Just as there are different kinds of institutions, there are different kinds of institutional change. Institutions may be habits, norms, customs, rules, or laws; change may take the form of evolutionary change or revolutionary change. The present paper is concerned with one specific type of change, namely, the drift of customs or traditions. Customs and traditions, like other institutions, generally exhibit a resistance to change due to their ceremonial character. The changes that do occur tend to be both incremental and gradual. Hence the fact of institutional drift is often obscured by its slow pace and is most frequently brought to notice by members of an older generation. In evolutionary terms, this may be seen as the imperfect reproduction of institutions over time.
This type of institutional change is not generally the result of deliberation or planning but is a process of adjustment to larger changes in the social environment. That is, the imperfect reproduction does not represent a random mutation but instead is directed by concurrent social or cultural forces. The result is a network of institutions that is "insensibly but incessantly" changing over time (Veblen  1914). The following outlines a mechanism underlying the process of institutional drift. I argue that individuals characteristically think about institutions in such a way as to maintain a consistent relationship among them so that if an important institution undergoes change, other institutions are subject to realignment.
Cognitive Processing of Institutions
What accounts for the dual properties of insensibly and incessantly in institutional drift? Three aspects of how the mind operates on institutions are of particular interest for the analysis of institutional drift. First, institutions are not isolated but are mentally associated with one another. Second, in consequence of these mental associations, people seek consistency in the relationships. Third, association and consistency can operate at the nonconscious level. The process of institutional adjustment has been observed in many societies and many times. Such a widespread and cross-cultural tendency suggests a biological basis for institutional realignment. Specific properties of the mind are outlined next, followed by a brief analysis of their impact on institutional drift. The subsequent section illustrates by examining gradual drift in a prominent holiday.
The Evolved Mind
The environment in which the human mind evolved was an environment featuring the presence of other evolving humans. The presence of other evolving humans is argued to be of central importance to the evolutionary path of the human mind (Ingold 1986; Nozick 1993). All humans rely on institutions, so it is thought that institutions have adaptational advantages for survival and is further thought that the human mind has evolved in ways that facilitate the use of institutions (Redmond 2004). Long-term memory in humans is structured by association (Shapiro and Eichenbaum 1997). (1) The associational structure of memory is a product of evolution but one which is shared with primates and other species. Extensive reliance on institutions, however, is the special province of humans and was shaped in specific ways by evolution. Concepts and beliefs are linked with related concepts and beliefs in the human memory (Kunda 1999).
Researchers from various disciplines have examined a characteristically human drive for what is variously referred to as consistency, coherence, congruency, or consonance (e.g., Festinger 1962; Piaget 1963). This is a tendency toward or bias in favor of beliefs and experiences which harmonize with, or which do not conflict with, one another. The conclusion of cognitive scientists, as well as others working from an evolutionary standpoint, is that the drive for cognitive consistency is inherited rather than learned (e.g., Leslie 1988; Hirshfeld and Gelman 1994). (2) The tendency toward consistency is not limited to critical or prominent situations: Lawrence Hirschfeld and S. Gelman (1994) noted that ordinary, everyday thoughts are characterized by a coherence of beliefs and causal principles.
In order to conserve active attention for important events, the human mind processes large amounts of information below the level of consciousness. This is known as the "cognitive unconscious" and operates in parallel with conscious processing (Euster 1995; Kunda 1999). Some believe that a majority of human cognitive processing takes place are on the nonconscious level (e.g., Lakoff and Johnson 1999). (3)
A large number of institutions operate to shape human behavior, and these are associated with one another. Such relatedness is reflected in terminology such as the "institutional fabric" (Veblen 1909) or the "organic complex" of institutions (Veblen  1965). Institutions are related because they impact related aspects of behavior, that is, they coordinate behaviors into a consistent pattern. Institutions, ranging from habits to formalized ritual, regularly show a process of adjustment to one another (e.g., Ingold 1986). The ongoing adaptation of institutions in a culture is also referred to as integration (Murdock 1971). Thus changes in one may necessitate changes in others in order to preserve...