Cake is to God What Ball Is To Chicken
Babies only a few months old know that books (which must be contacted in order to move) are unlike people or animals (which can happily move by themselves). This is a fundamental distinction. Inanimate objects obey the laws of physics and causality, they behave in predictable and mostly well understood ways. Agents on the other hand, have minds of their own and, as such, can act upon their surroundings according to their own rules.
Experiments with both children and adults have shown that whenever an inanimate object starts to behave in an unpredictable way, people immediately start to reason about it as if it were an agent. You can verify this by looking at the language they employ. Inanimate objects are spoken of in the passive voice (a book is read and an apple is eaten), while agents - in the active one (people read and go places). Thus, when you start talking about your computer as not wanting to work or your SatNav deciding to take you on a different route, you are succumbing to the view that things which do not behave following an obvious pattern must have a mind of their own.
A notion of God speaks directly to this inclination. From a wander at why the Sun rises and sets at regular intervals there is only one step to the notion of a Sun God. This sort of reasoning spawns what is known as 'natural religion' and it underwrites in great part our readiness to believe in the existence of intelligent invisible agents.
Keep It Simple
We have evolved to derive rules and find patterns. It is easy to reason about a metal ball shattering a glass window when thrown at it, because there is a reason for this to happen: it is a common pattern, the same one each time. It is difficult to become religious about things which are well understood, such as the ball shattering the window. There is no God of balls shattering windows in the same way that there is a God of Existence.
Keep It Neat
Explanations which involve design or purpose are far more readily absorbed, than whose which merely explain observation, but do not interpret it. Experiments have shown that children accept creationism as an explanation for the origin of life far more easily than evolution, even when they are formally educated towards the latter. One study showed that children aged 5 found it more sensible for a tiger to have been 'made for eating and walking and being seen at the zoo' than the idea that 'though it can eat and walk and be seen at the zoo, that's not what it's made for' (Journal of Cognition and Development, vol. 6, p.3). Again, the idea of a Designer falls immediately into place with this propensity.
Until Seen Otherwise
When reasoning about things, it makes perfect sense to formulate whichever hypothesis we perceive to be the easiest to falsify. This is why we have working ideas such as 'innocent until proven guilty' or mathematical proof by contradiction. When it comes to truthfulness, the easiest hypothesis to invalidate is that X is telling the truth: one instance of a lie is sufficient to show otherwise. When it comes to the minds of others, the easiest hypothesis to invalidate is that everyone else is all-knowing: one instance of their limitation is enough to disprove it.
One experiment gave a group of 5 to 7 year old Maya children a gourd which, while normally holding tortillas, held on this occasion boxer shorts. They were then asked which of a number of agents (including the Catholic god known as Diyoos, the Maya sun god, the forest spirits, a bogeyman-like creature Chiichi' and a human) would know without looking the contents of the gourd. The youngest of the children guessed that all of them would. By the age of 7, most guessed the gods would know, but the human probably wouldn't. That the minds of other agents are not all-knowing is something we learn by practice and are taught by culture.
Cleanliness Is Next To Godliness
Temples and sacred spaces, along with a notion of purity and the rituals which are meant to protect it speak directly to our need of recognising and staying away from contaminants. Incidentally, this sort of fear is very politically useful - a fear of contamination translates easily into an aggression towards possible contaminants. It is also shared by all types of humans - liberals as well as conservatives become religious about purity: whether it is the purity of the food and drinks they are willing to put inside their bodies, or that of the planet itself.
I'll Show You Mine If You Show Me Yours
Finally, religion speaks to our need to read the intentions of others, which is a prerequisite of collaboration. In smaller communities, kinship (being blood related) and reciprocity (expecting something in return) sufficed for enforcing this sort of behaviour amongst individuals. In small hunter-gatherer communities, where everyone knew everyone else, the Gods had no moral concern. There was no need to. Alas, as communities grew larger, individuals started to misbehave under the cloth of anonymity. This is when an all-knowing, all-seeing and morally concerned God becomes terribly useful. This too is where requiring adherence to a series of expensive and hard to fake rituals (such as praying five times a day) helps identify free riders.
Experiments have shown again and again that people who, prior to performing a task, were prompted to think of God or religion were far less likely to cheat at it. Unfortunately, the same effect was achieved by prompting people to think of secular reminders of moral authority, words such as civic, jury, or the police. Secular society has taken over the functions traditionally performed by religion, by way of juridical institutions and mechanisms for enforcing contracts, private property and so on. The worlds most cooperative, peaceful and prosperous societies are ones in which religion has become largely a private matter better kept outside of public life. To quote from Ara Norenzayan's article '[they have] climbed religion's ladder and then kicked it away'.
A Beautiful Mind
All of these 'maturationally natural' cognitive systems underwrite what is known as 'natural religion', which is largely unscrutinised and spontaneous. There is, of course, the other kind: slow, deliberate and conscious reflection about the meaning and truth of religious claims - 'theology'. Theology sets doctrines and abstract formulations of natural religions which are conceptually complex and difficult to understand, e.g. God being three persons. Because of this, theological correctness is difficult to enforce, as the mental propensities of natural religion constantly intrude.
Experiments across cultures and religious systems have consistently shown that even after being asked to recite and affirm a set of doctrines, people still immediately abandon theological correctness in favour of popular religion. Here, science might be warned by the woes of theology. If God being three persons is a difficult concept to grasp, then what hope is there for quantum mechanics, or evolution or Maths? To quote from Robert McCauley, 'science is far more complicated than theology. Its esoteric interests, radically counter-intuitive claims and sophisticated forms of inference are difficult to invent, learn and communicate'. Scientists and theologists alike might try to explain Easter, whether by a story of resurrection or an anthropologically traceable festival of Spring. But in the end we all know it's all about the eggs.
* Easter is a good time to talk about God. I recently read a series of articles which I thought were quite interesting, so what follows is a summary of all of them. The originals can be found in the 17 March 2012 issue of the New Scientist.
