Sensation and Perception

• 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-analysis that begins with the sensory receptors and works up to the brain’s integration of sensory information. Also called Stimulus-driven processing

• Top-down processing- information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations. Also called Concept-driven processing

• Selective attention-the focusing of conscious awareness on a particular stimulus

• Cocktail party effect- ability to attend to only one voice among many (and detecting your name in an unattended voice). This is evidence that we cannot multi-task

• **Inattentional blindness-**failing to see visible objects when our attention is directed elsewhere

• **Change blindness-**failing to notice changes in the environment

• Transduction- conversion of one form of energy to another

• **Receptors-**neurons that transduce (convert) a stimulus into a nerve impulse

• **Sensory adaptation-**diminished sensitivity as a consequence of constant stimulation- occurs because our sensory system is built to notice changes

• Sensory habituation (Perceptual adaptation)- learning not to respond to repeated presentation of stimulus (this is a learned process and not innate)

• **Absolute threshold-**Minimum amount of stimulation…needed to produce a sensory experience 50% of the time

• **Difference threshold-**Smallest amount a stimulus can be changed and difference is detected (just noticeable difference – JND)

• **Just noticeable difference (JND)-**Smallest amount a stimulus can be changed and difference is detected (same as Difference Threshold)

• Weber’s law- JND is proportional to size of a stimulus (ratio or percentage)- the difference is not linear. BTW, we don’t recognize the amount of change. We recognize the percentage of change

• Signal detection theory- theory predicting how and when we detect the presence of a stimulus amid background stimulation. This theory assumes there is no single absolute threshold, and depends somewhat on person’s frame of mind and the context.

• **Subliminal Messaging-**a message delivered to you below your threshold

• **Priming-**a message not below your threshold, something that can influence your behavior but becomes less effective if you can detect it

• Retina- the thin, light-sensitive layer at the back of the eyeball. The retina contains millions of photoreceptors and other nerve cells

• **Photoreceptors-**Light-sensitive cells (neurons) in the retina that convert light energy to neural impulses. The photoreceptors are as far as light gets into the visual system

• Rods-Photoreceptors in the retina that are especially sensitive to dim light but not to colors. Rod-shaped.

• Cones-Photoreceptors in the retina that are especially sensitive to colors but not to dim light. Cone-shaped

• **Fovea-**The tiny area of sharpest vision in the retina

• **Optic nerve-**The bundle of neurons that carries visual information from the retina to the brain

• **Blind spot-**The point where the optic nerve exits the eye and where there are no photoreceptors Any stimulus that falls on this area cannot be seen

• **Brightness-**A psychological sensation caused by the intensity of light waves

• Acuity- how sharp and clear a vision is. Three types: normal, nearsightedness, farsightedness

• **Color-**Also called hue. Color is not a property of things in the external world; rather, is is a psychological sensation created in the brain from information obtained by the eyes from the wavelengths of visible light

• **Electromagnetic spectrum-**Entire range of electromagnetic energy (we only see small portion of it)

• **Visible spectrum-**small part of E.S. to which our eyes are sensitive

• **Trichromatic theory-**we are sensitive to…three different colors- red, blue, and green

• **Opponent-process theory-**process colors in…complementary colors

• **Afterimages-**Sensations (of colors) that linger after the stimulus is removed

• **Color blindness-**the inability to see color/a certain color. Most common is red/green

• **Frequency-**The number of vibrations or cycles the wave completes in a given amount of time. Expressed in cycles per second (cps) or hertz (Hz)

• **Amplitude-**The measure of the physical strength of the sound waves (shown in its peak-to-valley height). Expressed in units of sound pressure or energy. when you turn down the volume, you are decreasing amplitude

• **Tympanic membrane-**ear drums

• **Cochlea-**primary organ of hearing; a coiled tube in the inner ear, where sound waves are transduced into nerve messages

• **Basilar membrane-**thin strip of tissue running through the cochlea. Converts vibrations into neural messages

• **Pitch-**A sensory characteristic of sound produced by the frequency of the sound wave.

