Module 17 – Basic Principles of Sensation & Perception Sensation – the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment Sensation – the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment ( ex.) light energy entering eye ( ex.) light energy entering eye Biological process Biological process Perception – the process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events. Perception – the process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events. (ex) recognizing your mom’s face, Psychological process (we create meaning)

Transduction Transduction - Conversion of one form of energy into another. In sensation, the transforming of stimulus energies, such as sights, sounds, and smells, into neural impulses our brain can interpret. Transduction - Conversion of one form of energy into another. In sensation, the transforming of stimulus energies, such as sights, sounds, and smells, into neural impulses our brain can interpret. Psychophysics – the study of relationships between the physical characteristics of stimuli, such as their intensity, and our psychological experience of them Psychophysics – the study of relationships between the physical characteristics of stimuli, such as their intensity, and our psychological experience of them

Thresholds Absolute Threshold - the minimum stimulation needed to detect a particular stimulus 50% of the time Absolute Threshold - the minimum stimulation needed to detect a particular stimulus 50% of the time Being able to hear the tick of a watch 25 feet away Being able to hear the tick of a watch 25 feet away Difference Threshold – the minimum difference that a person can detect between 2 stimuli Difference Threshold – the minimum difference that a person can detect between 2 stimuli Ex. Noticing a change in weight of backpack Ex. Noticing a change in weight of backpack Also referred to as JND – Just Noticeable Difference Also referred to as JND – Just Noticeable Difference

Thresholds Weber ’ s Law - The principle that, to be perceived as different, two stimuli must differ by a constant percentage rather than a constant amount Weber ’ s Law - The principle that, to be perceived as different, two stimuli must differ by a constant percentage rather than a constant amount Ex. Adding a quarter to an envelope will be a noticeable change in weight but not if you add a quarter to your wallet Ex. Adding a quarter to an envelope will be a noticeable change in weight but not if you add a quarter to your wallet

Thresholds Signal detection theory – A theory predicting how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise). Assumes there is no single absolute threshold and that detection depends partly on a person ’ s experience, expectations, motivation, and alertness. Signal detection theory – A theory predicting how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise). Assumes there is no single absolute threshold and that detection depends partly on a person ’ s experience, expectations, motivation, and alertness. Ex. Teacher speaking loud enough to break threshold for sound but student not motivated to pay attention Ex. Teacher speaking loud enough to break threshold for sound but student not motivated to pay attention With heightened responsiveness we have more false alarms…we become more sensitive (wartime more sensitive, peacetime less sensitive) With heightened responsiveness we have more false alarms…we become more sensitive (wartime more sensitive, peacetime less sensitive)

Subliminal Processing Subliminal – below one ’ s absolute threshold for conscious awareness Subliminal – below one ’ s absolute threshold for conscious awareness Can evoke a feeling Can evoke a feeling Priming – the activation, often unconsciously, of certain associations, thus predisposing one ’ s perception, memory, or response Priming – the activation, often unconsciously, of certain associations, thus predisposing one ’ s perception, memory, or response Not influential in marketing products Not influential in marketing products

Sensory Adaptation Diminished sensitivity as a consequence of constant stimulation Diminished sensitivity as a consequence of constant stimulation After constant exposure to a stimulus, our nerve cells fire less frequently After constant exposure to a stimulus, our nerve cells fire less frequently Eyes- always moving (not noticeable) to avoid this Eyes- always moving (not noticeable) to avoid this We perceive the world NOT exactly how it is, but as it is useful for us We perceive the world NOT exactly how it is, but as it is useful for us Ex. Adjusting to cold pool water after a few minutes Ex. Adjusting to cold pool water after a few minutes

Bottom-up Processing: Analysis that begins with the sense receptors and works up to the brain ’ s integration of sensory information Analysis that begins with the sense receptors and works up to the brain ’ s integration of sensory information Process built solely on physical stimuli Process built solely on physical stimuli Ex. Detecting lines, angles, and colors that form a picture. Ex. Detecting lines, angles, and colors that form a picture.

Top-down Processing: Information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experiences and expectations. Information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experiences and expectations. The processing of physical stimuli The processing of physical stimuli Considering the title of a picture when viewing it: Considering the title of a picture when viewing it: “ The Forest Has Eyes ” “ The Forest Has Eyes ”

Making sense of the world What am I seeing? Is that something I’ve seen before? Bottom-up processing: taking sensory information and then assembling and integrating it Top-down processing: using models, ideas, and expectations to interpret sensory information

Top-down Processing You may start to see something in this picture if we give your brain some concepts to apply: “tree” “sidewalk” “dog” “Dalmatian”

Perceptual Set Perceptual set – a mental predisposition to perceive one thing and not another Perceptual set – a mental predisposition to perceive one thing and not another Determined by the schemas that form from our experiences Determined by the schemas that form from our experiences Done through top-down processing Done through top-down processing

Context Effects - The brain works backwards in time to allow a later stimulus determine how we perceive an earlier one. Context Effects - The brain works backwards in time to allow a later stimulus determine how we perceive an earlier one. The context creates an expectation that influences our perception The context creates an expectation that influences our perception Our emotions and motives influence how we perceive things Our emotions and motives influence how we perceive things Emotions (ex.) If we are angry, we might be more likely to perceive hostility in others Emotions (ex.) If we are angry, we might be more likely to perceive hostility in others Motivation (ex.) When rooting for our favorite baseball team we will interpret close plays in our team’s favor Motivation (ex.) When rooting for our favorite baseball team we will interpret close plays in our team’s favor

Effect of Emotion, Physical State, and Motivation on Perception Experiments show that:  destinations seem farther when you’re tired.  a target looks farther when your crossbow is heavier.  a hill looks steeper with a heavy backpack, or after sad music, or when walking alone.  something you desire looks closer.