34

school, sex, type of educational background of the parents, in order to elicit a certain level of motivation required for the extra effort in memorizing Biochemistry. As regards distri- bution by sex, well-motivated males or females were balanced by non-motivated ones, the same pattern occurring when the nature of the secondary school is taken into account, or with the type of studies followed by the parents. The fact of obtaining a scholarship means a superior degree of motivation.

On the other hand, students whose families live outside the city and therefore have to make an extra effort in order to keep their student living in the city, have a clear motivation to study in order to obtain better qualifications. 4

However, that motivation, and consequently the effort put into obtaining higher marks in Biochemistry, related to academic or personal factors, does not guarantee that the knowledge acquired will last. Even one year after achieving those high scores, the students characterized by these aca- demic or personal factors could not be differentiated in the amount of biochemical knowledge maintained by the rest of the students, s The factors related to the different degrees of memorizing, after one year, have nothing to do with the effort made when passing examinations, but are dependent on what we could label as 'global understanding of concepts or models'. Students with a better cultural background or that have acquired a 'global understanding of the functioning of models', as opposed to a 'detail memorizing process of learning', are those who maintain more and better biochemical knowledge. This is what, in our opinion, helps to explain the experimental findings: 'A' students whose parents have either University degrees or other qualifications ('natural' cultural background or acquired through effort) or 'A' male students, after one year, retain more knowledge than the 'A ' students whose parents have only secondary studies or than the female 'A' students, respectively. 6

Nevertheless, after this first year, all differences due to extra efforts disappear, and the pattern of memory loss in biochemical knowledge has only to do with the use of each particular 'model ' in the medical disciplines which follow, and through them, in the medical behaviour with the patients. It is only a question o f repeated use of the knowledge, ie the more times carbohydrates, metabolism and enzyme 'concepts' or 'models' are used compared with the biomolecules or genetics ones, the better the respective concepts are maintained.

Another question open to discussion is the reason why the different biochemical models or concepts have been integrated in such a way that produce different usages. We think that it is an historically-determined question: the older ones are re- peated more often and are better understood, and as a result of this, the practical use they have been given in the diagnostic or therapeutic procedures, explains the academic repetition, whereas the recent biochemical models have not been wholly assimilated nor integrated into medical practice.

References 1 See Molina, J A (1978) Academic performance o f medical students at Murcia's Faculty o f Medicine since its foundation in 1969 until 1977. Murcia, Publ Univ Murcia, 1978

2 Rico, E, Galindo, J and Marset, P (1981) Remembering Biochemistry : A s tudy of the pat terns o f loss o f biochemical knowledge in medical studies. Biochem Ed, 9, 1 0 0 - 1 0 2

3As can be observed as a general trend in medical studies in Table 8 o f Molina's work (1978)

4Similar findings are coming from a recent study on the evolution of physiological knowlege in medical students, Table 33 from Ruip~rez, A (1982) Evolution of the pattern of memory of physiological know- ledge in medical studies. Murcia, Lic dissert

SThe same results have been obtained in the above mentioned study on physiological knowledge by Ruip~rez, A, Table 38 (1982)

6A different academic performance has been also obtained in relation to sex in the diverse medical disciplines by Molina (1978) and in Phy- siology studies by Ruip~rez, A (1982)

T h e Use o f Visual Aids in Publ ic L e c t u r e s

M K H A R G R E A V E S

Department o f Chemistry, North East London Polytechnic, Romford Road, London

Introduction I have been concerned for a number of years at the poor presentation of lecture material in public lectures and at conferences. The response to my 'Hints to Lecturers', (Chem- istry in Britain, 1981, p 552), shows that this concern is widely shared. (I am grateful to the Editor of Chemistry in Britain for permission to reproduce substantial parts of that article.)

