11th Sept - Supriya Gurtu (Group J)

Perceptual maps are sometimes called product maps, sociograms, sociometric maps, psychometric maps, stimulus-response diagrams, relationship maps, concept maps, etc. A perceptual map represents symbols that convey information about perceived relationships between the objects represented by the symbols.

Perceptual Map is a misnomer. Usually, a perceptual map is taken to be a map that involves object-to-object relationships that are not amenable to simple, physical measurement.

Perceptual Maps can be created in two ways – by ‘Overall Similarity Method’ and by ‘Attribute Similarity Method’.

Perceptual maps can have any number of dimensions but the most common is two dimensions. The first perceptual map below shows consumer perceptions of various automobiles on the two dimensions of sportiness/conservative and classy/affordable. This sample of consumers felt Porsche was the sportiest and classiest of the cars in the study (top right corner). They felt Plymouth was most practical and conservative (bottom left corner).

 

In Overall Similarity Method, attributes for comparison are not provided, hence the comparison is difficult. This should only be used if we have a thorough knowledge about the field. In Attribute Method, ratings based on certain attributes is used.

Objects can be anything. They can be stimuli, constructs, artifacts, characteristics, traits, people, companies, bones, arrowheads, words, discussion topics, and so forth. The MDS algorithm uses object-to-object proximity information to construct the map.

Proximity is some measure of likeness or nearness, or difference or distance, between objects. It can be either a similarity (called a resemblance in some disciplines) or a dissimilarity. If the proximity value gets larger when objects become more alike or closer in some sense, then the proximity is a similarity. If the opposite is the case, the proximity is a dissimilarity.

Proximity values can be calculated, measured, or just assigned based on someone's best judgment. If calculated, they typically are based on some mathematical measure of association (correlation, distance, interaction, relatedness, dependence, confusability, joint or conditional probability, pilesort counts, and so forth) operating on a set of attributes.

 An attribute is some aspect of an object. It may be called a factor, characteristic, trait, property, component, quantity, variable, dimension, parameter, and so forth. The attributes should be presented in a form where each is normalized (standardized) to some kind of range or standard deviation, but Permap can do the normalizing internally if so desired. 

Sources :

Wikipedia

Paper by Dr. Ronald B. Heady, University of Louisiana at Lafayette (retired)
Dr. Jennifer L. Lucas, Agnes Scott College on MDS Analysis using Permap