Perception

• Sensation


  Information that we receive through our senses.
• Perception


  When we receive sensory information and how we interpret/make sense of it.
• Depth Cue


  Source of information from the environment that assists perception of how far away objects are and therefore perceive depth
• Monocular Depth Cue


  A way of detecting depth/distance using just one eye. This allows us to judge distance well, but not perfectly.
• Height in Plane


  How high the object appears in the image. Objects higher up in the visual field appear further away.
• Relative Size


  How large an object appears in an image. Smaller objects in the visual field appear further away.
• Occlusion


  When one object seems to cover part of another object. Objects that obscure (hide) or are in front of others appear to be closer.
• Linear Perspective


  When straight lines are angled so they would converge (come together) at a point on the horizon. This point is known as the vanishing point, useful if we want to show distance in a landscape.
• Binocular Depth Cue


  A type of depth cue that provides information about distance using two eyes.
• Convergence


  Our brain detects the differences in our eye muscles. We focus our eyes differently in order to see closer objects, to how we focus them to see objects that are further away. The brain detects the differences in the muscles and uses it as a cue for distance.
• Retinal Disparity


  Comparing the images received by the eyes. If something is close to us, there is quite a difference in what each eye sees - the left and the right eye view slightly different images. If something is further away, there will be less of a difference between the two images.
• Motion parallax


  the way that the visual field changes with movement, with close objects seeming to move more than objects further away.
• Inference


  a CONCLUSION reached on the basis of past experience of knowledge.
• Nature


  the idea that our characteristics and behaviours are inherited.
• Visual Illusion


  When our visual perception is 'tricked' into seeing something inaccurately. They are 'unconscious mistakes' of perception.
• Ambiguity


  When an image could equally be one thing or another. For example, Rubin's Vase could equally be a chalice or two faces.
• Fiction


  Creating something that isn't really there, to complete an image. For example, our brain creates a white triangle in the Kanizsa Triangle illusion.
• Size Constancy


  Keeping our original perception of the size of an object, even when the information received by the eyes changes.
• Misinterpreted Depth Cues


  Wrongly applying the 'rules' of depth perception. Sometimes our brain detects distance when it is not actually there. For example the Muller Lyer illusion when our brain interprets the top line as longer, however they are the same size.
• The Necker Cube


  A visual illusion caused by AMBIGUITY. There is not enough information for us to know which face of the cube is closest and which is further away.
• The Ponzo Illusion


  A visual illusion caused by MISINTERPRETATION OF DEPTH CUES. The slanted lines resemble train tracks and so our brains perceive the top horizontal line as being further away and therefore longer, when in fact the two horizontal lines are the same length.
• The Müller-Lyer Illusion


  A visual illusion caused by MISINTERPRETATION OF DEPTH CUES. The arrow heads on the end of the lines make the left line appear to be longer than the right. When the arrows point inwards it creates the appearance of an inside corner of a room, and therefore pointing away from us. When the arrows point outwards, the line appears to be the outside corner of a building and therefore pointing towards us. This creates the illusion that the right line is longer than the left.
• Rubin's Vase


  A visual illusion caused by AMBIGUITY. There is not enough information in the image for use to know if we are looking at the sides of two faces or the outline of a vase.
• The Kanizsa Triangle


  A visual illusion caused by FICTION. The gaps in the lines and circles creates the illusion that there is a triangle there, but there isn't.
• The Ames Room


  A visual illusion caused by SIZE CONSTANCY. We look at this and see a normal shaped room, and therefore the people in it seem to be very tall and very small. Actually the room is misshaped to create the illusion that the two people are of equal distance from the viewer, when actually the smaller person is further away.
• Visual constancies


  How the brain perceives objects as being the same (constant). There are three visual constancies: Size, Shape and Colour.
• Shape constancy


  Our brains understand that objects maintain the same shape even if our view of them changes. A cup seen from above and from the side has a different shape from each angle, but we know that it is still a cup and hasn't changed its shape, so our perspective of it doesn't change - stays constant.
• Colour constancy


  Our brains understand that colours don't change just because it is in the light or the shadow.
• Gibson's Direct Theory of Perception