Here I am addressing myself particularly to Biochemists, and I would therefore like to begin with a word on nomen- clature and jargon. Some time ago I was asked to review a book on general biochemistry which was written almost entirely in terms of 'initial' shorthand. I could not read the book since no key was provided to the many initials involved. It is obvious that since biochemistry is now so central in scientific research, at any public lecture there will be people in the audience from other disciplines. It is therefore desirable that at the first mention o f a substance in a public lecture its full name be given with the initial shorthand symbolism in parentheses, so that all members of the audience can properly assess the biochemical processes involved. Even though some substances are household words in the initial form, such as DNA, it is better to err on the side of the pernickety rather than on the side of the slapdash, since the latter may lead to misunderstanding. The subsequent use of the initial shorthand alone is o f course essential since the full chemical names of the substances are too much of a mouthful. It would however, be unwise to allow the initial shorthand to become such a jargon that the structures never enter the mind. There is another problem in connection with the initial shorthand where it is combined with ordinary chemical symbolism; the lecturer must make it clear, en passant, how he is mixing his sym- bolisms. There should be no excuse for misunderstanding by the audience, and the lecturer should not rely on the fact that people in the audience are unwilling to show their ignorance. A simple example of this kind of problem is given in the equation:

COOH COOH I isocitrate I

H-COH dehydrogenase C=O

I NADP ÷, D20 I H O O C - C - H D - C - H

I I CH2 .COOH CH2 .COOH

B I O C H E M I C A L E D U C A T I O N 11(1) 1 9 8 3

where the different Ds represent totally different components, as they do in NAD-D. Similarly, confusion could arise with coenzyme A and cobalt. To avoid any ambiguity all that is necessary is that the lecturer should spell out his slide, prefer- ably with the aid of a pointer.

General considerations In a really good lecture, good material is presented in such a form that the audience can share the ideas and experiences of the lecturer. The basic requirements for satisfactory presen- tation using visual aids have been made clear by a number of people, but they have not so far been effectively presented to the scientific community. The scheme outlined below, if adopted, would improve the average standard of presentation of material and provide a guide for hard-pressed lecturers and for those organising conferences. Lecturers who have some- thing original to say, but who have little time to get it across and almost no time to prepare their lectures, are those most in need of help.

The choice of materials is entirely for the lecturer to decide, but he would be wise to be as simple as possible, preferably to limit the lecture to one main i d e a - possibly exemplified in a number of different ways. It has been force- fully put that a lecturer should first of all tell his audience what he is going to say, then say it, and finally tell them what he has said. But it is with his lecture aids that he most often needs advice. It is quite common for a lecturer to present a slide, blink at it and then, realising that no one can possibly read it, apologise and proceed to develop his argument on the basis of it.

Shortly after these words were written a distinguished scientist did exactly that and he had only one slide. If one has only one slide then, generally speaking, it is better to use a blackboard. As the nervous hand traces out a curve on the blackboard, the whole audience watches spellbound lest the hand refuses to go where it should. This all helps to provide impact and keep the attention of the audience.

Most people who attend lectures wish to keep awake; often, in a warm, darkened room after a good meal they find this difficult, and all too often the lecturer drones on in a semi-darkness, punctuated by flashes of illegible slides. If on the other hand the slides are clear and well set out they are a great help in holding the audience. In respect of presentation the first thing to do in improving one's lecture is to get the visual aids right. If a subject does not lend itself to the use of visual aids then the lecturer must hold his audience by the virtue of his subject matter, his voice or other physical charac- teristics alone. In order to provide a leavening some lecturers introduce humour as a matter of policy, but 'added' humour is best avoided because, even if successful, it suggests a certain contrivance, and a lecture is at its best when the audience has no feeling that something is being held back. Likewise, whilst a lecturer may have to wait for laughter to subside before he can make himself heard, it is better not obviously to wait for the laughter to begin.

There is a natural tendency on the part of those lecturers who are successful in making the audience laugh to overdo the humour. Whilst humour and anecdote may embelish a lecture they should never be allowed to reduce the impact of the main message.

35

Slides Often these are very bad; this is usually because they attempt to present too much information. It helps for clarity if the slides are prepared with white or yellow letters on a blue background, but the main thing to get right is the amount o f information which each slide contains.

Typescript and Tables Given that the projected image of the slide should fill the screen (see below), about 550 characters or 100 words is the absolute maximum that can be shown on any one slide. Given that only alternate lines should be used for clarity, 50 words is an effective maximum. Taking 100 dis- connected digits or 30 disconnected words per minute as a fair speed for reading wholly novel material (cf 100-150 wpm from Kant: Critique of Pure Reason) and halving this to allow time for comprehension, in a serious lecture a slide of 50 disconnected words would need to be shown for from one to three minutes according to the nature of the material. In general, therefore, a slide which is full of new information is not suitable as one of a series except for occasional reference to parts o f it, in which case several copies of the slide should be inserted in the series.

