sensation & perception

Which of the following answer choices does NOT accurately depict the differences between top-down and bottom-up processing? A) Bottom-up processing is data driven, while top-down processing is model driven. B) An intelligent battle plan is drawn up, but on the day of the battle the army's generals use data to quickly adapt their plan - this depicts a "top-down" approach. C) During court, an eyewitness who uses "top-down" processing would likely be more reliable than an eyewitness who uses "bottom-up" processing. D) Bottom-up processing is analogous to filling in a coloring book, while top-down processing is analogous to a freehand sketch.

C

Gestalt principles are an excellent example of visual top-down processing approach because

our models of the world, past expectations and experiences, and even context clues all affect the image we perceive from sensory information which we have acquired.

In the middle of the night, Martha turns her room light on. It seems extremely bright for a short period of time. This is an example of

sensory adaptation

absolute threshold

the minimum intensity needed in order for a sensory receptor to detect a particular stimulus at least 50 percent of the time. It is a yes/no situation.

False alarm

the subject perceives a signal when none was present

just noticeable difference

the threshold at which one can distinguish two stimuli that are of different intensities, but otherwise identical

Gestalt principles

theoretical ideas about how the brain perceives individual bits of sensory information as bigger, cohesive images

A man pours water into a pot and begins to heat the water. He sticks his finger into the water when it is 70 degrees Celsius and doesn't think it feels any warmer. However, once the water hits 80 degrees he realizes the water feels hot and hastily removes his finger. Find the "just-noticeable-difference" in temperature in this scenario.

10 degrees The JND is the minimum change in stimulus intensity required to be detectable 50% of the time. Weber's law predicts that this change will be a proportion of the original stimulus, and that this proportion is constant. Therefore, if Weber's law predicted that the JND was a relative change of 14% from the original stimulus, the intensity of the initial stimulus would have to increase or decrease by 14% to reach the JND. In this problem the original stimulus intensity is 70, and a change in intensity is undetectable until it reaches 80. Therefore, the JND is 10. Weber's law predicts any further change to the temperature will only be detectable if the temperature changes by at least 14%.

A man is watching the sunset from his garden, when a wasp unexpectedly stings him. What information will an activated nociceptor send to the CNS? Select all that apply. A) The extent of mechanical damage to the skin B) How badly the sting hurts C) The location of the sting D) The "type" of stimulus which interacted with the skin

A, C, D Sensory receptors typically detect an external stimulus (such as the mechanical force applied by a wasp's stinger) and communicate information about the stimulus to the CNS. This information includes the location of the stimulus (based on the location of the receptor), the type of stimulus (mechanical damage versus temperature change), the intensity of the stimulus (how strongly the receptor is activated by the stimulus), and duration of the stimulus (does the stimulus act all at once or produce a consistent effect?).

Sensory adaptation describes how sensory receptors adapt to the presence of certain stimuli. Which of the following descriptions of sensory adaptation are correct? Select all that apply. A) On a cellular level, sensory adaptation would be a greater number of action potentials produced from the same intensity of stimulus. B) If Homa was searching for her friend Anne in a crowd, sensory adaptation would cause her to experience more incorrect rejections. C) Mark is demonstrating adaptation when he slowly begins to tune-out his roommate's distracting music. D) Sensory adaptation would increase the absolute threshold of sensation of a sensory receptor.

B, C, D

True or false: Sensory receptors (such as photoreceptors) discriminate solely based on the "type" of stimulus which tries to activate it. In other words, any photon could activate any photoreceptor, but no chemoreceptor would ever become activated by a photon.

False. Rods respond to low energy photons (longer wavelength) while cones require much higher energy photons

Which of the following correctly depicts the concepts of absolute threshold and the threshold of conscious perception? A) The absolute threshold is the lowest intensity at which sensory information has the capability to activate a sensory receptor. B) A signal detection theorist might claim that a higher number of incorrect rejections is related to a lower absolute threshold. C) The threshold for conscious perception is a constant value, while context effects can lower or raise the absolute threshold. D) The value of the threshold for conscious perception is always higher than the absolute threshold.

D

True or false: A receptor's absolute threshold of sensation was achieved if the outcome of signal detection was a "correct rejection".

False. A correct rejection involves a person correctly realizing that a stimulus is NOT present Therefore, a correct rejection would occur if a sensory receptor was NOT activated and the person realizes that this means there was no stimulus, correctly rejecting any signal.

True or false: Internoreceptors detect proximal stimuli, while externoreceptors detect distal stimuli.

False. Internoreceptors are sensory receptors which detect stimuli inside of your body (e.g. muscle stretch detected by a propriocepter), while externoreceptors are sensory receptors which detect stimuli from outside of your body (e.g. light). Distal stimuli are stimuli out in the world which have not yet been detected by our body. For example, light might be emitted from the sun, but until it activates our photoreceptors it is considered "distal". Once a stimulus has been detected by one of our receptors, it is considered "proximal".

True or false: Mechanoreceptors detect mechanical stimuli while proprioceptors and baroreceptors do not.

False. Mechanoreceptors detect mechanical stimuli, while proprioceptors and baroreceptors are subtypes of mechanoreceptors that detect specific kinds of mechanical stimuli.

True or false: 'Painful' stimuli are perceived via a bottom-up approach and not a top-down approach.

False. Sensory perception is a complex phenomenon and more than one approach might be used when the brain attempts to perceive a stimulus. For example, bottom-up processing might be used to "figure out" exactly what a stimulus is based on sensory information, but then once a stimulus is identified, past-experience and our brain's expectations of that stimulus may take over, turning sensory perception into a top-down approach. Painful stimuli, and any other kind of stimuli, can be processed by BOTH bottom-up and top-down approaches depending on the context of the sensory experience.

