Some degree of formal similarity exists even if other formal or dynamic features are somewhat different. For example, the stimulus may have been low-pitched, whereas the response-product may have been very high-pitched.
A relationship between a stimulus that evokes a response and the response-product of that response with the following features:
The stimulus and the response-product are both in the same modality (e.g., they are both visual or they are both auditory)
Their physical patterns or sequences resemble one another (e.g., they may look or sound alike)
Specific formal or dynamic features of the stimulus and the response-product
The number of additional formal or dynamic features resembling one another