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examBoard: AQA
examType: GCSE
lessonTitle: Expectation and Perception
Have you ever seen faces in clouds or heard your name being called in random noise? These experiences happen because your brain doesn't just passively receive information it actively interprets it based on what you expect to see or hear. This session explores how our expectations dramatically shape what we perceive.
Key Definitions:
Your brain doesn't just passively receive information from your senses. Instead, it actively tries to make sense of the world by using what you already know. This means your expectations can dramatically change what you actually perceive.
This is when your brain uses existing knowledge to interpret sensory information. It's like having a template in your mind that helps you quickly make sense of what you see or hear. For example, you can read "Ths sntnce hs mssng vwls" because your brain fills in the gaps based on what it expects.
This is when perception starts with the sensory data itself. Your brain processes the raw information (like shapes, colours, sounds) before applying any expectations. This is more like building a puzzle piece by piece. Both processes work together in normal perception.
Perceptual set refers to our mental readiness to perceive certain things and not others. It's like wearing a pair of glasses that filters what we see based on our expectations, motivations and emotions.
What we've encountered before shapes what we expect to see now. If you've only ever seen red apples, you might be surprised by a green one.
What we want or need affects perception. If you're hungry, you're more likely to notice food-related cues in your environment.
The situation or surroundings influence what we perceive. The word "bank" means something different when you're near a river versus in a financial district.
Researchers showed participants an ambiguous figure that could be seen as either the letter 'B' or the number '13'. When shown in the context of letters (A, ?, C), participants typically saw 'B'. When shown in the context of numbers (12, ?, 14), they saw '13'. This demonstrates how context creates a perceptual set that influences what we perceive.
Schemas are mental frameworks or 'packages' of knowledge that help us organise information about the world. They're like mental shortcuts that help us make sense of new situations quickly.
When we encounter something new, we try to fit it into our existing schemas. If you see a four-legged animal with a wagging tail, you might quickly categorise it as "dog" based on your dog schema. This helps us process information efficiently, but it can also lead to errors when our expectations don't match reality.
Schemas can cause us to:
- Notice things that fit our schema
- Ignore things that don't fit
- Interpret ambiguous information to match our schema
- Even "remember" things that weren't there but would fit our schema
Frederic Bartlett asked British participants to read and recall a Native American folk tale that contained unfamiliar cultural elements. When recalling the story later, participants changed details to fit their own cultural schemas, making the story shorter, more coherent by Western standards and removing culturally unfamiliar elements. This shows how our existing schemas shape not just perception but also memory.
Several key studies have demonstrated the powerful effect of expectations on perception:
Participants who were hungry judged pictures of food as brighter than non-food pictures, while participants who weren't hungry didn't show this difference. This demonstrates how our physiological needs can create a perceptual set that affects basic sensory judgments.
Researchers showed participants an ambiguous image that could be seen as either a rat or a man's face. Those who had previously been shown animal pictures were more likely to see a rat, while those shown human faces tended to see a man. This shows how recent experience creates expectations that influence perception.
Understanding how expectations influence perception has important applications in many areas:
Doctors may have a perceptual set that leads them to interpret symptoms according to common diagnoses, potentially missing rare conditions. Being aware of this bias can improve diagnostic accuracy.
Brands use packaging and advertising to create expectations that influence how we perceive products. Wine tastes better when we believe it's expensive, even if it's actually cheap!
Teachers' expectations of students can create a self-fulfilling prophecy, where students perform according to how they're expected to perform (the "Pygmalion effect").
While expectations powerfully shape perception, they don't completely determine it. Several factors limit how much our expectations can override sensory information:
Very clear, strong sensory signals are harder to misinterpret. You might mistake a quiet sound for something you expect to hear, but a loud, clear sound is harder to misperceive.
Being aware of your expectations can help reduce their influence. This is why scientists use double-blind procedures in experiments to prevent expectation effects from biasing results.
Try reading the colour of these words, not the words themselves: RED BLUE GREEN (where "RED" is printed in blue ink, etc.). It's difficult because your expectation to read the word conflicts with the task of naming the ink colour. This demonstrates how automatic expectations can be and how they can interfere with perception even when we're trying to override them.
Our expectations don't just influence what we perceive they're a fundamental part of how perception works. Without expectations, we would be overwhelmed by sensory information and struggle to make sense of the world. However, being aware of how expectations can bias our perception helps us become more accurate observers.
Remember that perception isn't a passive process of receiving information it's an active process of construction where your brain uses expectations to fill in gaps, resolve ambiguities and make sense of complex sensory input. This makes perception efficient but sometimes inaccurate when our expectations don't match reality.
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