perception

Question 1

Explain the difference between sensation and perception

Answer 1

Perception is the way we interpret and make sense of information we receive, whereas, sensation is the information we receive from the senses, such as vision. For example our eyes pick up light from objects (lightness dark, and color). This is sensation. Each sensation picks up tiny dots from the visual field, and perception allows us to see those tiny dots as a whole image.

Question 2

Define the term ‘monocular depth cue’

Answer 2

a way of detecting depth or distance which will work with just one eye

Question 3

Explain the monocular depth cue of height in plane

Answer 3

A cue where things that are further away appear to be higher up and things closer appear to be lower down

Question 4

Explain the monocular depth cue of relative size

Answer 4

A cue where things closer to you appear larger on the retina whereas things further away appear smaller on the retina

Question 5

Explain the monocular depth cue of occlusion

Answer 5

An object covering up another object appears to be nearer, and when you can’t see the whole of an object, it appears to be further away

Question 6

Explain the monocular depth cue of linear perspective

Answer 6

When parallel lines appear to be pointing to a vanishing point on the horizon, we can use this to infer distance in a landscape.
An object closer to the vanishing point appears to be further away, and an object further away from the vanishing point/beginning of the parallel lines appears to be closer

Question 7

Define the term binocular depth cue

Answer 7

A way of detecting depth or distance which requires two eyes in order to work

Question 8

Explain the binocular depth cue of convergence

Answer 8

In convergence, which is a binocular depth cue, we focus our eyes differently to see things that are closer to how we focus on things that are far away. The brain detects these difference in how eye muscles are working and uses it as a cue to tell how far away the object is.

Question 9

Explain the binocular depth cue of retinal disparity

Answer 9

In retinal disparity (a binocular depth cue), you compare the images between the left eye view and right eye view. The brain then compares the difference between those two images. If the difference between those two images is big, the object is closer. If the difference between the views is small, the object is perceived to be further away.

Question 10

Outline and evaluate Gibson’s direct theory of perception

Answer 10

Direct perception is the idea that we perceive things based simply on the information we receive from our senses. Gibson said that we are active in our world where our perception changes the images we receive. Things close to us appear to move faster as we move past them, but things further away seem to move slower. This is known as motion parallax. Things closer to us appear to be more detailed whereas things further away appear to be less detailed. This is known as texture gradient. The same thing happens with color. Gibson’s theory is said to be ecological, where he believes our perception has evolved to help us deal best with our environment. For example, humans, animals and birds have developed color vision to help us pick the ripest fruits from trees. Gibsons theory tells us we live in a perceptual world not just 3D. It relies simply on information from our senses to understand the world around us rather than making inferences of guesses, like Gregory’s theory of perception.

A strength of Gibson’s theory is that it has supporting research evidence to support that perception is due to nature and not nurture. This is because the ‘Visual Cliff Experiments’ with babies, showed that depth perception may be innate, as all babies stopped at the edge of the ‘cliff’. This increases the validity of Gibson’s theory.

A weakness of Gibsons theory is that it is challenged by Gregory. This is because Gregory’s theory suggests that perception is due to nurture, and not nature. This decreases the validity of Gibson’s theory.

Another weakness of Gibson’s theory is that it struggles to explain visual illusions. This is because Gibson tells us that perception is always accurate, however, visual illusions trick our brain into misperception. This shows us that there is more to perception than Gibson suggested.

One strength of Gibson’s theory is that it has real world meaning. This is because research was based on the experience of pilots from the Second World War. Therefore, this makes it more relevant to explain how we perceive the world on a daily basis

Question 11

Define the term visual illusion

Answer 11

a visual perception which is wrong or misinterprets what is actually there in reality

Question 12

Explain why the ponzo illusion works

Answer 12

This works because of converging lines that give the impression of distance. Our brain applies the rule of size constancy, mentally enlarges it, making the top longer than it is. So the line at the top is not really longer, it is just perceived as being that way

Question 13

Explain why the muller-lyer illusion works

Answer 13

One explanation of the Muller-Lyer illusion is that our brains perceive the depths of the two shafts based upon depth cues. When the fins are pointing in toward the shaft of the line, we perceive it as sloping away much like the corner of a building

Question 14

Explain why the necker cube illusion works

Answer 14

The Necker cube is an ambiguous figure. It can either be perceived upwards, downwards, to the right or to the left

Question 15

Explain why the rubin’s vase illusion works

Answer 15

In the classic Rubin’s vase optical illusion, neurons in the brain must decide whether the border between black and white belongs to the white area or to the black area, which determines whether you perceive the scene as either a black vase on a white background, or white faces on a black background. This is ambiguity

Question 16

Explain why the Kanizsa triangle illusion works

Answer 16

An optical illusion, illustrated above, in which the eye perceives a white upright equilateral triangle where none is actually drawn. This is an example of fiction

Question 17

Outline and evaluate Gregory’s theory of perception

Answer 17

Gregory argues that we use our past experiences to make sense of the world around us. He says we take incoming information from our senses and what we already know, therefore perception is a construction. Past experience means we can infer what should be there and draw a conclusion. When making inferences features of the environment give the brain information about depth and distance. Gregory said visual illusions occur because the brain has drawn the wrong conclusion from these cues, by misinterpreting depth cues and wrongly applying size constancy. For example, he explains the Muller-Lyer by using depth cues. The inwards facing fins are perceived as close, whereas the outwards facing fins are perceived as far away. This means we use size constancy to scale the inward facing fins shape down and the outward facing fins shape up. This makes the inward facing fins shape look smaller and the outward facing fins shape look bigger.

