An evolutionary perspective
"Human phenomena are biological in their roots, social in their ends and mental in their means."
The origins of trust and the reasons why individuals decide to trust have a long evolutionary history that connects our brain structure, personal experience, knowledge, emotions, needs, circumstances, evolutionary memory, and the conditions in which we live.
For some researchers, our ability to trust is primarily due to a biological instinct that translates a type of (pre-programmed) aptitude or adaptive capacity to accept some things at face value. This allows us, with or without evidence, to believe that things are as they appear.
Human beings have always lived in an environment of uncertainty and incomplete information. The first function of trust is precisely to enable decision-making under uncertainty and risk, and, consequently, move on!
In addition, it seems we have an inborn propensity to seek and find patterns, whether or not they have meaning, and to find and believe in relationships between things, even if they do not exist. This mental process is called "apophenia" and can generate two types of errors: false positive (type-1 error), the false identification of patterns, or false-negative (type-2 error), missing the identification of patterns, even when they exist. However, human beings are evolutionarily programmed to commit more type-1 errors, since this type of error is generally more cost-effective when compared to the type-2 errors.
Research has also shown that this tendency for "patternicity" is heightened by feelings of uncertainty and discontent, leading people to believe, see, or discover illusory patterns when they feel on the verge of losing control of themselves and/or their lives, making them therefore more sensitive to the detection of patterns.
The whole process can be seen as an adaptive response caused by evolutionary pressure since trust and “trustworthiness” allow for and facilitate preservation, cooperation, survival, and adaptation.
That’s why, I and other researchers consider that trust has biological roots because, together with this evolutionary pressure, it will have improved the human species ability to survive.
From this biological and evolutionary perspective, it appears humans have inherited neural mechanisms that have evolved in a way that allows for a continuous assessment of the threat levels around them. This means that we are constantly monitoring and evaluating the circumstances to which we are exposed as positive or negative, promoting flight or fight approach. This continuous evaluation of our environment results in a form of belief that is a type of "certainty" that allows us to act.
If we lived in an environment of "complete uncertainty," without any kind of "minimal certainty," we would be paralysed by hesitation. Therefore, trust generates a sense of uncertainty control and enables our decision making and action.
In addition, the underlying idea of this theory postulates that we will only survive in an uncertain world if we cooperate; and we cannot genuinely cooperate without trust. In fact, across all societies, we can see that trust seems to be directly linked to cooperation. As such, our instincts will have probably been the generators of the first phenomenon of trust.
Based on what Rousseau called the "Social Contract," we assume that human society is composed of a group of equal individuals who act in a rational way. That is, if individuals cooperate, each one is better off than if everyone fights each other or abandons the group. This continuous "game" of "social contract" suggests that it is easier for a group of equal individuals to behave "rationally" or to seek a "non-zero" outcome, and to cooperate among themselves in order to ensure their preservation, adaptation, and reproduction because, as a group, they are better able to respond to environmental pressures.
This process becomes so internalised that when we trust in our daily lives, we do not think too much about it in most situations, and we tend to make decisions to trust people, machines, and systems unconsciously. However, behind every decision we make, evolution, and our life experience has prepared us for that moment.
If you would like to know more about this, meet me in Helsinki on November 26th and 27th for a workshop on The Trust Factor.
 M. O'Hara, 2004; M. Shermer, 2011; P. Churchland, 2011
 P. Finuras, 2015
 J. Bering, 2010; A: Todorov, 2011
 M. O'Hara, 2004; P. Churchland, 2011
 R. Wright, 2000