I read an article from the economist subtitled "The evolutionary origin of depression" which puts forward the following hypothesis:

As pain stops you doing damaging physical things, so low mood stops you doing damaging mental ones—in particular, pursuing unreachable goals. Pursuing such goals is a waste of energy and resources. Therefore, he argues, there is likely to be an evolved mechanism that identifies certain goals as unattainable and inhibits their pursuit—and he believes that low mood is at least part of that mechanism. ...

[Read the whole article]

This ties in with Kaj and PJ Eby's idea that our brain has a collection of primitive, evolved mechanisms that control us via our mood. Eby's theory is that many of us have circuits that try to prevent us from doing the things we want to do.

Eliezer has already told us about Adaptation-Executers, not Fitness-Maximizers; evolution mostly created animals which excecuted certain adaptions without really understanding how or why they worked - such as mating at a certain time or eating certain foods over others.

But, in humans, evolution didn't create the perfect the perfect consequentialist straight off. It seems that evolution combined an explicit goal-driven propositional system with a dumb pattern recognition algorithm for identifying the pattern of "pursuing an unreachable goal". It then played with a parameter for balance of power between the goal-driven propositional system and the dumb pattern recognition algorithms until it found a level which was optimal in the human EEA. So blind idiot god bequeathed us a legacy of depression and akrasia - it gave us an enemy within.

Nowadays, it turns out that that parameter is best turned by giving all the power to the goal-driven propositional system because the modern environment is far more complex than the EEA and requires long-term plans like founding a high-technology startup in order to achieve extreme success. These long-term plans do not immediately return a reward signal, so they trip the "unreachable goal" sensor inside most people's heads, causing them to completely lose motivation.

However, some people seem to be naturally very determined; perhaps their parameter is set slightly more towards the goal-driven propositional system than average. These people rise up from council flats to billionaire-dom and celebrity status. People like Alan Sugar. Of course this is mere hypothesis; I cannot find good data to back up the claim that certain people succeed for this reason, but I think we all have a lot of personal evidence that suggests that if we could just work harder, we could do much better. It is now well accepted that getting into a positive mood counteracts ego depletion, see, for example, this paper¹. One might ask why on earth evolution designed the power-balance parameter to vary with your mood; but suppose that the mechanism is that the "unreachable goal" sensor works as follows:

{pursuing goal} + {sad} = {current goal is unachievable} ==> decrease motivation

{pursuing goal} + {happy} = {current goal is being achieved} ==> increase motivation

And the "mood" setting takes a number of inputs to determine whether to go into the "happy" state or the "sad" state, such as whether you have recently laughed, whether you received praise or a gift recently, and whether your conscious, deliberative mind has registered the "subgoal achieved" signal.

In our EEA, all of the above probably correlated well with being in pursuit of a goal that you are succeeding at: since the EEA seems to be mostly about getting food and status in the tribe, receiving a gift, laughing or getting more food probably all correlated with with doing something that was good - such as making allies who would praise you and laugh and socialize with you. Conversely, being hungry and lonely and frustrated indicate that you are trying something that isn't working, and that the best course of action for your genes is to hit you with a big dose of depression so that you stop doing whatever you were doing.

Following PJ Eby's idea of the brain as a lot of PID feedback controller circuits, we can see what might happen in the case of someone who "makes it": they try something which works, and people praise them and give them gifts (e.g. money, business competition prizes, corporate hospitality gifts, attention, status), which increases their motivation because it sets their "goal attainability" sensor to "attainable". This creates a positive feedback loop. Conversely, if someone does badly and then gets criticism for that bad performance, their "unreachable goal" sensor will trip out and remove their will to continue, creating a downward spiral of ever diminishing motivation. This downward spiral failure mode wouldn't have happened in the EEA, because the long-term planning aspect of our cognition was probably useful much more occasionally in the EEA than it is today, hence it was no bad thing for your brain to be quite eager to switch it off.

So what are we to do? Powerful anti-depressants would seem to be your friend here, as they might "fool" your unreachable goal sensor into not tripping out. In a comments thread on Sentient Developments, David Pearce and another commenter claimed that there are some highly motivating antidepressants which could help. Laughing and socializing in a positive, fun way also seem like good ideas, or even just watching a funny video on youtube. But we should definitely think about developing much more effective ways to defeat that enemy within; I have my eye on hypnosis, meditation and antidepressants as big potential contributors, as well as spending time with a mutually praising community.

1. Restoring the self: Positive affect helps improve self-regulation following ego depletion, Ticea et al, Journal of Experimental Social Psychology