The Unreliable Senses

To understand why we get fooled, we must distinguish between sensation and perception. Sensation is the raw data collected by our organs—like light hitting your retina or sound waves vibrating your eardrum. Perception is the process where your brain interprets that data to make sense of the world. Because the brain receives so much information, it uses 'shortcuts' to process things quickly. Sometimes, these shortcuts lead to illusions, where the brain's interpretation doesn't match the physical reality. Our reality is not a direct video feed; it is a 'best guess' constructed by our neurons.

Our senses have physical limits. For example, every human has a blind spot in each eye. This occurs because the optic nerve passes through the retina to reach the brain, leaving a small area with no light-detecting cells. Similarly, our hearing is limited to a specific range of frequencies, typically from $20$ Hz to $20,000$ Hz. If a sound vibrates at $30,000$ Hz, it exists in reality, but it is 'invisible' to our ears. Our brains often 'fill in' the gaps in our blind spots using surrounding information, meaning we are often seeing a hallucination of what the brain thinks should be there.

In the legal system, eyewitness testimony was once considered the 'gold standard' of evidence. However, cognitive science shows that memory is not a recording; it is reconstructive. When we witness a fast-moving event, our brains often miss details due to change blindness (failing to notice a change in the environment). Later, when we try to remember, our expectations and 'leading questions' from others can actually change the memory itself. If someone asks, 'How fast was the car going when it smashed into the pole?', you are likely to remember a higher speed than if they used the word 'hit'.