New Stars for the Teacher to Steer by? A. H. Johnstone The University, Glasgow GI2 8QQ, Scotland Overload of Working Memory Hypothesis
For at least the last 25 vears teachers have been aware that students have ronsideratde diffirulties with certlin areas of chemistry. It would be helpful if we were to stand back and examinethe sources of these difficulties. There are a t least three possibilities The nature of the science itself makes it inaccessible. The method* hy which we have traditionally uught raise the problems. 3) The methods by which students learn are in conflict with either or both of the above. 11 21
In a nrevious naDer (1) it was shown that much of the trouble>ould he ~ t ~ r i b to u ~a conflict d between (2) and (3) above in which severe overload of the working memory was caused by the teaching and testing methods commonly adopted. The workina memorv is that art of the brain where we hold information;work upon it, organize it, and shape i t before storing it in long-term memory for further use. The important fa& is that this working memory space is severely limited in size. Anv overload of it leaves us no space for thought and organization and so faulty (or even no) iearning takes place. The teacher's working memory is already organized, but this is not the case for the learner. I t is easy for the teacher to fall into the trap of imagining that he or she is transmitting a complete set of ideas, fully organized, which the pupil can take on board intact. This is just not so. Every learner has to analyze the information coming in and organize it for him- or herself, if the learning is to become part of him or her. If he or she tries to take on the teacher's information and structure, he or she has to resort to rote memorization which certainly does not guarantee understanding. Recent research has supported this working hypothesis.
A plot of facility (proportion of shrdents answering correctly) in objective chemisby questions versus the number of pieces of infwmation needed to process the questions.
El-banna (2) has made a study of multiple-choice questions in chemistry. With the help of a team of independent researchers he has analyzed each question for the number of steps or pieces of information required for a novice (a student) to answer it. A plot of the percentage of students answering each question correctly versus the number of thought steps is shown in the figure.
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There is a strong negative correlation between the two variahles (r = -0.8). hut the curve of best fit is S-sha~ed, reminiscent of a pH &me. The vertical part of thecurvecomes between 5 and 6 steos. This is in the region of the ca~acityof the working memo6 measured by other means. ~ h e s re;& have been confirmed hv studies in various Darts of the chemistry curriculum. he reader might well deny that he or she sets questions of such complexity, hut one example may suffice to show that this can be done almost unconsciously because the teacher already has his or her knowledge organized. Wbat volume of 1.0M hydrochloricacid would react with exactly 10.0 g of chalk? A typical student might take 10 steps to solve this problem, although not always in exactly this order. Student: 1) Chalk is calcium carbonate. 2) Calcium carbonate is CaCOx. 3) Formula weight = 1 W g/moi. 4) 10.0g = %o of a mole. 5 ) Write equation for the reaction. 6) Balance this equation. 7) Recognize the mole relationahip. 8) Determine that %omol CaC03= %moleHCI. 9 ) Remember that 1.0M means 1mole HCL in 1L. 10) Determine that % mole HC1 requires 200 mL of 1.0 M HCI. The teacher might solve the same prohlem in as few as 4 steps. Teacher: ~~~
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1) 10.0g chalk =
mole CaC03. 2) This requires2/100rl/n mole HCI. 3) Need '1s mole HCl. starting with 1.0M HCI. 4) Thus, need 200 mL HCl. Because of experience and previously organized knowledge, the teacher has combined pupil steps (1-4)into one step, and pupil steps (5-7) into another, and thereby reduced the load on working memory. To the teacher the problem is trivial, but to the student it is not so. In fact only 9%of our 16-year-old students got it correct! Overload of Worklng Memory and the Laboratory In almost all writing about chemical education, practical or laboratory work is advocated. This is particularly evident in the report of the Task Force on Chemistry Education of the ACS (3).However, attempts to measure learning outcomes in laboratories have usuallv shown disaooointinelv gains .. " - small (4). When we consider the cost in materials, time, and staff, we have to