Kahneman-Tversky and Tversky on Heuristics and Biases

In their classic 1974 article, Judgment Under Uncertainty Heuristics and Biases, Kahneman-Tversky outlined three heuristics and biases. Which of those three do you think is the most descriptively accurate? None of them, sorry. So what I think is our contribution is to take off where Kahneman and Tversky start descriptively and turn these into a testable model.