Lecture 4 Flashcards
Gestalt psychologists - 6 perceptions
- simplicity
- closure
- continuity
- similarity
- proximity
- common fate
Simplicity
We perceive the simplest shape possible.
Closure
We fill in missing elements.
Continuity
Edges or contours of shapes that have similar orientation provide ‘good continuation’.
Similarity
Similar looking areas of a visual display are perceived as belonging to the same object.
Proximity
Objects close together tend to be grouped together.
Common fate
Elements that move together are part of the same moving object.
Image based theories + problem
An object you have seen before is stored in memory as a template which can be compared to the retinal representation.
- Problem: variability in position, size, shape, and orientation.
Other race effect (own race bias)
People are better at recognising/discriminating faces from their own race compared to other races (evident among all people from all different races).
The basic subcomponents of features + problem
Theory: About 36 geons are needed to recognise all visual objects.
- Problem: the theory does not provide a mechanism that reduces complex real scenes to geon representations and geons fail to distinguish many real objects.
Current view of perception
Checking expectations (priors) with sensory evidence.
Fusiform face area (FFA)
The FFA responds strongly to faces, whereas other pictures like houses, objects, scenes, bodies are scrambled pictures.
The Thatcher effect
Upright races are processed differently than upside-down ones.
Important topics for perception (6)
- Object size
- Monocular depth cues
- Familiar size
- Binocular depth cues
- Binocular disparity
- Motion
Object size (equation)
Retinal Representation x Distance
Monocular depth cues
- Relative Height: Things at a distance look like their base is higher.
- Relative Size: Objects farther away from other objects are smaller.
Familiar size
Judging size based on what you already know (e.g., adult male height).
Binocular depth cues
A large part of central visual field is registered in both eyes.
The size of the retinal representation in the left and right eye is slightly different (because of the different positions of the two eyes).
- Binocular cues are depth cues that require the use of two eyes. For instance, trying to touch the tip of two pencils together in front of your face may be rather easy to do with both eyes open; however, attempting this task with one eye open is significantly challenging.
Binocular disparity - size
Left and right eye see the world in a different perspective. The brain creates a 3D image of this difference (stereopsis).
The bigger the difference, the closer the object.
- Hollow mask illusion
Motion
- Object close to observers seem to move faster than objects further.
- Before motion can be inferred, the visual system has to know whether the movement on the retina is caused by a displacement of the (1) eye, head, body or (2) movement of the object.
Apparent motion
Successive alternating signals induce a motion perception (if not, a movie would look like a slide show).
- In the ‘green dot’ illusion this is combined with the colour afterimage and is replaced by an illusory green circle.
Waterfall illusion
An aftereffect of movement that occurs after viewing a stimulus moving in one direction. Viewing the waterfall makes other objects appear to move in the opposite direction.
Spatial acuity
- Visual system
- The ability to distinguish two features that are very close together in space.
Temporal acuity
- Auditory system
- The ability to distinguish two features that are very close together in time.
Damage to V4
Causes achromatopsia (cortical colour blindness):
Person sees everything in shades of grey.
Damage to V5
Causes akinetopsia (motion blindness)
- Bilateral.
