1. 18. Perception Unit 3 - Neurobiology and Communication
CfE Higher Human Biology
18. Perception

2. Learning Intentions
I can state that perception is the process by which the brain analyses and makes sense out of incoming sensory information
I can state that the three areas of perception involve segregation of objects, perception of distance and recognition
I can describe segregation of objects using figure and ground perceptional organisation using examples such as ‘vase and face’
I can describe segregation of objects using perceptual organisation of stimuli into coherent patterns
I can describe segregation of objects using visual cues such as relative size, superimposition and relative height in field
I can state that the image received from each eye is different and this called binocular disparity
I can explain perception of distance using binocular disparity in judging distance
I can explain the term perceptual constancy as objects become closer or further away or the viewing angle changes
I can describe why shape is more important rather than its detail when recognising an object
I can explain the importance of previous memories in recognition of unfamiliar objects
I can explain the concept of perceptual set as past experience, context or expectation and how it influences the way a stimulus is perceived

3. Perception
Perception is the process by which the brain analyses and makes sense of incoming sensory information passed to the brain.
A persons perception of their environment can depend on information from many sense organs, although only visual perception will be studied.
There are three areas of perception:
Saegregation of objects from one another and from their background
Perception of distance from the person
Recognition of different objects

4. Perceptual Organisationinto Figure and Ground – segregation of objects
The ‘figure-ground’ phenomenon allows objects to be distinguished from their background.
For example, we can see words on printed paper as the ‘figure’ and the paper as the ‘ground’.
A vase or two faces?

5. Perception – segregation of objects
The ‘figure-ground’ perceptual organisation is often used in advertising.
A field of view that contains contrasting components is known as “figural” parts of the image become segregate as figures that stands out fro the rest of the field.
In each image there is a dominant image that stands out in front of the “ground” although they are displayed on the same 2D surface

6. Is a zebra white with black stripes or black with white stripes

7. Perception – segregation of objects
When perceiving an object, the brain will typically organise visual stimuli into a coherent pattern rather than into separate parts.
For example, the image below shows 7 lines but the brain tends to perceive this as three groups of 2 lines (plus an extra line).

8. Perception – segregation of objects
The brain can organise objects in a number of ways by grouping them into ordered relationships:
1 Group
3 Groups
Orientation – the brain can also recognise shapes formed by multiple moving objects e.g. extreme sheep herding – google it!

9. Perception of distance
The distance of objects from the eye can be determined using visual cues, such as:
Relative size
Superimposition
Relative height

10. Relative Size Perception of distance by relative size
Objects which are further away from the eye are perceived to be smaller in size.
As the road appears to reduce in size, this indicates its increasing distance from the eye.
This illusion shows that the relative size of the circles can imply that they are further away or closer to the eye.

11. Superimposition Perception of Distance by superimposition
When an object partially blocks the view of another, it is perceived to be closer to the eye than the object which is blocked.
Due to superimposition, the circle is perceived to be the closest object.
The mountains in the foreground appear closer as they overlap the mountains in the background.

12. Relative Height Perception of distance by relative height
When the base of an object in the field of view appears higher than the base of another, it is perceived to be further away.
In this image, the base of clear nail varnish is lower than that of the red and so appears closer to the eye.
Note: this also displays the effect of relative size.

13. Texture and Linear Perspective
In 1498 "The Last Supper" by Leonardo Da Vinci, demonstrates linear perspective through the point of view and shape of the room. The walls of the room are parallel and when they are represented as converging towards one another, they illustrate the depth of the room. This cue allows the viewer to see how the image would look in 3-dimensions.
As the texture of the grass changes from the foreground to the back of the image gives the perception of depth.

14. Which of the following lines is the longest?
Müller-Lyer illusion
Which of the following lines is the longest?
The Müller-Lyer illusion results in us perceiving the line with two ‘tails’ as being the longest, when in fact they are all of equal length.

