes, in terms of selection of topics I am committed to studies of insect matingbehavior. The basic technique is the standard one. I am using evolutionary theoryto come up with questions. Once I have questions, I am developing hypothesesthat are consistent with selection theory and testing them the old-fashioned way.What is the old-fashioned way?By using them to generate predictions for whichit is possible to collect data so that we can examine the validity of the predictions.Once you have data, how do you examine their validity?Well, by matching theexpected results against the actual ones.How do you draw conclusions from that?


Or do you?Yes, in my case the conclusions are invariably in the form of the datathat support or invalidate the particular hypothesis.

How generalizable is this technique of generating and testing hypotheses? Forexample, is it limited to your field of research?I believe it is fundamental to allscience. It is the essence of what is called the scientific method.The scientificmethod? Is there only one?I think, well, there is descriptive science, which isthe foundation for asking causal questions. And the kind of science which has thegreatest significance for everybody – the causal question answering science forwhich this hypothesis-testing technique is, I believe, fundamental. I have never seenany study, never had anyone explain to me how any study did not use this particularapproach, even if they claimed that there are multiple scientific approaches.Doesthe scientific method, this thinking process actually guide your research?Very selfconsciously, yes.

Thus, Alcock claims to self consciously employ theIf/then/Thereforepattern ofhypothesis testing in his work. But Alcock is only a single scientist. What aboutother scientists? Do they also try to use a process in which hypotheses lead topredictions, which then are compared with subsequent observations so that conclu-sions can be drawn? To find out, the following two questions were submitted to 31other scientists who are members of a biology department at a large university inthe United States. The number of biologists selecting each answer choice is shownin parentheses.1. Testing biological explanations

(a) always involves the generation of an expectation. (22)(b) often involves the generation of an expectation, but sometimes involves

only making observations. (4)(c) involves the generation of an expectation about half the time and only

making observations about half the time. (2)(d) often involves only making observations, but sometimes involves the

generation of an expectation. (2)(e) always involves only making observations. (1)

2. To arrive at a biological conclusion one must(a) always make observations. (0)(b) often make observations, but sometimes compare expectations with obser-

vations. (1)(c) about half of the time make observations and about half of the time

compare expectations with observations. (5)(d) often compare expectations with observations, but sometimes make obser-

vations. (5)(e) always compare expectations with observations. (20)

Based on the present view of the leaning process, the correct answer choices are(a) for item 1 and (e) for item 2 – choices selected by 22 and 20 biologists respect-ively. As these numbers represent 71% and 65% respectively, we can conclude thatthe majority of these biologists agree with Alcock that this is the way science is

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done. But what about the others? Do they think science is done some other way?Or do they in fact use theIf/then/Thereforeprocess without being aware of whatthey are doing? The following additional remarks made by Alcock support thislatter view.

How did you come to use this method?At this stage, I can not recreate the stepsthat led to my current firm views. But it did have something to do with thinkingthrough teaching biology to undergraduates.How about when you were a graduatestudent at Harvard? Did you use the method then?I was definitely unaware of whatI was doing, just following through. Well, the scientific method is common sense,logic I’d say, and not that obscure. But I wasn’t self conscious. It was intuitiveand intuitive throughout much of my early career. I only became aware of it in thepast 10 to 15 years, perhaps in conjunction with teaching undergraduates. I do notknow.

4. Does Sensory-Motor Learning Employ the Same Pattern?

The previous examples suggest that knowledge acquisition, whether in a familiarsetting or at the level of modern science employs a pattern ofIf/then/Thereforethinking. Let us now return to pre-verbal, sensory-motor learning and ask how chil-dren initially learn about their world. Are the objects in that world simply “seen”,or does their perception require an active use of the process? Van Senden (in Hebb1949) reported observations of congenitally blind adults who had gained sight fol-lowing surgery. Initially these newly-sighted persons could not distinguish a keyfrom a book when both lay on a table in front of them. Also they were unable toreport seeing any difference between a square and a circle. Only after considerableexperience with the objects including touching and holding them, were the newly-sighted persons able to “see” the obvious (to others) differences. Observations suchas these strongly suggest that visual experience alone is insufficient for learning.

