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The design, development and operation of any system or product which fails to take account of the need for a full study and understanding of the associated human factors will always be imperfect.


The fundamental problem is one of time scale. Whilst developments in avionics and cockpit displays were moving on at a pace, research into the human factors relating to the successful processing of such visual information takes much longer and was clearly trailing behind.


Returning to my original challenges, teachers of all academic subjects which rely partly, or fully, on students’ spatial perception of any two-dimensional representation of a three dimensional object – from primary school onwards – need to be aware of how we may perceive or misperceive such illustrations, particularly with an ever increasing multicultural classroom population.


In the field of engineering design, spatial perception of orthographic views of technical components is a demanding task and my approach to the second challenge was to try to understand how we perceive two-dimensional line drawings of three-dimensional objects by studying misperception using visual illusions, particularly any cultural differences in the visual perception or misperception of such line figures.


To that end, with the support of the Ministry of Overseas Development and the British Council, I made a number of visits to South Africa and Swaziland and carried out a short programme of cross-cultural visual perception tests. One set of tests was carried out with groups of Cardiff High school boy pupils and similar Swaziland High school boy pupils.


Using the Muller-Lyer illusion line figure (figure 1) engraved in black on white traffolyte, six slide rule illusion figures were made to form two sets of display conditions. A fin length of 25% of shaft length was chosen, together with three different fin angles. These three Muller-Lyer figures were displayed either centrally within the traffolyte slide-rule displays of off-centre by 10%. Pupils were required to adjust the variable horizontal line to match the fixed length. Ten repeated measures per condition were undertaken.


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What effect would the fins have on this line judgement and would there be any difference in the test results between the two groups of pupils?


The overall results of this study are given in Table 1 and are also illustrated graphically in Figure 2.


Briefly, the results indicated that:


• Identical overall mean scores were achieved with the balanced and unbalanced conditions for the three fin angle conditions. The Swaziland boys were not influenced by a lack of balance, or symmetry, existing in one set of displays.


• The influence of the illusion on the Swaziland boys was less than that of the similar UK sample by 3% across all three fin angle conditions. Plotting these results, two parallel lines are formed.


The control test used at the beginning of each subject’s test, both in the UK and in Swaziland (‘the error of the standard’) consisted of a co-linear, horizontal straight line stimuli in which the subject was required to set the variable line equal in length to the standard line. Overall, the mean results for both sets of pupils were identical; the error was in line with other published work. This suggests that if perceptual differences do exist between these two cultures, it exists within situations where the processing of peripheral information, or apparently redundant information, is influential on any main task, rather than in a situation which is devoid of ancillary, secondary, visual data associated with the task in hand.


The comprehension of an engineering drawing requires a series of visual scanning actions as we endeavour to assimilate associated line data. There are cultural differences in how we write and scan the written word – in its various forms. Can this have an impact on the comprehension of a technical illustration? Does tunnel vision play a part?


Whilst recognising the major developments in computer-generated three-dimensional graphics and paperless manufacturing, the development of spatial perception of line illustrations still forms an essential part of a young person’s development. Illustrations – in their various forms – provide a necessary


aid to support the written information given in many text books.


Visual and spatial perception begin in infancy and the perception of two-dimensional representation of the three-dimensional world is influenced not only by our cultural environment but during constant contact with pictorial illustrations throughout infant, junior and secondary education. Growth in our multi-ethnic school population may pose similar problems for teachers to that experienced by the author, albeit at a more fundamental and general level of education.


In conclusion, this small extract of my research work also serves to illustrate the fact that research into man’s ability to cope with rapidly expanding technology is, by its nature, slow and time consuming. The danger arises when the design engineer fails to wait for the outcome of the human factor studies associated with the manufacture, installation and operation of the product.


If the problems I experienced those years ago still exist, then support for more research in the field of engineering design education, and the teaching and understanding of the graphic language involved, should be encouraged, particularly as technical education spreads across the expanding developing world.


Members should take advantage of the opportunity offered by the Winston Churchill Memorial Trust Travelling Fellowship Scheme. With ever increasing worldwide market opportunities, cultural differences – in whatever form – need to be fully understood.


About the author


Neil Davies is a retired college principal, a Chartered Engineer and has a Masters degree in psychology.


He has had a lifetime career in education – both military and civilian. During his RAF service, Neil received a Guinness Award for science and mathematical teaching, reflecting the support, encouragement and resources available to promote the development of educational initiatives.


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