Absolute Thresholds of the Senses

Absolute Threshold: Definition and Examples

  • Definition: The absolute threshold refers to the minimum amount of stimulus energy needed for sensation to be detected by the human sensory system. It is the point at which a stimulus can be consciously perceived.

  • Illustrative Example (Sound):

    • Imagine a sound at a very low volume; it is below the absolute threshold, meaning it cannot be heard.

    • As the volume is gradually increased, there comes a point where individuals begin to identify the sound. If this trial is run 10 times, the absolute threshold is crossed when everyone can consistently hear the very low, slight music.

    • This crossing signifies the detection of the energy from the stimulus.

Absolute Thresholds for the Five Senses

  • The concept of absolute threshold applies to all five senses, indicating the minimum intensity at which each sense can detect a specific stimulus.

Vision

  • Remarkable Sensitivity: The human eye possesses an extraordinary sensitivity to light.

  • Specific Example: On a truly dark night, a candle flame can be detected from a distance of 30 miles.

    • Conceptualization: This extreme darkness can be experienced, for instance, when on a boat at night, far from city lights (no street lamps, car lights, or billboards), where one truly experiences profound darkness.

    • Threshold Boundary: If one were 35 miles out, the candle flame would not be perceivable, as it would fall outside the absolute threshold for sight.

Hearing

  • Dated Example: A classic, though now somewhat dated, example involves the sound of a ticking clock.

  • Specific Example: Under appropriate quiet conditions, the ticking sound of an analog clock (like those found in older homes or former classrooms) can be detected from up to 20 feet away.

    • Context of Example: Before digital clocks became prevalent, analog clocks were common in classrooms (elementary, middle, high school). There were instances of such profound quietness in a room that every student could hear the clock ticking.

    • Anecdotal Sidenote: The speaker, referencing their experience in urban schools, notes that such extreme quietness often prompted someone to break the silence with a joke, as it was an unusual state of quietness for many people.