Why did farmers start building barbed wire fences on their farms in the Great Plains?

In piaget's stage, you would expect one to develop interest in ethics, politics, and social and moral issues.

Researchers have found that it takes to view a mental image that is larger or covers more distance than a smaller or more compact one.

Martha participates in a research study in order to receive extra credit for her psychology class. when she arrives in the research office she is given a can of what looks and tastes like beer, but which actually contains no alcohol. in the adjoining room martha's classmate karen is also participating in the study. karen receives a can of alcoholic beer. if the experiment was designed to test the effects of alcohol on concentration, then who is exposed to the independent variable?