At the simplest level, recognition is based on superficial similarity, such as that between a tablespoon and a teaspoon. However, the similarity-based approach to recognition and categorization is incapable of accounting for fuzzy boundaries and different concepts of relative similarity (Robinson-Riegler, 191). Other forms of similarity-based approaches such as that based on prototypical similarity and exemplars resolve only some of the deficiencies of the classical similarity-based understanding of human recognition (Robinson-Riegler, 200). The essentialist approach, for example, provides a much more comprehensive understanding of the process and roles of concepts and classifications in human recognition because it accounts for the learned context in which recognition occurs (Robinson-Riegler, 200-201).

The classical, prototype, and exemplar explanation for human recognition cannot adequately account for the functional and contextual difference...

However, the essentialist approach incorporates those functional and contextual issues and distinctions as they relate to and explain human recognition through categorization and conceptualization (Robinson-Riegler, 202). Likewise, the fact that judgments of similarity and category are susceptible to variable manipulation also undermines the viability of the prototype and exemplar approaches, at least to the extent they suggest that judgment of apparent similarity and categorization are attributable to the same process (Robinson-Riegler, 200).
References

Ackerman, D. (1991). A Natural History of the Senses. New York: Random House.

Robinson-Riegler, G., and Robinson-Riegler, B. (2008). Cognitive Psychology:

Applying the Science of the Mind, Second Edition. New Jersey: Allyn and Bacon/Pearson.