Table 5.

Methods used to assess reward value of a given taste.

	Method	Procedures
Appetitive reward domain	Progressive ratio task (PRT)	The subject must work for a rewarding stimulus; for example, this could involve clicking a computer mouse several times. The response requirement rises progressively until the subject stops making an effort for the reward, known as the breakpoint. The pioneering study of Hodos (1961) demonstrated that the number of responses made to obtain the last reward, termed the breakpoint, serves as an index of reward strength.
Consummatory reward domain	Category scales	Category scales are numeric and usually comprise descriptors equally spaced on a line (For example, from “1 = no taste” to “9 = extreme taste”. Common examples are the 9-point scale or the visual analogue scale (VAS).
	General labelled hedonic scale (gLHS)	The gLHS assesses pleasantness. It includes a neutral midpoint extending in opposite directions. The top anchor indicates the ‘strongest liking of any kind ever experienced’, and the bottom anchor indicates the ‘strongest disliking of any kind ever experienced’, with intermediate labels in between.
	Two series forced-choice tracking procedure	Subjects are presented with different concentration pairs of the stimulus being tested (e.g., sucrose) to identify their preference. The procedure lasts until the subject either selects a particular stimulus concentration when it is paired with a higher or lower concentration together or chooses the highest or lowest concentration two times repeatedly. The entire task is repeated with concentration pairs presented in reverse. The most preferred stimulus level is determined by the geometric mean of the concentrations chosen during the two series.
	Just about right	The participants are asked whether a sensory characteristic of the stimulus (e.g., sucrose) is too high, too low, or just about right. The scales typically comprise 5 or 7 points, ranging from too little to too much for the different stimuli.