4.1. LEARNING THAT OBJECTS ARE PERMANENT

How then do children learn about the objects in their world? Consider Piaget’sclassic object permanence task in which children eventually learn that commonobjects continue to exist even when out of sight. During the task, an experimenter– in full view of the infant – hides a ball under one of two covers. Diamond (1990)found that infants of five months, but not younger, will reach under the cover forthe hidden ball indicating that they retain a mental representation of the ball eventhough it is out of sight. Such behavior suggests that the infant has learned thatobjects are permanent more or less in the following way:If . . . the ball no longer exists when it is no longer visibleand . . . I reach under the cover where it was last seen (test condition)then. . . I should not find the ball (expected result).But . . . I do find the ball (observed result).


Therefore. . . apparently I was wrong. Perhaps the ball, and other similar objects,continue to exist even when not directly visible (conclusion).

Conversely,If . . . the ball continues to exist even through it is no longer visibleand . . . I reach under the cover where it was last seen (test condition)then. . . I should find the ball (expected result).And. . . I do find the ball (observed result).Therefore. . . it seems that the ball, and other similar objects continue to exist evenwhen not directly visible (conclusion).

Of course the claim here is not that infants are using verbally-mediated argu-ments of this sort. The claim is merely that they propose representations abouthow the world might work and that these are tested by using them as the basis forthe generation of an expectation. Then a comparison of this expectation with whatactually happens allows the infant to either reject or retain their initial represent-ations. Importantly, one of the first conclusions drawn by use of this “method” isthat the world consists of permanent objects. This conclusion is not only crucialfor successful behavior in their sensory-motor world, but it is also crucial for sub-sequent intellectual development because the behavior of those permanent objectscan then used to test subsequent higher-order representations. This point will bereturned to later.

4.2. LEARNING THAT BOTTLES HAVE TWO DIFFERENT ENDS

Another example of learning about the objects in the infant’s sensory-motor worldwas reported by Piaget while making observations of his son Laurent (from sevento nine months of age). Piaget (1954) reports:

From 0:7 (0) until 0:9 (4) Laurent is subjected to a series of tests, either beforethe meal or at any other time, to see if he can turn the bottle over and find thenipple when he does not see it. The experiment yields absolutely constantresults; if Laurent sees the nipple he brings it to his mouth, but if he does notsee it he makes no attempt to turn the bottle over. The object, therefore, hasno reverse side or, to put it differently, it is not three dimensional. Neverthe-less Laurent expects to see the nipple appear and evidently in this hope heassiduously sucks the wrong end of the bottle. (p. 31)

Laurent’s initial behavior consisted of lifting and sucking whether the nipplewas oriented properly or not. Apparently Laurent does not notice the differencesbetween the bottom of the bottle and the top and/or he does not know how tomodify his behavior to account for the presentation of the bottom. Thanks to hisfather, Laurent has a problem.

Let us return to Piaget’s experiment. On the sixth day of the experiment whenthe bottom of the bottle was given to Laurent, “. . . he looks at it, sucks it (hence triesto suck glass!), rejects it, examines it again, sucks it again, etc., four or five times

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in succession” (p. 127). Piaget then held the bottle out in front of Laurent to allowhim to simultaneously look at both ends. Although his gaze oscillated between thebottle top and bottom, when the bottom was again presented to Laurent he stilltried to suck the wrong end.

The bottom of the bottle was given to Laurent on the eleventh, seventeenth, andtwenty-first days of the experiment. Each time Laurent simply lifted and begansucking the wrong end. But by the thirtieth day he, “. . . no longer tries to suck theglass as before, but pushes the bottle away, crying” (p. 128). Interestingly, when thebottle was moved a little farther away, “. . . he looks at both ends very attentivelyand stops crying” (p. 128).

Finally two months and ten days after the start of the experiment, when thebottom of the bottle was given to Laurent he was successful in first flipping it over,“. . . he immediately displaces the wrong end with a quick stroke of the hand, whilelooking beforehandin the direction of the nipple. He therefore obviously knowsthat the extremity he seeks is at the reverse end of the object” (pp. 163–164).

