In psychology and education, learning is the process of acquiring new or modifying existing knowledge, behaviors, skills, values, or preferences. The ability to learn is possessed by humans, animals, and some machines; there is also evidence for some kind of learning in certain plants. Some learning is immediate, induced by a single event (e.g. being burned by a hot stove), but much skill and knowledge accumulate from repeated experiences. The changes induced by learning often last a lifetime, and it is not always easy to specify what has been learned. Potential mechanisms for how learning occurs in animals and humans include classical conditioning, operant conditioning, perceptual learning, motor learning and memory consolidation. At any given time, some individuals may be more susceptible to learn than others because of genetic makeup or previous experience (i.e., nature vs. nurture).