Hiding in plain sight
Can you spot the changes in this video? This is an example of inattentional blindness – the failure to notice fully-visible but unexpected objects because our attention is otherwise engaged.
Hearing with your eyes
The McGurk effect shows how our eyes can influence what we hear.
“There’s the classic old stage illusion of the ventriloquist. You hear a sound, it’s actually coming from the ventriloquist of course, but vision’s telling you the speech signals are here, and so you end up, your vision overrides your sense and you perceive the sound coming from there.” – Prof David Alais, University of Sydney
Do you think you're colour-blind?
Perceptual illusions – what can you see?
Where is the front of the cube?
The necker cube was published by Louis Albert Necker - the Swiss geographer and crystallographer.

Source: Wiki Commons
Is this an old woman, or a young woman?

Source: Wiki Commons
Do you see a duck or a rabbit?

Source: Wiki Commons