Visual Perception Flashcards

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1
Q

What happens when lights hits the eye?

A

Light waves travel through the lens and are focused on the retina by the lens (controlled by ciliary muscles). The retina contains photoreceptors. Once processed the information goes via the optic nerve to the occipital lobe.

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2
Q

What does the lens do?

A

It bends the light to focus light on the retina.

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3
Q

What do ciliary muscles do? When do they tire?

A

Are responsible for changing the shape of the lens. Around 45. That is why vision gets blurred and people need glasses

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4
Q

What is sclera?

A

White fatty tissue that surrounds the eye

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5
Q

What is the retina?

A

The wall of the eye that contains photoreceptors that get excited about light

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6
Q

What is the iris?

A

The coloured muscle that changes the size of the pupil to allow different amounts of light to enter the eye.

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7
Q

What is the pupil?

A

A hole into the eye

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8
Q

What is the aqueous humour?

A

Fluid in the front of the eye that gives shape and provides oxygen, nutrients and removes waste

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9
Q

What is the cornea?

A

It is a thin, clear skin that protects the front part of the eye

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10
Q

What does the vitreous humour do?

A

Provides shape to the eye, is clear fluid which provides oxygen and nutrients and removes waste

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11
Q

What is the blind Spot? How does the brain deal with it?

A

The area where the optic nerve leaves the eye where there are no photoreceptors. The brain uses psychological processes to fill in missing details of the image

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12
Q

What is the fovea?

A

The area that only contains cones. Vision is best and clearest here. Visual acuity is greatest here as there are only cones.

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13
Q

How many cones are there? Where are they located? What are they specialised in?

A

6.5 million in each eye. Located in the middle of the retina. Detect longer wavelengths, they are responsible for day and colour vision. They have high visual acuity.

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14
Q

What are photoreceptors?

A

Cells that are specialised to detect and respond to light. There are a 1/4 of a million in the back layer of the retina. They absorb light and convert it into electrochemical energy

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15
Q

How many rods are there? Where are they located? What are they specialised in?

A

100 million in each eye. Mainly in the edges of the retina. Detect shorter wavelengths. Responsible for night and black and white vision. More sensitive to light than cones and function best in dim light. Poor visual acuity. Responsible for peripheral vision.

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16
Q

Once in the occipital lobe, where does visual information go?

A

The primary visual cortex

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17
Q

Describe visual perception

A

Everyone’s eyes and brains see and receive the same sensory stimuli (sensation) but we interpret the picture differently (perception)

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18
Q

Describe sensation

A

When you receive information and transmit it to the brain for interpretation. It is a purely physiological process involving neural impulses. It involves the detection of light energy by photoreceptors. Everyone’s eyes work the same way

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19
Q

Describe perception

A

The process of organising and interpreting sensory stimuli in the brain. Sensory information becomes meaningful. Influenced by factors such as past experience. It is subjective, different and unique to everyone

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20
Q

Describe the visible light spectrum

A

Light travels in invisible waves measured in nanometers (nm). The electromagnetic spectrum is the full range of wavelengths of light energy that exist in the environment. What our eyes see is known as visible light, and it only occupies a small amount of the spectrum

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21
Q

Describe the colours we see

A

Wavelengths are seen as colours and also have different heights or amplitudes. The greater the amplitude the brighter the colour. We see the colours of the rainbow. Red is 750nm and violet is 380nm.

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22
Q

What are the visual perception processes?

A

Reception, transduction, transmission, selection, organisation and interpretation

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23
Q

What is reception?

A

Light enters the eye through the cones and lens and is detected by the photoreceptors in the retina.

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24
Q

What is transduction?

A

Electromagnetic energy can’t be understood by the brain so it is converted to electrochemical energy required for neural impulses. This is done in the rods and cones.

25
Q

What is transmission?

A

Electrical impulses are carries front the photoreceptors along the bipolar cells to the ganglion cells. The axons of the ganglion cells are long and join together to form the optic nerve which leads to the occipital lobe, taking the images in tiny pieces.

26
Q

What is selection?

A

The brain selects useful info and discards useless info so that the brain is not overwhelmed. The image is analysed by nerve cells called feature detectors which respond to certain features (lines etc.). The image is broken down into features and is transported to the brain.

27
Q

What is organisation?

A

Before the brain can interpret visual stimuli must be organised into a meaningful pattern. When it reaches the occipital lobe it is put together or reorganised to be made sense of. Perceptual organisation is done using visual perception principles.

28
Q

What is interpretation?

A

This is the process which the brain gives meaning to info. It allows us to make sense of the objects and events by filling in pieces based on past experience and individual differences.

29
Q

What are visual perception principles?

A

Rules our brain automatically follows to help us organise visual stimuli. The way we apply these rules influences our interpretation of stimuli, it helps us understand things. They are gestalt principles and the depth principles.

30
Q

What are gestalt principles? What is the belief?

