Sensation & Perception What is the difference?

Sensation Detection of physical energy emitted or reflected by physical objects Sense organs –eyes, ears, tongue, nose, skin, internal body tissues Without sensations, we would not experience reality

Perception A set of mental operations that organize sensory input into meaningful patterns Perception allows us to interpret our sensations and thus reality

How many Senses? Five? Actual many more

The Riddle of Separate Sensations Sense receptors –specialized cells in the sense organs that convert physical energy from the environment into electrical energy to be transmitted as nerve impulses to the brain

Johannes Muller doctrine of specific nerve energies –Different sensory modalities exist b/c signals received by the sense organs stimulate nerve pathways leading to different brain areas –Because different brain areas are stimulated, different sensations are experienced –Synesthesia Stimulation of one sense evokes sensation of another

Functional Codes Doctrine doesn’t account for variations within a sense –Seeing gold versus yellow Functional code account for this –Within a sense certain neurons fire or don’t, fire fast or slowly, or in a pattern to create different sensations

Measuring the Senses Psychophysics –How the physical properties of stimuli are related to our psychological experience of them

Absolute thresholds Smallest quantity of energy that can be reliably detected 50% of time Very sharp senses –candle flame on a clear, dark night from 30 miles away!)

Difference thresholds just noticeable differences (jnds) Smallest difference in sensory stimulation that can be detected reliably between two stimuli

jnds The larger, or more intense, stimulus 1 is, the greater the jnd needs to be

Signal-detection theory Theory that accounts for response biases in absolute threshold and difference threshold measurements An observer’s response in a detection task is divided into a sensory process (which depends on the stimulus’s intensity) and a decision process (which is influenced by the participant’s response bias)

Signal-detection theory A mathematical formula separates estimates of a person’s sensory process and decision process, yielding a predicted value for one’s true sensitivity to a particular stimulus

Sensory Adaptation When stimulation is unchanging or repetitious, sensory receptors “tire” and fire less frequently, resulting in a decline in sensory responsiveness Sensory adaptation to touch/pressure –(the feel of the clothes on your body) –smell (of one’s perfume or cologne)

We rarely adapt to visual stimuli because our eyes are constantly moving back and forth

We never completely adapt to very intense stimuli (e.g., noxious fumes, intense pain)

Sensory deprivation Absence of normal sensory stimulation –Heron (1957)—visual, auditory, an tactile stimulation was deprived, resulting in disorientation, feelings of edginess and confusion, and many reports of hallucinogenic visions

Don’t oversimplify!!— sensory deprivation may be a form of relaxation for some, but torture for others it all depends upon the context –meditation/relaxation versus solitary confinement in prison

Sensory without Perceiving Selective attention is necessary to focus on and filter out numerous sensory stimuli from being consciously perceived all at once “Cocktail party phenomenon”