Perception-How do we see our world?

What are the strengths of Charmichael's study?

-12 pictures and 95 participants meant that there was lots of evidence and the findings were not just a fluke. -There were over 3000 drawings 905 were almost completely changed from the original picture. -The control group made sure that it was the words affecting recall- it wasn't just that people always have changed memory of what they have seen.

What are the weaknesses of Palmer's study?

-Because the participants were told what they would be doing, this may have caused them to try harder in some conditions. -As data for some participants couldn't be used, this meant that there was fewer results. -It was a lab experiment, so is not generalizable to real life.

What are the strengths of Bartlett's study?

-Both repeated and serial reproduction tasks were done many times. This helped to show that changes in the story showed the same patterns. -Other stories were also used in serial reproduction. This showed that the changes weren't just special to 'The war of the Ghosts'.

What are the weaknesses of Bartlett's study?

-By choosing unfamiliar material, Bartlett could not be sure that the changes

What are the strengths of Palmer's study?

-Palmer controlled how long the participants saw the context and the object for, so the difference in accuracy were not caused by having longer to remember some objects. -The participants had instructions, so they knew exactly what to do. -Data from two possible participants was not used as they had forgot their glasses.

What are the weaknesses of Charmichael's study?

-The study was not like real life, it is unusual for us to see something and it have a misleading verbal label for it. -Other studies show word labels given when identifying an object don't affect recall of the object, this means that the findings do not apply to many situations.

Who were Palmers participants and what type of experiment was it?

64 students were tested in a Laboratory experiment.

Who were Charmicheal's participants and what type of experiment was it?

95 people took part in the experiment, and were tested in Laboratory environment.

Define depth cue.

A depth cue are the visual clues that help us understand depth or distance.

What is right to withdraw?

A participant has a right to stop the study at any time if they want to, and they need to know how to do this.

What is informed consent?

A participant has the right to know the aims of an experiment and exactly what they'll be expected to do before they take part.

Explain superimposition.

A partly hidden object that must be further away than the object covering it.

Define experiment.

A research method which measures Participant's performances in two or more conditions.

What is a schema?

A schema is a framework of knowledge about objects, events, or groups of people. Our schemas can affect what we perceive and what we remember.

What is an Ambiguous figure illusion?

A stimulus with two possible interpretations in which it is possible to see only one of the alternatives at one time.

What is a hypothesis?

A testable statement of the difference between the conditions in an experiment. It describes how the independent variable will affect the dependant variable.

What was Charmichael et al's procedure?

All participants were shown 12 pictures. Between each picture, the experimenter said 'the next picture resembles..' followed by a word from list 1/2, depending on which group they were in. The control group heard no label. After seeing the pictures, all participants were asked to draw the pictures they had seen. The experimenter collected the pictures in and compared them to the original pictures that were actually shown.

What is an eye witness?

An eye-witness is someone who sees a crime or aspects of a crime scene, and helps the police by their recount to work out what happened and catch the criminal.

What is an after-effect illusion?

An illusion caused by focusing on a coloured stimulus and perceiving opposite colours immediately afterwards.

What is a fiction illusion?

An illusion caused when a figure is perceived even though it is not present in the stimulus. E.g. Kanizsa triangle.

Explain relative size.

An object that makes a bigger image on the retina, compared to another similar object which is smaller, is perceived to be closer.

Eyewitness and schemas: Bartlett

Bartlett showed that in order to remember a complicated story we try to make sense of it. We tend to reconstruct our memory of something using our previous experiences rather than remembering things exactly.

What did Bartlett conclude?

Bartlett's study demonstrates that unfamiliar material changes when it is recalled, it becomes shorter, simpler and stereotyped. This may be due to the effect of schemas upon memory.

What does the optic nerve do?

Carries nerve impulses from the rods and cones the visual cortex in the brain.

What was the aim of Charmichael et al?

Charmichael and his colleagues wanted to find out whether words shown with pictures would affect the way the pictures were remembered.

Eyewitness and schemas: Carmichael

Charmichael showed that the label given to a drawing will affect our recall and reproduction of that drawing. This demonstrates the effects of perceptual set and schemas on our memory.

What do cones detect?

Cones are found mainly in the centre of the retina, opposite the pupil. This area helps us to see clearly in detail as there is lots of cones packed closely together. Cones are less sensitive to light than rods, so only work in bright light and detect colour.

What is independent groups design?

Different participants are used in each condition of the experiment.

Give two examples of distortion illusions.

Ebbinghouse illusion, Muller lyer.

Explain figure and ground.

Figure: more complex or detailed, smaller in comparison to the ground, the figure is symmetrical. Ground:Simple, larger, disorganised.

Using gestalt laws to explain illusions.

Gestalt theory of illusions suggests that we can use the gestalt laws of closure, proximity, similarity, continuity, figure and ground to explain all visual illusions.

Evaluate Gestalts theory of Illusions.