Where a full slide is needed, it would generally be better to present the information to the audience in some other form eg blackboard, auxiliary overhead projector or hand-out, so that the audience can refer to it as the lecture proceeds.

Handwriting When the lecturer is able to prepare hand-written work of sufficient quality to be acceptable for presentation before an audience, this will generally be clearer than type if the 60 x 90 mm template with normal-sized writing is used, and much clearer if large, bold handwriting is used. Since the quality of the lecturer's scientific work may be judged by some people in terms of the appearance of his slides, those with irregular writing would be well-advised to employ an artist for this work.

Equations, formulae, etc The same criteria apply as for ordin- ary script. It should, however, be remembered that, in terms of the printers' type and in terms of handwriting, sub- and super-scripts are smaller than the main letters. It is thus the size o f the sub- or super-script which determines the legibility of the slide. In most applications it is as important to be able to read the sub-scripts as the main characters.

Diagrams, art-work, etc There are no rules as to the size of the original, though 10" x 12" is often a convenient size of card to use. The main point is that the lines should be bold and the diagram uncluttered, ie generally simplified for the purpose o f making a slide. Where a slide requires anything other than simple line diagrams and simple lettering, the lecturer would be well-advised to employ an artist, since any imperfection in the presentation tends to distract the attention of the audience.

Screens Given that there are minor advantages to be obtained by choosing the best material for the screen in association with a particular shape o f the lecture theatre, the main requirement is that the projection screens should be of adequate size. Two standards have been proposed to ensure that the projected image is visible to all in the lecture theatre - these are known as the 6W and 8H standards. Either is acceptable and, in most cases, the difference will be negligible.

B I O C H E M I C A L E D U C A T I O N 11(1) 1983

36

6W Standard The distance from the screen to the back row of the audience should not be more than six times the width of the screen (assuming that this is to be filled with the projected image).

8H Standard The distance from the screen to the back row of the audience should not be more than eight times the height of the projected image on the screen (assuming a slide of horizontal format).

The organisers should ensure that the width of the screen is at least 1/6th of the distance from the screen to the back row of the seats. They should also ensure that the screen is at least as high as it is wide. The 8H standard is slightly higher than the 6W standard for a 24 x 36 mm aperture in a 50 mm (2" square) slide. If, however, a square format is used, the standard will depend on whether this is of 24 x 24 mm, as can be accommodated on a 35 mm film or, where a larger film is used, 36 x 36 ram.

from a position close to the lecture bench. It is, however, possible to have appropriate lenses for this situation. Lecture organisers should give attention to the provision of special lenses where circumstances require it.

The lecturer who wishes to avoid difficulties in unknown circumstances can minimise them by writing four or five times as large as for the domestic situation. Simple curves will generally be seen satisfactorily even where the projected image is far too small for typescript to be read.

Cine projectors Purchased films will give a satisfactory image provided that the projector screen conforms to the 6W or 8H standard in re- lation to the hall, and provided that the projected image fills the screen. If making personal films then the same templates for slides will be satisfactory if photographed so as to fill the cine camera frame.

Format So far, it has been assumed that the usual 24 x 36 mm format will be used. It is, however, possible, to use a square format in the same apparatus under identical conditions, since it must always be possible to use vertical as well as the horizontal projection of the 24 x 36 mm aperture. Clearly the use of the square format provides the possibility of presenting half as much material again as in the usual rectangle. It thus can be useful for the presentation of graphs where the distribution of the plot leads to a square original. There is no technical reason why such slides should not be used for general presentation since, in a properly fitted lecture theatre, the screen must be big enough to take both vertical and horizontal 35 mm slides and thus those 36 mm square in aperture. Generally, however, there is no advantage in the larger square format, since the most important requirement for the satisfactory presentation of material through slides is limiting the information on one slide. This is not merely a matter of readability but also of comprehension in the time available.

