• Incremental - Continuous Testing and Refinement. Starts from an existing product. Called also Hill Climbing (move your foot in one direction - if it is uphill, take one step. If not, change direction. Do that until the top of the peak). Con: cannot find a higher hill. 
• Radical - Starts fresh, many times from scratch. Offers potential very high opportunities. Con: the hill might be even lower than the one previously tried.

There are 2 types of errors:

• slips (a person intends to do an action and ends up doing something else). Can be: action-based(correct action applied to the wrong object), mem...