4.1—sensation and perception Flashcards Preview

🚫 PSY100H1: Introduction to Psychology (Winter 2016) with J. Vervaeke > 4.1—sensation and perception > Flashcards

Flashcards in 4.1—sensation and perception Deck (20)
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4.1 Learning Objectives


4.1 Focus Questions



the process of detecting external events by sense organs and turning those stimuli into neural signals.



involves attending to, organizing, and interpreting stimuli that we sense.



  • transduction: when specialized receptors transform the physical energy of the outside world into neural impulses.
  • raw sensations detected by the sensory organs are turned into information that the brain can process through transfuction.
  • this ultimately gives rise to our internal representation of the world.
  • all of our senses use the same mechanism for transmitting information in the brain: the action potential.
  • in order to separate different sensory signals from one another so that we can experience distinct sensations, the brain sends signals from different sensory organs to different parts of the brain.


Doctrine of Specific Nerve Energies

  • doctrine of specific nerve energies: first proposed in 1826 by the German physiologist Johannes Müller; the idea that different senses are separated in the brain.
  • these pathways are built through experience.


Sensory Adaptation

  • sensory adaptation: the reduction of activity in sensory receptors with repeated exposure to a stimulus. 
  • unchanging stimuli elicit less activity in the nervous system, and are percieved as being less intense over time.
  • e.g. directors changing camera angles so that your brain can't adapt and will keep hold of your attention.



  • psychophysics: the field of study that explores how physical energy such as light and sound and their intensity relate to psychological experience 
  • e.g. how much perfume would need to be spilled in a three-you apartment for you to detect the odour?


Absolute Threshold

  • absolute threshold: the minimum amount of energy or quantity of a stimulus required for it to be reliably detected at least 50% of the time it is presented.
  • this varies among individuals (and species) and across the life span.


Difference Treshold

  • difference threshold: the smallest difference between stimuli that can be reliably detected at least 50% of the time. 
  • e.g. adding one pinch of salt to fries with no salt will create a different taste from adding one pinch of salt to fries that already have four pinches of salt.


Stimulus Threshold Limitations

  • the study of stimulus thresholds has its limitations.
  • whether someone perceives a stimulus is determined by self-report—an individual reporting that she either did or did not detect a stimulus.
  • not all people are equally willing to say they sensed a weak stimulus; some will wait until they're 100% certain.
  • e.g. real-world implications: radiologist trying to detect tumours in a set of images.
    • if there are differences in the absolute threshold of different radiologists, then one might miss tumours that the other would have detected.


Signal Detection Theory

  • signal detection theory: whether a stimulus is perceived depends on both sensory experience and judgment made by the subject.
  • sensory process: signal detection experiment conducted in the laboratory, the experimenter presents either a faint stim- ulus or no stimulus at all.
  • decision process: subject is asked to report whehter or not a stimulus was actually presented.
  • hit: correct that you heard a sound.
  • correct rejection: correct that you didn't hear a sound.
  • false alarm: think you heard something that's not there.
  • miss: fail to detect that a stimulus was presented.
  • by analyzing how often a person’s responses fall into each of these four categories, psychologists can accurately measure the sensitivity of that person’s sensory systems.

  • motivational changes are likely to affect your decision process, changing your sensitivity. (i.e. you're more likely to hear a bear growl or twig snap on your own at night in the woods than with friends hiking.)


Subliminal Messaging

  • we can perceive subliminal stimuli under strict laboratory conditions.
  • subliminal perception can occur, and it can produce small effects in the nervous system.
  • claims that subliminal perception can influence behaviours may be inaccurate.
  • e.g. Greenwald study
    • even if changes were to occur after a subject heard subliminal tapes, these effects may be due to the participants' expectations.
    • people were given two sets of tapes (e.g. a memory cassette with memory label, and a memory cassette with a self-esteem label).
    • participants experienced improvement based on the labels, and not what they actually heard.
  • subliminal messages are unlikely to create motivations that hadn't previously existed.
  • therefore, it's definitely not a form of mind control.


Gestalt Psychology

  • Gestalt psychology: "the whole is greater than the sum of its parts."
  • figure-ground principle: objects or "figures" in our environment tend to stand out against a background.
  • proximity; we tend to treat two or more objects that are close in proximity to each other as a group.
  • similarity; experienced by viewing groups of people in uniform.
  • continuity: "good continuation"; lines and other objects tend to be continuous, rather than abruptly changing direction.
  • closure: the tendency to fill in gaps to completely a whole object.
  • Gestalt concepts are not simply a colelction of isolated examples; they demonstrate how we create our own organized perceptions out of the different sensory inputs that we experience.


Phonetic Reversal

  • in 1985, two teens committed suicide (one lived), claiming their actions were influeced by "subliminal messages" found in the heavy metal music by Judas Priest.
  • the family sued the band, claiming that when played backwards, the song "Better by You, Better Than Me" contained the phrase "do it."
  • most examples of backward messages are due to phonetic reversal: where a word pronounced backwards sounds like another word.
  • after this, John Vokey and Don Read (in 1985) conducted experiments about backwards messages.
    • when asked to make judgments about the con- tent of the backward messages, participants' performance fell to chance levels.

    • they were unable to distinguish between nursery rhymes, Christian, satanic, pornographic, or adver- tising messages (19.1% correct, where chance performance is 20%) 


Top-Down Processing

  • top-down processing: when our perceptions are influenced by our expectations or by our prior knowledge.
  • in backward messages experiments, participants use top-down processing to perceive specific phrases.  


Bottom-Up Processing

  • bottom-up processing occurs: when we perceive individual bits of sensory information (e.g. sounds) and use them to construct a more complex perception (e.g. a message). 


Divided Attention

paying attention to more than one stimulus or task at the same time.


Selective Attention

focusing on one particular event or task.


Inattentional Blindness

  • inattentional blindness: a failure to notice clearly visible events or objects because attention is directed elsewhere.
  • accounts for many common phenomena; for example, people who witness automobile accidents or criminal behaviour may offer faulty or incomplete testimony  

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