A pharmaceutical company is testing how much sugar should be added to a pediatric oral liquid suspension to make the medication more palatable. Researchers determine that adding 0.2 g of sugar to 20 mL of oral suspension Z results in children detecting a just noticeable difference in taste. Based on Weber's law, should the addition of 0.2 g of sugar to 50 mL of oral suspension Z be detectable 50% of the time?

Question

A pharmaceutical company is testing how much sugar should be added to a pediatric oral liquid suspension to make the medication more palatable.  Researchers determine that adding 0.2 g of sugar to 20 mL of oral suspension Z results in children detecting a just noticeable difference in taste.  Based on Weber's law, should the addition of 0.2 g of sugar to 50 mL of oral suspension Z be detectable 50% of the time?

Quizplus · Accepted Answer

11ecba2d_0d9c_1478_a3bf_bbcb4f12bacb_MD0008_00 The smallest difference between two stimuli a person can detect 50% of the time is called the just noticeable difference (JND), or difference threshold. As the intensity of the original stimulus increases, the difference threshold also increases. For example, although the difference between weights of 100 and 102 g may be detectable, the difference between weights of 500 and 502 g is not, even though the difference is also 2 g. This relationship is quantified by Weber's law, which states that the ratio of the size of the JND to the original stimulus intensity remains constant. In other words, the change in a stimulus needed to detect a difference is a constant proportion (ie, if one can just detect a difference between weights of 100 and 102 g, the difference between weights of 500 and 510 g would also be just detectable). If the addition of 0.2 g of sugar to 20 mL of suspension Z is just noticeable 50% of the time, then for a volume that is 2.5 times bigger (20 mL × 2.5 = 50 mL), 0.5 g of sugar (0.2 g × 2.5 = 0.5 g) would be the JND. Therefore, the addition of 0.2 g of sugar to 50 mL of oral suspension Z would not be detectable because Weber's law is based on a ratio. (Choice A) The addition of 0.2 g of sugar is the JND for 20 mL of suspension; for 50 mL of suspension the JND is 2.5 times greater, or 0.5 g. Therefore, anything less than 0.5 g should not be detectable 50% of the time. (Choice B) Weber's law is based on a constant proportion, not a constant value, so the addition of 0.2 g of sugar to 50 mL of oral suspension Z should not be detectable 50% of the time. (Choice C) The absolute threshold is the intensity value at which an individual can detect a stimulus 50% of the time; 0.2 g represents the difference threshold, or the smallest difference between two stimuli that can be detected 50% of the time, not the absolute threshold. Educational objective: Weber's law states that the proportion of the just noticeable difference (the smallest difference between two stimuli a person can detect 50% of the time) to the original stimulus intensity is a constant.

A Pharmaceutical Company Is Testing How Much Sugar Should Be