Gestalt's theory provides a good explanation for ambiguous figures. However, it is not good at explaining distortions other than Muller-lyer. These are better explained by Gregory's perspective theory. Gestalt's theory explains fictions, although it sometimes uses different explanations at different times and cannot just use one rule to explain some illusions.

Explain Gregory's theory of illusions.

Gregory's perspective theory of illusions suggest that we use depth cues such as linear perspective and Relative size to explain all visual illusions.

Explain similarity.

Grouping things together down to figures sharing the same size, shape or colour.

Give some examples of general weaknesses of experiments.

Hiding experimental aims, Deception(lying about the aim, problem because there is no informed consent, Representing real life(situations can be unrealistic and act in an unnatural way).

What was the dependant variable of Bartlett's experiment?

How much the story changes after each reproduction, in each condition.

What is a perceptual set?

Ideas about what we expect to see in a situation. We notice and remember things more when we expect to see them than things that we don't expect to see.

Explain texture gradient.

If a surface is textured it can help you to perceive depth, this means that the detail is reduced on a gradient.

Give an example of how texture gradient can show depth.

If grass is close to you, you would be able to see the blades, but if it was further away it would look like a green surface with no texture.

What were the results of Bartlett's study?

If the order of events changes then it stays in that order. Details are quite often lost e.g. names, numbers and are only remembered if significant. The story is often simplified.

How does gestalt's theory of illusions explain fictions?

Illusions like the Kanizsa triangle can be explained using closure. When we see a figure which is incomplete our perception makes a whole figure using closure. We complete the edges to make a regular or familiar shape.

What were the results from Charmichael's study?

In list 1 group, 73% of the drawings resembled the word they were given. In list 2 group, 74% of the drawings resembled the word they were given. In the control group, 55% drew what they had seen.

What are monocular depth cues?

Information about distance that comes from one eye e.g. superimposition.

What are binocular depth cues?

Information about distance that needs two eyes e.g. stereopsis.

Explain stereopsis and how it helps us see depth.

It is a binocular depth cue, which uses both eyes because they are on different positions on our face so we see two slightly different images from each eye. The image from the left eye is added to the image on the right eye, the more different it is the closer it is, the further away it is the more similar it is.

What is a visual illusion?

It is a conflict between reality and what we perceive.

Give two examples of ambiguous figures.

Leeper's lady, and the Necker cube.

Explain closure.

Lines or shapes are perceived as complete figures even if parts are missing.

Explain proximity.

Objects close that are close together are perceived to be related.

Explain Serial reproduction.

One person reads the story waits 15-20 minutes, pass it down the chain, there was 10 people in the chain and keep passing it down.

Explain Repeated reproduction.

One person reads the story, and keep recalling it after certain amounts of time e.g. 20 hours, 8 days, 6 months, 10 years.

Eyewitness and schemas: Palmer

Palmer showed that our perception can be influenced by what we have seen just before we are asked to recall something. The picture of a kitchen meant that participants saw ambiguous objects they are most likely to remember items associated with kitchens.

What was Palmers aim?

Palmer wanted to find out whether context would affect perception.

What did Palmer conclude?

Palmer's study demonstrates that context affects perception. People have a perceptual set based upon context that affects the accuracy of their recall.

Explain Linear perspective.

Parallel lines appear to converge in the distance.

What is perception?

Perception is the way we make sense of a visual image. This happens in the brain and allows us to understand what we can see.

What are gestalt laws?

Perceptual rules that organise stimuli groups. ''The whole scene is more important than the individual parts''.

Evaluation of Gregory's perspective theory of illusions.

Perspective theory provides a good explanation for distortions because angled lines are used as depth cues explains many illusions. Gregory's theory can also explain some ambiguous figures such as the Necker cube, which clearly affects depth perception. Depth cues are also useful to explain some fictions. Sometimes these figures include lines that are placed closer together to suggest depth. However more fictions can be explained using gestalt theory than by perspective theory.

Designing and understanding experiments.

Psychologists conduct experiments on Animals and humans. An experiment is a way to find out the affect that one variable has on another. Participants can be used in different ways in an independent groups design, or in a repeated measures design.

What do Rods detect?

Rods are very sensitive to light and they also respond to movement. A rod cell will respond even in very dim light. They are mainly found around the edge of the retina.

Studies of eye witness testimony: Allport and Postman

Showed participants 2 pictures of men in an underground station. They had to look at the picture and explain to someone else what had happened. One of the pictures showed a black man in a suit talking to a white man in overalls who was holding a razor and pointing with his other hand. Half of the reproductions reported that the black man had the razor and was threatening the white man. This suggests a schema linking black people to crime.

Studies of eye witness testimony: Boon and Davis

Showed participants slides of a violent knife attack by a white man on the London underground. Some participants then saw two white men fighting whilst others saw a white and a black man fighting. When shown pictures and asked to recognise the scene many chose a picture showing a black man holding a knife. They did not make this mistake if they just asked to recall the scene. This suggests that recognition tasks by eyewitnesses such as line ups may not be accurate.

Explain continuity.

Straight lines, curves and shapes are perceived to carry on being the same.

