Perceptual Thresholds and Subliminal Influence

Weber's Law

• The just noticeable difference (JND) for a stimulus is proportional to its original intensity.
• Example: Adding $1$ candle to $20$ is noticeable, but adding $1$ candle to $120$ is not; $6$ candles are needed to detect a change in $120$ candles, maintaining the ratio $1/20$.
• This law applies broadly, including emotional states, requiring a larger change to be noticeable from an already intense feeling.

Subliminal Perception

• Refers to detecting information below conscious awareness (absolute threshold).
• The 1957 claim by James Vicary of increased sales due to subliminal messages ("EAT POPCORN," "DRINK COKE") was a hoax.
• Research shows brain and cardiovascular systems respond to information presented outside awareness.
• The impact of subliminal stimuli ("primes") on behavior remains controversial and is inconsistent across studies.