An Empirical Investigation of the Dimensions of Product Similarity used in Design by Analogy of Electromechanical Products
Tsoka, Arnold Nkoane
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Analogical reasoning is known to be a core cognitive mechanism behind creative human tasks including the creativity in engineering design. Research shows that during product ideation, designers use analogy to transfer information from prior designs stored in their memory (the source of the analogy) to the task in hand (target of analogy). However, similar to any search process, the source product must be first identified as a potential candidate for analogy before this information transfer can take place. Two products can be similar along multiple dimensions such as their form, function, etc. The dimensions of similarity between two products that designers use in their cognitive domain to identify a product as a potential source of analogy for a given target product have not been investigated in prior research. This research addresses this gap through multiple empirical human-subject experiments that show evidence for up to eight different dimensions of product similarity that designers (experiment subjects) used for this purpose. Two different studies, namely the “pilot study” and the “main study”, were conducted using total one hundred voluntary participants. Each participant was presented with a product to be designed (target), described with a photo and name. The designer was asked to identify potential source products of analogy for the design from a list of options, where each potential source was also described with photos and names. Designers were then asked to indicate the reason why they thought each source would be useful for the design. In the pilot study, fifty designers designed three target products each, and they indicated their rationale by choosing dimensions of similarity from a list of five options, thus producing 50 designers × 3 target products× 5 source product options× 5possible dimensions= 3,750data points. In the main study, an additional fifty designers solved two target products each, and they explained their rationale in plain-English. Semantic analysis of this written text revealed the possibility of eight different dimensions, thus producing 50 designers × 2 target products × 5 source product options × 8 possible dimensions = 4,000 data points (although only 2,440 were used after rejecting the invalid ones). Analysis of this large amount of data shows that designers use up to eight dimensions of analogy, namely, working principle, function, structure, energy flow, human interaction, material flow, behavior and purpose of the products. The data suggests that the first six dimensions account for over 99% of the analogy instances, while evidence for the last two dimensions is insufficient. Among the first six, the first four account for 86% of analogies. Thus, this research shows that there are at least six discernable dimensions of product similarity that designers use to identify potential source products of analogy for designing a given target product.