Which period of learning shows no improvement in the learning curve?

A plateau is the flat period of the learning curve where no improvement in performance appears despite continued practice.

Irregular progress (A) describes uneven gains, not a flat no-improvement stretch.

Spurts (B) are sudden bursts of rapid improvement, the opposite of a plateau.

Initial stage (D) usually shows slow early progress, not a standstill after learning.

Plateaus arise from fatigue, boredom, loss of interest or shifting attention among skill phases.

Renewed motivation and a better method often help a learner move beyond the plateau.