3.1 : 感覚

Sensation is the ability to detect external stimuli using specific sensory receptors present in the eyes, ears, nose, skin, and taste buds.

For instance, when light enters the eye, it triggers chemical reactions in the photoreceptor cells. These reactions alter the electrical activity in retinal cells, leading to the generation of action potentials by a process called transduction, which is then transmitted to the central nervous system.

The absolute threshold measures the minimum stimulus energy detectable 50% of the time, such as the lowest volume level a person can hear half the time in a quiet environment. It reflects the sensitivity of sensation to stimulus.

In addition, subliminal stimuli refer to the inputs below the threshold of conscious awareness that are strong enough to activate sensory receptors but insufficient for conscious detection.

The difference threshold, also known as the just noticeable difference or JND, is the smallest detectable change in the intensity of a stimulus. For instance, adding 10 grams to a 100-gram weight may go unnoticed, but an increase of 200 grams will likely be noticeable.