| Psychophysical Questions | Answers |
|---|
| Detection Question: What is the minimum amount of energy in a stimulus that humans can detect? | Absolute threshold: The minimum amount of energy in a stimulus that can be detected 50% of the time |
| Signal detection theory: Detection of faint stimuli depends not only upon physiological sensitivity to a stimulus but also upon a person’s decision criterion for detection, which is based on nonsensory factors |
| Difference Question: What is the minimum difference in stimulus energy between two stimuli that humans can detect? | Difference threshold: The minimum difference in stimulus energy between two stimuli that can be detected 50% of the time |
| Weber’s law: The measured difference threshold is a constant fraction of the standard stimulus used to measure it and this constant is different for each type of sensory judgment |
| Scaling Question: How are human perceptual scales of measurement related to physical scales of measurement? | Stevens’s power law: The perceived magnitude of a stimulus is equal to its actual physical intensity raised to some constant power for each type of sensory judgment |