Procedural knowledge tends to be retained longer than declarative knowledge in our memory. All skills start as declarative knowledge and gradually transition to procedural through practice.
Book: Ultralearning and The Design of Everyday Things
What's the phone number of your mom? In the last house you lived, as you entered the front door, was the doorknob on the left or right? These two questions both involved long-term memory, but in different ways. The first question requires recalling factual information, known as declarative knowledge. The second question is usually easier answered by recalling the actions performed to open the door, called procedural knowledge.
Evidence suggests that procedural knowledge, like riding a bike, is stored differently from declarative knowledge, such as understanding trigonometric functions. This difference between "knowing how" and "knowing what" highlights that procedural skills, which are permanently memorized, are less likely to be forgotten than declarative knowledge, which requires a clear recall.
An important learning theory argues that most skills are developed in stages, starting with declarative knowledge but becoming procedural with practice. Typing serves as a clear example of this progression. We need to remember letter positions consciously when we first start typing. After enough practice, looking down at the keyboard becomes unnecessary. We can even remember all letter positions by imagining typing on an invisible keyboard.
The fact that procedural knowledge can be retained longer suggests a valuable strategy. Instead of trying to memorize a large amount of information or skills on average, focusing on consistently reinforcing a core set of information can allow it to become procedural knowledge and be stored for a longer duration.