• **Frequency Theory-**says that neurons on the basilar membrane respond with different firing rates for different sound wave frequencies, allowing us to hear low frequencies, below 5,000

• **Place Theory-**Says that different frequencies activate different locations on the membrane, as they send out neural codes for different pitches to the auditory cortex of the brain. This allows us to hear high tones above 1,000

• **Loudness-**a sensory characteristic of sound produced by the amplitude (intensity of the sound wave)

• **Timbre-**the quality of a sound wave that derives from the wave’s complexity (combination of pure tones)

• **Conduction deafness-**an inability to hear resulting from damage to structures of the middle or inner ear

• Nerve deafness-(also known as sensorineural hearing loss)- the inability to hear, linked to a deficit in the body’s ability to transmit impulses from the cochlea to the brian, usually involving the auditory nerve or higher auditory processing centers

• **Vestibular sense-**the sense of body position and movement of body parts relative to each other (where are your body parts located)

• **Kinesthetic sense-**the body position sense the orients us with respect to gravity (how we are postured) (balance)

• **Olfaction-**sense of smell

• **Pheromones-**chemical signals released by organisms to communicate with other members of their species. Often used by animals as sexual attractants

• **Gustation-**the sense of taste

• **Skin senses-**sensory systems for processing touch, warmth, cold, texture, and pain

• **Gate-control theory-**an explanation for pain control that proposes we have a neural “gate” that can, under some circumstances, block incoming pain signals. Why we rub parts that we hit to distract from the pain

• **Placebo effect-**a response to a placebo (a fake drug) caused by subject’s belief that they are taking real drugs

• **Percept-**product of perception- something that’s associated with concepts, memories of events, emotions, and motives

• Feature detectors- (important names Hubel and Wiesel did this research)- occipital cortex brain cells that identify parts of the human face

• **Binding problem-**we don’t know how our brain ties all of these facial features (percepts) into a face

• Parallel processing- the brain’s ability to deal with multiple stimuli at once

• **Perceptual constancy-**the ability of the brain to make a precept stay the same, even if the stimulus or the way it is viewed has changed temporarily

• **Size constancy-**the brain’s ability to perceive someone or something as the same size at different distances

• **Color constancy-**the brain’s ability to perceive the color as the same even if the light has changed around it

• Shape constancy- the brain’s ability to perceive a shape as the same even if it’s altered slightly

• **Illusion-**a response to stimulus patterns when the brain misinterprets an image

• **Ambiguous figures-**stimulus patterns that can be interpreted two or more different ways (top-down processing)

• **Gestalt psychology-**a pattern that the brain recognizes- also a theory that we organize incoming stimuli into meaningful perceptual patterns according to how our brains are structured from birth (innate) -underlying is that the whole is greater than the sum of the parts

• Figure-ground- a pattern (Gestalt) that grabs attention, and everything else is ground that we perceive the pattern against

• Figure- the pattern

• Ground- the background behind the pattern

• **Closure-**when the brain fills in incomplete figures

• **Laws of perceptual grouping-**The Gestalt principles of similarity, proximity, continuity, and common fate. These “laws” suggest how our brains prefer to roup stimulus elements together to form a percept.

• **Law of similarity-**The brain groups similar things together, things that share a look, sound, feel, etc

• Law of proximity- The brain groups nearby things together

• Law of continuity- The brain prefers continuous figures over disconnected ones

• Law of common fate- The brain groups similar objects because they share a common motion or destination

• **Law of Pragnanz-**The brain sees the simplest pattern possible

• **Stroboscopic motion-**a series of similar but separate stimuli appearing quickly, giving the appearance of moving (like in a movie)

• **Phi Phenomenon-**where the quick flashing of two nearby light objects appear to create a moving object blocking the picture

• Autokinetic effect- when a small point of light is dark surroundings, making it seem to move

• **Binocular cues-**depth perception info received from both eyes

• Monocular cues- depth info received from only one eye

• **Learning-based inference-**The view that perception is primarily shaped by learning (or experience) rather than innate factors

• **Perceptual set-**readiness to detect a particular stimulus in given context (ex. Scared person thinks a noise in the dark is a threat)