Thurstone and Likert are associated with measurement of

Attitude measurement in psychology and educational testing uses standardized psychometric scaling techniques that convert a person's subjective disposition — favourable or unfavourable — toward an object, issue, or person into a numerical score. The two classical techniques for this are the equal-appearing-interval scale and the summated-rating scale.

L. L. Thurstone introduced the method of equal-appearing intervals in "Attitudes Can Be Measured" (1928), where judges pre-rate a pool of statements on an 11-point favourability continuum and respondents are scored by the average scale value of the statements they endorse. Rensis Likert introduced the summated-rating method in "A Technique for the Measurement of Attitudes" (1932), where respondents mark their level of agreement (e.g., Strongly Agree to Strongly Disagree) with a set of statements, and the item scores are summed. Both techniques were designed for exactly the same purpose: quantifying attitude.

• Intelligence is measured through cognitive-ability instruments such as the Stanford–Binet or Wechsler scales — a separate testing tradition from Thurstone's and Likert's scaling work.

• Values are measured through dedicated instruments such as the Allport–Vernon–Lindzey Study of Values, not through the attitude-scaling methods Thurstone and Likert devised.

• Personality is assessed through inventories such as the MMPI or the 16PF, which are unrelated to the equal-appearing-interval or summated-rating techniques.

Since both scholars' contributions are specifically attitude-scaling methods, the option that matches their shared association is attitude.