As mechanisms of social cooperation, institutions are manifest in both objectively real, formal organizations, such as the U.S. Congress, or the Roman Catholic Church, and, also, in informal social order and organization, reflecting human psychology, culture, habits and customs. Most important institutions, considered abstractly, have both objective and subjective aspects: examples include money and marriage. The institution of money encompasses many formal organizations, including banks and government treasury departments and stock exchanges, which may be termed, "institutions," as well as subjective experiences, which guide people in their pursuit of personal well-being. Powerful institutions are able to imbue a paper currency with certain value, and to induce millions into cooperative production and trade in pursuit of economic ends abstractly denominated in that currency's units. The subjective experience of money is so pervasive and persuasive that economists talk of the "money illusion" and try to disabuse their students of it, in preparation for learning economic analysis.
Marriage and family, as a set of institutions, also encompass formal and informal, objective and subjective aspects. Both governments and religious institutions make and enforce rules and laws regarding marriage and family, create and regulate various concepts of how people relate to one another, and what their rights, obligations and duties may be as a consequence. Culture and custom permeate marriage and family. In the United States and western Europe, a transition from a conception of marriage, as license for sexual intercourse granted by Church and State, to a conception of marriage as a form of contract, freely entered into, has occasioned momentous social and political controversies regarding laws and customs governing the freedom of women, divorce, cohabitation outside marriage, contraception, and homosexuality.
Gilles Deleuze compared emergent institutions with legal codes, such that,
...tyranny is a regime in which there are many laws and few institutions; democracy is a regime in which there are many institutions, and few laws. Oppression becomes apparent when laws bear directly on people, and not on the prior institutions that protect them.
The relationship of institutions to human nature is a foundational question for the social sciences. Institutions can be seen as "naturally" arising from, and conforming to, human nature -- a fundamentally conservative view -- or institutions can be seen as artificial, almost accidental, and in need of architectural redesign, informed by expert social analysis, to better serve human needs -- a fundamentally progressive view. Adam Smith anchored his economics in the supposed human "propensity to truck, barter and exchange". Modern feminists have criticized traditional marriage and other institutions as elements of an oppressive and obsolete patriarchy. The Marxist view which sees human nature as historically 'evolving' towards voluntary social cooperation, shared by some anarchists, is that supraindividual institutions such as the market and the state are incompatible with the individual liberty which would obtain in a truly free society.
Economics, in recent years, has used game theory to study institutions from two perspectives. Firstly, how do institutions survive and evolve? In this perspective, institutions arise from Nash equilibria of games. For example, whenever people pass each other in a corridor or thoroughfare, there is a need for customs, which avoid collisions. Such a custom might call for each party to keep to their own right (or left -- such a choice is arbitrary, it is only necessary that the choice be uniform and consistent). Such customs may be supposed to be the origin of rules, such as the rule, adopted in many countries, which requires driving automobiles on the right side of the road.
Secondly, how do institutions affect behaviour? In this perspective, the focus is on behaviour arising from a given set of institutional rules. In these models, institutions determine the rules (i.e. strategy sets and utility functions) of games, rather than arise as equilibria out of games. For example, the Cournot duopoly model is based on an institution involving an auctioneer who sells all goods at the market-clearing price. While it is always possible to analyse behaviour with the institutions-as-equilibria approach instead, it is much more complicated.
In political science, the effect of institutions on behavior has also been considered from a meme perspective, like game theory borrowed from biology. A "memetic institutionalism" has been proposed, suggesting that institutions provide selection environments for political action, whereby differentiated retention arises and thereby a Darwinian evolution of institutions over time.
Public choice theory, another branch of economics with a close relationship to political science, considers how government policy choices are made, and seeks to determine what the policy outcomes are likely to be, given a particular political decision-making process and context.
Sociology traditionally analyzed social institutions in terms of interlocking social roles and expectations. Social institutions created and were composed of groups of roles, or expected behaviors. The social function of the institution was executed by the fulfillment of roles. Basic biological requirements, for reproduction and care of the young, are served by the institutions of marriage and family, for example, by creating, elaborating and prescribing the behaviors expected for husband/father, wife/mother, child, etc.
In history, a distinction between eras or periods, implies a major and fundamental change in the system of institutions governing a society. Political and military events are judged to be of historical significance to the extent that they are associated with changes in institutions. In European history, particular significance is attached to the long transition from the feudal institutions of the Middle Ages to the modern institutions, which govern contemporary life.