There is sometimes an observed inverse correlation between a student's inherent talent/intelligence and the amount of effort expended. The trend is one that I see everywhere in high school. Smart students just sort of shrug and coast by to get an acceptable grade. Or, on the other side, students that don't grasp material as quickly give it an extra push, knowing that it will take some work in order to get the grades they want.
The similarity between the two is that both types of students are adjusting the amount of work they need to put in, based on the given standard. Given an average, or a benchmark to aim at, they just figure out how much work they need to put in. Students find the equilibrium, the balance between their intelligence and the work they have to put in, that allows them to scrape by.
For students that have less inherent talent in a particular subject, this may be an incentive to improve. But for the students that are never challenged in school, who easily fly through classes that do not provide the adequate learning environment, this drills into their minds that they don't need to work hard.
And this lesson is definitely not desirable to teach to bright students. Some are never exposed to anything besides the monotony and apparent irrelevance of schoolwork (When will we ever use this in the real world?) and fall into the habit of filing everything new under the "pay attention only enough to scrape by" category of their minds. So, when faced with something like, say, global existential risk, the weight of the subject is ignored.
Of course, there are many other factors involved. It isn't that everyone has been trained to adjust to put in minimal work based on an average. If that was the case, then all smart students in public school would be slackers. On a larger scale, then there would be no deviations on either side - everyone would just fall exactly on the average line.
So there is clearly something that lets some people ignore the average. Most motivated and thoughtful people probably don't pay attention to what is considered typical or the standard, anyway. But for many students, a certain test score is a signal to just stop.
Back to the larger scale, now. The problem of using an external standard doesn’t apply only to high school students. There are a multitude of other areas in life, areas in which it is easy to reach a certain point that serves as a mental stopping point.
This may help to account for people that find themselves in an unsatisfying job, wondering why they’re unhappily stuck – based on the standards of salary and stability, the job could look fine. One level further, if meeting a standard is the sole basis of effort, then the job certainly could be done – but without creativity or innovation.
If the goal becomes to reach a certain average, then you could go checkmark, checkmark, checkmark down the row of criteria, without really getting anywhere, or doing anything meaningful. Who creates those standards in the first place? Are they actually a good measure of effectiveness, usefulness, or mastery? Basing work and effort on external stimulus will not compare to having the internal source of motivation, desire, or cause.
One last note: the TED talk and this post have focused on the concept of hard work, or "grit." It is worth pointing out that there is a difference between just working hard, possibly ineffectively and working smarter. It doesn't help to do the same thing over and over again and wonder why the results aren't getting better. Real improvement takes some reflection - identifying weak areas, prioritizing, etc. Though this is probably commonly known, it is a vital distinction to keep in mind with the subject this discussion.
Edit: The links to this TED talk (and an older version here) were originally featured at the very beginning of the post. Since the talk wasn't relevant in any way, except for a single remark, I removed the links from the prominent focus to increase clarity.