Chapter 4 -- Sensation and Perception Flashcards
What is perception?
The selection, organization,
and interpretation of sensory input
What is sensation?
The stimulation of sense organs – receiving energy from the environment, and transforming it into action potentials.
What is transduction?
The process by which specialized receptor cells convert energy from an external stimulus to relay info to the brain
What is bottom-up processing?
Sensory receptors register information about the external environment and send it up to the brain for interpretation. (ex: feeling the tune of a new song)
What is top-down processing?
Cognitive processing in the brain allows us to apply that framework to incoming info from the world. (ex: Having a perceptual experience of a song you’ve heard before)
What are the three main categories of sensation?
Photoreception (detection of light)
Mechanoreception (detection of pressure, vibration and movement)
Chemoreception (detection of chemical stimuli)
What is an absolute threshold?
The minimum amount of stimulus energy that a person can detect
What is a difference threshold or a “just noticeable difference”?
The degree of difference that must exist between two stimuli before the difference is detected.
What is Weber’s law?
The principle that two stimuli must differ by a constant minimum percentage (rather than a constant amount) to be perceived as different.
Candle example: Adding 1 candle to a bundle of 20 is noticeable (5% increase); adding 1 to 120 candles is unnoticeable (<1% increase)
What is the detection of information below the level of conscious awareness.
Subliminal perception
Is subliminal perception possible according to studies?
Studies show that the brain responds to info presented below the conscious threshold but it is often only a weak effect, and sometimes it can shape our behaviour.
What is signal detection theory and what does it help us understand?
Signal detection theory is an approach to perception that focuses on decision making about stimuli under conditions of uncertainty. It helps us examine processes that reveal our ways of judgement when it comes to whether we perceive stimulus or not, and the mistakes (misses/false alarms) we may make and why.
What are the four outcomes in signal detection?
Hit (correct) – SIGNAL EXISTS
Miss (mistake) – SIGNAL EXISTS
False alarm (mistake) – NO SIGNAL
Correct rejection (correct) – NO SIGNAL
What are the two components of signal detection theory?
Information acquisition (gathering relevant indicators)
Criterion (standards used to make a decision)
What is attention vs selective attention?
Attention is the process of focusing awareness on a narrow aspect of the environment while selective attention is focusing on a specific aspect of experience while ignoring others.
What is a perceptual set?
Readiness to perceive something in a particular way. Reflect top-down perception.
What is sensory adaptation?
The sensory system changes responsiveness to the average level of stimulation.
Why is vision functional?
It allows for the detection of movement (predator/prey) and colour (ripe/spoiled) which is crucial for survival.
What are the two types of photoreceptors?
Cones (sensitive to fine detail and colour)
Rods (sensitive to movement)
How does the transduction of light work?
Light travels through the retina to impinge on photoreceptors at the back of the eye
Light bleaches a pigment contained within the photoreceptors
Bleaching leads to a graded receptor potential that eventually produces an action potential in the ganglion cell
How does the brain process visual information?
- The optic nerve leaves the eye, carrying information about light toward the brain.
- Stimuli from left/right visual fields stimulate rods and cones in the OPPOSITE half of the retina in both eyes.
- At the optic chiasm, the optic nerve fibres separate, and half of the nerve fibres cross over the midline of the brain.
- The visual information originating in the right halves of the two retinas (from objects in the left visual field) is transmitted to the right side of the occipital lobe in the cerebral cortex,
and the visual information coming from the left halves of the retinas (from objects in the right visual field) is transmitted to the left side of the occipital lobe.
- The visual stimuli is then processed in the visual cortex of the brain.
What is a feature detector?
Neurons in the brain’s visual system that respond to particular features of a stimulus.
What did David Hubel and Toren Wiesel discover about humans from their research on feature detectors?
Humans “learn” to perceive through experience.
What is parallel processing?
The simultaneous distribution of information across different neural pathways that allows information to be processes quickly.
