Jamais Cascio writes in the atlantic:

Pandemics. Global warming. Food shortages. No more fossil fuels. What are humans to do? The same thing the species has done before: evolve to meet the challenge. But this time we don’t have to rely on natural evolution to make us smart enough to survive. We can do it ourselves, right now, by harnessing technology and pharmacology to boost our intelligence. Is Google actually making us smarter? ...

 ... Modafinil isn’t the only example; on college campuses, the use of ADD drugs (such as Ritalin and Adderall) as study aids has become almost ubiquitous. But these enhancements are primitive. As the science improves, we could see other kinds of cognitive-modification drugs that boost recall, brain plasticity, even empathy and emotional intelligence. They would start as therapeutic treatments, but end up being used to make us “better than normal.”

Read the whole article here.

This relates to cognitive enhancement as existential risk mitigation, where Anders Sandberg wrote:

Would it actually reduce existential risks? I do not know. But given correlations between long-term orientation, cooperation and intelligence, it seems likely that it might help not just to discover risks, but also in ameliorating them. It might be that other noncognitive factors like fearfulness or some innate discounting rate are more powerful.

The main criticisms of this idea generated in the Less Wrong comments were:

The problem is not that people are stupid. The problem is that people simply don't give a damn. If you don't fix that, I doubt raising IQ will be anywhere near as helpful as you may think. (Psychohistorian)

Yes, this is the key problem that people don't really want to understand. (Robin Hanson)

Making people more rational and aware of cognitive biases material would help much more (many people)

These criticisms really boil down to the same thing: people love their cherished falsehoods! Of course, I cannot disagree with this statement. But it seems to me that smarter people have a lower tolerance for making utterly ridiculous claims in favour of their cherished falsehood, and will (to some extent) be protected from believing silly things that make them (individually) feel happier, but are highly unsupported by evidence. Case in point: religion. This study¹ states that

Evidence is reviewed pointing to a negative relationship between intelligence and religious belief in the United States and Europe. It is shown that intelligence measured as psychometric g is negatively related to religious belief. We find that in a sample of 137 countries the correlation between national IQ and disbelief in God is 0.60.

Many people in the comments made the claim that making people more intelligent will, due to human self-deceiving tendencies, make people more deluded about the nature of the world. The data concerning religion detracts support from this hypothesis. There is also direct evidence to show that a whole list of human cognitive biases are more likely to be avoided by being more intelligent - though far from all (perhaps even far from most?) of them. This paper² states:

In a further experiment, the authors nonetheless showed that cognitive ability does correlate with the tendency to avoid some rational thinking biases, specifically the tendency to display denominator neglect, probability matching rather than maximizing, belief bias, and matching bias on the 4-card selection task. The authors present a framework for predicting when cognitive ability will and will not correlate with a rational thinking tendency.

Anders Sandberg also suggested the following piece of evidence³ in favour of the hypothesis that increased intelligence leads to more rational political decisions:

Political theory has described a positive linkage between education, cognitive ability and democracy. This assumption is confirmed by positive correlations between education, cognitive ability, and positively valued political conditions (N=183−130). Longitudinal studies at the country level (N=94−16) allow the analysis of causal relationships. It is shown that in the second half of the 20th century, education and intelligence had a strong positive impact on democracy, rule of law and political liberty independent from wealth (GDP) and chosen country sample. One possible mediator of these relationships is the attainment of higher stages of moral judgment fostered by cognitive ability, which is necessary for the function of democratic rules in society. The other mediators for citizens as well as for leaders could be the increased competence and willingness to process and seek information necessary for political decisions due to greater cognitive ability. There are also weaker and less stable reverse effects of the rule of law and political freedom on cognitive ability.

Thus the hypothesis that increasing peoples' intelligence will make them believe fewer falsehoods and will make them vote for more effective government has at least two pieces of empirical evidence on its side.

1. Average intelligence predicts atheism rates across 137 nations, Richard Lynn,  John Harvey and Helmuth Nyborg, Intelligence Volume 37, Issue 1,

2. On the Relative Independence of Thinking Biases and Cognitive Ability, Keith E. Stanovich, Richard F. West, Journal of Personality and Social Psychology, 2008, Vol. 94, No. 4, 672–695

3. Relevance of education and intelligence for the political development of nations: Democracy, rule of law and political liberty, Heiner Rindermann, Intelligence, Volume 36, Issue 4