A psychologist named Rensis Likert refined Thurstone's procedures in 1932. Likert recommended that researchers devise a series of opinion statements and ask individuals to indicate their agreement or disagreement with each statement along a numerical scale. A Likert scale assumes that each item taps the same underlying attitude and there are significant interrelationships among items. It also presumes that there are equal intervals between categories. For example, on a 5-point (Strongly Agree, Somewhat Agree, Neutral, Somewhat Disagree, Strongly Disagree) scale, researchers assume that the psychological difference between Strongly Agree and Somewhat Agree is the same as between Strongly Disagree and Somewhat Disagree.