In: Psychology
Stimulus Delta is a stimulus in the presence of which a response will not be reinforced. For example, in an educational programme, a child is asked to pick up a card written with the alphabet B from a deck of cards written with the rest of the alphabets. If a child picks up a card written with the alphabet B, then it's called a correct stimulus also known as "Discriminative Stimulus". If the child can't pick a card with letter B then it's called an incorrect stimulus also known as "Stimulus Delta".
Negative reinforcement is a term used to describe the strengthening of a response or behaviour by stopping or removing the unwanted or aversive stimulus. For example, leaving the house early (the behaviour) to avoid arriving late at work (aversive behaviour).
In short Stimulus Delta is a stimulus that won't be reinforced and negative reinforcement is the strengthening of a behaviour by removing a particular stimulus.