Index selection

Index Selection is a method of artificial selection in which several useful traits are selected simultaneously. First, each trait that is going to be selected is assigned a weight, the importance of the trait. I.e., if you were selecting for both height and the darkness of the coat in dogs, if height was more important to you, one would assign that a higher weighting. For instance, heights weighting could be ten and coat darkness' could be two. This weighting value is then multiplied by the observed value in each individual animal and then the score for each of the characteristics is summed for each individual. This result is the index score and can be used to compare the worth of each organism being selected. Therefore, only those with the highest index score are selected for breeding via artificial selection.

This method has advantages over other methods of artificial selection, such as tandem selection, in that you can select for traits simultaneously rather than sequentially. Thereby, no useful traits are being excluded from selection at any one time and so none will start to reverse while you concentrate on improving another property of the organism. However, its major disadvantage is that the weightings assigned to each characteristic are inherently quite hard to calculate precisely and so require some elements of trial and error before they become optimal to the breeder.