WHAT IS MULTIDIMENSIONAL SCALING?

Multidimensional scaling (MDS), also known as perceptual mapping, is a procedure that allows an experimenter to determine the perceived relative image of a set of objects (firms, products, ideas, or other items associated with commonly held perceptions). The purpose of MDS is to transform consumer judgments of similarity or preference (e.g., preference for stores or brands) into distances represented in multidimensional space. Assume that objects A and B are judged by respondents to be the most similar compared with all other possible pairs of objects. MDS techniques will position objects A and B so that the distance between them in multidimensional space is smaller than the distance between any other two pairs of objects. The resulting perceptual map, also known as a spatial map, shows the relative positioning of all objects.

Multidimensional scaling is based on the comparison of objects. Any object (e.g., product, service, image, aroma) can be thought of as having both perceived and objective dimensions. For example, Thisvi's management may see their product (a car) as having two color options (red and green), a 100-horsepower motor, and a 124 inches wheel-to-wheel base. These are the objective dimensions. On the other hand, customers may (or may not) see these attributes. Customers may also perceive the Thisvi car as expensive-looking or fragile. These are perceived dimensions, also known as subjective dimensions. Two products may have the same physical characteristics (objective dimensions) but be viewed differently because the different brands are perceived to differ in quality (a perceived dimension) by many customers. Thus, the following two differences between objective and perceptual dimensions are very important:

1. Individual Differences: The dimensions perceived by customers may not coincide with (or may not even include) the objective dimensions assumed by the experimenter. We expect that each individual may have different perceived dimensions, but the experimenter must also accept that the objective dimensions may also vary substantially. Individuals may consider different sets of objective characteristics as well as vary the importance they attach to each dimension.

2. Interdependence: The evaluations of the dimensions (even if the perceived dimensions are the same as the objective dimensions) may not be independent and may not agree. Both perceived and objective dimensions may interact with one another to create unexpected evaluations. For example, one soft drink may be judged sweeter than another because the first has a fruitier aroma, although both contain the same amount of sugar.

The challenge to the experimenter is first to understand the perceived dimensions and then to relate them to objective dimensions, if possible. Additional analysis is needed to assess which attributes predict the position of each object in both perceptual and objective space.

A note of caution must be raised, however, concerning the interpretation of dimensions. Because this process is more an art than a science, the experimenter must resist the temptation to allow personal perception to affect the qualitative dimensionality of the perceived dimensions. Given the level of researcher input, caution must be taken to be as objective as possible in this critical, yet still rudimentary, area.