Psychological Science Ch.5

What are the 5 absolute thresholds of the 5 senses? Describe them.

Vision - A candle flame 30 miles away on a clear, dark night

Hearing - A clock's tick 20 ft away when all is quiet

Touch - A fly's wing falling on the cheek from 1 cm away

Smell - A single drop of perfume diffused though an area equivalent to the volume of 6 rooms

Taste - A teaspoon of sugar dissolved in 2 gallons of water

Absolute threshold

Minimal intensity needed to just barely detect a stimulus (usually identification on 50% of trials)

EX: when you start to hear music at a certain level (minimum amount of sound needed for it to be heard)

Psychophysics

Methods that measure the strength of a stimulus and the observer's sensitivity to that stimulus

Psychophysicists

Often measure the minimum amount of a stimulus needed for detection

What 5 senses convert physical energy from the world into neural energy? Which is sent to the brain? Explain the sensory inputs of each.

Vision - light reflected from surfaces (i.e. a leaf) provides the eyes with info. about shape, color, etc. of objects

Audition (hearing) - vibrations (i.e. guitar string) cause changes in air pressure that move thru. space to ears of listener

Touch - pressure of a surface against the skin signals its shape, texture, & temperature

Taste & Smell - molecules dispersed in the air or dissolved in saliva reveal the identity of substances that we may or may not want to eat

Can we perceive things that don’t exist?

Yes, depends on how you conceptualize perception. Sometimes we perceive things that aren’t actually there.

EX: illusion (i.e. magic)

Cognition is not simply an ___________ ____ _____________

extension of perception

Object unity

our perception of one object moving, when in actuality there are two objects moving simultaneously

Illusory conjuction

mistake: features from multiple objects are combined incorrectly

Perceptions differ between _______________

people

Threshold

boundary

Just noticeable difference (JND)

Minimal change in a stimulus that can just barely be detected

EX: when playing music in car, once you can hear it you start really having fun. However, afterwards a song starts playing that you don’t like and you tell the passenger to turn the volume down as you’re merging

the passenger turns it down a little but it doesn’t sound to have changed, so you ask them to turn it down a little more…. when you are able to notice a difference in the volume, this is JND (threshold has been crossed)

Weber’s Law

JND of a stimulus is a constant proportion despite variations in intensity

EX: if you’re carrying a 5lb box upstairs, and your mom says “since you’re going upstairs, can you also put this paper on my desk” …. you won’t feel a difference in weight of the item

BUTTT if you were walking without anything in your hands, then you would feel the change in weight of the paper being in your hands; to feel a difference with the box, your mom would most likely have to use a textbook (or smth of heavier nature than a paper)

• the intensity of the stimulus in the beginning drives how much change we need to pick up on it

sensory signals are perceived among environmental ____________

“noise”

Signal detection theory

the response to a stimulus depends both on the person’s sensitivity to the stimulus in the presence of noise and on a person’s response criterion

• takes into account individual perceptual sensitivity (we all have different levels and abilities)

Sensory adaptation

sensitivity to prolonged stimulation tends to decline over time as an organism adapts to current conditions

EX: when smelling eggs after cooking them, at first it’s really strong, but overtime, you loose ability to smell it

When is signal detection theory important?

example: in military they study sensitivity in targets, for this job, recruiters identify who might be best for a particular job

example: mammogram, how sensitive doctors and nurses need to be in understanding and interpreting the xray to determine whether there is a tumor or not(even though it may be hidden)

Visual acuity

ability to see fine detail

EX: looking at Monet’s art (have to look closely to see the details)

Visual light

portion of electromagnetic spectrum seen

What are the 3 properties of light waves

Length: determines color (hue)

Intensity/amplitude: determines brightness

Purity: corresponds saturation or richness of color

Cornea

light reflected from a surface enters the eyes via this transparent feature

Pupil

reflected light from a surface that entered the cornea bends to pass through this feature at the center of the colored iris

behind the iris, the thickness and shape of the __________ adjust to focus light on the ________

lens; retina

fovea

where vision is the clearest

retinal surface

light-sensitive receptor cells are found here

the optic nerve creates a ________

blindspot

what enters through the optic nerve?

