Chapter 4B Thresholds and Sensory Adaptation Ms SaintPaul

Chapter 4(B): Thresholds and Sensory Adaptation Ms. Saint-Paul A. P. Psychology

Transduction • The process of converting one form of energy into another that your brain can use. All of our senses • Receive sensory stimulation from a physical stimulus • Transform that stimulation into neural impulses • Deliver the neural information to our brain Example: Think of this as the way a bar-code reader converts a series of lines into an electrical signal that a computer can match with a price.

Psychophysics § The study of relationships between the physical characteristics of stimuli (such as their intensity) and our psychological experience of them Physical World Psychological World Light Brightness Sound Volume Pressure Weight Sugar Sweet

Thresholds § Absolute Threshold: Proportion of “Yes” Responses 0. 00 0. 50 1. 00 § The minimum stimulation needed to detect a particular stimulus 50% of the time 0 5 10 15 20 Stimulus Intensity (lumens) 25

Difference Threshold • The minimum difference that a person can detect between two stimuli. • Also known as Just Noticeable Difference (JND) • https: //youtu. be/w. Vhiez. By. MSU

Thresholds § Subliminal: § Below one’s absolute threshold for conscious awareness

Let’s look at a few subliminal clips Wendy’s http: //www. youtube. com/watch? v=7 hpuc. DMi. Zmc Frozen https: //www. youtube. com/watch? v=WLS 5 jb. SWc. Ak Disney https: //www. youtube. com/watch? v=5 Qa. Ydph-a. NM

Laws of sensation : Weber’s Law • Ernst Weber noted that for people to really perceive a difference, the stimuli must differ by a constant "proportion" not a constant "amount". https: //youtu. be/-1 e 0 u. IS 5 j 2 Q

Signal Detection Theory • Assumes that we do not have an absolute threshold. • Predicts how we detect a stimulus amid other stimuli. • We detect stuff based on our experiences, motivations and fatigue level. • Reactions to a stimulus can be categorized as: • hit, miss, false alarm, correct rejection

Sensory Adaptation • Sensory adaptation is the diminishing responsiveness of our sensory systems to prolonged stimulation. • Unless it is quite intense or painful, stimulation that persists without change in intensity usually shifts to the background of our awareness. • Until now, many of you are probably unaware that your sense of touch had adapted to the pressure of the chair against your legs. Do you feel your underwear all day?

Review § What is psychophysics? How does it connect sensation with perception? § What is an absolute threshold? § What are some implications of Signal Detection Theory? § What does Weber’s Law suggest about difference thresholds?