Lecture 12: Perception

Question 1

What is the process of sensation to perception?

Answer 1

Stimulus energy (Light, sound, smell) -> Sensory Perception (Eyes, Ears, Nose) -> Neural impulses -> Brain (visual, Auditory, olfactory areas).

Question 2

What is Sperling’s full report procedure?

Answer 2

• About our short term memory
• Found that participants reported an average of 4.5 letters (roughly a third in a 12 letter display).
• Concluded, therefore that not all information was stored in sensory memory.
• However, in another condition, participants were cued to recall letters from only one row.
• A tone (high, medium, or low) was played after the display had disappeared.
• Participants had to recall the letters from the row that corresponded to the tone. (high tone = recall top row, medium tone = recall middle row, low tone = recall third line).
• Its called partial report because participants are not asked to remember all of the items - only some of them cued by the tone.
• Found that participants could recall 3 out of 4 of the letters on the cued row.
• Participants did not know beforehand which row was going to be cued (the tone was played after the letters had disappeared).
• Sperling concluded that sensory memory retained almost all of the stimulus information, but only for a short time.

Question 3

What is sensory memory?

Answer 3

• It holds more information than we can process.

* We need to attend to certain items in order to remember them because information is lost rapidly from sensory memory.

Question 4

What are perceptual thresholds?

Answer 4

• It is best described that we register stimuli as a continuous curve. For example using a dimmer switch to gradually increase the brightness.
• Our thresholds are determined by subjective factors (bored/excited’ happy/sad, drunk/sober).
• You don’t passively receiving sensory inputs from the environment , your decisions were made about whether or not the stimulus passed your perceptual threshold enough for you to report what you could see it.

Question 5

What is the picture theory?

Answer 5

*Argued that the world in represented literally as a picture in the brain.

Question 6

What problems are there with the picture theory?

Answer 6

• It implies the perception is a literal copy of info in the world.
• Relies entirely on incoming information.
• But the incoming information is not always random - it can be structured in meaningful ways that mean it requires less interpretation.

Question 7

What were Gibson’s ideas about light?

Answer 7

• Gibson disagreed that light is a stream of rays with different qualities which the observer then interrupts.
• He proposed ecological optics.
• perception depends on the structure of the light picked up by the observer, not simply on stimulation of the observer by the light.
• Second world war - how to improve pilot’s’ ability to land planes. He suggested either, *select those with better depth perception. OR *Train to perceive depth more effectively. Neither of these worked well because….
• Structure in the light or optic array seems to be as important as structure in the head.

Question 8

What are Gibson’s views on environmental cues?

Answer 8

• Gibsonian speed control on roads
• Works by changing the structure of the perceived world, not by appealing to the internal perceptual or cognitive mechanisms with a reduce speed now sign.

Question 9

What form does the structure of light take?

Answer 9

• Texture gradients
• Horizon ratio - objects which are the same size but different distances away from the observer are cut by the horizon in the same ratio, whereas, object of different sizes at the same distance away have different horizon ratios.

Question 10

What are perceptual invariants?

Answer 10

• Texture gradients and horizon ratios are examples of what Gibson called perceptual invariants unchanging aspects of the environments from the observer’s viewpoint.
• But we are not static and passive perceivers of our environment - we move through it.
• Motion results in the flow of optic information around the perceiver.

Question 11

What are the Gestalt principles?

Answer 11

*Prior to Gestalt psychology the classical associationist approach suggested that we break down the perceived world into a number of separate sensations.
*We build up a picture of the whole from the available parts = reductionist.
*People tend to organise visual elements into groups or unified wholes when certain principles are applied.
*To deal with this, the Gestalt psychologists turned the the traditional argument on its head and claimed that perception of the whole, not the parts came first = holistic.
Similarity: Things are often perceived as being similar even though they consist of different parts.

Question 12

What is Anomaly?

Answer 12

*When similarities occur, an object can be emphasised if it is dissimilar to the others.

Question 13

does perception = interpretation?

Answer 13

• top down approach comes into play because neurophysiology and structure of light is not enough on its own, we need psychological explanations too.
• Because top down processing is involved in perception - sometimes our perception is faulty.
• Gregg (1968) suggests illusions are a classical case of this.
• For example the Muller - Lyer illusion.

Question 14

Are there Culture differences in perception?

Answer 14

*Different cultures differ in the extent to which they are susceptible to the Muller - Lyer illusion.

Question 15

What is the signal detection theory?

Answer 15

• As an aside this framework has been used to try and and describe/ model behaviour in a lot of applied (forensic settings).
• Choosing behaviour in police line ups.
• Memory performance in eyewitness testimony settings.
• Remembering childhood trauma.

Question 16

Why do we need to move our eyes?

Answer 16

• 3 brief movements per second - saccades
• Critical for a high acuity, wide angled, coloured perception.
• Without eye movements retinal images disappear after a few seconds.
• reasons: Neurons in the visual system respond to change rather than steady input.
• Visual system temporally integrates information from saccades.
• Reason for our high quality perception.
• Reason why world does not vanish when we blink.