Research on operant conditioning has found that behavior is most affected by unconditioned positive reinforcers (stimulus which is innately rewarding, such as food) without delay in delivery. Reward as a means of behavioral conditioning also tends to lead to better outcomes than punishment, and the more immediate the reward, the stronger the conditioned behavior.
The shorter the amount of time between a behavior and presenting positive reinforcement, the stronger the connection will be. If a long period elapses between the behavior and the reinforcement, the weaker the connection will be. The longer the time, the more likely it becomes that an intervening behavior might accidentally be reinforced. (Verywell Mind)
An example of this principle would be rewarding a dog by giving them a treat immediately after they listen to a command. If the reward is significantly delayed, the dog may begin barking. At that point, receiving a treat may lead to an association between barking and reward rather than performing the desired behavior.
Learned behavior dependent on reward is also learned more quickly on a continuous reinforcement schedule, meaning that the reward is consistently (and ideally immediately) given each time the subject performs the desired behavior. However, a continuous reinforcement schedule can also lead to extinction or loss of the desired behavior. Since the subject expects the reward each time the behavior is performed, they may lose interest when the reinforcer is withheld. The alternative to continuous reinforcement is a partial reinforcement schedule. Sometimes the reward is given in response to the desired behavior, and sometimes it is not. Using this method, the behavior is typically learned more slowly than with continuous reinforcement, but once it is mastered it is more likely to be continued even in the absence of reward. This method of reinforcement is especially effective in teaching and maintaining more complex behaviors.