Visual Perception

Vision is not only possibly our most heavily relied upon sense, but also the most frequently researched and discussed. As you navigate the following websites regarding the role of vision in sensation and perception, be sure to take notes on important terms and concepts. You'll also need to answer on a separate sheet of paper the questions posed on each page in bold.

We've all heard the term "blind spot"--more than likely while learning how to drive--but what are the physical mechanisms behind this phenomenon?

The blind spot is just one way your brain fills in the gaps when interpreting sensory (specifically visual) information. To see it in action, try the activity below. What happens?

Now try this trick with colored backgrounds. Click the link below to switch the positions of the colored boxes. How does this result compare to the initial example?

Would you expect this result? How would you explain this phenomenon with regard to the eye's anatomy? (If necessary, refer back to the previous page.)

Here is a more detailed depiction of the anatomy of the eye. Click the labels for definitions of each structure.

Which structure houses the photoreceptors mentioned in the previous pages? Which structure controls the intake of light?

All things considered, do you find this structure suitable for humans (think about how we use vision in comparison to animals)? Does the blind spot present a significant shortcoming in human sensation? Why or why not?

As you know, vision is one of several ways in which humans gather sensory stimuli from the environment. However, how does the gathering of information differ from the interpretation of information?

Think about what you are sensing right now. Are you sensing anything that you weren't attending to before reading this question? How did your sensory experience change when you attended to these sensations?

You will want to take notes on this information as you read, particularly the Gestalt principles. You'll need them later.

As noted in the previous page, perceptual expectancy is largely responsible for how we interpret cues in our environment. This is particularly evident when examining how the brain handles optical illusions.

Look at the blue shaded circles in the illustration to the right and consider the explanation provided in the text. How might the brains of people from other parts of the world interpret other cues about lighting? The brains of other mammals? The brains of sea animals?

Take a look at this very famous optical illusion. What was your initial judgment about the sizes of these two lines? Try playing with them by moving the various segments. Is the effect the same if you create, for example, two arrows pointing in opposite directions? Why or why not?

When you're finished, read the explanation at the link at the bottom of the page. How might this be explained by perceptual expectancy?

Take a look at this video on Gestalt principles (and be prepared to add to your notes from earlier). Do you see the images described? What individual differences (e.g. cultural, experiential) do you think might be attributable to the variations in perception mentioned in the video? Cite specific and/or personal examples. For example, why might one individual see the Virgin Mary and another see Madonna in a lemon slice?

Take a look at each of the examples of optical illusions illustrated at the links to the left. Which principle do you think best describes perception of the old versus the young lady? The Müller-Lyer illusion?

How might these illusory errors assist us in interpreting our environment? How might they prove maladaptive?

For fun, take a look at these other well-known illusions and their explanations. Can you match them with a Gestalt principle? Do you find that some correspond to multiple principles? Do some seem not to correspond to any of the principles mentioned?