Which principle refers to the speeding up or slowing down of movement in animation?

The principle that refers to the speeding up or slowing down of movement in animation is timing. Timing is crucial in animation as it governs the pace at which actions occur, impacting the overall fluidity and realism of motion. By controlling timing, animators can create varying effects, such as making a character's movement appear more dynamic or exaggerated. For instance, faster movements typically convey excitement or urgency, while slower movements can suggest weight or deliberation.

The other principles mentioned, while important in their own right, focus on different aspects of animation. Stretch and squash deals with the deformation of objects to emphasize weight and volume, enhancing the believability of animated actions. Anticipation refers to the setup of an action to prepare the audience for what is about to happen, making movements more impactful. Slow in and slow out describes the gradual acceleration and deceleration of movements, which is often an aspect of timing but specifically refers to how motion begins and ends rather than the overall pacing of actions.

Overall, timing is the overarching principle that encompasses the rhythm and dynamics of movement within animation, making it vital for creating engaging and compelling animations.