In sensory psychology, the term just noticeable difference is synonymous with which type of threshold?

Introduction / Context:
Psychology often uses precise terms to describe how humans sense and perceive changes in stimuli. The just noticeable difference, often shortened as JND, is a key concept that refers to the smallest change in stimulus intensity that a person can detect. This question tests whether you know the formal term for this concept in psychophysics.

Given Data / Assumptions:

• The just noticeable difference concerns detecting a change between two stimulus levels.
• Thresholds in psychology include absolute threshold and difference threshold.
• We assume a basic understanding of psychophysics terminology.

Concept / Approach:
The difference threshold is defined as the minimum difference in intensity between two stimuli that a person can detect at least half the time. This is exactly what the just noticeable difference measures. The absolute threshold, by contrast, is the smallest intensity of a stimulus that can be detected at all. Other terms given in the options are distractors and are not standard names in psychophysics.

Step-by-Step Solution:
Step 1: Recall that the just noticeable difference measures the smallest detectable change in stimulus intensity. Step 2: Link this idea with the concept of a threshold that deals with differences between two stimuli. Step 3: Recognise that psychology textbooks use the label difference threshold for this idea. Step 4: Note that separation threshold and change threshold are not widely used technical terms. Step 5: Choose difference threshold as the correct synonym for the just noticeable difference.

Verification / Alternative check:
In psychophysics, the law associated with JNDs is often called Weber law, which relates the size of the just noticeable difference to the original stimulus intensity. Definitions of Weber law explicitly mention that JNDs are measured via difference thresholds. This confirms that the two terms refer to the same underlying concept.

Why Other Options Are Wrong:
Option b, separation threshold, is not a standard psychophysical term and may mislead by sounding similar.

Option c, change threshold, is a general phrase but not the precise technical label used in textbooks.

Option d, response threshold, would more likely refer to the point at which a response occurs, not specifically to a change between two stimuli.

Common Pitfalls:
Students may confuse absolute threshold with difference threshold or think that just noticeable difference is its own independent concept with no related technical term. Another pitfall is to select an answer that sounds intuitively correct but is not the established term used by psychologists. Learning the standard labels used in research helps avoid this confusion.

Final Answer:
The term just noticeable difference is synonymous with the difference threshold.