whether the retinal surface is excited or inhibited by sports of lights, specialized neurons that signal the brain’s visual centers though their bundled axons

The anatomy of the human eye is composed of ____________ organs of the eye evolved to __________ ________.

specialized; detect light

What is the order of organs in which light passes through the human eye?

cornea → pupil → lens → retina (phototransduction)

Accommodation (in terms of the human eye)

the process by which the eye maintains a clear image of the retina

Retina

light-sensitive tissue lining the back of the eyeball

What occurs if accommodation (in terms of the human eye) occurs improperly?

myopia (nearsightedness) or hyperopia (farsightedness) may occur

What do the 2 types of photoreceptor cells in the retina contain? What do they do?

light-sensitive pigments; transduce light into neural impulses

Cones (vision)

detect color, operate under normal daylight conditions and allow us to focus on fine detail

EX: in daylight we can see color moreso

Rods (vision)

become active under low-light conditions for night vision

EX: at dusk as you’re driving these become active (cones take backseat)

EX: transition from being outside in the sun to inside, it takes a minute for your eyes to adjust to the change of brightness

Blind spot (in vision)

a location in the visual field that produces no sensation on the retina because the corresponding area of the retina contains neither rods nor cones and therefore has no mechanism to sense light

Fovea (in terms of vision)

an area of the retina where vision is the clearest and there are no rods at all (only cones)

color afterimage demonstration

EX: looking at pink and yellow dot; cones become fatigued in each eye after so long, so other cones compensate (and they are sensitive to other colors)

synesthesia

the perceptual experience of one sense that is evoked by another sense

EX: people with this see colors when they aren’t there; i.e. every time someone sees the letter “C” it looks green

EX: a synesthete could smell music i.e. every time someone hears a song, they smell gasoline

Grouping

involves separating a figure from its (back) ground; reversible figure/ground relationship

How does Rubin’s classic reversible figure-ground illusion work?

perception can alternate between two things, even as the sensory stimulation remains constant

To sense motion, what must the visual system do?

encode information about both space and time

Waterfall illusions, apparent motion

the perception of movement as a result of alternating signals appearing in rapid succession in different locations (phi phenomenon)

sometimes we fail to ___________ ________________ on a changed object

focus attention

change blindness

when people fail to detect changes to the visual details of a scene

EX: looking to find a difference game on App Store, failing to detect a change is change blindness

inattentional blindness

failure to perceive objects that are not the focus of attention

EX: if one is being animated and they say pay attention to a magic trick, you may not see the people walking behind the person because you are focused on something else

What is the primary visual cortex in the brain?

Area V1

From the eyes, where in the brain does visual info. go first?

Occipital lobe

Dorsal Stream

the “where pathway”

• info. about where something is in space is taken up into the cerebral cortex

EX: when driving you see a figure in the road, this information about where on the road this figure is is processed

What is known as the “what, where pathway"?”

the dorsal and ventral streams

Ventral Stream

the “what pathway”

• information about what something is is taken to the temporal lobe

EX: as you approach the figure as you’re driving, you notice that it is a deer, which this info. is processed in the brain

Gestalt

how we organize the outside world (the whole is greater than the sum of its parts); understanding the mistakes the brain makes

• Grouping rules

  • similarity - idea that things that are similar are automatically grouped by the brain (ex: two football teams wearing different jerseys - so we can keep track)

  • closure - dotted lines in a formation, we perceive a circle and a rectangle even when there isn’t one there

  • proximity - we tend to group things together by proximity automatically

  • simplicity - brain goes to the simplest answer to answer the question (brain picks up on the simplest answer to a question; i.e. the faces that aren’t actually faces, but people and a background)

  • common fate - perceive something to be connected when actually not (ex: moving rod behind rectangle actually being two separate pieces moving simultaneously)