Geraniums have been popular garden perennials for a long time, and have lots of devotees. Consequently, there are lots of good sources of information on the internet. A good start is provided by the Open Directory Project's geranium category. For a primer on erodiums, this page from the UK gives a good overview.
Stimulus control is the phenomenon of a stimulus increasing the probability of a behavior (operant response) because of a history of that behavior being differentially reinforced in the presence of the stimulus.
Here is a brief explanation: 1  Stimulusâ produces a change to a variable (the factor being regulated). 2  Receptorâ detects the change. 3  Inputâ information travels along the (afferent) pathway to the control center. 4  Outputâ information sent from the control center travels down the (efferent) pathway to the effector.