1. Most visual illusions and stereograms don't work for me but they do on all my friends. Why?
How the brain organizes and interprets sensory information is a little miracle that scientists are still trying to solve. Clearly, some experience these illusions and stereograms differently than others. Why this is so is not entirely known but some visual variations in individuals can produce appreciable differences in the image data that appear on their retinas.

2. Can people perceive things that are below their conscious detection?
Some subliminal perception enthusiasts make great claims about this. How accurate are these claims? Weak sensory stimuli can be registered by sensory receptors and possibly encoded beneath our awareness. However, no evidence supports the claims of advertisers that such subliminal information has any substantial impact on our thoughts and behavior. Rather, we are influenced by the sounds and views we are consciously aware of and can attend to effectively.

3. How real is ESP?
It's not. Our eyes, ears, mouth, nose, and skin provide us with sensory information about the external world. Our perceptions are based on our interpretation of this incoming sensory information. The claims of extrasensory perception (ESP) advocates have not held up to scientific scrutiny.