Give some examples of general strengths of experiments.

That they have informed consent, right to withdraw. Only the IV affects the DV(in lab experiment because everything else is controlled), measuring the DV accurately (in lab experiment).

What are ethical guidelines?

The British Psychological Society produces a code of ethics and Conduct to help psychologists deal with ethical issues. It says aim of the study should be clear before the study, and can only deceive people if it is essential to the research and the participants are told the truth as soon as possible.

Explain what you know about Visual context.

The Ebbinghouse Illusion happens because we use the context to help us make sense of what we see. If the surrounding context is bigger we make the circle smaller, if the surrounding context is smaller we make it larger.

What is the visual cortex?

The area at the back of the brain that interprets visual information.

What is the blind spot?

The area of the retina where the optic nerve leaves the eye, so it has no rods or cones so cannot detect light and therefore an image.

How does gestalt's theory of illusions explain ambiguous figures?

The gestalt law of figure and ground is used on ambiguous figures because our brain can't work out which is the figure and which is the ground, so the brain gets confused.

What was Palmer's independent variable?

The groups of relevance that the images had to the scene. -Appropriate -Inappropriate/similar objects -Inappropriate/different objects -No context.

What was Palmers procedure?

The groups were shown a visual scene e.g. Kitchen. Then were shown pictures of individual things out of the scene e.g. a loaf of bread. And then had to recall as many objects as they could remember.

What is the Retina?

The light reflected from an object enters the eye and makes an image on the retina, a layer of receptors; rods and cones at the back of the eye. The retina is sensitive to light and sends nerve impulses to the brain.

How does Gregory's perspective theory explain the Ponzo illusion?

The line at the top looks longer than the line at the bottom. The railway lines are used as cues for linear perspective and the top line is scaled up using size constancy.

How does Gregory's perspective theory explain The Herring illusion?

The lines have been turned into a road, the man further away has been scaled up by our brain using size constancy and linear perspective.

What was Palmer's Dependant variable?

The number of correctly identified objects.

Explain the Optic Chiasma.

The optic nerve takes information from each eye to each side of the brain. The information crosses over in an 'X' shape.

What were Palmer's findings?

The participants correctly identified the most objects after seeing an appropriate context and the least after seeing an inappropriate context.

What was Bartlett's procedure?

The participants would read 'The war of the ghosts story', and would be either asked to Carry out Serial reproduction, or Repeated reproduction.

What is Repeated measures design?

The same participants are used in all the conditions of an experiment.

How does Gregory's perspective theory explain the Muller-Lyer illusion?

The top arrow is seen as an outside corner of a building, whereas the bottom arrow is seen as an inside corner of a building. Therefore the inside corner is seen as further away and so we scale it up, causing it to look bigger/longer than the top arrow.

What did Charmichael conclude?

The two different lists of words for the same pictures clearly showed that the words affected memory. We use reconstructive memory, which is when we rebuild things when we remember them, it is affected by schemas and other information given at the time.

Define Experimental design.

The way that participants are used in different conditions in an experiment.

Who was Bartlett's participants and what type of experiment was it?

There were 20 participants, 13 men and 7 women, who were tested in a Lab experiment.

Why are depth cues important?

They help us see 2D images in three dimensions. They give us an idea of where things are in the world, so we don't walk into things.

Studies of eye witness testimony: Tuckey and Brewer

They wanted to find out what was in a bank robbery schema. They showed the participants a video of a bank robbery with 3 facts fitting to the schema. And they asked the participants to recall what happened immediately and over 12 weeks. Participants remembered best things that fitted the schema.

Explain Height in the plane.

Things that are closest to the horizon are perceived to be further away than those above or below the horizon.

What is an eye-witness testimony?

This is the statement that an eye-witness gives to the police. This can be affected by schemas held by the witness and can therefore sometimes be inaccurate.

What is size constancy?

This is when we perceive an object as the same size even when its distance from us changes.

What is a distortion illusion?

This is where our perception is deceived by some aspect of the stimulus. This can affect the shape or size of an object.

What was Charmichael's dependant variable?

This was how different people's drawings were from the original pictures they had seen.

What was Charmichael's Independent variable?

This was which group each participant was in either group 1,2 or the control group.

What was Barlett's aim?

To investigate how information changes with each reproduction and to find out why the information changes.

Explain Schemas and Perception.

Visual context is important in the wider world. When we are tying to recall a situation we make use of our schemas which have been built up through our experiences of the world. This causes a phenomenon called perceptual set which makes us more likely to notice some things rather than others.

What are controls?

Ways to keep variables constant in all conditions of an experiment.

How does gestalt's theory of illusions explain distortions?

We try and use continuity to understand the image, but our eyes see it as not straight.

Explain what you understand about ethical issues.

When we carry out experiments we need to think about how the participants may feel and whether they will be harmed by the procedure, this harm may be physical or psychological.

Give an example of size constancy.

When you look at a picture of a car up-front it looks closer, but the smaller car is higher up the image, the road looks the same size just further away. We know that both cars are the same size.