People can be classically conditioned to fear something, and classical conditioning can be used to remove that same fear through a process called

The process by which a previously neutral stimulus acquires the capacity to elicit a response through association with a stimulus that already elicits a similar or related response, also called Pavlovian or Respondent Conditioning, process by which a neutral stimulus becomes a conditioned stimulus, since Pavlov many involuntary automatic responses (like heartbeat and blood pressure) have been classically conditioned, optimal interval is very short between presentation of neutral stimulus and of US, this occurs in all species as an evolutionary adaptation that enables organisms to anticipate and prepare for a biologically important event.