Laurent’s learning behavior, although relatively simple, follows a pattern thatconsists of an initially successful behavior driven in part by a response to anexternal stimulus and in part by hunger. The initially successful behavior is con-tradicted when it is misapplied beyond the situation in which it was acquired. Thisleads to frustration (reminiscent of Piaget’s concept of disequilibrium) and to aneventual shutting down of incorrect behavior so that he can attend more closely tothe external stimulus that initially provoked the behavior. Attention, once aroused,allows the child to notice previously ignored cues and/or relationships among thecues, which in turn allows him to couple those cues with modified behavior to dealsuccessfully with the new situation. Hence, a new procedure has been actively ac-quired as has a more differentiated and useful representation of his external world,i.e.:If . . . the bottle consists of an object with but a single end or perhaps one with twoidentical ends (initial undifferentiated representation)and . . . I lift and suck whenever the bottle is visible (test condition)then. . . I should get a drink of milk (expected result)But . . . on several occasions, I do not get a drink of milk (observed result).Therefore . . . either there is something wrong with my initial undifferentiatedrepresentation or with my test (conclusion).

Notice that like the case of the unlit barbecue where it took three unsuccessfultries to relight the barbecue before the wind hypothesis was rejected, it took severalunsuccessful attempts by Laurent to get milk from his bottle before he modified hisbehavior and differentiated his initial representation of the bottle into one with twodifferent ends:If . . . the bottle consists of an object with a nipple present on only one of twodifferent ends (differentiated representation)and . . . I lift and suck on the bottle when the nipple is visible (test condition)then. . . I should get a drink of milk (expected result).


Further,If . . . the bottle consists of an object with a nipple present on only one of twodifferent ends (differentiated representation)and . . . I flip the bottle over when the nipple is not visible (test condition)then. . . I should get a drink of milk (expected result).

5. Can Use of the Learning Pattern Be Demonstrated Experimentally?

As evidence that knowledge acquisition employs active use of anIf/then/Thereforepattern of thinking, the previous examples all suffer from the same shortcoming.Each consists of after-the-fact reconstructions of prior learning. Thus, the iden-tified pattern may exist only in the mind of the reconstructor - not in the mindsof the learners. Can evidence of the pattern’s use be experimentally demonstratedindependently? Lawson (1993) used several tasks involving descriptive conceptacquisition that attempted to do so. One of the tasks appears in Figure 1. As shown,the top row contains several Mellinarks (Elementary Science Study 1974). None ofthe creatures in the second row are Mellinarks. The task is to figure out whichcreatures in the third row are Mellinarks.

Previously Lawson et al. (1991) found that substantial percentages of childrenfail to solve Mellinark-type tasks when administered without prior instruction.To find out if these failures were due to developmental deficiencies or to easilyresolved confusion regarding task objectives, the Lawson (1993) study employedbrief one-on-one training that amounted to showing children a similar task andthen verbally describing how theIf/then/Thereforepattern could be used to solvethe task. If children learn in this way, then the brief verbal training should enablethem to successfully employ the pattern to solve the tasks. On the other hand, ifthey do not normally learn this way, then the training should be confusing and theyshould not be successful.

For example, suppose one glances at the Mellinarks in the first row and sees thatthey all contain one large dot. Could one large dot be the key feature of Mellinarks?This idea can be tested as follows:If . . . Mellinarks are creatures with one large dot (proposed key feature),and . . . we look at thenon-Mellinarks in row two (test condition),then. . . none of them should contain a large dot (expected result).But . . . when we actually look at row two, we see that creatures one, two, and fourin row two each contain a large dot (observed result).Therefore. . . Mellinarks are not creatures defined solely by the presence of onelarge dot. So we need to generate and test another idea (conclusion).

Interestingly none of the 30 six-year-olds were successful as evidenced by theircomplete failure to solve any transfer tasks. However, 15 of the 30 seven-year-oldssolved the transfer tasks as did virtually all of the eight-year-olds (29 of 30), andall of the 9 through 16-year-olds. Thus, the results provide experimental evidencethat theIf/then/Thereforepattern can easily be assimilated and used by children

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Figure 1. Which of the creatures in row three are Mellinarks? What reasoning did you use tofind out?

ages 8 and older to learn in this context. Therefore, we have experimental evidencethat supports the hypothesis that knowledge acquisition involves active use of theIf/then/Thereforepattern, at least among children eight years and older.

