Discrimination is a core ability of living beings and adaptive for survival. Evolution has made our information processing systems sensitive to differences and changes to the point of our ability to contrast objects actively At the same time, our sensory systems adapt to, ignore, and actively inhibit invariant input. By ignoring invariant input, we maximize our capacity for more informative input (Lindsay & Norman, 1972).
Attending to variation and ignoring invariance are pervasive phenomena in lay personality assessment and self-concept formation. Social comparison is crucial for the acquisition of knowledge about ourselves and about others (Festinger, 1954). Observing individual differences makes us aware of potentially relevant information for social interaction. The lexical approach assumes that human language has created names for personality differences, which allow for the prediction of behavior and thus provide the basis for effective social interaction Cohn, Angleitner, & Ostendorf, 1988).
Measurement in scientific psychology follows the same basic logic. Measurement is about discrimination, and discrimination is a basis of knowledge. Scientific psychology strives for precise and parsimonious discrimination. Parsimony is desirable because it eases scientific communication and the application of knowledge. Precision is a sine qua non criterion of scientific quality. Without precise measurement instruments, scientific psychology loses a crucial tool for the advancement of knowledge.
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