Let me explain the psychology using grammar. My background is teaching English, and the psychology of reading correlates to the psychology of learning. This quick grammar analogy makes the conditioning clear. When we use a subordinate clause, we create expectation. Look at how that last sentence starts:

When we use a subordinate clause,

That is a subordinate clause, also called a dependent clause. Readers experience a natural expectation reading such clauses because they know the clause is incomplete—grammar conditions readers to anticipate the completion of that thought:

…we create expectation.

Templates create similar expectations, which is why designers make headings consistent in font and font size. Consistent choices say, in effect, “Hey learner, this is the header for this screen.” A smart template can say a lot.

Don’t Look at the Designer Behind the Curtain