A

They refer to the numerous ways in which we organise elements in our visual field by grouping them into the perception of the whole complete form. They help us construct a meaningful form from an array of meaningless pieces. The belief is the whole is greater that the sum of its parts.

31
Q

What are the four gestalt principles?

A

Figure-ground, closure, similarity, proximity

32
Q

What is figure-ground?

A

Enables you to differentiate between figures and the ground. We organise visuals by separating important aspects from the background with an invisible line called the contour line. Figure ground allows us to read. Camouflage means that figure-ground isn’t working

33
Q

What is closure?

A

The tendency to close off or fill in or ignore gaps in a visual to see them as complete.

34
Q

What is similarity?

A

The tendency to perceive stimuli as having similar features and thus belonging together. They must be grouped according to size, shape, texture and colour.

35
Q

What is proximity?

A

The tendency to perceive parts of an image that are positioned close together as belonging together.

36
Q

What are the depth cues?

A

Binocular- convergence, retinal disparity
Monocular- accomodation- pictorial depth cues- linear perspective, relative size, interposition, height in the visual field, texture gradient

37
Q

What is retinal disparity?

A

Eyes are 6-7cm apart so have slightly different images due to the different angles of view. There are slightly different images on the retinas. The brain knows that the greater the difference between the images, the closer the object.

38
Q

What is convergence?

A

Brain detects depth according to the tension in eye muscles when eyes turn inwards to focus on nearby objects. Greater the tension= closer object

39
Q

What is accomodation?

A

Automatic focusing of the lens to adjust shape in response to differing distances to the object. This happens to fit the picture onto the lens. Bulged lens= nearby, elongated = faraway. Brain monsters ciliary muscles to determine distance.

40
Q

What is linear perspective?

A

The apparent convergence of parallel lines as they recede into the distance. Closer lines = further away

41
Q

What is relative size?

A

Tendency to perceive objects that have larger retinal images as being closer than those casting a smaller image. The objects must be comparable.

42
Q

What is interposition?

A

An overlap when one object is partially covered or blocked by another object so is perceived as being further away.

43
Q

What is height in the visual field?

A

Objects closer to the horizon are seen as further away than objects further away from the horizon.

44
Q

What is Texture gradient?

A

Gradual diminish of detail that occurs on surfaces as they recede into the distance.

45
Q

What is the perceptual set?

A

A readiness to perceive stimuli in accordance to certain expectations. Select Certain aspects of the visual environment while ignoring others. Allows us to anticipate and interpret something quickly.

46
Q

How can perceptual set help or hinder us?

A

Can assist us by enabling us to quickly perceive and interpret a stimulus. It can lead to misinterpretations as things do not always fit in with our expectations

47
Q

What are the factors leading to perceptual set?

A

Motivation, emotional state, cultural factors, context, past experience

48
Q

What is context?

A

The environment or setting in which a perceived event occurs or an object exists. It provides a framework which the object or event is considered within. As context changes so does your interpretation. Eg. Examples with letters and numbers

49
Q

What is past experience?

A

Personal experiences that are unique may lead to different interpretations. These experiences predispose people to interpret things in certain ways. It can lead to mistakes. Drive down a street everyday at the same speed and don’t notice when the speed sign changes

50
Q

What is motivation?

A

Refers to our motives which activate behaviour and is directed towards achieving a particular goal. Eg. When you are hungry everything is perceived as food.

51
Q

What is emotional state?

A

Different emotions can set us up to perceive information in a way that is consistent with the emotion being experienced. Eg child scared of the dark perceives a dressing gown as a ghost

52
Q

What is culture?

A

Experience within a community or group can influence the way we perceive stimuli. Women in some cultures perceive all men as being dominant

53
Q

What is a perceptual distortion?

A

It involves an inconsistency between a perceptual experience and a physical reality. We can be told it is an illusion but we will still see it the same way. Moon looks bigger on the horizon

54
Q

What is a visual illusion?

A

An error in interpreting a real external stimulus. Stimuli provides us with cues that mislead our perception. We mismatch our perception and what we understand as visual reality.

55
Q

Explain Muller-Lyer biological

A

For each different amounts of eye movement is necessary. Feather tail requires more eye movement so appears longer

56
Q

Müller-Lyer psychological

A

They are similar to architectural features. The arrowhead looks like a nearer, outside, vertical corner and the feather tail looks like the farthest inner corner of a room. The lines appear at different differences so appear different lengths

57
Q

Describe muller-lyer social

A

Culture changes how people see the lines eg. Tribes in Africa see the lines as the same possibly because they live in round houses.

58
Q

What is the Ames room illusion?

A

An illusion in which a person appears that they change in size as they travel from one side of the room to another.

59
Q

How does the Ames Room work?

A

The peephole only allows monocular depth cues to be used. It is a lopsided room but the two back corners appear at equal distances even though one is further. The person in this corner is seen as smaller as they cast a smaller retinal image but in reality they are just further away. Our brain tries to keep the room a square shape by applying shape constancy but misapplied size constancy,