The propensity to prevaricate, and thus the prevalence of prevarication, is influenced by the incentives to prevaricate.
1. Psychiatric drugs have a low efficacy – roughly 75% ineffective. Want to bet the real number is higher, even much higher? There is incentive to prevaricate if the drug makes a person feel better, even though it is doing nothing for his paranoia, for example. Here there is actually also an incentive to say that it is not working in the hopes of getting something even stronger. Both sides of the equation can be and probably are tainted by prevarication.
2. Teenagers say that most of them (66% in a Princeton Survey Research Study and 71% in a Consumer Reports study) do not text while driving but also say that 75% have friends (plural? – not at least one? In particular, the statement is not saying that teens estimate that 75% of their friends text and drive) who text while driving (since each teen has many friends, the two statements can both be true, but do you want to bet that the true percentage of teens who text while driving, at least now and then, is closer to 75% than to 30%, when sense demands 0% texting while driving?). There is clearly more incentive to prevaricate about one’s own poor judgment and reckless behavior than about one’s friends’ poor judgment, even though friends are chosen and thus one’s friends’ judgments reflect on the individual’s judgment. Yet there remains a clear difference between indirect vs direct in the incentive to prevaricate. Since 0% texting and driving is the only sensible result, is there much practical significance in whether the true percent of teens who text while driving is closer to 30% or to 75%? Should teens be driving? As I have argued before, teens should not be doing a lot of adult things. Not before the age of reason, the age at which judgment reaches its peak, however low that may be, at roughly 25. What percent of those over 25 text and drive?
3. People say they eat and drink one thing, as revealed in the NHANES surveys, but a simple walk down the aisles of a grocery store shows what people are actually buying. Assuming they eat and drink most of what they buy, it is a sad tale, particularly when the most nutritious foods that are bought are the most perishable and what is thus probably consumed is a fair amount less than what is bought, and in the case of produce, what is bought is not nearly enough for good health.