Personalized Assessments & Learning Animals

My 22-month old daughter plays a game on Momma's iPhone called "Animals".  It's a multiple-choice animal-identification game.  The game displays three-five different animals and asks for one animal to be identified.  The game rotates different animals each time.

What intrigued me most about this game is how the number of options fluctuates based on the performance of the student.  The student starts off selecting from two animals.  Once they have correctly answered three consecutive attempts, the game provides three animals to choose from.  This pattern continues, up to five animals.