ask whv the copnitive gain is so low. Once more our working memory'bverlo& hypGhesis offers a model which goes some way to explaining this. Letton (5) has devoted her research to working in a chemistry lahoratory as an "undergraduate" to obtain a student-eye-view of the lahoratory process: to be on the receiving end of laboratory manuals, graduate instructors, and faculty. Her view of the scene is disquieting. A lahoratory is a "noisy" place in terms of information and students are not in a position to discriminate hetween "signal" (the things the teacher thinks are important) and "noise" (the Deri~herdinformation which the teacher knows is unimpo&t): Letton gives this as an example of such a situation. The manual says, "Diasolve some ferrous ammonium sulfate in water and add some ammonia solution. What do you observe? Explain your observation.Now add some solid ammo~umchloride and shake the mixture. What do you observe? Explain your ohsewation." Three times in this short paragraph "ammonia" and "ammonium" occur, but only once does it have any significance. The effect on the students is to focus their attention on 848
Journal of Chemical Education
"ammonium" and deflect them from the point of the exercise. Letton has found dozens of examdes of this sort of "noise" versus "signal" phenomenon. o f c o k e the teacher knows that ferrous ammonium sulfate is more stable than ferrous sulfate, and that ammonia solution contains hydroxide ions, hut how are the students to know? They take in both "signal" and "noise" and suffer overload. Wham (6).in his analvsis of high school chemistrvlaboratories, sees similar over and over again. He describesstudents meeting acids and bases for the first time. The teacher provides the students with pH paper and asks them to dip the paper into various substances. The aim of the leason is to establish that things are either acidic, alkaline, or neutral, but the exercise generates a range of numbers. The teacher then explains that numbers geater than 7 mean alkaline and less than 7 acidic. The intelligent pupil asks such questions as: "Why is more acid given asmaller number?;" "Is pH = 3 twice (or half) as acidic as pH = 6?"; "Why is it asmall p and a big H?"; and, "What has hydrogen to with it." All of this is noise obscuring the signal. If the teacher had used litmus paper the noise would have been instantly stripped away revealing the message. The progressive, apparently modem, use of pH paper has, in fact, ruined the learning. I t is little wonder that students get lost in the lahoratory. There has to he an urgent reappraisal, at all levels of chemical education, of our lahoratory practice so that we can shut out the noise and give the simal a chance. Manuals rewritten to take cognizance of this are already showing promise (5) in terms of student learning and motivations. Overload ot Worklng Memory and Language . . Another contributor to information overload is our use of language. Unfamiliar vocabulary, familiar vocabulary chahging its meaning as it moves i n t o chemistry, use of pompous language where plain language would do, use of unfamiliar constructions, and the unconscious use of double or triple negatives all make for poor learning in chemistry
(7). Posslble Ways of Rectlfylng thls Situation At this point it isappropriate toask what positive s t e p can he taken, in both the short and long term, to rectify this situation. Some pointers have already been mentioned above, but more have to he explored. Laboratory Work A thorough gutting of manuals and laboratory books is essential to remove the accretions and the noise. Pages have to he redesigned to allow the students to process workingmemory-sized chunks and stiU have room left for thought and processing. Pages of contimuous prose instructions will receive the treatment from students which thev deserve-that is. students will treat them like recipes (line"-by-line) with the& brains in neutral. Apparatus also needs to be redesigned (8)to remove the extraneous artifacts that detract from the messaee of the experiment. Rubber pipet fillers with their multip6city of buttons add massively to the noise surrounding volume measurement. For electrolysis experiments, why not replace a combination of ammeters, stop watches, and calculations linking coulombs to Faradap to moles of el&trons with simple electron counting meters? The directness of such a meter would trim away YO much that isdistractingand would allow undirectly to "titrate with electrons" and give us instant access to ion-electron half-equations. Curriculum Content Order The theoretical language of chemistry is another potential source of working memory overload. Most high school and college textbooks devote their first chapters to atomic theory, line spectra, Aufbau, Schrodinger equations, orbitals, hy-
