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Why can two identical gray squares look different?

Two squares in a checkerboard image can look like different grays even when their displayed values match. Edward Adelson’s checker-shadow illusion makes the surrounding scene part of the puzzle: our visual system is interpreting surfaces and shadows, not simply reading pixels.

3–5 min

Questions you could explore

  • What changes when the two squares are viewed without their surroundings?
  • Why might compensating for a shadow usually be useful?

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Psychology

Can an option nobody wants change what people choose?

Choosing between two offers can feel different when a third appears beside them. A decoy is less attractive than one option on the relevant features, but its presence does not reliably change every decision.

5–7 min

Can an option nobody wants change what people choose?

Psychology5–7 minChoosing between two offers can feel different when a third appears beside them. A decoy is less attractive than one option on the relevant features, but its presence does not reliably change every decision.

How can you miss something that is right in front of you?

Psychology3–5 minLooking at a scene does not mean noticing everything in it. When attention is occupied by one task, something plainly visible can go unreported, a pattern called inattentional blindness.

Psychology

Can a question change what someone remembers?

A question can ask for a memory while also suggesting what might have happened. Research on eyewitness reports separates what someone originally saw from information introduced afterward, making wording part of the evidence problem.

3–7 min

Can a question change what someone remembers?

Psychology3–7 minA question can ask for a memory while also suggesting what might have happened. Research on eyewitness reports separates what someone originally saw from information introduced afterward, making wording part of the evidence problem.

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