15. Binocular disparity
Each eye looks at an object from a slightly different position relative to the other eye.
Due to this, there is a slight disparity (or difference) between the image each eye forms.
The closer the object is, the greater the disparity between the two images.
The two images are merged into one in the brain and produce a binocular image which allows us to better judge depth and distance better than either single-eye, monocular image.

16. Binocular disparity
This process may fail if excessive quantities of alcohol have been consumed. The person may see “double”.
How does it work?
"It slows down the brain so you can't get the eyes tracking on something quickly. The time it takes to get your two eyes — their images — to fuse to give you a single image increases when you drink." Covering one eye can help, he notes, "because then you don't have your brain comparing the two images. You just have the one image."
binocular image
left eye image
right eye image

17. Perceptual constancy
The size of the image an object makes on our retinas will change as it moves closer or further away.
We do not perceive the object as increasing or decreasing in size although it may become closer or the angle at which we view it may change, the object has size constancy.
Our perception of the size of an object as being constant is partly due to past experience and stored knowledge, as we remember the size of familiar objects.

18. Perceptual constancy
Perceptual constancy also applies to the shape of objects.
We still perceive an objects shape as constant even when the angle at which we view it changes.
For example, the shape of the door below appears to change but we are aware that its shape is actually constant.

19. Recognition
Object recognition is the ability to perceive an objects physical properties, such as shape, colour and texture.
The shape of an object, particularly its outline, is more important than colour or texture when recognising an object.
During early learning, we use view and touch an object to establish its shape and use this to initially distinguish objects; this information is then stored in our long-term memory.

20. Recognition
When we perceive a shape, our brain subconsciously attempts to match it with a shape description which is already stored in the brain. If the shape is familiar, it is matched to a memory and the object is recognised.
If the shape is not matched then the brain can match it to previously experienced objects which may have a similar shape and infer that the objects are related in some way.

21. Recognition – perceptual set
The tendency of a person to perceive certain aspects of available sensory information and ignore others is known as perceptual set.
This is influenced by expectation, context or past experience.

22. Recognition – perceptual set
Expectation and context When the following diagram is covered up in different ways it affects the way we perceive it. This is due to the context in which we are exposed to it and what we expect to see.

23. Recognition – perceptual set
Past experience
Expectations are typically linked to past experience.
The example below contains a writing error which most people typically overlook due to expectation and past experience.

24. Recognition – perceptual set
Past experience
If a group is shown pictures of mammals, some which include rodents, they will see a rat in the ambiguous image below.
If shown pictures of men, some which include bald men with glasses, they will see a man in the image.

25. Recognition – perceptual set
The tendency of a person to perceive certain aspects of available sensory information and ignore others is known as perceptual set.
This is influenced by expectation, context or past experience.

26. Questions Define the term ‘perception’
2. State the areas of perception.
3. Describe what is meant by the ‘figure-ground’ phenomenon.
4. State how stimuli are grouped when perceived.
5.Describe the visual cues which allow for perception of distance.
9. State how objects are recognised.
10. Describe what is meant by ‘perceptual set’ and describe how it is influenced

27. Answers Define the term ‘perception’
Perception is the process by which the brain analyses and makes sense of incoming sensory information.
2. State the areas of perception.
segregation of objects, perception of distance, recognition
3. Describe what is meant by the ‘figure-ground’ phenomenon.
This allows objects to be distinguished from their background.

28. Answers (continued) 4. State how stimuli are grouped when perceived.
The brain will typically organise visual stimuli into a coherent pattern
5.Describe the visual cues which allow for perception of distance.
relative size, superimposition, relative height

29. Answers (continued)
6. Describe what is meant by ‘binocular disparity’. Each eye looks at an object from a slightly different position relative to the other eye. 7. State how objects are perceived when distance or viewing angles change. Our perception of the object remains the same. 8. State the most important aspect when recognising objects. Past experience and stored knowledge

30. Answers(continued)
9. State how objects are recognised. Physical properties, such as shape, colour and texture although shape is most important. 10. Describe what is meant by ‘perceptual set’ and describe how it is influenced This is the tendency of a person to perceive certain aspects of available sensory information and ignore others It is influenced by expectation, context or past experience.