6. Does the External World Really Exist?

Having identified a thinking pattern that appears to underlie knowledge acquisitionat different ages and different levels of intellectual development (cf. Levine 1975),


two key points about the nature of the knowledge acquired can be made. First, itshould be emphasized that this view regards learning as a hypothesis generationand testing enterprise where the term hypothesis is defined in its broadest sense,i.e., any statement under test, no matter whether it purports to describe some par-ticular fact or event or to express a general law or some other more complex causalproposition. Importantly, in order to test any and all such hypotheses, each hypo-thesis must first be assumed to be true. This may seem backwards. But accordingto our examples, this is the way learning occurs. Importantly, hypotheses includeentities such as ghosts, photons, vital forces and phlogiston. This means that wehave to assume that these entities exist so that test conditions can be imagined andpredictions can be drawn. In the end we may decide that the entities do not exist.But to arrive at thisconclusion, we first had toassumethat they do exist.

To emphasize this point, briefly consider the Needham–Spallanzani controversyover the concept of the vital force. As you may recall, during the 1700s, JohnNeedham, among others, believed that living things possessed a special vital force.Further, when this force entered dead material it would spontaneously give it life.But Lazzaro Spallanzani thought otherwise. So to test Needham’s vital force idea,Spallanzani reasoned something like this:If . . . the vital force exists and acts onnonliving matter to bring it to life (vital forcehypothesis),and . . . some bottles are heated for a few minutes and others for an hour, and someare corked and others sealed with a flame (Spallanzani’s planned test),then . . . after several days, microbes should be found in all the bottles (expectedresult). All bottles should contain microbes because the vital force should actregardless of length of bottle heating or method of sealing (theoretical rationale).But . . . days later after conducting his experiment, all of the corked bottles werefull of microbes. The sealed bottles boiled only a short time were also teamingwith microbes. However, no microbes were in the bottles boiled for an hour andthen sealed (observed results).Therefore . . . Spallanzani concluded that Needham’s vital force does not exist(conclusion).

Thus the key point is that entities such as the vital force, epicycles, heavy water,and N rays must be assumed to exist in order to test their existence and to possiblyconclude that they do not exist after all. Awareness of this aspect of the knowledgeacquisition process is extremely important because it allows us to set aside thedebate about the existence or non-existence of the external world. In short, thedebate is not settled by concluding that the external world exists independent ofan observer (the realist position). Rather the debate is set aside by the realizationthat to learn at higher levels, the learner mustassumethe external world’s inde-pendent existence, regardless of whether it actually exists or not. Thus, contrary tothe constructivist position advanced by Staver (1998) in which “. . . constructivistsbegin this work without first assuming an independent reality” (p. 503) to learn athigher levels onemustbegin by assuming that the external world exists (and that

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it is knowable). In fact this proposition and its alternative (i.e., the external worlddoes not exist – unless it is in direct view) has already been generated and testedby every single child during their sensory-motor stage of development. Thus as ascientist, if you fail to make the initial assumption that the external world existsyou get nowhere. Worse yet, if you refuse to assume the independent existenceof the external world in spite of your sensory-motor knowledge that is telling youotherwise, you could suffer some rather unfortunate consequences. Suppose, forexample, you find yourself in the middle of a freeway staring down an oncom-ing car and fail to make the assumption. If you do, you will likely end up dead.Clearly it pays to make the assumption that the oncoming car exists, even thoughthe present analysis reveals why we can not be certain that it does.

