Seeking a standard term for the "Where's Waldo?" effect
Learned recognition

The evolution of signal form: effects of learned versus inherited recognition (The Royal Society Publishing)


  Organisms can learn by individual experience to recognize relevant
  stimuli in the environment or they can genetically inherit this
  ability from their parents...We analyse the joint effects of receiver
  biases, signal cost and mode of acquisition, investigating the
  circumstances under which learned recognition gives rise to more
  exaggerated signals than inherited recognition.


Curse of knowledge

Your quote:


  Usually after learning one of these things, one tends to underestimate
  its difficulty for someone who hasn't solved it.