Sesson 1: Sensory Thresholds

Key Idea

The human body, like that of other animals, relies on a system of specialized organs to interpret the world. Each sense organ contains specific sense receptors tuned to a particular type of energy or chemical.

Receptors in the nose detect chemicals (smell), receptors in the skin detect pressure (touch), and receptors in the ear detect vibration (hearing). These receptors function independently; a receptor designed for one task cannot perform another.

Key Idea

Senses are not infinitely sensitive. There is a minimum level of stimulation required for a receptor to activate and send a signal to the brain. This minimum level is called the sensory threshold.

If a sound is too quiet or a smell is too faint, it falls below the threshold, and the brain remains unaware of it. A stimulus is only perceived when its intensity meets or exceeds this threshold.

Key Idea

To investigate how senses work, scientists must conduct fair tests. In a complex environment, many things happen at once. To isolate a specific sense, scientists must control the conditions of the experiment.

This means changing only one variable at a time (such as the volume of a sound) while keeping all other factors constant. This rigorous method ensures that the results accurately reflect the capability of the sense being studied.