Dominique is making a rice dish for 5 people that requires 4 teaspoons of salt. If she were to add just one more teaspoon of salt to the rice after tasting it, half of the time she would be able to notice a difference. If Dominique decides to triple her recipe to feed 15 people, which would call for a total of 12 teaspoons of salt, how many teaspoons of salt would need to be added for a person to be able to taste the difference half of the time?

• A. 1
• B. 2
• C. 3
• D. 4

Answer: (C)

Verified step by step guidance

1. Understand the concept of Weber's Law, which states that the just noticeable difference (JND) is a constant proportion of the original stimulus.
2. Identify the original amount of salt in the recipe for 5 people, which is 4 teaspoons.
3. Note that adding 1 teaspoon to 4 teaspoons allows Dominique to notice a difference half of the time, indicating the JND is 1 teaspoon for 4 teaspoons of salt.
4. Calculate the new amount of salt when the recipe is tripled for 15 people, which is 12 teaspoons.
5. Apply Weber's Law to find the JND for 12 teaspoons by maintaining the same proportion as the original recipe, which is 1 teaspoon for every 4 teaspoons of salt.