Predictable changes in adult personality are at the heart of the model. trait timing-of-events typological normative-stage

The correct answer is Normative Stage Model.
The Normative Stage Model refers to the theoretical models, which depicts the psychosocial developments with relation to a specific sequence of age-associated changes.The Normative-stage model is the one, which holds the age-associated socially and emotionally changes, which emerges in successive periods which are sometimes marked by crisis.

The changes to agriculture in the united states since 1900 is that increased mechanization has increased food production, thereby increasing the need for labor. there has been an increased need for higher speeds of food production due the fact that the population in the united states continues to rise.