The image on the retina is different from the image we "see". In many cases round shapes such as cups have elliptical designs and doors are not represented as rectangles. But our brains depict them as objects of "normal" shape and size, regardless of how the images are displayed on the retina. Essentially, our brains "correct" images to make objects look permanent.
Persistence scaling
Real objects show a larger image on the retina when they are close, and a smaller one when they are far away. Again, the brain corrects for this by making distant objects appear larger.
This can be demonstrated using afterimages. If you stare at a bright light for a few seconds (never look directly at the sun for this) and then look away, you will see an afterimage that has a fixed size and shape on the retina. However, when you look at the nearest object and then (quickly) farther away, the afterimage seems to change in size - it seems to be larger when we look far away.
Another example of permanence can be seen by looking at telegraph poles or trees. The pillars look vertical no matter how you tilt your head. What seems to be happening is that the brain is trying to create a stable view of the world, no matter what the body may be doing. Think about moving around the room, climbing stairs, traveling in a bus.
Your eyes must be presenting to your brain a jumbled series of images from all angles.
However, the brain receives information from other senses that tells the brain where the body is in space and what movements it is making. The brain combines this with visual information to take away the awareness of movement when needed - so-called location persistence.
Without it, the world would spin in crazy ways when we move our head and eyes. Interfering with this process causes some of the characteristic side effects of alcohol.
Other forms of persistence:
- Brightness constancy
Paper always appears white, even in dim light, and charcoal is black, despite the fact that it glitters in the sun.
- Color Constancy
Objects tend to retain their properties under various lighting conditions. The brain modifies the information it receives about light, darkness, and color in order to maintain these constancy.
تعليقات
إرسال تعليق