But where does a scientist arrive if s/he starts with the assumption that theexternal world exists and is knowable? The answer turns out to be somewhere shortof absolute Truth (for the reasons stated above), but certainly closer to developingworkable mental representations of that assumed-to-exist external world than socialconstructivists would have us believe. This is because, in addition to our ability toargue the merits and demerits of our various representations with others, we haveour assumed-to-exist external world against which we can test our representations,i.e., our hypotheses and theories. Thus, the issue amounts to one of whether or notscience makes progress. The answer is that it does, but that progress is by no meanswithout fits and starts and some backtracking. Convincing evidence for scientificprogress surrounds us everywhere from computers that run on electrons, to carsand airplanes that run on exploding fossil fuels, to doctors that save lives each daywith prescriptions of antibiotics, not to mention satellites that orbit the earth, andspace ships that have gone to the moon and back. To deny that these technologicaladvances rest on sound scientific theory is simply nonsense.

An additional point should be made. It makes sense to refer to the initial mentalrepresentations as constructions in the sense that they are not directly “given” in thecontext of current learning experiences. Instead, mental representations are eitherculled from past experiences stored in long-term memory or are “constructed”from sensory input. For example, neurological research reviewed by Mishkin andAppenzeller (1987) makes it clear, at least with respect to vision, that complexmental representations do not arise from direct sensory input. Rather, as shownin Figure 2, visual sensory input is processed along two separate pathways andthat processing results in progressively more complex mental “constructions”. Asshown, initial processing of visual input, which arrives from the retina by way ofthe lateral geniculate body, takes place in the striate cortex. Individual neuronsin the striate cortex respond to simple elements in the visual field such as spotsof color and edges. Visual processing continues along the lower pathway, whichextends down toward the inferior temporal cortex. Along the way, a number ofdiverging and converging channels “construct” broader properties of objects, suchas overall shape and color. At the lower end of the pathway neurons are sensitive toa variety of properties and a broad expanse of the visual field, which suggests that


Figure 2. Neutral pathways used to process visual input and “construct” the visual world (afterMishkin and Appenzeller 1987).

fully processed information about objects converge there. Also as shown in Figure2, spatial relationships among two or more objects are processed along an uppercortical pathway.

7. A Further Thought About the Primacy of Physical Feedback

Several years ago following administration of the task shown in Figure 3, two boyswere overheard arguing. The argument went something like this. First boy: I thinkthe water will rise higher when the steel marble sinks because it is heavier than theglass one. Second boy: No, you are wrong! They will push the water up the sameamount because both marbles are the same size. Weight does not matter. First boy:Yes, weight matters. My brother is a lot heavier than I am and when he gets in thebath tub the water goes up a lot higher than when I get in!

How can this dispute be settled? How do these boys, or anyone for that matter,learn which variable, weight or volume, is key? It would seem that no amount ofsocial negotiation will do. Rather what needs to be done is to perform two simpleexperiments more or less as follows:If . . . the amount of water rise depends on an object’s weight (weight hypothesis)and . . . two objects of different weight, but equal volume, are submerged in water(test conditions)then. . . the heavier object should produce more water rise (expected result).But . . . the heavier object does not produce more water rise (observed result).Therefore. . . the weighthypothesis is not supported (conclusion).

On the other hand,If . . . the amount of water rise depends on an object’s volume (volume hypothesis)

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Figure 3. The displacement volume task.

and . . . two objects of different volume, but equal weight, are submerged in water(test conditions)then. . . the larger object should produce more water rise (expected result).And. . . the larger object does produce more water rise (observed result).Therefore. . . the volumehypothesis is supported (conclusion).

Thus, the present view is that physical feedback (i.e., the water rises the same inthe first experiment and higher in the second) is the primary vehicle for resolvingdisputes about alternative knowledge claims. The primacy of physical feedback inknowledge acquisition is at odds with social constructivism in which, accordingto Latour and Woolgar (1979, 1986), success depends on a theory’s proponentsability to ‘extract compliance’ from others (cf. Slezak 1994a, 1994b). This is not tosay that social interaction may not be helpful. But it can not be the central meansof knowledge acquisition. In fact, as Gardner (1994) points out, the acquisition ofnew knowledge is typically associated with distinctly asocial behavior. Based ondetailed case studies of seven highly creative people, Gardner concludes, “. . . at thetime of greatest breakthrough, our creators were in one sense very much alone.Often they had physically withdrawn from other individuals” (p. 154). And inreviewing several decades of research on the nature and measurement of creativity,Eysenck (1994) makes much the same point when he lists several characteristicsassociated with creative people such as quarrelsomeness, asocialability and evenoutright hostility. As mentioned, this is not to argue that social interaction can notbe helpful. It can be helpful in many ways (e.g., in sharing and clarifying prob-lems, in suggesting alternative hypotheses, in suggesting possible test conditions,in criticizing conducted tests, in collecting and analyzing results). But in the end,feedback from the physical world is the ultimate arbitrator of which knowledgeclaims are accepted or rejected.


