Sensation & Perception

Sensation & Perception

The Lion King

Do you see the message hidden?

Political Subliminal Message • What impact does this message have? • Will it last? • Commercial

Subliminal Messages • Hidden messages targeted at our subconscious mind. • Examples: • 1. Small images inside a larger picture • 2. An audio message hidden inside a recording • 3. Messages in song played backward • 4. Hidden words or pictures that quickly appear • 5. Powerful marketing tools • Effects us on a emotional level • Short lived results

Sensation & Perception • Sensation- stimulation of the sense organs • Raw data of experience: smells, sights, sounds, pain, etc. • Perception- creating meaning from the raw sensory information

Basic Process • Sensory organs absorb energy from a physical stimulus in the environment • Sensory receptor cells detect stimulus energies and convert them into neural impulses (transduction) • Electrochemical message is sent to the brain • Specific areas of the brain organizes the input and transforms them into something meaningful

Attention • Selective Attention- focusing our awareness on a particular stimuli • Cocktail Party Phenomenon- filter out many sounds to maintain one conversation but will notice your name in another conversation

Psychophysics- how physical stimuli are translated into psychological experience • Gustav Fechner’s work on thresholds • Threshold- is a dividing point between energy levels that do and do not have a detectable effect • Absolute Threshold- minimum amount of stimulation that an organism can detect 50% of the time • Environment can affect detection of a stimulus • Examples of absolute threshold under ideal conditions • Online demo: http://www.garyfisk.com/anim/threshold.swf

JND- just noticeable difference is the smallest difference in the amount of stimulation that a specific sense can detect • The absolute threshold is the jnd from nothing (no stimulus) • JND is greater for stronger stimuli than for weaker ones • As a stimulus increases in magnitude, the JND becomes larger

Weber’s Law- states that the size of a jnd is a constant proportion of the size of the initial stimulus • This portion is called the Weber Fraction • It can apply to all the senses but different fractions apply to different types of sensory input • Ex: Weber fraction for weights is 1/30, which means you should detect the difference btw a 30 ounce weight and a 31 ounce weight • Envelope/Book EXPERIMENT!

Fechner’s Law • The magnitude of a sensory experience is proportional to the # of JNDs that the stimulus causing the experience is above the absolute threshold. • Constant increments in stimulus intensity produce smaller and smaller increases in perceived magnitude of sensation. • EX: Dark room with lamp and three bulbs. • Three equal increases in stimulus intensity produce progressively smaller differences in the magnitude of sensation.

Imagine you are monitoring a radar screen

Signal Detection Theory • The detection of stimuli involves decision processes as well as sensory processes, which are influenced by many factors besides stimulus intensity • Radar Screen with four possible outcomes: • Hits-Detecting signals when present • Misses-Failing to detect signals when present • False Alarms-detecting signals when they are absent • Correct Rejection-Not detecting signals when they are absent

Setting Criterion • Depends on our expectations and on the consequences of missing a signal or of reporting a false alarm. • Ex: Waiting for the pizza guy at a party.

Sensory Adaptation • Gradual decline in sensitivity to prolonged stimulation • Ex: Garbage • In reality, the stimulus intensity (the odor) stays the same but with continued exposure your sensitivity to it decreases • Ex: Jumping into a swimming pool • It allows people to ignore the obvious but you can notice CHANGES in sensory input • A behavioral adaptation that has been sculpted by natural selection

Sensation & Perception