A stimulus, or new event, initiates a learned response in animals when they reorganize neuronal synapses to enable the response. The excitatory postsynaptic potentials characteristic of habituation occur when the original environmental change that was a stimulus reappears so often as to appear to be a non-change. The nonresponsiveness of habituation derives from perceived lack of difference over time. The heightened response of dishabituation derives from perceived significant difference over time. Difference is all the mind's input devices can detect, and difference is in a sense all the mind is there to consider and respond to.
Perception is modeling.
Biological success or failure are somewhat dependent upon the statistical reliability of such modeling for future action. Such modeling is very resource-intensive, and animals' neurons are equipped with proteins, called calpain and fodrin, that physically limit response to stimuli that so resemble previous stimuli as to be likely to prove insignificant. Complacency, however, breeds danger. Imputing sameness is known as stereotyping, and information that might prove vital to our interests may be unavailable to us due to our tendency to rely on shorthand reality. As a species we require constantly updated data on otherness.