  Gibson believed that the brain receives enough information from the senses to be able to form perceptions. He said that perception is innate and this was demonstrated by the Visual Cliff study showing that a baby as young as 6 months old won't step off an apparent cliff as they can see that there is a drop. Gibson also stated that we use motion parallax to judge distance and that perception is a Bottom Up process.
• Evaluation of Gibson's Direct Theory of Perception

  STRENGTHS: Supported by the Visual Cliff study, showing that babies as young as 6 months have depth perception. We are active in our environments and that movement helps us to judge distance is realistic as we are rarely static in our environment. WEAKNESSES: not supported by illusions, that are able to trick us based on how we understand the world and our experiences in it. Studies by Bruner and Minturn, and Gilchrist and Nesberg, show that our perception is affected by more than just sensation.
• Gregory's Constructivist Theory of Perception


  Gregory believed that the brain uses more than just the information from the senses to form perceptions. That perception uses past experiences and is influenced by the Perceptual Set - culture, emotion, expectation and motivation. Gregory's theory is supported by studies from Bruner and Minturn, and Gilchrist and Nesberg.
• Evaluation of Gregory's Constructivist Theory of Perception

  STRENGTHS: Bruner and Minturn, and Gilchrist and Nesberg support Gregory's Constructivist Theory of Perception. These studies show that perception is affected by factors that make up the perceptual set. WEAKNESSES: Studies such as the Visual Cliff, show that perception is also innate and we are born with some ability to perceive a situation, without the need for past experiences.
• Perceptual Set


  A state of readiness to perceive information. We might focus on certain aspects and ignore others.
• Expectation


  The beliefs we have about what we are going to experience.
• Culture


  Where we are from, how we are brought up, our background, etc. - and how this affects the way we interpret things.
• Emotion


  A strong feeling/mood that can increase our sensitivity to certain aspects of the environment and influence perception.
• Bruner and Minturn's Study

  AIM: To investigate whether expectations affect perception. METHOD: Participants were shown a sequence of letters, a sequence of numbers, then a sequence of mixed numbers and letters, after each sequence the participants were shown the test stimulus. The test stimulus was an ambiguous figure that could be seen as either a letter 'B' or the number '13'. Counterbalancing was used. The participants were asked to draw what they saw. RESULTS: Most of the participants drew an open figure like a 13 when they were expecting to see a number, and closed figure like a B when they were expecting to see a letter. When they were expecting a letter or a number this gave mixed RESULTS. CONCLUSION: The researchers concluded that the participants' expectations had directly affected how they interpreted the stimulus figure.
• Evaluation of Bruner and Minturn's study


  STRENGTHS: It was a laboratory experiment, it was well controlled and easy to replicate, increasing the reliability of the findings. Supports Gregory's Constructivist theory of Perception, that states that experience influences perception. WEAKNESSES: Only a few participants that were all from a similar background, therefore these findings can't be generalised to the wider population. The study does not reflect a real life situation and so lacks ecological validity.
• Gilchrist and Nesberg's Study


  AIM: Gilchrist and Nesberg wanted to investigate how motivation affects perception. METHOD: Participants volunteered to go for 20 hours without any food, and to only drink water. They were randomly allocated to be in one of two groups: one which actually went without food, and the other, a control group, which had their normal meals during the 20 hours. Participants were asked to look at a series of photos of food, each photo was shown twice. This was at the start of the study, after 6 hours and after 20 hours. The second time the participant was shown the photo, the researcher had adjusted the brightness of the photo and the participant was asked to change it back to its original brightness using a handle on the monitor. RESULTS: after 20 hours, the participants that had not eaten and were therefore hungry, made the greatest adjustments to the brightness of the photo. This shows their memory of the original photo was brighter than it really was. CONCLUSION: Hunger can affect the way that we perceive images of food, which suggests that motivation affects perception.
• Evaluation of Gilchrist and Nesberg's study

  STRENGTHS: It has ecological validity because the participants' hunger was real. It took place in a laboratory and so was carefully controlled. WEAKNESSES: Being shown photos and adjusting the brightness does not reflect a real life situation and so the study lacks ecological validity. Participants were volunteers and so they knew they were taking part in a study, therefore their behaviour might not have been natural.