Factors in the Use of Lap‐dissolve Presentation Methods for Teaching the Visualisation of Spatial Transformations

Abstract

Two experiments were performed to study the effects of varying the exposure-time and the dissolve-time in the use of a lap-dissolve control unit in presenting programmes intended to teach 14-15-year-old students to visualise the effects of performing reflections and rotations on molecules represented in diagrams. Both experiments employed a two-dimensional design with three levels for each of the two factors. The Rotations Programme was not effective with any of the combinations of exposure-and dissolve-times. The effectiveness of the Reflections Programme showed a significant U-shaped relationship as the exposure-time changed from 5 through 7.5 to 10 seconds. There was no significant effect involving dissolve-time.In all the natural sciences there are topics which require students to visualise the effects of performing spatial operations on three-dimensional structures as represented in diagrams. For example, in order to understand the ideas of three-dimensional symmetry-a recurring theme which pervades many subjects-students should be able to visualise rotations, reflections and inversions. However, Seddon, Tariq & Santos Veiga (1982) have reported the results of an investigation which demonstrated that high proportions (i.e. 17-73%) of very able science students in English sixth-forms and a Portuguese university were unable to perform these tasks satisfactorily on diagrams of molecules. For example, such students were unable to understand that the lower diagrams in Fig. 1 represented the structures in the upper diagrams after rotation about the three Cartesian axes respectively. These results have alarming implications, and it is obviously necessary to devote considerable effort in devising special teaching methods which can be used, either in a remedial way for students in sixth-forms and universities, or as an integral part of lower levels of the curriculum.Two different methods of teaching students to visualise rotations have recently been described by Seddon, Eniaiyeju & Jusoh (1984), who reported successful results with Nigerian students at college and university level. In one method, students were required to observe real models actually rotating, and simultaneously to 189

An unexpected effect in the use of models for teaching the visualization of rotation in molecular structures

“…However, there was a significant difference between the mean of the control and that of the experimental group that had not used the models (p<0-05). The results of the present experiment differ from those of Seddon El Farra and Jusoh (1984) in that the programmes based only on diagrams brought about significant learning with students of this age group. It seems probable that the different results arise because the speeds of rotation were different in the two experiments.…”

“…While the technique based upon the models has been found to be effective with a variety of age groups (Seddon, Eniaiyeju andJusoh 1984, Jusoh 1979), it has also been found that the sequential presentation of the diagrams was not at all effective in teaching the visualization of rotations to 15-year old English students (Seddon, El Farra and Jusoh 1984). Perhaps the demands of understanding the diagrammatic sequences were too abstract for students at this level of cognitive development, whereas the models provided a more appropriate concrete form of representation.…”

“…The choice of the period of time over which diagram was exposed or visible was a matter of considerable concern because previous research shows that this is a factor which determines how well students learn from these sequences applied to the teaching of reflections (e.g. Seddon, El Farra and Jusoh 1984). In the absence of direct information as to suitable exposure times for teaching rotations, it was decided to make two different videotapes, in which the exposure times for successive diagrams were 0-10 and 025 seconds, respectively.…”

“…In another, students study a sequence of diagrams which represent a threedimensional structure at successive stages during a rotation. In the original experiment, Seddon, Eniaiyeju and Jusoh projected the diagrams from 35 mm slides, but it is also possible to present the diagrams effectively using videotape (Seddon, El Farra and Jusoh 1984), overhead projection transpao Original orientation…”

The Effects of Colour in Teaching the Visualisation of Rotations in Diagrams of Three‐dimensional Structures

“…The teaching method of Seddon & Shubber was based on that developed and used extensively by Seddon and various co-workers (e.g. Seddon, Eniaiyeju & Jusoh, 1984;Seddon, Tariq & Dos Santos Veiga, 1984;Seddon, El Farra & Jusoh, 1984), and uses instructional programmes in which students observe sequences of diagrams each representing a three-dimensional structure at successive stages during a rotation. Seddon & Shubber hypothesised that using colour in the drawing of different parts of the diagrams would enable students to compare more easily the position of corresponding parts of a structure in successive diagrams, and thereby help students to see what should happen to the different parts of the diagrams as the structure rotates.…”