I'm tallring to you" is a "YOU" messare that could be replaced hy th~"l"~e&~e:.l get fruwated when I srnse peoplearen't liscenina to me." Researrh indicates that "YOIJ" mtiwaes are rejectedby people; "I" messages are accepted. T o avoid having students fight you or your computer, give them a s many "I" messages a s possible (22,23). Examples of Good Programmlng Some specific ideas in electronic computer programs t h a t seem compatible with the way human computers operate are these: 1) Human comouters resoond well to verv that .comolex . oroerams . do not force them to know all that the eomouter kn~ws.~~xamole: WordSlar ( T M II learned tu"usen ~ o r d ~ t a ; i n a b o u t w ohoun,'hut two y c m later it isstiil capable ul doing thinys that I do nor know how to do. Whenever I get to the point that I need to know more about the program, I know Ican retrieve the information from the program. It is a complex program that does not force me to learn more than I am ready to know at one time. Human eomputers respond well to this. 2) Human computers respond well to clever programs that make them aware of what they already know in a way that they did not know it. Example: In a general chemistry program teaching Avogadro's number a counter is shown on the screen. It counts and records the number of molecules formed in a reaction, "1,2,3,4,. . .",on and on until the student gets tired of watching numbers and pushes a button to stop it. To teach the bigness of Avogadro's number, do that. Grayson Wheatley, a mathematics educator at Purdue, uses a simple calculator to teach the concept of place value in decimal numbers. Every time you push the sign, the calculator adds whatever you have entered to the number already stored. First graders can do it. After a while, they get the idea that the digits on the right of the display change quickly, those on the left change very slowly. These are clever .oraerams that make users aware of somethine"thev. .. already know,hut in a different and dramatic way. Human runlputcrs build new connerta,n* as a result d s u c h interaction. 3) Human computers respond well to programs that juxtapose ideas so that the relationships between new ideas and old ideas are revealed. Example: Paul Groves' program from Moles, Inc., intraduces a golfball factory where orders are taken in three ways--by the ball, by the dozen, or by mars (24).A balance is on the screen and golfballs are dropped onto the balance pan. Three d e s increment as each hall is added: # of balls, # of dozens, and # of grams. Three pieces of information are juxtaposed in a new way. This continues until the balance breaks! The balance will no longerreeord mass or dozens,hut orders continue to come in in these units. Users must find some information on the scales that still function to calculate the orders. The program quickly moves from ordering golfballs to ordering chemicals by molecules, moles, or mass, therehy juxtaposing information so the user is aware of relationships that were not previously obvious. Human computers often store information without making the connections that have been made by others. Helping students "merge files" is an important part of teaehing. 4) Human computers respond well to electronic computers that foster human cooperation. Example: Paul Groves gets four to six students around a computer and they sign on. He gives them numbers: e.g., Lamy, 32; Dudley, 46; John, 65, and they push a button to continue (24). Then the program tells the group that the numbers represent the mass of comer . . in a mixture of comer . . oxides and asks the mule percent i,fwpper in rhe mixturr. Each studenr uses his or her numller t u work the prohlrm and puu m an answer. Then the interaction takes place: ~fnnyhody ir. tvrung, nobody can go on. They all have to he right. If you have a free atmosphere where people can work together, students will work with eaeh other and help eaeh other understand. Human computers seem to value other human computers and assist them when it is mutuallv beneficial. 5) Human computers respond well to programs that let them manipulate variables and discover relationships. There are many simulations available that illustrate this kind of program; Paul Cauchon's ammonia synthesis is one (25).Human computers work well when they can look at a situation, decide what might be sensible to do. trv it. and then eet feedback on the decisions. This helm construct knbwiedge in a sensible form. 6 ) Human computers do not respond well to programs that force them to think as others think. I do not think as you think. Nobody does. Human computers are human. No two are exactly alike and they ~~~
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do not respond well to efforts by other computers, of either kind, to remake them in their own image. By describing similarities between human and electronic computers I have tried to suggest a model of human cognition. This model might guide the development of software so t h a t it is sufficiently powerful and flexible to be of value to human computers a s they construct new knowledge in chemistry. Literature Cited (1) Andermn. J.,"Cwitive Psycholorn and itp Implications." Freeman, San Frandam,
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(19) Foradiscusisonoftheinterplaybet-"d~pIwel"veraus"aurfsalcvel"pwo~ing me: Bransford, J.. and MeCarrell. N., in "Cognition and the SymbolicPwoasrs." (Editors: Waimer, W., and Pslermo, D.l.Law~naErlbaumAsaoeiaks.Hilladale, N.1 18112. . .., . ...
(20) dT'dewalle,G.,andLena, W.,"Cognition in HwnsnMotivationandLearning,"Cawrena Erlbaum hwiates, Hill8dale. NJ, 1981. (21) Caae, R.,in "1980 AETS Ycarbwk: The Payehology of Teaching for T h i n g and Creativity." (Editor: L a m n . A ) . ERIC Clearioghow far Science, Mathemati-, and Environmental Education, Columbus, OH, 1979,pp.5S102. (22) Gordon. T., "T.E.T. Teacher Effectiveness Training." Pete. H.Wydm, Now York, lWd. ... ~.
