Sensation + Perception Exam 3

What is the relationship between sensation and perception?

Sensory neurons convert energy in the environment into action potentials (the language the nervous system and brain communicate)

What happens during sensation?

Sensory organs absorb energy from physical stimuli in the environment, and sensory receptors detect stimulus energies and convert them into neural impulses ( action potentials) sent to the brain.

What happens during perception?

The brain organizes this input and translates it into something meaningful.

What are the three properties of light and what does each determine in vision?

(Visions: the stimulus)

Amplitude: perception of brightness

Wavelength: perception of color

Purity: mix of wavelengths → perception of saturation (richness of colors)

What is sensation?

Stimulation of sense organs.

What is perception?

Selection, organization, editing, and interpretation of sensory input - the subjective experience of physical reality.

What is psychophysics?

The study of how physical stimuli are translated into psychological experience.

How does perception begin?

Perception begins with a (consciously) detectable stimulus.

What is the absolute threshold?

The intensity with which a stimulus occurs so that it can be detected 50% of the time or more.

What is the Just Noticeable Difference (JND)?

The smallest difference in stimuli that can be detected 50% of the time (or more).

What does Weber's Law state?

Size of JND is directly proportional to size/intensity of initial stimulus.

What is subliminal perception?

Existence vs. practical effects; something briefly seen in less than a 20th of a second that you cannot identify other than that it happened; ephemeral, fleeting, disappears very quickly.

What is sensory adaptation?

Decline in sensitivity to an unchanging stimulus.

What is the cornea?

The outermost layer where light enters the eye; used to protect the rest of the eye.

What does the lens do?

Focuses the light rays on the retina; shape changes and lets you focus on close or distant objects.

What is the iris?

Colored ring of muscle that constricts or dilates via amount of light needed to see; in dim light, iris relaxes and opens the aperture of the pupil so more light can reach it.

What does the pupil do?

Regulates amount of light.

What does the retina do?

Innermost layer of the eye where sensory neurons are located; retina is projected an upside down image of reality/outside world and the brain alters it in your mind (difference between sensation and perception).

What does the retina do?

Absorbs light and processes images.

What is the optic disk?

- Where the optic nerve leaves the eye (connection/blind spot);

- no sensory neurons where it leaves the eye, creating a blind spot we don't perceive.

- No more than 2mm in diameter

What do rods do?

- Black and white / low light vision;

- objects and contours in the environment;

- good at motion detection; not good for precise detail vision

- not evenly spread around the retina.

What do cones do?

- Color / daylight vision

- adaptation: biochemical process allows us to become more or less sensitive to light as needed

- repeated exposure to light or dark alters the chemical composition.

How many receptor cells are in each eye, and how is their information processed?

Cones: 6 million

Rods: 125 Million

- Action potentials are passed upwards to fewer bipolar cells and then even fewer ganglion cells, where they are consolidated.

Why do we see the world in three dimensions?

Because of perception, even though there is only one layer of rods and cones.

What are two key components of information processing in the retina?

Receptive fields and lateral antagonism.

What happens in the occipital lobe of the brain?

Depth perception, blind spot removal, and image flip all happen in the occipital lobe in the brain.

What is the fovea and what is its role in visual input?

- The center of the eye (focal point); has almost all cones and very few around the periphery

- rods are all over the periphery, and the count goes far down near the focal point

- Peripheral vision was critical for evolution as we need to see predators/dangers.

What is the visual pathway from light to the brain?

Light → rods and cones → neural signals → bipolar cells → ganglion cells → optic nerve → optic chiasm → opposite half brain; main pathway: lateral geniculate nucleus (thalamus) → primary visual cortex (occipital lobe).

What is the dorsal stream?

- The "Where pathway"

- identifies where the object is / where it is going

- occurring in the parietal lobe.

What is the ventral stream?

- The "What pathway"

- identifies the object in front of us

- occurring in the temporal lobe (language processing).

What did Hubel and Wiesel discover about visual processing?

Discovered feature detectors: neurons that respond selectively to lines, edges, etc., in certain orientations; evidence that vision works by recognizing the most basic elementary elements of vision.

What is bottom-up processing in vision?

Vision is processed based on its most elementary component

- Peature Detection Theory: any visual input can be

recognized as elemental components and then assembled

into a holistic perception.

What is top-down processing?

Form perception: look for a whole interpretation instead of looking for individual components; effectively forming a hypothesis and looking to confirm it.

What is inattentional blindness?

Most people can only pay attention to one thing at a time.

How do bottom-up and top-down processing differ?

Bottom-up: detect specific features of stimulus → combine features into more complex forms → recognize stimulus.

Top-down: formulate perceptual hypothesis about the

nature of the stimulus as a whole → select and examine features to check hypothesis (sometimes skipped) → recognize stimulus.