9A - Errors of sight Flashcards
Fallibility definition
the quality of being prone to error or experiencing difficulties in judgement
Fallibility of perception
Our perceptual systems are subjective (unique to you) and prone to error (bias). These errors in the judgement or interpretation of sensory stimuli can be considered perceptual distortions
Perceptual distortion definition
an error in the judgement of interpretation of sensory stimuli
Visual illusion definition
the perception of a visual stimulus that conflicts with how it is in physical reality
- a consistent misinterpretation of real sensory information
Why do we see illusions?
- The physical nature of the visual stimulus
- The characteristics of the eyes
- The characteristics of our visual perceptual process
Examples of visual illusions
- Müller - Lyer illusion
- Ames room illusion
- Ponzo illusion
Müller - Lyer illusion definition
an illusion where the length of the central line of a stimulus is misjudged because of the lines attached to either end of the stimulus
Müller - Lyer illusion explanation - Biological
Eye movement theory: The arrow head and the feather tail head require different types of eye movement in the sensation process, therefore the two shapes/lines are physically perceived differently.
- This theory however is outdated and has been disproven!
Müller - Lyer illusion explanation - Psychological
Carpenter world hypothesis: suggests that the Müller - Lyer illusion is perceived because the lines at the end of the stimuli imply depth due to our frequent past experience with right angles.
Müller - Lyer illusion explanation - Social
The social/cultural reasons such as past experience and social environment.
- e.g. people who live in undeveloped countries without buildings etc. aren’t as familiar with angled shapes and architecture, therefore may not fall for the illusion due to lack of past experience
Ames room illusion definition
an illusion that causes difficulty in accurately perceiving size based on an apparatus that manipulates depth cues
Ames room illusion explanation - How is the room built?
The room appears rectangular because secondary (pictorial) depth cues are manipulated by the room.
- The room slopes up and outward as lines move further from the observer, to compensate for linear perspective
- This effect is strengthened by distorting the appearance of objects in the room (such as clocks, pictures and floor tiles) so that they look the same size and shape on both sides of the room to the observer
Ames room illusion explanation - What happens to perception?
We maintain the shape consistency of the room as rectangular at the expense of the size constancy of the people inside the room.
- The observer applies perceptual set from their past experience of rooms being rectangular, not trapezoidal
- Thus, people in the far corner appear to be the same distance from the observer as the objects in the nearer corner
- The peephole allows us to only use one eye to look into the room
Ponzo illusion definition
an illusion where diagonal lines converge above two parallel lines leads observers to misjudge the length of the parallel lines
Ponzo illusion explanation
- The Ponzo illusion is perceived because of a misapplication of the pictorial depth cue of linear perspective
- Because we expect parallel lines to converge as they recede into the distance, the diagonal stimuli have depth implications
- The top parallel line is then perceived to be further away and the bottom line is closer to the observer
- As the two lines cast the same sized retinal image, but the top line is perceived as being further away from the observer, it is perceived as being longer than the bottom line (and vice versa)