(23) Rogers, C."Rmdom tolesrn," Memill, 1969. 1%) Groves, P., "Mole Calculations."Think Moles Software, 1012 Fair O s h Ave. #356, So. Pasadena, CA, 1984.
(25) Haber, W. E. Sfhweikwt,Micmmmputer pmgramof-oniasymhesisdemanatrafed by Paul A. Cauchon at Dreyfus Imtitute, Princeton Uniu., Princeton. NJ, 1982.
CAPE: A Computer Program to Assist with Practical Assessment Peter M. May, Kevln Munay, and David R. Williams University of Wales Institute of Science and Technology. CardiffCF1 3XF, Wales, United Kingdom One effect of the financial squeeze widely imposed on universities in t h e United Kingdom two years ago was t h e prospect of a significant reduction in the number of graduate student demonstrators assisting academic staff in charge of laboratory classes. Our department sought t o mitigate this, at least in part, by increasing t h e role of computers in the laboratory. As all those who have been involved with the running of practical classes well know, the marking of student repor& is a substantial job. Done conscientiously, it requires a great deal
of time, much of which is spent in checking fine details. This is especially true when numerical calculations are involved. As these are often hased on the experimental results of individual students, different calculated values occur throughout each report. Although, with experience, it may he possible to iudae whether the final answer is correct or not, the only way i o be certain is to work through the calculation oneself. Moreover, if the student has made a mistake, there is often no other way of locating the error. However, it is clear that this time-consuming and repetitive practice is a task well suited for the -.~ - comnuter. ~- ~~ ~ The g e n e k c o m p u t e r system that we have developed for this numose is called CAPE for Comnuter Assisted Practical ~vaiuation.It is hased on a FORTRAN program that, for each exoeriment. executes a seauence of instructions contained in a computerfile. Copies ofihe CAPE program, together with more detailed instructions for use, are available to the interested reader upon request.' r verification Bv restrictina the main role of the c o m ~ u t eto ol'c~culations,'inl,ut from thestudent tail he almost entirely confined to numerical values. This is of considerable benefit since it means that complicated grammatical analysis of the response becomes unnecessary.z It also narrows the type of information that must he conveyed by the computer to the student. T h e nature of the problem is thus much simpler. It is consequently easier to make the computer interface more plausible and to limit the complexity of the coding necessary to implement it. Another advantage of a system oriented towards the numerical side of laboratory work is that the results can he eraded as an indication of exnerimental techniaue. This can heldone automatically hased on statistical distribu-, tions from classes of previous years. The following procedures have been adopted to ensure that the system does not give students any unintended assistance. 1, Every studenr is registered personally and given a secret password This ensuresthat the ~nd~wdual ir responiil,it fur thcacti\,ity conducted under his or her name.
Summary of Commands Executed by CAPE Communicstive READ prompts input from student TEXT prints alphanumeric text at the student's terminal PRNT prints numerical values of variables at the studenvs terminal Manipuilative LOAD sets specifiedvariable to given value CALC performsaddition, subtraction, multiplication,division or exponentiation on variables SQRT provide common mathematical functions, etc. LOGE.
SINE WHEN
pwrnlts conditional execution of blocks of commands
ELSE ENDS LINE
TEXT
T
performs linear regression analysis
P r e p a r a t i o n of a standard s o l u t i o n of 1 c u b i c d e c i m e t r e of a p p r o x i m a t e l y 0 . 0 1 H m p p e r s u l p h a t e .
TeXT
TEXT
What is t h e
ma68
( i n grams1 of m p p e r s u l p h a t e used?
TEXT =AD A Enter mass TEXT REM
C E n t e r your calculated n a l a r i t y
TZXT
LOID
8-219.68
CALC *BEN
8-&/H
BiCIO.10 TEXT Well d o n e .
Your l n l a r i t y has been c a l c u l a t e d
correctly. ELSE TEXT TEXT
Your m l a r i t y has cot h e n m r r e c t l y c a l c u l a t e d . Check your calculation and t r y a g a i n .
ENDS
TEXT STOP
Figure 2. Example CAPE program illusrmting typical commands.
2) A record of every computer session is kept. This is done by orintine a summarv of the dialome that takes dace between the computer and the student. These sumnlaries must he appended to the lahmtory repurts when they are handed in ior n,arking.'l'he r o d number of sessions initiated by each student is recorded separately. 3) Students are made to commit themselves by supplying an answer before the computer reveals any information. The details of this approach are shown as a flow diagram in Figure 1.Generally, whenever an incorrect answer is supplied, the student is asked to do the calculation again and to suhmit a revised value. However, with some common errors there is no need for this (e.g., when a change of units has been neglected). If the calculation is rather involved, the computer can help to locate a mistake by checking intermediate values. Students are thus advised to have their work (and not just their final answers) with them.
High priority was given to "user friendliness," clarity, and reliahilitv. An attemot was made to eliminate the nossihilitv of "harderashes" ndmatter what the student should do. All CAPE instructions commence with a four-character
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Figure 1. General assessment procedure.
