The emphasis has to be on preventing fear memories. Cows and other animals tend to develop fear memories which are linked to either bad places or prominent objects. Animals are most likely to become fearful of a specific place or of a person wearing a certain type of clothing associated with a painful or scary experience. It would be very detrimental for milk production if a cow becomes afraid of the milking parlor. It is essential that a heifer's first experience in the milking parlor is a good experience.
First experiences make a big impression on animals.
If a heifer falls down or is shocked with an electric prod the first time she enters the parlor she may develop a fear memory that is associated with the parlor. Research done with rats shows the powerful effects of forming a fear memory. Rats were placed in a maze and allowed to explore all the alleys. If a rat was given a shock the first time it entered a new alley it would never enter that alley again. However, if the rat entered the alley several times and found food, that provided a positive memory.