Eligibility Trace
Eligibility traces are one of the basic mechanisms of reinforcement learning. They unity and generalize TD and Monte Carlo methods.
Frequency heurisitic: assign credit to most frequent states Recency heurisitic: assign credit to most recent states
Eligibility traces combine both herusitics.
https://www.youtube.com/watch?v=PnHCvfgC_ZA&list=PLzuuYNsE1EZAXYR4FJ75jcJseBmo4KQ9-&index=4