Sensation and Perception

Sensory input and Psychophysics

Sensation and Perception

What do you hear? What do you see? What do you taste? What do you smell? What do you feel? (not emotion) What conclusions can you draw from

these answers?

Sensation

Starts with a stimulus (any aspect of change in our environment to which we respond)

Can be measured in size, duration, intensity and wavelength

Occurs anytime a stimulus activates a receptor

Sensory Receptor

Living cell that responds to certain type of energy

Often located in sense organsSpecialized structure that collects

energy particularly well… (eye, ear, etc)

Detect physical changes in energy such as heat, light, sound, and physical pressure

Eye- notes changes in light

Ear- notes changes in sound

Skin- notes changes in heat and pressure

Perception

Organization of sensory information into a meaningful experience

Comes from a combination of sensations and past experiences Translating the stimulus into the language of

the nervous system (neural impulse) comprehending the basic components of

the stimulus, size, shape, color Organizing the components into an

understandable explanation

Psychophysics

The interaction between the physical world (stimuli) and the psychological world (internal experience)

What is the relationship between color and wavelength?

How does changing a light’s intensity affect your perception of it’s brightness?

Threshold

How much energy is required for someone to hear a sound, or see a light?

How much of a scent must be in a room for someone to smell it?

How much pressure must be put on the skin for someone to feel it?

Is it the same for everyone?

How strong must a stimulus be in order for detection? Threshold- dividing line Not exact Absolute threshold- point at which a very

weak stimulus can be detected 50% of the time

Difference threshold- smallest change a person can detect 50% of the time.

(JND) just noticeable difference

Absolute threshold for 5 senses

Vision- seeing a candle flame 30 miles away on a clear night

Absolute threshold

Hearing- watch ticking 20 feet away

Absolute Threshold

Tasting- 1 teaspoon of sugar dissolved in 2 gallons of water

Absolute threshold

Smell- 1 drop of perfume in a 3 room house

Absolute threshold

Touch- feeling a bee’s wings falling a distance of 1 centimeter onto your cheek

Weber’s Law- related to the Just Noticeable Difference (also known as the difference threshold), which is the minimum difference in stimulation that a person can detect 50 percent of the

time.

The larger the magnitude of the stimulus, the larger the JND

25 watt light bulb / 50 watt light bulb very different

175 watt light bulb / 200 watt light bulb hard to notice

Weber’s Law

The JND increases in direct proportion to the intensity of the stimulus.

Often not true when stimuli approach extreme values.

Sensory adaptation

Our senses are tuned to change and respond to increases and decreases in stimuli, or new events rather than constant stimulation.

We adapt to change/deviation in stimulation

Movie theater Clothes on body

Signal Detection theory- how good are you at recognizing stimuli?

Study of people’s tendencies to make correct judgments in detecting the presence of stimuli

Recognizing stimuli against a competing background of stimuli

Individuals vary based on situation Radar operator

Signal Detection theory

Pre-attentive process- getting info automatically and simultaneously when presented with stimuli

Attentive process- paying attention to only one of the stimuli at a time when presented with multiple stimuli

All tasks require attention, but some require more than others.

P.212-213