Final answer:
A 'special agency' is established when a broker signs a buyer representation agreement, which grants the broker authority to perform specific tasks for the buyer, such as property negotiation, without broader decision-making powers.
Step-by-step explanation:
When a broker signs a buyer representation agreement with a buyer, a special agency is created. This is because the broker is authorized to perform one or more specific acts on behalf of the buyer, but does not have the power to bind the buyer to all potential actions in the same manner that a general or universal agent would. The special agency typically pertains to the purchasing of property; the broker will look for properties that meet the buyer's criteria and negotiate the purchase but will not have the broader powers of making decisions on the buyer's behalf.