One strength Gregory’s constructivist theory is that there is supporting evidence to show that the way that we process information from our senses depends on past experience. This is because many studies have shown that perceptions were affected by participants’ expectations and experiences. This means that nurture affects perception

One weakness of Gregory’s theory is that it struggles to explain how perception ‘gets going’ in the first place. This is because as seen in the ‘Visual Cliff Experiment’ with babies, babies showed the ability to perceive visual cues. This means that Gregory is not completely correct, and that some perceptual abilities may be innate.

Another weakness of Gregory’s theory is that he struggles to explain visual illusions. This is because he stated that the Muller-lyer manages to trick our perception through wrongly applies size constancy and depth cues, however, the Muller-Lyer still works when fins are replaced with circles, which have no depth cues. Hence this decreases the validity of his theory

Question 18

Outline & evaluate a study where the effect of motivation on our perception

Hint: Gilchrist and Nesburg

Answer 18

The aim of the study was to see how the perception of food-related images would change after 20 hours of food deprivation. There were 2 groups: a control group and a food deprived group (20hrs). They separated the group and showed them pictures of food for 15 seconds per slide. The pictures were shown again and participants were asked to adjust the lighting to match the original picture. Gilchrist and Nesburg found that the food deprived group perceived the images as brighter than they were, but the control group adjusted it to a similar brightness to the original. They concluded being deprived of food increased perceptual sensitivity. Hunger served as a motivating factor affecting the way food is perceived.

A strength of the study is that other studies have found similar results. In a separate study, participants were asked to interpret food related ambiguous figures. Participants had been food deprived for various different lengths of time. They found that the longer a participant had been deprived of food, the more likely they were to interpret the ambiguous figure as food. This increases the validity of the study

Another strength of the study is that it can be replicated to obtain similar results. This is because Gilchrist and Nesburg used standardised procedures and controls, like showing the same slides to each group, (even though they said the slides were different), and showing the slides for the same amount of time each time (15s). This means the study can be replicated to obtain similar results, increasing the validity of the study

Another weakness of Gilchrist and Nesberg’s study is that depriving people of food and water may not be ethical. In the study participants were deprived of food for 20 hours. Although this is not a huge amount of time, it may have caused the participants some discomfort. Participants would have given their informed consent but may not have fully understood what it would feel like to go without food. These ethical considerations are a weakness of the study, as it may notbe fair to deprive people of food for the purpose of a Psychology experiment.

Question 19

Outline & Evaluate how perceptual set influence what we perceive

Hint: Bruner & Minturn

Answer 19

The aim of the study was to see how expectations can affect direct perception. 24 university students were flashed numbers or letters faster than the eye could see at 30 milliseconds and increasing to 20 milliseconds each time. The participants were asked to recognise the letter or number as soon as they recognised it. The test stimulus was a broken B, meaning it could be seen as a B or 13. Half the participants were shown letters (L,M,Y,A), then the test stimulus, and then, were shown the numbers (16,17,10,12) followed by the test stimulus. They were then shown a mixture of letters and numbers before the test stimulus.The other half of participants were counterbalanced, meaning that they did the conditions in reverse. They found that most participants drew a 13 when they expected a number to come up, and a B when they expected a letter to come up. When they were expecting either a letter or a number to come up, they produced mixed results. The researchers concluded that the participants expectations directly affected their perception.

One weakness is that the study was conducted in an artificial environment. This is because, in a real life situation, we do not write down letters or numbers we see off a screen. This reduces the ecological validity of the study because the task lacks mundane realism

Another weakness is that the sample size is too small. This is a weakness because only 24 participants were used, and since they were all in university, they were roughly the same age. Therefore, it would be very difficult to generalise these results to a wider population such as old people or children.

One strength of this study is that it can explain errors that people make. Gregory argues that perception is an active process in which the person comes up with a hypothesis about what they are seeing. Gregory also says that this guess is influenced by past experience. There are many examples where expectations have led people to ‘see’ a mistaken image. For example. One well known case occurred in 1988 when a US Navy Cruiser shot down a civilian airplane having mistaken it for a military plane. The ship commander was aware that there had been military action in the area and therefore had raised expectations that it was a military plane. Therefore, this increases the ecological validity of the study

Question 20

Define what is meant by perceptual set and how it affects our perception

Answer 20

• Perceptual set is the tendency for our brain to notice certain aspects of the environment over others
  Every day we are bombarded with information, so we need to focus our perception on just what’s important - select what we need to ignore and what we don’t. Developing a state or readiness to perceive certain kinds of stimuli rather than others is called a perceptual set

Question 21

Explain how expectations can affect our perception

Answer 21

Our set can affect our memory, learning and decision making. We remember different things when we are in different moods. Eg, when we are in a bad mood, we only remember the annoying things. We are more likely to perceive things if our perception is set to notice that kind of thing. This is where expectations play a role, as the belief of what we are going to experience affects our perception

Question 22

Explain how culture can affect our perception

Answer 22

The cultures we are brought in influence our perception. In western cultures kids are exposed to cartoons, which are not realistic but are used lots in children’s books. If a western child is asked to draw an elephant he will likely draw it with a side on sense of perspective.

Question 23

Explain how emotion can affect our perception

Answer 23

Sometimes we are happy sometimes we are sad. These emotions can influence what we perceive. They contribute to our perceptual set by making us perceive things in a way that is in line with how we feel. Eg. excited children at Christmas draw pictures of Santa with more presents, and then after Christmas they are not so excited anymore

Question 24

Explain how motivation can affect our perception

Answer 24

Motivation is what makes us do things. We have a range of motives from physical (being hungry, thirsty) to social (wanting to get respect from friends). Our perception can be affected by our social motives eg. whether we want somebody to like us, in this case, we often notice actions that fit with our motivations and ignore those which don’t