What is the name of the survey question style that forces a choice between non-opposite pairs of items, and why is it used? I've seen personality tests and industrial / organizational psychology tests that force one to choose between non-opposing concepts. What is the name of this question style, and what are the reasons to use it over a more standard question style that forces you to choose between opposing pairs?

Example questions:

In general, I prefer [Assertiveness / Clear communication]

I prefer my direct reports to be [Self-directed / Punctual]
Short answer
Forced-choice task

Background
You have answered your own question: 


  ...tests that force one to choose...


Such tests are generally referred to as forced-choice tests in psychophysics. There are many applications of these tests. In general, AFC tasks are less biased than for example yes/no tasks (Yushurun et al, 2008). A sample paper on an AFC test for personality testing is Christiansen et al. (2005).

References
- Christiansen et al. Human Performance (2005); 18(3): 267-307
-  yushurun et al. Vis Res (2008); 48(17): 1837-51