Overhead projectors The main point about overhead projectors is that, as with slides, it is a common mistake to try to convey too much information on one sheet. Generally they are most effective where the writing or drawing is done in front of the audience, but they can be used similarly to slides and can also be effec- tive used as auxiliary sources of information, particularly if they can be operated easily in conjunction with a slide pro- jector. This will often not be possible because most large lecture theatres have only one space for a screen big enough to be seen by the whole audience. In small theatres the combin- ation of a slide projector and overhead projector capable of working simultaneously can be most effective. The standards required for an overhead projector are the same as for a slide projector (see 6W standard).

Because of the shape of a lecture theatre it is often not possible to conform to these standards and thus the overhead projector tends to be more effective in the small lecture room and, consequently, with audiences of up to about 100. The difficulties arise because the standard overhead projectors do not have lenses capable o f filling the whole of a large screen

Black or White Boards These are, perhaps, the most effective of all lecture aids because they are so versatile, but here again it just will not do to write the same size on the blackboard before an audience of 500 as before the usual audience of 50. The shape of the lecture theatre is important but, in general, the larger the audience the larger the lecturer should write and the thicker should be the lines. Variations in the thickness of the lines can be most easily obtained with chalk but, for lectures in large halls provided with white boards, very thick grease pencils should be provided.

Checklist for Lecturers (1) When selecting your slides limit each slide to a single point which you wish to make. (2) Use a series of slides to disclose information progressively. (3) Check that your slides are in standard 50 mm square (2" sq) mounts and between 1 and 3.2 mm thick. If you are making new slides, photograph the material on to 35 mm film and mount between 50 x 50 mm (2" x 2") glass plates so that the slide is not more than 3.2 mm thick. (4) Check that a white spot is placed so that when the slide is correctly in the projector the white spot is facing the operator and on his upper right-hand side, ie so that the operator (behind the projector) can see it. (This is the lower left-hand side when viewed in the hand.) (5) Check the order of your slides. Have them numbered if this is possible. Ensure that there is only one set of numbers on the slides. (6) Remember that, generally speaking, photographs from books are not suitable for direct use as slides. In general, the legends need to be in larger letters and the lines need to be thickened. If it is necessary to reproduce graphs or diagrams from books or journals, obtain a print size 60 x 90 mm, cover over the old lettering, type in new lettering, thicken the lines in the diagrams and re-photograph to 24 x 36 mm, ie on 35 mm film. (7) In order to present typescript material properly, type on to a 60 x 90 mm template and then photograph so as to fill a frame on 35 mm film. (Mount your slide between 50 x 50 mm (2" x 2") glass plates, so that the slide is not more than 3.2

B I O C H E M I C A L E D U C A T I O N 11( 1 ) 1983

37

PICA

90 mm > <

ELITE

90 ram- >

For a satisfactory impact

type not more than 15-20

words or 25-30 figures for

each slide in this space.

(19 words.)

USE CAPTTAL LETTERS AND

EXTRA SPACTNG FOR EVEN

BETTER IMPACT WITH THE

SAME MESSAGE. THIS SPACE

CONTATNS ONLY TWENTY

WORDS.

90 mm > <

Pica type, (10 characters

per inch, 4 per cm.) Will

have greater impact than

Elite type, (12 characters

per inch, 5 per cm.) shown

at right.

For a satisfactory impact

type not more than 15-20

words fo~ each slide or

25 - 30 figures in this

space (19 words).

This shows the effect of attempting to get the maximum amount of information on to a slide. The effect will be worse when projected than with type on paper. It is not possible to show in ordinary print the beneficial effect of using a carbon ribbon but wherever possible carbon ribbon should be used, as a great increase in clarity results. The use of a reversed carbon paper behind the paper is not so important but it gives some benefit.

(83 words)

The use of an electric typewriter is

also important, as the even pressure of

the machine gives a noticeable increase

in clarity. The use of double spacing

between lines of type also gives a

worth-while increase in readability.

(37 words) 9oma >

mm thick.) Spot the slide to give immediate recognition of its proper orientation in the projector (see 4 above).

Leave at least the height of a capital letter between each line. Remember that if you use only capital letters the slide will be clearer. Use carbon ribbon and an electric typewriter, preferably of the pica size, (which is ten characters to an inch).

