Mentally challenging optical illusions test your perception and observation skills.
These problems help scientists learn how the brain processes visual information.
Creative thinking and cognitive enhancement are also possible with optical illusions.
Regular practice improves memory and problem-solving.
A flock of sheep returns from the field in the photograph above.
They have company. This photo shows a dog lurking amid the sheep.
Readers must find the dog in 3 seconds. Practice observation with this assignment.