Contracted forms

Contracted verb forms are generally avoided in academic writing:

It is doubtful that such a project ever existed.
(instead of It’s doubtful that…)

[discussing the influence of the philosopher Schopenhauer on the novelist D.H. Lawrence]
I am not saying that Lawrence did not read the other essays or even ‘The World as Will and Idea’; I am saying that there is no evidence that he did, and we cannot assume any but the briefest familiarity with Schopenhauer’s system.
(instead of I’m not saying that Lawrence didn’t read the other essays or even ‘The World as Will and Idea’; I’m saying that there’s no evidence that he did, and we can’t assume any but the briefest familiarity with Schopenhauer’s system.)

Spoken academic presentations, however, often use contracted forms:

[university tutorial group; lecturer speaking about the writer, Jane Austen]
Maxims usually express a commonsense point of view and Jane Austen’s full of that commonsense.

[immunology lecture]
And you can see that this is very similar to the picture we’ve looked at previously but we’ve added on two more molecules. So here’s our surface of the T cell.