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examBoard: AQA
examType: GCSE
lessonTitle: Role of Inferences in Perception
Richard Gregory (1970) proposed that perception is not simply about receiving sensory information - it's an active process where we build or 'construct' our understanding of the world. According to Gregory, what we see is not just a copy of what's out there, but our brain's best guess about what the information means.
Key Definitions:
Gregory believed that perception is like detective work. Our brains receive incomplete information through our senses (only about 10% comes directly from our eyes) and we must fill in the gaps using our existing knowledge and past experiences. This process of making educated guesses is what Gregory called "making inferences".
Gregory suggested that only about 10% of what we perceive comes directly from our eyes (the sensory information or "bottom-up" processing). The remaining 90% comes from our brain's interpretation based on our expectations, previous experiences and knowledge (the "top-down" processing).
Inferences are at the heart of Gregory's theory. They are the educated guesses our brain makes to interpret sensory information based on our past experiences and knowledge.
When we look at something, our brain doesn't just passively record what's there. Instead, it actively tries to make sense of the information by:
We draw on memories of similar objects or situations we've encountered before.
Our brain completes missing information based on what would make sense in that context.
Our brain makes a best guess (hypothesis) and checks if it matches what we're seeing.
Gregory's theory emphasises top-down processing, where our existing knowledge influences how we interpret sensory information. This is different from bottom-up processing, which is purely driven by the sensory data itself.
Starts with the raw sensory data (light, shapes, colours) and builds up to recognition. Like building a jigsaw puzzle from the pieces.
Starts with expectations and knowledge, which guide how we interpret the sensory data. Like having the picture of the completed jigsaw to help you place the pieces.
When you read, you don't process each letter individually. Your brain uses context and expectations to speed up reading. That's why you can raed tihs snetnece eevn thouhg the ltetres are jmubeld up. Your brain is making inferences based on your knowledge of English words and sentence structure.
Gregory used visual illusions to support his theory. These illusions show how our brain can be tricked when it makes incorrect inferences based on incomplete information.
A concave (pushed in) mask of a face appears to be convex (pushed out). This happens because our brain has a strong expectation that faces are convex, so it overrides the sensory information suggesting it's hollow.
Two lines of equal length appear different because of the arrow heads at their ends. Gregory suggested this happens because we interpret the lines as representing corners in 3D space, with one appearing further away than the other.
The Ames Room is a distorted room designed to create an optical illusion. When viewed from a specific point, people standing in different parts of the room appear to be dramatically different sizes, even though they're actually similar in height. This illusion works because our brain makes the inference that the room is a normal rectangular shape (based on past experience) and interprets the visual information accordingly. This demonstrates how strongly our perceptions are influenced by our expectations about the environment.
Understanding how we make inferences in perception has practical applications in many areas:
Artists can create optical illusions by manipulating how viewers will make inferences about what they're seeing.
Road markings are designed to help drivers make accurate inferences about speed and distance.
Doctors must be aware of how their prior knowledge might create biases in how they interpret symptoms.
Like all scientific theories, Gregory's constructivist approach has strengths and limitations:
Gregory's constructivist approach contrasts with Gibson's direct theory of perception. While Gregory emphasises how we actively construct our perceptions using inferences, Gibson argued that all the information we need is available in the environment (in "invariant" features and "affordances") and we simply pick it up directly without needing to make inferences or use prior knowledge. This debate between constructivist and direct approaches continues to influence how psychologists understand perception.
Gregory's theory highlights how our perception is not a passive recording of reality but an active process of construction. The inferences we make allow us to:
However, these same inference processes can sometimes lead us astray, as demonstrated by visual illusions. Understanding how inferences shape our perception helps us appreciate both the remarkable abilities and the limitations of human perception.
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