WK4

• What does an illusory perception refer to?


  A consistent and persistent discrepancy between perceived and real physical properties of a stimulus
• How are illusions described in terms of consistency and persistence?


  Illusions are consistent as they occur whenever the stimulus is presented and persistent as they resist suppression efforts
• What distinguishes an illusion from something that is undetectable?


  Failing to perceive something undetectable is not considered an illusion
• Why is the image of a pipe not considered an illusion?


  Because you are not fooled or deceived; you recognize it as a picture
• What does "Ceci n’est pas un violon" illustrate in terms of perception?


  It illustrates that one might be fooled by an image that is hard to distinguish from reality
• How does the pencil illusion differ from other illusions?


  It is a different kind of illusion because knowing it isn't split doesn't change what you see
• What causes optical illusions?


  Optical illusions arise due to optical effects
• What is the difference between optical illusions and perceptual illusions?


  Optical illusions occur due to physical processes outside the head, while perceptual illusions occur due to biological processes inside the head
• What characterizes perceptual illusions?


  They are surprising or unexpected discrepancies between sensory perception and the distal stimulus
• What happens to perceptual illusions when the rest of the image is removed?


  The illusions disappear
• Why are the blue squares considered illusory?


  Because they are not really blue, leading to a deception about the nature of the stimulus
• What does "not really blue" imply in terms of reflectance?


  It means that the blue type reflectance should look blue, but it is misperceived
• How does the visual system estimate the reflectance of the blue squares?


  By dividing out the contribution of its estimate of the illuminant from its representation of the light from the blue squares
• What is the result of the visual system's estimation process for the blue squares?


  A reflectance that should look blue with a hint of red
• Why does the visual system get the illumination wrong in perceptual illusions?


  Because it incorrectly estimates the illumination, leading to a misperception of the squares' lightness
• What is the significance of retinal images in perception?


  Retinal images are not important for life; understanding the world and its properties is crucial
• How can an illusory red be produced?


  By painting on an illumination that, when discounted, results in a red-type reflectance estimate
• What color of illuminant is needed to produce an illusory red?


  Cyan/bluish-green
• How can illusory yellow be produced?


  By using a blue or mauve illumination
• What are the three basic reasons for individual differences in color perception?


  Short term adaptation effects, long-term adaptation and learning effects, and acquired and congenital anomalies of the nervous system
• What occurs as a result of prolonged exposure to a particular kind of stimulus?

  Adaptation effects
• What are complementary color aftereffects?


  They are the opposite color of the inducing stimulus that occurs after prolonged exposure
• How long do short-term adaptation effects last?


  They do not last as long as the initial exposure
• What is the significance of the dress image in color perception studies?


  It illustrates how different people can perceive the same stimulus differently
• What percentage of viewers saw the dress as blue and black/dark grey?


  About 60%
• What could explain the differences in color perception of the dress among viewers?


  Differences in how individuals attribute a bluish wash to the illumination and their long-term experience with different lighting conditions
• Why do some people see the dress as white while others see it as blue?

  Because the image was actually of a blue dress, leading to misperception in those who see it as white
• How does the presence of a blue wash affect the perception of the dress?


  It may encourage complete removal of the bluish wash for some viewers, affecting their perception
• What is the role of the visual system in extracting information about the world?


  The visual system extracts information about the world from images, focusing on the properties of objects rather than the images themselves
• What does it mean to be colour blind?


  It means having a limited ability to use the spectra of images to obtain information about surfaces and light sources.
• Can colour blind individuals see certain colours like red or green?


  No, they may have difficulty distinguishing between these colours.
• Why can't we know what colours other people or animals see?

  Because we cannot access their consciousness.
• What is the subjective nature of colours?


  Colours are mental qualities used for the conscious representation of spectral information.
• How do colour blind individuals perceive stimuli compared to colour normal individuals?


  They see stimuli as the same colour, while colour normal individuals see them as different colours.
• How many primary colours do colour normal people need to produce all visible colours?


  Three primary colours.
• How many primary colours do colour blind people typically need?


  They usually need only two or sometimes only one primary colour.
• What is the Ishihara colour blindness test based on?


  It is based on a person's ability to see a figure defined by spots of one colour displayed amongst spots of a different colour.
• How does a colour normal person perform on the Ishihara test compared to a colour blind person?


  A colour normal person can see the colour defined figure quickly, while a colour blind person may fail to see it or take much longer.
• What is the physiological basis for colour blindness?


  It is almost completely understood and can arise anywhere in the visual pathway from the retina to the cortex.
• Where do most instances of colour blindness originate?


  Almost all instances are due to issues with the cones themselves.