● Sensation and perception are actually parts of one continuous process
● Sensation: process by which our sensory receptors and nervous system receive and
represent stimulus energies from our environment
● Perception: process of organizing and interpreting sensory information, enabling us to
recognize meaningful objects and events
● Bottom-up processing: sensory analysis that begins at the entry level, with information
flowing from the receptors to the brain
● Top-down processing: information processing guided by high-level mental processes, as
when we construct perceptions by filtering information through our experience and
expectations
All our senses
- Receive sensory stimulation, often using specialized receptor cells
- Transform that stimulation into neural impulses
- Deliver the neural information
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
● Absolute threshold
○ Minimum stimulus energy needed to detect a particular stimulus 50% of
the time
○ Tested by defining the point where half the time a stimulus is detected
and half the time it is not
● Signal detection theory
○ Predicts how and when we will detect a faint stimulus (signal) amid
background stimulation (noise)
○ Individual thresholds vary depending on the strength of the signal and on
our experience, expectations, motivation, and alertness
● Subliminal: Input below the absolute threshold for conscious awareness
● Difference threshold (or the just noticeable difference): Minimum difference that a person
can detect between any two stimuli half the time
○ Increases with a stimulus size
● Weber’s law: for each sense, the size of a just noticeable difference is a constant
percentage of the initial stimulus
○ The exact percentage varies, depending on the stimulus
, Sensory Adaptation
● Is diminished sensitivity as a consequence of constant stimulation
● Aids focus by reducing background chatter
● Influences how the world is perceived in a personally useful way
● Our sensory receptors are sensitive to novelty, sensory adaptation even
influences how we perceive emotions
Perceptual set: Mental tendencies and assumptions that affect (top-down) what we hear,
taste, feel, and see
- Schemas organize and interpret unfamiliar information through experience
Context Effects
● A given stimulus may trigger different perceptions because of the immediate context
Motivation and Emotion
● Perceptions are also influenced by our motivation and emotions
○ Walking destinations look farther away when we are fatigued
● Slopes look steeper when we are wearing a heavy backpack (or after listening to sad,
heavy classical music)
● Water bottles look closer when we are thirsty
Vision
Light Energy- translated into neural messages
● Wavelength: Distance from the peak of one light wave or sound wave to the peak of the
next. Electromagnetic wavelengths vary from the short blips of gamma rays to the long
pulses of radio transmission
● Hue: Dimension of color that is determined by the wavelength of light, what we know as
the color names: blue, green, and so forth
● Intensity: Amount of energy in a light wave or sound wave, which influences what we
perceive as brightness or loudness. Intensity is determined by the wave’s amplitude
Eye Structures
● Cornea: Portion of the eye through which light passes (to the pupil and lens) and
is bent to help provide focus
● Pupil: A small adjustable opening through which the light then passes
● Iris: A colored muscle surrounding the pupil that controls its size
● Lens: Focuses incoming light rays onto an image on the retina on the eyeball’s
sensitive inner surface
● After entering the eye and being focused by a lens, light energy particles strike
the eye’s inner surface, the retina
● Retina: contains sensory receptors for vision, layers of neurons begging the
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