What is the minimum level of energy required for a stimulus outside our body to be detected by our internal senses called?

The minimum level of energy required for a stimulus to be detected by our internal senses is known as the absolute threshold. This concept refers to the smallest intensity of a stimulus that can be experienced and is critical in understanding sensory perception. For example, the absolute threshold for hearing might be the faintest sound that a person can detect. It essentially marks the boundary between the stimulus being present and not being perceived.

The other options, while related to sensory perception, refer to different concepts. The difference threshold pertains to the smallest detectable difference between two stimuli, which is often termed just noticeable difference (JND). Signal detection theory involves the methodology for distinguishing between the presence and absence of a stimulus in the presence of noise, focusing on decision-making under uncertainty. Perceptual threshold is less commonly used and may refer more broadly to an individual's ability to discern stimuli, rather than specifying the minimum energetic level required for detection.