Visual Perception Principles

1. Visual Perception Principles

2. What are visual principles? • Visual principles are ‘rules’ that we apply to visual information to assist our organisation and interpretation of information in consistent and meaningful ways. • Visual perception relies on three key principles to organise information: • Gestalt principles • Perceptual constancies • Depth Perception

3. Gestalt Principles • It is believed that we organise stimuli into categories or groups to understand them. • The following are the categories we put visual information into: • Figure-Ground organisation • Closure • Proximity • Similarity

4. Figure-ground organisation A stimulus appears to stand out (figure) against the background (ground).

5. Closure We complete the gaps in a figure to view the stimulus as a whole.

6. Similarity We perceive objects that have similar features (size, shape, colour) as belonging to a group.

7. Proximity We perceive objects that are physically close together as belonging to a group.

8. Perceptual Constancies • Our ability to understand that an object’s size, shape, brightness or orientation will stay the same even though it has a different retinal image. • Size constancy • Shape constancy • Brightness constancy • Orientation constancy

9. Size Constancy Involves recognising that an object’s actual size remains the same, even though the size it casts on the retina changes.

10. Shape Constancy Is the tendency to perceive an object as maintaining its shape despite any change in shape of the image on the retina.

11. Brightness Constancy Is the tendency to perceive an object as maintaining its level of brightness in relation to its surroundings, despite changes in the amount of light being reflected from the object on the retina.

12. Orientation Constancy Is the tendency to perceive an object as maintaining its orientation despite any change in orientation of the image on the retina.

13. Depth Perception Is the ability to accurately estimate the distance of objects and therefore perceive the world in three dimensions. Depth cues are sources of information from the environment or from within our body that help us to perceive how far away objects are.

14. Binocular Depth Cues Use both eyes to judge depth Convergence - inward turning of the eyes to focus on nearby objects........try looking at the end of your nose Retinal disparity - the difference between the images of both eyes....line an object up in the distance with your finger. Try looking at this with the left eye and then the right eye separately. What happens

15. Monocular Depth Cues • Use one eye to judge depth • Accommodation - the bulging and flattening of the eye to focus • Pictorial Cues - found in pictures, drawings and photos. • Linear perspective • Interposition • Texture gradient • Relative size • Height in the visual field

16. Linear Perspective • Two lines that converge (come together) as they go into the distance.

17. Interposition An object that sits in front of / obscures another object is perceived as being closer.

18. Relative size • The object that has a smaller retinal image is seen as being further away.

19. Texture Gradient An object that is further away from the person will have less detail.

20. Height in the visual field An object that is closer to the horizon is seen as being more distant.

21. More examples