What is binding in the sense of vision?
Bringing together and integrating what is processed by different neural pathways or cells to paint a whole picture of what we see.
What is the trichromatic theory?
- Thomas Young’s theory
- Colour perception is produced by 3 types of cone receptors in the retina that are sensitive to different and overlapping ranges of wavelengths.
What is the opponent-process theory?
- Ewald Hering’s theory
- Cells in the visual system respond to complementary pairs of red-green and blue-yellow colours.
- A given cell might be excited by red and inhibited by green, whereas another cell might be excited by yellow and inhibited by blue.
How are both the trichromatic theory and the opponent-process theory correct?
Red, blue and green cones in the retina are connected to retinal ganglion cells, therefore the three-colour code is immediately translated into the opponent-process code which is sent to the optic nerve and brain.
What is Getsalt psychology?
People naturally organize their perceptions according to certain patterns.
What are the 3 Getsalt principles and what do they do?
Closure: we fill in disconnected figures to see them as complete
Proximity: Objects near each other are seen as a unit.
Similarity: similar objects tend to be seen as a unit
They identify how we innately connect stimuli together.
What is the place theory?
- The inner ear registers the frequency of sound
- Each frequency produces vibrations at a particular spot on the basilar membrane.
Why is the place theory acceptable and flawed?
It explains high-frequency sounds and says they stimulate a precise area on the basilar membrane.
It does not identify an exact location on the membrane that is associated with hearing low-frequencies.
What is Frequency Theory?
- The inner ear registers the frequency of sound
- The perception of a sound’s frequency depends on how often the auditory nerve fires.
Why is the frequency theory limited and what principle did researches come up with?
The frequency theory was limited because it does not apply to frequencies that would require a neuron to fire more rapidly. One neuron fires at a max rate of 1000 times per second
The volley principle states that a cluster of nerve cells can fire neural impulses in rapid succession or alternating turns, producing a volley of impulses.
How does the brain process sounds via the auditory nerve?
The auditory nerve receives information about sound from the hair cells of the inner ear and carries these neural impulses to the brain’s auditory areas.
How do we know where sounds are coming from?
Timing and intensity help us localize the source of sounds. From equal distances, the pinna distorts sounds based on where they come in space and our brain cells can detect the difference.
What is the perpetual dimension of amplitude (intensity) of a sound?
Loudness
What is the perpetual dimension of frequency of a sound?
Pitch
What is the perpetual dimension of complex sounds (voices, music, intersecting frequencies)?
Timbre: tone saturation
How do we feel touch and how are signals sent to our brain?
We detect mechanical energy (pressure against skin). Touch receptors produce action potentials that go to the spinal chord, brain stem, then the opposite sides, to the thalamus which projects to the parietal lobes.
How do we feel temperature?
Thermoreceptors, sensory nerve endings under the skin that respond to changes in temperature at or near the skin and provide input to keep the body’s temperature at 37 degrees Celsius.
How do we feel pain?
Pain receptors detect when a stimulus is too intense that it could cause danger to our bodies. They are unevenly distributed throughout the body.
Neuroscientists believe that the experience of pain is signalled by endorphins. Motivation and expectation could impact the perception of pain.
How do we taste?
We detect chemicals dissolved in our saliva. Papillae increase the surface area of our tongue to make more room for taste buds which transmit stimuli to the brain for analysis.
How do we smell?
The olfactory epithelium lining of the roof of the nasal cavity, contains a sheet of receptor cells for smell. The neural pathway goes to the olfactory areas in the temporal lobes then various brain regions, especially the limbic system responsible for emotion and memory.
What are kinesthetic senses and vestibular senses?
Kinesthetic senses provide information about movement, posture, and orientation. Vestibular sense provides information about balance and movement.
How does vestibular sense make its way to the brain?
Via the auditory nerve. Semicircular canals and vestibular sacs transmit info about movement and head position. Messages go to the medulla or directly to the cerebellum.
