This work investigates how consumers make preference judgments when taking into account both product form and function. In prior work, where aesthetic preference is quantified using visual conjoint methods, aesthetic preference and functional preference were handled separately. Here, we introduce a new methodology, metaconjoint analysis, for testing the hypothesis that when consumers make decisions taking into account both a product's form and its function they employ a more complex decision-making strategy than when basing their decisions on form or function alone. We anticipate that this strategy will involve both analytical and emotional processes. When compared with participant ratings of form and function combinations across 28 subjects, the metaconjoint model is shown to have a correlation that was not statistically different from an additive model of form and function. However, unlike the additive model, the metaconjoint model gave additional information about how participants make tradeoffs between form and function. Next, we developed a novel paradigm using functional magnetic resonance imaging (fMRI) to determine what parts of the brain are primarily involved with a given tradeoff between form and function. While in the scanner, study participants were asked to make decisions in trials where only form varied, where only function varied, and where both form and function varied. Results from 14 participants suggest that choices based on products that vary in both form and function involve some unique and some common brain networks as compared to choices based on form or function alone; notably, emotion-related regions are activated during these complex decisions where form and function are in conflict. These results are consistent with the inclusion of emotion in decision-making with regards to product choice and demonstrate the feasibility of using fMRI to address questions about the mental processes underlying consumer decisions. Studying preference decisions together with their accompanying neurological activity will give engineers and designers greater insight into the consumer decision-making process.

Design fixation refers to blind adherence to a set of ideas, which can limit the output of conceptual design. Engineering designers tend to fixate on features of pre-existing solutions and consequently generate designs with similar features. The objective of this study is to leverage functional magnetic resonance imaging (fMRI) to study the brain activity of engineering designers during conceptual design in order to understand whether/where design fixation can be detected in a person’s brain when solving design problems. Design solutions indicated that fixation effects were detectable at a statistically significant level. fMRI results show increased activation in areas associated with visuospatial processing when comparing ideation activities using an Example solution to No Example solution. Activation was found in the right inferior temporal gyrus, left middle occipital gyrus, and right superior parietal lobule regions. The left lingual and superior frontal gyri were found to be less active in the example condition; these gyri are close in proximity to the prefrontal cortex, associated with creative output. The spatial patterns of activation provide evidence that a shift in mental resources can occur when a designer becomes fixated. For designers, the timing of ideation relative to the timing of benchmarking existing solutions should be considered.

In this work we investigate how consumers make preference judgments when taking into account both product form and function. In prior work, where aesthetic preference is quantified using visual conjoint methods, aesthetic preference and functional preference were handled separately. Here we introduce a new methodology for testing the hypothesis that when consumers make decisions taking into account both a product’s form and its function they employ a more complex decision making strategy than when basing their decision on form or function alone. We believe that this strategy will involve both cognitive and emotional processes. We used a two stage conjoint analysis to develop a preference function that takes both form and function into account. When compared with participant ratings of form and function combinations across 14 subjects, the model is shown to have a correlation of approximately 0.56, p < 0.001. Next we developed a novel paradigm using functional magnetic resonance imaging (fMRI) to determine what parts of the brain are primarily involved with any given tradeoff between form and function. While in the scanner, study participants were asked to make decisions between options where only form varied, where only function varied, and where form and function both varied. Results from 7 participants suggest that choices based on products that vary in both form and function involve some unique and some common brain networks as choices based on form or function alone; most important, emotion-related regions are activated during these complex decisions where form and function are in conflict. These results demonstrate the feasibility of using fMRI to address questions about the mental processes underlying consumer decisions.

In conjoint analysis, interaction effects characterize how preference for the level of one product attribute is dependent on the level of another attribute. When interaction effects are negligible, a main effects fractional factorial experimental design can be used to reduce data requirements and survey cost. This is particularly important when the presence of many parameters or levels makes full factorial designs intractable. However, if interaction effects are relevant, main effects design can create biased estimates and lead to erroneous conclusions. This work investigates consumer preference interactions in the nontraditional context of visual choice-based conjoint analysis, where the conjoint attributes are parameters that define a product's shape. Although many conjoint studies assume interaction effects to be negligible, they may play a larger role for shape parameters. The role of interaction effects is explored in two visual conjoint case studies. The results suggest that interactions can be either negligible or dominant in visual conjoint, depending on consumer preferences. Generally, we suggest using randomized designs to avoid any bias resulting from the presence of interaction effects.

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