Representing the cell in diagrammatic form: a study of student preferences.
Diagrams in textbooks continue to play an important role in biological science teaching for the conveying of information. Certain types of diagrams can enhance textual explanations of particular scientific concepts (Sheredos et al., 2012). What makes diagrams effective for explanation is their ability to group information that is to be used together in a way that other representations, such as photographs, can not. There is general agreement in the education community that the use of diagrams and visualisation is an effective teaching strategy (Vavra et al., 2011).
The teaching and learning of biology frequently involves communication about types of things that vary in their details, though they are the same in terms of generic properties (Perini, 2012). Biologists and biology educators face this issue when communicating about any sort of biological structure, from organelles to whole organisms. 'Real' images such as photographs and electron micrographs convey detailed content about the properties of the particular individual structure pictured in the figure, whereas schematic drawings convey information about a broad category by conveying content about properties all or most of its members share, while often remaining silent about the detailed properties that vary among the members. Compared to the other types of diagrams, schematic drawings lack capacity for precision, but this form of representation is nevertheless well suited to convey information that generalises about objects that differ in terms of specificities, but share 'higher order' (i.e., definitive for that category) features.
A number of studies provide insight into the characteristics of students who benefit from specific visualisations and the effect of visualisation on student performance in science. Huk (2006) studied the educational value of three-dimensional visualisations in cell biology using a CD-ROM with 106 German biology students at college and in high school. Complex 3-D models of plant and animal cells most benefited students with high spatial visualisation ability by assisting the recall of auditory and visually presented material. However, the 3-D model resulted in cognitive overload for students with low spatial visualisation ability. The finding was similar to that of Wu and Shah (2004), who showed that highly developed visuospatial ability is a prerequisite for understanding in science.
Although there are studies that show that students who used integrated (diagrambased with text) explanations are better able to understand concepts (e.g., Butcher, 2006; Davenport et al., 2007), applied research in education suggests that student's visualisation literacy could be more explicitly linked to their own observations, representations and reasoning (Tytler & Hubber, 2011). Most biology books include more text than diagrams, and students may try to learn biology mainly from the text with little recourse to the diagrams. Conversely, they may focus on given diagrams with a view to memorisation rather than as conceptual aids.
A common form of scientific diagram is a line drawing, typically presented in black pen or pencil and generally used to show a two-dimensional schematic or sectional representation of objects. In biology, subject matter frequently includes cell morphologies and contents, tissues, organs and whole organisms, as demonstrated in works such as Bracegirdle and Miles (1971, p. 37) and Stevenson and Mertens (1976). Some contemporary representations conform to this style, but in more recent publications (e.g., Miller & Levine 2004, p. 175) biological drawings commonly contain elaborations such as shading, colour, and three-dimensionality. Amongst school science resources, there is a continuum of visualisations from schematic line drawings to photo-realistic images.
This article reports the findings of a study into student preferences for diagrammatic representation of cells at a qualitative level. Two hundred and twenty first-year science students at an Australian university were involved in this study that took place during their first week in higher education, prior to any teaching about cell biology. This was part of a larger survey-based study into the problem of scale in the interpretation of pictorial representations of cell structure, previously reported by Vlaardingerbroek, Taylor and Bale (2014). At the end of this largely quantitative survey students were presented with three items depicting different ways of representing cells. For each item, the students were asked for their preference between A and B and to briefly justify their choice. The three items used in the study are presented below. This qualitative part of the study has not been reported previously.
A ten-item instrument was devised to probe student's interpretation of scale as it pertains to pictorial (both diagrammatic and 'real' in the form of photographs) representations of cells and cell structure. The findings of this component of the research have been reported by Vlaardingerbroek, Taylor and Bale (2014). Three additional qualitative items were included to determine whether students had particular preferences for diagram type. In each of the three items, cell diagrams were presented in what the authors considered to be 'opposite' pairings, namely, 'three-dimensional' and 'two-dimensional; 'shaded' and 'line'; and 'colour' and 'greyscale'. Only the findings based on these three qualitative items are reported here.
The instrument was administered to over 200 first-year biology students at an Australian university prior to the commencement of lectures. Participation was both voluntary and anonymous. Participants were, however, asked about their high school background as well as indicating their gender and their target degree major.
Responses to each item were initially categorised according to preference choice. Then, for each item, the responses where categorised according to the stated reason for the choice.
Of the 218 valid responses received, 59 (27%) selected response option A while 159 (73%) selected response option B--a ratio of 2.7; 1 in favour of B (Chisquare = 45.87, p<0.001). This reveals a marked preference for the shaded three-dimensional representation of the animal cell. In general, students explained their preference for the shaded three-dimensional representation in terms of the clarity with which this form portrayed the organelles and internal structure of the cell. Others felt that it was a more realistic representation, as cells are actually three dimensional in nature. Representative comments are presented here.
* I like the depth perspective. There is also a lot more detail.
* Contains more depth with organelles being more distinct to one another.
