"Introduction to Psychology" Notes (6) —— Perception

Lecture 7: Perception

Perception is our way of making contact with our environment, of discovering what's happening outside our body and our brain.

To sense, perceive, and understand our world, we utilize two very different processes:

1. bottom-up processing: our sensory receptors detect external stimulation and send this raw data to the brain for analysis.
2. top-down processing:It adds what we already know about such stimulation, what we remember about the context in which it usually appears, and how we label and classify it.In this way, we give meaning to our perceptions.

How to perceive:

• hardware: in the form of sensory apparatus
• software: to process the information and make sense of it

The characteristics of our perception:

• We tend to see what we expect to see.
• Our previous experience, our expectations, interests, and biases are constantly giving rise to different perceptions.
• We see things with our minds as well as our eyes.
• We are constantly selecting only a small part of the available sensory information to attend to and process.
• One of the ways we perceive something actively is by taking into account its context.This context can even determine the nature of the perception itself, with the same object looking very different in different contexts.
• To be effective, perception also has to work fast and extract the minimal amount of information necessary to form an impression of the entire pattern.

Why we have vision illusion: We got a two-dimensional retina and have to figure out a three-dimensional world. Our minds contain certain assumptions about how things should be that enable us to make educated guesses from the two-dimensional array on to the three-dimensional world.

3 problems can cause vision illusion:

1. Color: Objects' color is not merely a matter of what material they're made of but of the amount of light that hits it.
2. Object: There are certain cues in the environment so that you can segment a scene into different objects based on them. These cues are often described as Gestalt principles.
• Proximity: When you see things that are close to each other, you're more likely than not to assume that they belong to the same thing.
• Similarity:
• Closure
• Good continuation
• Common movement: If things move together they're a single object
3. Depth: need to figure out a three-dimensional world via a two-dimensional retina.
• Binocular disparity
• Interposition
• Relative size
• Texture gradient
• Linear perspective
• the Mueller-Lyer illusion
• Ponzo illusion

Edges and boundaries in particular convey lots of information about an object.They provide a visual shortcut which can help the brain fill in the whole patterns from the fewest identifying parts.Sometimes the brain will even register a pattern that doesn't exist.A boundary or an edge can powerfully influence the way we see things.