True or false: Signal detection theory presupposes that the range of intensities for which we detect a signal in our environment are constant.

False. The context in which we are attempting to detect a signal can increase or decrease the signal intensity required for us to notice the signal. For example, if you are incredibly focused on driving your car you might notice road hazards even if they present at a relatively low intensity. However, if you are sleepily driving your car, then a road hazard may need to present itself at a much higher intensity for your brain to correctly detect it and produce a "hit".

True or False: The absolute threshold is the lowest intensity at which sensory information has the capability to activate a sensory receptor.

False. The threshold of sensation is a relative value which tells us the intensity that a stimulus must have in order to register with a sensory receptor and activate that receptor at least 50% of the time. This means that if a photon contained energy required for the absolute threshold of photoreceptor activation, it would only have a 50% chance of activating that photoreceptor. Before the absolute threshold, sensory information may still have the ability to activate a receptor, but less than 50% of the time.

True or false: Linda can detect when a smell becomes 10% more smelly. Weber's law predicts that any time any smell changes in intensity by 10%, Linda will detect it half of the time.

False. Weber's law breaks down at the extremes of sensory detection. Linda's nose will likely not be able to detect a change in smell intensity if a smell was originally extremely smelly (near the limits of smelliness) or not very smelly at all. Weber's law holds up only in moderate ranges of sensory intensity.

Weber's Law equation

JND = K*I JND = the difference threshold I = the intensity (magnitude) of the standard stimulus K = change in I / initial I, a constant, Weber fraction

principle of similarity

Objects with a shared feature (shape or color) will likewise be perceived as a single group

Scientists put Anna in a room and showed her cards covered in red dots. Each card had a slightly different shade of red coloring the dots. The scientists determined the change in color intensity Anna could differentiate between 50% of the time. What is the name for this sort of testing?

Psychophysical Discrimination

Sensation

Real, physical object's information is detected by our body - is objective

exteroreceptors

Sensory receptors that detect stimuli from outside the body, such as light/heat/pressure/chemicals.

proprioceptors

Sensory receptors, located in the muscles and joints, that provide information about the relative position position and movement of the body in space.

Perception

The brain's subjective interpretation of sensory information

John is a weightlifter doing bicep curls at the gym. He loads up 40 lbs on his barbell and curls a few reps. He adds extra pounds to his barbell, but notices they don't feel any heavier until 50 lbs. If he reduces the weight, at what weight will he notice the barbell feels lighter?

Weber's law suggests that the just-noticeable difference (difference to notice a stimulus change 50% of the time) for a change in stimulus intensity is a constant proportion of the original stimulus. John notices the weight has increased after it gets 25% heavier (in this case, 10lbs added to the initial 40lbs). Therefore, he will only notice the weight has decreased when it gets 25% lighter. 25% of 50 is 12.5; therefore, he will notice the weight has lightened when it reaches 37.5 pounds.

proximal stimulus

a stimulus that has been detected by the body and activated a receptor protein

Both the absolute threshold and the threshold of conscious perception are variable values which can change in response to factors such as

adaptation, habituation, context

top-down processing

allows us to fill in a "picture" or "model" of the world using only limited information and based on expectations we construct

bottom up processing

analysis that begins with the sensory receptors and works up to the brain's integration of sensory information

olfactory and gustatory receptors both respond to

chemicals

ganglia

clusters of cell bodies in the PNS

What is the end result of perceptual processing?

conscious awareness

A woman loses vision in both eyes, but soon realizes her sense of smell is extremely heightened. This is an example of

decrease absolute threshold

binocular cues

depth cues, such as retinal disparity, that depend on the use of two eyes

Osmoreceptors

detect concentration of solutes in the blood

distal stimulus

exists out in the world and a person's body is not detecting it

Weber's Law

for any given sensory input, the just noticeable difference will be a constant proportion of the original input

what type of receptors are responsible for hearing

hair cells

A higher number of incorrect rejections means

higher absolute threshold

principle of continuity

if multiple objects intersect or overlap, we tend to perceive them as relatively few uninterrupted objects

correct rejection

involves a person correctly realizing that a stimulus is NOT present

sensory receptors communicate four properties to the CNS:

location, modality (type of stimulus), intensity, duration

Which receptors respond to auditory information

mechanoreceptors respond to pressure of sound waves in cilia

threshold of conscious perception

minimum of stimulus energy that will create a signal large enough in size and long enough in duration to be brought into conscious awareness and perception

If a stimulus was present but had an intensity below the absolute threshold, it would lead to a _________ because _____

miss; it would not activate a sensory receptor and the person fails to detect the stimulus

Kinesthetic sense

sense of the location of body parts in relation to the ground and each other, monitored by proprioceptors

sensory adaptation

reduced action potential signaling in response to a stimulus, often leads to incorrect rejection

interoreceptors

respond to stimuli within the body

The difference in an object between your two eyes in terms of perceiving objects is called

retinal disparity

proprioceptors and baroreceptors are

specific subtype of mechanoreceptors

principle symmetry

symmetrical objects are more likely to be perceived as part of a whole than asymmetrical objects

psychophysical discrimination testing

tests whether research subjects can tell the difference between two stimuli and comparing the results to physical properties

principle of proximity

the closer two figures are to each other, the more likely we are to group them and see them as part of the same object

signal detection theory

the combined effects of perceptual processing and sensory detection can cause us to correctly or incorrectly detect stimuli in the environment.

Law of Pragnanz

the logical link between Gestalt Principles is that we try to interpret objects in the simplest and most meaningful ways.

Gestalt theory is a theory which describes the visual component of

top-down processing

Principle of closure

we infer the presence of whole/complete objects even when they are incomplete

miss

when the person fails to detect/perceive a signal

hit

when the person perceives the signal that is present