Engineering drawing is a common subject across engineering disciplines. Development of spatial visualisation skills has often been cited as one of the goals of teaching this subject to engineering students (Osborn & Agogino, 1992; Olkun, 2003). Spatial visualisation ability is defined as having the ability to mentally manipulate, rotate, twist or invert pictorially-presented stimulus objects (McGee, 1979). Examples of spatial tasks used for measuring spatial visualisation skills are paper folding tasks (Lohman, 1996), cube construction tasks (Alias et al, 2002), whole object rotation tasks (Vandernberg & Kuse, 1971) and engineering drawing tasks. Enhancing spatial visualisation skills in engineering students is important as this ability has been associated with success in problem solving in engineering (Alias et al, 2003).
Teaching spatial visualisation skills through engineering drawing have produced mixed results (Atman et al, 2000), depending on a combination of factors such as the teaching approach and the students prior knowledge and skills (Sheppard & Jenison, 1997). Basically there are two approaches to teaching engineering drawing, the "parts-to-whole" (PTW) approach and the "whole-to-parts" (WTP) approach. The PTW approach is a traditional teacher-centred approach whereby drill and practice is emphasised (Dori & Belcher, 2005), and students are taught in a sequential manner. A typical example of a unit of teaching in the PTW approach starts with drawing points, progressing to lines, to area (two-dimensional; 2D) and finally progressing to volume (three-dimensional; 3D). The authors' over 20 years' experience of teaching the subject using this method to post-secondary technical students indicates that even after receiving instructions at the 3D stage, students still find it hard to visualise the 3D object given the 2D representations of the same object. Similar observation was made by Kosse (2005) on his students who were still facing difficulties in producing professional drawings upon completion of a 13-week module on engineering graphics.
The WTP approach, on the other hand, is the reverse of the PTW approach whereby students start from 3D object representations, constructing orthographic projections first that consists of plans, elevations and sections progressing to detail drawings. Using this method students get a feeling of the relationships between 2D drawing and their related 3D objects straight away (Chen et al, 2002; Olkun, 2003). It is therefore expected that the WTP approach can produce accelerated learning of engineering drawing skills and spatial visualisation skills among students. The PTW approach is often seen by many as the appropriate method to teach a potential draughtsperson as their major task will be to construct engineering drawings. The WTP teaching approach tend to be less used by engineering instructors as most available engineering drawing text books follow the PTW sequence in the presentation of the learning materials (Bausys & Ziurene, 2010). Thus, using the WTP approach would demand more creative efforts from instructors to design suitable learning tasks. The outcome of the WTP approach, however, is hypothesised to induce accelerated learning among engineering students.
1.1 Engineering drawing curriculum
In Malaysia, engineering drawing is taught at all technical and vocational schools in the fourth and fifth year of studies. Only a few selected academic schools provide engineering drawing training to students. The fact that not all schools offer engineering drawing means that new students in the engineering program will not have even the basics of engineering drawing skills. Since engineering drawing experience contributes to spatial visualisation skills, it was therefore hypothesised that spatial visualisation skills of students with an engineering drawing background is not similar to students without the background. …