Use a high-standard negative material such as Kodalith for monochrome slides. The templates on page 37 show the effect of possible variations in technique. (8) If a full slide (50 words) is used, up to three minutes is required for reading and comprehension. It is better to use several slides if you can, but if it is necessary to refer to the

BIOCHEMICAL E D U C A T I O N 11 ( 1 ) 1983

38

slide a number of times it is better to repeat the slide in the series. (9) If a table needs to be displayed repeatedly possibly it would be better to write it on a blackboard beforehand.

(10) It is even more effective to build up a table on the black- board. (11) Ask the organiser for the depth of the hall. Letters on blackboards or other visual aids need to subtend an angle of about 0.3 ° at the eye - thus, for a hall which is 30 feet (about 10 metres) to the back row from the screen or blackboard, letters need to be at least 50 mm (2") high. If you write smaller than this those at the back of the audience will have to use their imagination rather than their eyes. (12) Graphs should contain not more than three curves. (13) Tables should contain not more than 30 entries, eg 6 lines x 5 columns. (14) Lastly, check just before you leave your base that you have the right set of slides (a well-known chemist once flew the Atlantic to give a special lecture with the wrong set of slides.) Check once again that your slides are in the right order.

To Organisers of Pubfic Lectures and Conferences ( I ) Ask your lecturers to conform to the standards recom- mended here, so far as slides, overhead projectors and other visual aids are concerned. (2) Advise lecturers on the size of the hall, size of screen and distance from projector to the screen, distance from back row to screen and blackboard, and send them the check-list. (3) Further to the same point, advise lecturers of the size of letters needed on the blackboard or any display material, eg letters should be 50 mm (2") high and at least 25 mm (1 inch) wide for a hall 30 feet to the back row, and proportionately for other sizes. (4) Check that your projector accepts standard 50 mm (2") square slides, 1 mm to 3.2 mm thick. (5) Check that the width of your screen is at least 1/6th of the distance from the screen to the back row of seats (see below). If the screen is bigger than this it will not matter. The screen should be at least as high as it is wide (see 2 above). (6) Check that when the projector is suitably situated the full image of the slide (aperture 24 x 36 mm) just fills the smallest dimension of the screen (at 6W standard) (see above). (7) Remember that the normal overhead projector is designed for a relatively small audience. If an overhead projector is to be used with a larger audience, obtain a special lens. If this is not possible, arrange for the overhead projector to be placed into the audience so that, with a normal lens, the image just fills the main screen. (8) Advise lecturers of the facilities which will be available. Give them as much information as possible. (9) If possible, arrange for the lecturer to meet the pro- jectionist some time before the lecture begins. (10) Alternatively, if an automatically-operated slide projector is used, make sure the lecturer is familiar with the operation of this machine before the lecture.

(11) Check that the black-out system works. (12) Check that the ventilation works with the hall blacked- out. (13) Check that a suitable pointer is available and that it works. (14) Check that spare bulbs for the projector(s) are available and accessible. (15) If the lecture requires substantial use of a cine-projector or tape recorder, make sure that a spare tested machine is available and fitted with the necessary plugs and sockets. (16) Check that during the lecture there will be no extraneous noise in the theatre from discos, pneumatic drills, steam hammers, etc. (17) Check that the room booking is OK the day before the lecture. (18) The tables given on pages 38-39 enable the suitability of projectors to be ascertained before trying them in the lecture theatre. The distances are given in feet and also in metres.

Slide Projectors. Focal length o f lenses required to fill a semen o f widths shown at various projection distances with a 50 mm

sq slide from 35 mm film

Focal Screen length width mm metres

1 1.5 2 2.5 3

50 ~ 1.5 2.2 2.9 3.7 4.4 75 ~ ~ ~ 2.2 3.3 4.4 5.5 6.9

l OO 2.9 4.4 7 3 8.8 150 ~ ~ '~_ 4.4 6.6 8.8 10.9 13.2 200 ~ E~ 5.8 8.8 11.7 14.6 17.6 300 ~ 8.8 13.2 176 22.0 26.3

Useful References (1) Let's Stamp Out Awful Slides, published by Kodak Ltd (2) R Kingslake, Section 18, Handbook of the Society of Photographic Science and Engineering, New York, 1973 (3) P J Evennett and M J W Webb, Preparation and Projection of Slides, Proc Royal Microscopical Soc, March 1978, Vol 13 (4) Kodak Data Book

Acknowledgements I should like to thank my colleague, Mr B D Peacock, for help- ing with the preparation of this guide. The mistakes, if any, are entirely my own.

