知覚の限界を見つけるため階段のプロシージャ

Psychophysics is a set of methods designed to relate the actual intensity of stimuli to their perceptual intensity. It addresses fundamental questions about human sensation: how bright must light be to detect it, or how soft can sound be and still be heard. Understanding these perceptual thresholds reveals the smallest amounts of stimulation humans can sense, which is essential for studying sensation and perception.

The staircase procedure is an efficient technique that systematically adjusts stimulus intensity based on participant responses. A tone starts at an inaudible level; if undetected, volume increases by 1 dB on the next trial. If detected, volume decreases by 1 dB. After 30 trials, this creates staircase-like fluctuations. The threshold is calculated by averaging the last 10 trials, identifying the narrow range where responses shift between 'no' and 'yes'.

Perceptual thresholds vary across different frequencies because of the vibration properties of the ear's filaments and bones. The staircase procedure tests six frequencies independently—from 1 to 6 kHz—to measure how volume thresholds change at each pitch. This reveals that low-pitched tones are generally easier to hear than high-pitched ones, providing a complete profile of auditory sensitivity.

Researchers using the staircase procedure found that volume thresholds increase as people age. For individuals aged 60, high-frequency sounds needed to be four times as loud as they would for 20-year-olds to perceive them. This demonstrates age-related sensory decline in hearing, with older adults requiring greater stimulus intensity to detect sound across frequencies.

The staircase procedure identifies specific frequencies affected by disease or damage versus general aging effects. When comparing normal hearing to impaired hearing, researchers found that certain frequencies like 4 and 5 kHz showed elevated thresholds while others remained normal. This pattern suggests targeted damage rather than uniform age-related decline, helping clinicians diagnose the nature of hearing deficits.

Studies using threshold measurement approaches found that exposure to loud heavy-metal music temporarily increases volume thresholds. When researchers tested participants before and 30 minutes after a concert, thresholds were elevated, meaning sounds needed to be louder to be detected. This demonstrates that intense acoustic exposure can cause temporary hearing sensitivity loss, illustrating how environmental factors affect auditory perception.

For each frequency tested, create a data table with trial number, volume level, and participant responses (yes or no). Graph volume changes across trials to visualize the staircase pattern. Calculate the threshold by averaging the last 10 trials of each block, then graph thresholds across all frequencies. This analysis reveals how detection sensitivity varies by pitch and identifies the minimal audible intensity at each frequency.