* Shows the organelles in 3-D so you can better understand the arrangement of the cell.
* The 3-D structures allow you to understand the shape of each organelle.
* It is easier to differentiate between organelles.
* The image drawn as 3-D helps to remind the student that cells are not flat, and better represents the size and shape of each organelle.
* More realistic, makes it easier to visualise when looking at cells under a microscope.
Those who preferred the two-dimensional representation generally made reference to clarity and ease of learning.
* Easy to memorise, not confusing.
* Simple to understand.
* More simple to understand and learn.
For this two-dimensional representation of a plant cell there was a significant preference for the shaded depiction with 129 responses (60%) opting for A against 85 (40%) choosing option B (non-shaded) (Chisquare = 9.05, p<0.001).
Those who preferred the shaded version of the diagram generally commented that it allowed them to distinguish the cytoplasm, vacuole and organelles more easily, as exemplified by the following comments.
* Can see vacuole and cytoplasm easily.
* The contrast/shading shows up the different organelles much better.
* The grey background shading allows an easier viewing and separation of the organelles. It is also easier to remember than B.
* The different colours help distinguish the different parts and organelles of the cell. Makes it easier to understand and study the plant cell.
By contrast, those students who preferred the non-shaded depiction of the cell generally found this clearer and easier to interpret.
* Simpler, easier to understand. Shading in 'A' is confusing.
* Simple, no shading, easier to duplicate.
* Simple, uncluttered, straightforward.
* The white background in the cell makes the lines of the organelles stand out, making the cell easier to see.
In this item, preferences for black and white or colour resulted in 116 of the 211 valid responses (55%) opting for B and 95 (45%) opting for A. These preferences did not differ significantly (Chi-square = 0.15, NSD).
ITEMS USED IN THE SURVEY INSTRUMENT
Item 1 depicted a typical animal cell drawn in two and three dimensions.
Item 2 depicted a typical plant cell with and without shading.
Finally, Item 3 presented a cell (this time, part of an algal filament) using black-and-white and colour.
However, there were qualitative differences in the reasons offered in support of the chosen preference. Many of those who preferred the coloured version of the cell indicated that this was for reasons of aesthetics or clarity.
* Colours are aesthetically pleasing, makes the image easier to look at, and distinguishes organelles clearer.
* Colour shows the different organisms and the pretty colours keep me interested.
Others found that the colours assisted them in distinguishing structures and organelles.
* Defines cell wall and chloroplasts more easily.
* Can see the differences between colours of structures--chloroplasts: green.
* Colour coding can work well with memorising.
* Shows chloroplasts for photosynthesis-- essential for memorising.
However, those with a preference for the black and white depiction generally found the colours distracting or unrealistic.
* These colours are distracting. Do they represent the real-life colours? And are the real-life colours relevant?
* The colours in the other picture are confusing because the nucleus and vacuole have same colour.
* Colour is unnecessary and does not display the cell correctly.
* Cytoplasm has no colour therefore the yellowing calls for a false interpretation.
Clearly references to memorisation above suggest that students have an eye towards assessment and thus have a preference for anything in the cell representation that helps them to remember structures.
INTERACTIONS BETWEEN ITEMS
The three questions and two options per question produced eight possible interactions. Responses for each interaction are presented in Table 1.
Of respondents who chose two-dimensional, 68% also chose no shading. The least popular combination was two-dimensional, shade and colour. Of those who chose three-dimensional, 72% also chose shading. The most popular combination with 30% of all responses was three-dimensional, shade and colour (Chi-square = 92.80. This value applies to the whole table, not to any single combination). The next most common combination was three-dimensional, shade and no colour (22% of all responses).
Significant divergence occurred between student preferences in cell diagrams. A small cohort favoured schematic representations without shading, colour or three-dimensionality. Other small cohorts favoured similar simple two-dimensional visualisations. Arguments for schematic styles of representation tended to relate to learning tasks such as duplication, labelling, differentiation, interpretation, memorisation and understanding. For these students, it seemed that the clarity and simplicity associated with schematic visualisation of selected relevant structures were preferred to the realism of photo-like referents. Two broad reasons appear to underpin student arguments. The first is the congruence, at least for some respondents, between schematic representations and practical in-class tasks such as drawing and labelling. Secondly, some responses appear to be based on the notion that emphasising selected critical details in schematic representations facilitates cognitive processes.
At the other end of the visualisation continuum, a large cohort of students preferred realism in cell representations, represented in this study by three-dimensional, shading and colour. Another large group favoured three-dimensional and shading without colour. Many arguments advanced in favour of realistic representations pertained to visual attributes such as depth, shape, detail, perspective, colour, aesthetics, codification and interest, although some responses also alluded to differentiation of structures, memorisation and understanding. Amongst these cohorts, it appeared that attributes that contributed to the construction of an 'accurate' mental image were preferred whether or not they contributed to understanding or interpreting cell structure. For some, the preference was for realistic or artistic attributes rather than scientific utility.