B I O C H E M I C A L E D U C A T I O N 11 (1) 1983

Focal length o f lenses required to fill a screen o f widths shown (using a 2" sq slide from 35 mm film) at various projection distances

39

Focal Screen length width (inches) (feet)

3' 4' 5' 6' 7' 8' 9' 10'

3" ~ 6.6 9.0 I 1.2 13.6 15.7 17.9 20.1 22.4 4" ~ 8.8 12.0 14.9 15.1 20.9 23.9 26.8 29.9 5" ~ *~ 11.0 15.0 18.7 22.7 26.1 29.9 33.6 37.3

• , - m ~ D

6.5" ~ ~ 14.3 19.5 24.3 29.5 34.0 38.8 43.7 48.3 7" ~ ~ 15.4 21.0 26.1 31.7 36.6 41.8 47.0 52.3 ~.~,, ~ 1~.~ ~ . ~ ~ . ~ ~ . ~ 44.~ ~0.~ ~%, 6~.4

10,, ~ ~ ~ . 0 ~0.0 ~ . ~ 4~.~ ~ . ~ ~9.~ 6%~ ~4.0 1~,, ,~ ~6.4 ~6.0 44.~ ~4.4 6~.~ ~4.~ ~0.4 9~.~ ~0,, ~ 44.0 60.o ~4.6 90.6 ~04.6 ~19.4 1~4.9 14~.0

Overhead Pro/ectors. Focal length o f lenses required to fill a screen o f widths shown at various projection distances 10" with a 10" x platen (distances in feet and inches)

Focal Screen length width

(inches) (feet) 3' 4' 5' 6' 7' 8' 10' 12'

8.8" 2.7 3.5 4.4 5.3 6.2 7.0 8.8 10" 2 3.0 4.0 5.0 6.0 7.0 8.0 10.0 12" ~ 3.5 4.8 6.0 7.2 8.4 9.6 12.0 12.5" ,~ ~ 3.7 5.0 6.3 7.5 8.8 10.0 12.5

'5~ ~ 4.2 5.6 7.0 8.4 9.8 11.2 14.0 14" 15.5" E "~ 4.7 6.2 7.8 9.3 10.9 12.4 15.5 18" o ,~ 5.4 7.2 9.0 10.8 12.6 14.4 18.0 22" 8 ~ 6.6 8.8 11.0 13.2 15.4 17.6 22.0 24" ~ 7.2 9.6 12.0 14.4 16.8 19.2 24.0 30" ~ 9.0 12.0 15.0 18.0 21.0 24.0 30.0 36" 10.8 14.4 18.0 21.6 25.2 28.8 36.0

10.6 12.0 14.4 15.0 16.8 18.6 21.6 26.4 28.8 36.0 43.2

Overhead Pro/ector (distances in metres) Aperture o f platen 25 cm sq

Focal length of lens in cms

Width of screen in metres

1 2 3 4 5 6 8 10

22 Distance 0.88 1.76 2.64 3.52 4.40 5.28 7.04 8.80 25 between 1.00 2.00 3.00 4.00 5.00 6.00 8.00 10.00 30 lens and 1.20 2.40 3.60 4.80 6.00 7.20 9.60 12.00 40 screen 1.60 3.20 4.30 5.40 8.00 9.60 12.80 16.00 50 in metres 2.00 4.00 6.00 8.00 10.00 12.00 16.00 20.00

The figure s in all the above tables were calculated using the approximate formula:-

width of screen distance of projector lens from screen width of aperture of slide = focal length of projector lens

all the distances being in the related units. A more accurate formula requires the addition of the focal length of the lens to all the distances between projector lens and the screen in all the tables.

B I O C H E M I C A L E D U C A T I O N 11( 1 ) 1983