Elsevier

Design Studies

Volume 42, January 2016, Pages 110-136
Design Studies

The effects of representation on idea generation and design fixation: A study comparing sketches and function trees

https://doi.org/10.1016/j.destud.2015.10.005Get rights and content

Highlights

  • Representations in engineering design promote clarity, but cause fixation.

  • A representation influences the creativity of the designer.

  • During idea generation, function trees offer advantages for reducing fixation.

Representations in engineering design can be hand sketches, photographs, CAD, functional models, physical models, or text. Using representations allows engineers to gain a clearer picture of how a design works. We present an experiment that compares the influence of representations on fixation and creativity. This experiment presents designers with an example solution represented as a function tree and a sketch, we compare how these different external representations influence design fixation as they complete a design task. Results show that function trees do not cause fixation to ideas compared to a control group, and that function trees reduce fixation when compared to sketches. Results from this experiment show that function tree representations offer advantages for reducing fixation during idea generation.

Section snippets

Background

In the engineering design process, conceptual design is the front-end phase that relies on favorable idea generation. Idea generation can be defined as the process of generating, developing, and communicating ideas, where an idea is understood as a basic element of thought that can either be visual, concrete, or abstract (Jonson, 2005). During the conceptual design stage, engineers consider numerous possible solution concepts and ideas (Pahl & Beitz, 1996) while addressing potential feedback

Experimental overview

This paper presents an experiment designed to assess if, and to what extent, fixation occurs in engineering idea generation based on the representation of the example given. The participants were asked to solve a design problem with an example as an aid. Participants viewed a poor design example in the form of a sketch, function tree, or a combination of both, which are the designated conditions for the experiment. A control condition where participants did not receive an example was also

Experiment

This experiment was designed to assess the effectiveness of function trees on fixation to features of a design. We investigate if an example represented as a function tree reduces fixation compared to the same example represented as a sketch. We have an additional condition that includes both representations, and we check to see if there are any advantages in having a function tree presented with a sketch.

Hypothesis 1:

Fixation. Function trees will reduce fixation compared to sketch representations. This is

Evaluation metrics

To measure fixation, creativity, and the overall effectiveness of the solutions generated, six metrics were used: quantity of non-redundant ideas, number of repeated example features, percentage of example features used, quality of concepts, novelty of concepts, variety of concepts, and percentage of solutions using a gas engine. Four of these metrics, the quantity (non-redundant), quality, novelty, and variety of ideas are based on definitions proposed by Shah, Kulkarni, and Vargas-Hernandez

Results

Non-parametric Kruskal–Wallis tests were performed on the data in this experiment because the data does not satisfy the normality and homogeneity of variance requirements; therefore, one-way parametric analysis of variance (ANOVA) results would not be reliable. Additionally, pair-wise a-priori comparisons using Mann–Whitney tests were employed, which are equivalent to t-tests for non-parametric data. A summary of these results is given in Table 2.

Discussion

The results from this experiment provide important and interesting results concerning the role of function trees in idea generation. We see from the results in this paper that function trees do not cause fixation. The results also further support that sketch representations cause fixation, which has also been seen in other fixation studies.

The results from the quantity of non-redundant features show that function trees reduce fixation compared with sketches; this supports Hypothesis 1 which

Conclusions and future work

The experiment performed in this study investigated how the representations of an example given during idea generation affect and reflect on design fixation. In the experiment, we explored function tree and sketch representations while using a poor design example. We found that function trees are not fixation inducing, and that combining a sketch with function trees tends to reduce idea fixation, while reinforcing and increasing example feature fixation.

The results from this experiment provide

Limitations

The data for this paper were collected from students in the same course given during two consecutive semesters. The same instructor taught both classes, and the same material was taught during both semester. It is unlikely that this semester split affected the results in anyway. There were no significant differences comparing the results from both semesters with each other (after all the data had been blindly analyzed).

The students participating in the study were not calibrated with a pre-test

Acknowledgements

Partial support for this work was provided by the National Science Foundation Award Nos. CMMI-100095 and CMMI-1322335. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. We are grateful to the anonymous reviewers for providing feedback and advice that greatly strengthened this paper.

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