These divergent preferences appear to be based in part on different conceptions of visual representations in science. Some students perceived diagrams as models (symbolic or schematic visualisations of represented structures) whilst for others the purpose of diagrams was to present an image as analogous as possible to its referential object.
Whether or not student perceptions related to learning are realised remains untested in the current study and the literature is inconclusive on the educational merits of different styles of representation. In an early study of static representations, Arnold and Dwyer (1975) noted that better conceptual understandings were achieved using realistic rather than schematic visualisations, yet, using dynamic representations, Scheiter et al. (2009) advanced contrary evidence. Nevertheless, many of the arguments advanced by respondents in the current study indicated that they believed that their understandings were enhanced by one or more visualisation styles.
The discordance in student views exposes a paradox in the use of scientific diagrams in secondary science teaching, and perhaps also in their underpinning pedagogies. The use of photo-like three-dimensional cell representations in science texts has increased markedly in the last two decades and similar static and interactive diagrams are now common via Internet sources. The aesthetic appeal and perceived 'quality' of such representations are no doubt important, but these attributes should not be used to construe that complex three-dimensional representations interpret reality better than simple two-dimensional schematics commonly used in secondary science drawing activities.
The scope of the present project does not elicit clear reasons for the discordant preferences observed. We might suppose that some of the variability relates to differences in so-called 'learning modes' (see, for example, Fleming, 1995) and 'intelligences' (see, for example, Gardner & Hatch, 1989). However, based on the student responses reported here, we expect that some of the variability derives from differing student exposure to diagrams in school science praxis. For example, to what extent were students engaged in constructing their own representations of cells? Did their secondary science experience explore the purpose of diagrammatic representations? Were the differences between models and images explored in the context of the biology laboratory or classroom? We argue that a clearer articulation of the purpose and praxis of drawing in secondary school biology is needed to address the confusion evident in student conceptions and preferences.
Our work suggests that functionality, like beauty, is in the eye of the beholder. Some students clearly approach diagrams from a largely instrumental perspective, as an aid to memorising material that they will need to recall in an examination. To at least some of these students, whether or not a diagram clearly represents the reality they purport to represent would be a moot point. The aesthetic attributes of a diagram are rated highly by some students, and not at all by others. One common theme that emerged is the underlying assumption on many student's part is that a diagram is supposed to show what an object actually looks like. This view represents a fundamental misunderstanding of the nature of diagrams as models as opposed to 'photographic' images. Teachers need to be aware that every student in their class is looking at a given diagram in a slightly different way, with different perceptions of the information that it is supposed to convey. A better integration of the use of diagrammatic representations with practical work in microscopy and a deeper understanding of the technology used by scientists to build up conceptual images of cellular structure would help students gain a better insight into what diagrams are, and what they are for.
In summary, this study reinforces the point made by various authors including Vlaardingerbroek, Taylor and Bale (2014) that many students do not see diagrams for what they are, which is models and not photographic likenesses. Some students adopt a markedly instrumental approach to diagrams--they are there to help students pass exams, whatever their scientific merit. There arises a potential paradox in that the diagrams that students like' (for any of a number of reasons-- aesthetics included) are not necessarily 'good' diagrams from a scientific point of view. Student preference is not a guide to either the technical merit of diagrams or even necessarily their usefulness as learning tools. Teachers need to be aware of these caveats when using diagrams in their teaching. They need to avoid using statements such as, "This is what a cell looks like" and draw student's attention to the nature of diagrams with a view to weaning them off the idea that a diagram is a 'snapshot' of the real thing. One of the objectives of science education is to instil in students an awareness of how science builds up models to portray reality at levels beyond the realm of human sensory perception and models of cell structure provide an excellent vehicle for addressing this goal.
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Colin Bale is a retired biology lecturer who formerly worked at the New England Institute of TAFE in Armidale, NSW.
Neil Taylor is a Professor of Science and Technology Education in the School of Education of the University of New England in Armidale, NSW.
Barend Vlaardingerbroek is an Associate Professor in the Faculty of Education of the American University of Beirut in Lebanon.
Table 1: Number of responses for each interaction for three questions. NUMBER OF INTERACTION RESPONSES * 2D, shade, colour 8 (i.e., A,A,B) 2D, shade, no colour 10 (i.e., A,A,A) 2D, no shade, no colour 20 (i.e., A,B,A) 2D, no shade, colour 19 (i.e., A,B,B) 3D, shade, colour 61 (i.e., BAB) 3D, shade, no colour 46 (i.e., B,A,A) 3D, no shade, no colour 16 (i.e., B,B,A) 3D, no shade, colour 26 (i.e., B,B,B) ^ The number of respondents in the interactions is 206, less than the total number of respondents. This is because some respondents either did not answer one or more questions or because they answered "A, B" for one or more questions, in which case they were not included in the count.
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|Author:||Bale, Colin; Taylor, Neil; Vlaardingerbroek, Barend|
|Date:||Mar 1, 2015|
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