8. The Existence of Stages of Intellectual Development

Before turning to instructional implications, a word about stages of intellectualdevelopment seems in order. In short, the present view of learning implies theexistence of stages – although not necessarily discontinuous stages. Initially sensedcolors, lines, and angles and the child’s ability to create “undifferentiated wholes”provide the mental representations that are either rejected or retained by virtueof their ability to produce expectations that are either met or unmet in a worldof sensory-motor feedback (e.g., lifting the cover either does or does not revealthe ball, sucking on the bottle either does or does not produce milk). Once suchsensory-motor representation testing has created a stable world of interacting ob-jects, these objects and their characteristics and behaviors can then be used to testthe validity of mental representations at higher stages. In other words, intellectualdevelopment is a process in which the products of one stage must be largely inplace before progress can be made on subsequent stages because prior construc-tions are used to test subsequent higher-order representations. For example, Daltoncompared predicted and observed outcomes regarding the measurable weights ofgases to test the hypothesis that nonmeasurable atoms exist. Similarly, Mendelcompared predicted and observed outcomes regarding the ratios of observable peaplant characteristics to test the hypothesis that unobservable genes exist. And Pas-teur compared predicted and observed outcomes regarding the observable growthof microbes to test the hypothesis that an unobservable vital force exists. None ofthese tests could have been conducted had the scientists not previously construc-ted a sensory-motor world of interacting and observable objects during their earlychildhoods.

9. Instructional Implications

According to Matthews (1994), “. . . Western science is not natural, is does notautomatically unfold as children either confront the world, or participate in culture”(p. 161). In a sense, the difficulty that many adolescents and adults experience inusing If/then/Thereforethinking in theoretical contexts supports this view (e.g.,Lawson 1992). Yet the main implication of the present argument is that at leastat its roots,If/then/Thereforethinking is natural. Indeed, it is one way in whichwe all learn, presumably because evolutionary forces (i.e., natural selection) havewired the mind to work this way. But this is not to say that use of the pattern atlower stages (e.g., levels that involve constructing language, constructing descript-ive classificatory schemes), means that it will automatically be used at higher stages(e.g., constructing causal relationships where the causal agents are observable,constructing causal theories where the causal agents are merely imagined).

One might wonder how characteristic this learning pattern is of learning in thescience classroom. Clearly, if instructional tasks are of the sort in which studentsare told specific “facts” (e.g., the phases of mitotic cell division are prophase,metaphase, anaphase and telophase) and asked to recite these “facts” on tests,

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then the learning pattern is of little or no use. However, if the instructional taskallows students to generate and test ideas about how multicellular organisms mightgrow – including by mitotic cell divisions, among several other possibilities (e.g.,Lawson 1991), then the pattern is of considerable use. Further, whenever studentsencounter conceptual change instruction (e.g., Wandersee et al. 1994) in whichconcepts introduced during instruction contradict prior concepts, then pattern isalso called into use. Recall the previously described debate between the two boysover which variable – weight or volume – determines water displacement in thetask shown in Figure 3.

Clearly knowing how to help students develop skill in usingIf/then/Thereforethinking at the highest level, the level of scientific thought, is still an unmet educa-tional challenge. Importantly, the present view of the learning process implies thatprogress toward this goal will not be made by adoption of a social constructivistview that ignores or denigrates the key role played by the external world in thetest of alternative hypotheses and theories, even though we can not be absolutelycertain that such an external world really exists.

Acknowledgements

This material is based upon research partially supported by the National ScienceFoundation under grant No. DUE 9453610. Any opinions, findings, and conclu-sions or recommendations expressed in this publication are those of the author anddo not necessarily reflect the views of the National Science Foundation.

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