Address to Mav. FORTRAN nrwram develooed on a VAX .- ~ reouests ~, 111780 computer, comprising 1302 statementsand requ/rmg23K byte memory. Documentation includes detailed coaing instructions, printed listing and sample data files. Enclose E 30 to cover postage and administrative costs, payable to Department of Applied Chemistry, UWIST. Enuc., 59, 129 (1982).(b) Eilers, J. (a)Anderson, R. H., J. CHEM. E., Cronin, J., and Joshi, B. D., J. Cn~~..,Enuc., 59, 209 (1982). ~~
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command, as summarized in the table. They encompass two fundamental programming concepts, namely, (1) communication with a student located a t a computer terminal and (2) manipulation of information supplied by the student. A simple example of a CAPE program embodying these concepts and illustrating some typical commands is shown in Figure 2. CAPE programs are always executed sequentially, i.e., it is not possible to loop hack to earlier statements. This limitation arises because the commands are read from a FORTRAN seaueutial file. Experience has confirmed that more complicated options are unnecessary. Manipulation of information from the student is largely of a numerical nature: numerical values are stored either as specified by the LOAD command (within the CAPE program) or as received from the computer terminal in response to a READ command. Single alphabetic characters are used in the program as symbols for the memory locations in which the numbers are stored. Subsequently, calculations can be performed involving any of the common arithmetic operations (using the CALC command) or a variety of mathematical functions. Output to the computer terminal is accomplished mainly hv the'rEXT and PRNT commands. TEXT is used to convey tke main body of information supplied to the student: each line is transmitted exactly as it appears alongside the initial TEXT code, free from any formatting requirements. The PRNT command displays numerical values which are currently being stored. I t is also possible to output a short line of information as a prompt associated with the READ command. T o prevent format errors occurring when entries are mistyped hy the student, numerical input is read in as a string of characters and converted by CAPE to a real, floating point value. Exnonents are desienated by the conventional letter Ef"llowed by an integer ;ipresent;ng the power of 10. It is possible for the CAFE programmer to impose limits on the size of the numbers which the program will accept from the student. Provision is also made for input and output of very limited alphabetic information, i.e.; individual letters or words. The sequential execution of commands hy program CAPE does not exclude the possibility of conditional programming. i.e., the ability to execute commands under certain circumstances and not others. There are three commands for this purpose: WHEN, ELSE (which is optional), and ENDS. They are implemented in a manner similar to FORTRAN77 IF block$.~Theyenable one tospecify a test,e.g., wdetermine if A = H (to within a given tolerance) or M < N,etc.. and hence to .. control ..-. whether a block of codine is to be implemented or not. These blocks can be nested iniefinitely, i.;., there is no limit to the number of tests a t lower levels that can be carried ------~ out within the span of higher ones. One aspect of practical work that arises very frequently, concerns the analysis of a series of pairs of experimental data.
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Journal of Chemical Education
This is accommodated by reserving each of the alphabetic symbols W, X, Y, and Z for the storage of an array of numbers. For example, the command READ X,YEnter pressure (dtm.) and volume (ml)
repetitively prompts the student for these pairs of values. It is then possible to perform any of the usual mathematical operations on the data,all theelementsofeither array being treated in exactly the same way. Of panicular value is a special command. LINE. for linear remession analvsis on the values held in the arrays X and Y. At the time of writine. the CAPE svstem has been in operation in our department for one full academic year. ~ h o u t 1 2 0 students have been reaistered on it, mostly from first- and second-year courses. 1tpresently covers some 30 experiments, mainly in inorganic and analytical areas. The initial reaction of staff has been favorable but rather cautious. For obvious reasons, most of those expressing interest have wanted to see how the system works in practice before they commit themselves to developing their own programs. The dozen or so simple, yet powerful, CAPE commands ought t o be readily mastered, even by those with no previous programming experience. Program development times are considerably shorter than they would be using conventional high-level languages such as FORTRAN or BASIC, and it is much easier to write error-free code. Reaction of students involved some initial uncertainty; however, this was soon followed (as their confidence immoved) bv an acceotance of the svstem as a routine part of the practical assessment procedure:^ questionnaire was issued at the end of the first term to nearly 100 of those taking, firstand second-year courses. Replies were made nnonymously by indicatine. with a cross on a scale of one to five, the extent to which each student agreed with a variety of statements. The opinion that the system bad proved to be a satisfactory method of checking the numerical calculations associated with practid work was widely accepted (81%answered with a four or five). Only six students felt that the extra effort which CAPE required of them was not reasonable (responses one or two). Finally, it is interesting t o assess CAPE in terms of its cost-effectiveness. As Ayscough has pointed ouL3 all computer-based teaching systems incur an add-on cost which needs to be iustified in terms of ~erceivedbenefit. When compared wiih the advantages gained over the life of a practical experiment, the initial time required for program development is well worthwhile. CAPE provides a consistency and thorouehness in the markina of laboratory work that would othekise be difficult, if not impossible; to achieve. Moreover, by reducing the marking load, it should permit laboratory supervisors to spend more time instructing students a t the bench. 3
~yscough,P. B.. Chem. Brit., 12,348 (1976).