hridization, bonding, and periodicity. Not far behind are formulas, eauations, halancine, -. ionic eauations. calculations and stoichi&etry. Only after this barren, desert exoerience do students get anywhere near "real" chemistry ils they see it. They then have to dip hack continually into this theoretical owl to exdain the chemistry. A logical outworking of the overload theory might be to proceed as follows. Introduce only the minimum theory to enable students to come to grips with some recognizable chemistry, and then develop the theoretical model when, and only when, the chemistry demands it. In this way the theoretical model can grow naturally and be seen in its correct role, as a support to thinking about and systematizing observed facts. I t is an interestine exercise to see how far one can teach useful chemistrv by considering only the elements carbon, nitrogen, oxygen, and hvdroeen and their valencies of 4.3.2. . . .and 1..resoectivelv.. and only covalent bonding. A meat deal of useful oreanic chemistrv can be taueht (and learned) on this model. when one arrives a t the c&boiylic acids the ~ossibilitvof a new bondine. tvDe has to be introduced to cope with the ohservations:d;adually one might introduce unbalanced equations (as is common in organic chemistry) and later balanced equations when (and only when) required for quantitative purposes. This might suggest a radical alteration in content order, but it would at least be against the backmound of a working educational model rather than be seen frog an adult point of hew as at present. The two chapters devoted to organic chemistry near the end of most texts would become the beginning of chemistry for most students. The immediate apueal of its recognizable comoounds (fuels, foods, soaps, solviits, etc.) wouldcommend idto students. For most students, the inorganic chemicals we make so much fuss about are pr~hahlyno more real or relevant than moon dust! Inorganic chemistrv with its concomitant ions. solubilities, net ionic equations, and, often, industrial and domestic irrelevance is likelv to lead to more of an overload (and hence difficulty) than-organic chemistry with its intrinsically simpler theoretical base (at least at the beginner
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level). A high school text which takes this approach is now available (9). Computer Programs
Here we have a technique in search of a use. So much of the software available does little more than could be done with a pencil and paper and possibly a pocket calculator. There s e e m to be little sense of direction and people throughout the world are reinventing the same rickety wheels. Where programs could make a unique contribution to chemical education, would he in a noise-reducing role. So often the nature of chemistry itself makes it imperative for the student to devise and practice for him- or herself, noise-reducing procedures. For example, the ability to look at complex organic structures and to see the functional groups in all sorts~oforientations must be worked on by the individual until it is mastered. Reaction pathways have t o be explored (both forwards and backwards) to obtain a feeling for more advanced organic chemistry. Strategies have to be built up and practiced. These and many others are begging for the ingenuity of those with computing skills. Conclusion I t would be foolish and arrogant to claim that all our chemical education problem will disappear if we pay heed to this message about overload of working memory, but this message has the virtue of being capable of implementation almost at once in any classroom or laboratory anywhere. The immediate benefits could become visible tomorrow. Literature Cited I11 Johnafone,A.H., J. C m .~ E D U C80,968 ., (1983).
I21 Johnstone, AH., and El-Banna, H..work in promesa, Univenity of GI-, 1981. I31 "ReportaftheTaskForce lor the StudyofChemutnEdveatioointheunitedstatea." American Chemical Saeiety, 1984. 14) L u n e t k V.,and Hofstein, A,, Rau. Educ. Ra~.,52121.201l19821. 1s Johnstone, A. H..and lalton, K.M.. ~~~ublished&rk, UnivDnity of Glasgow, 1984. (61 Johnatone, A. H., and Wham, A.J. B.,Educ. Chsm., 19[3], 71 (1982). (71 Cssseh, J. R T.,and Johnstone, A. H.,J. CHeM.EDUC., in p-. IS1 Wham, A. J. B..and Storie, H., Sch. Sci. Re"., 64, [2291.719 (1981). I91 Johnstone. A. H..Morrison. T. I.. and Reid. N.. '"Chemistrv A b u t 11s." H~inemenn
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