The factors that initially elicit stereotypic behaviours can be very different.
Species differ regarding the shape and timing of these stereotypies and within a particular specie, individual differences can be observed when it comes to shape, frequency, ability to resist interruptions and the propensity to carry out the stereotypies.
Stereotypies do not develop "overnight" but run through a phase, arbitrarily divided into Developing stereotypies and Established stereotypies.
Established stereotypies differ from the Developing in that they are more difficult to interrupt, disturb and eliminate (e.g. by improving the housing conditions). They vary less and can show a phenomenon called "Emancipation". That means that the behaviour can be "released" from the initially eliciting factors (or; "Taken out of the initiel context") and be performed in other circumstances/connections. Furthermore, Established stereotypies show less response towards treatment with neuroleptica, and can be very persistent/long-lived.
Next topic: Examples of various stereotypic activities.