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Review key ideas from Chapters 5 & 6. Sensation & Perception. Sensory processing starts with transduction… t. Transduction = transformation of physical energy into a neural code (changes in membrane potential, generation of action potentials)
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Review key ideas from Chapters 5 & 6 Sensation & Perception
Sensory processing starts with transduction…t Transduction = transformation of physical energy into a neural code (changes in membrane potential, generation of action potentials) Transduction is the responsibility of specialized neurons called “receptors” A receptor is specialized to respond best to one particular type of stimulus energy
Absolute Threshold Smallest detectable level of a stimulus. For example, in an experiment on sound detention, researchers may present a sound with varying levels of volume. The smallest level that a participant is able to hear is the absolute threshold. Think of an electric burner on a stove. Imagine turning that burner on and then placing your hand directly on it. At first you won't feel much heat because is takes time for the burner to heat up. But at some point it will get hot enough for you to detect…meaning, there is some temperature that is just hot enough for you to notice it.
Difference Threshold The minimum difference in stimulation that a person can detect 50 percent of the time. We experience the difference threshold as a just noticeable difference. For example, let's say I asked you to put your hand out and in it I placed a pile of sand. Then, I add tiny amounts of sand to your hand and ask you to tell me when you notice any change in the overall weight. As soon as you can detect any change in the weight, that difference between the weight of the sand before I added that last bit of sand and the amount of sand after I added it, is the difference threshold.
Signal Detection Detection of stimulus depends on both the intensity of it and the physical and psychological state of the individual. For example, when you walk to your car that is parked in an empty parking lot late at night all by yourself, you might be much more aware of noises because the situation is somewhat threatening (you are primed and listening carefully to hear anything and everything). In this case, you may hear some slight noises that you might otherwise not hear if you were in a different situation that was not as threatening. Thus, your ability to detect signals or noises has been affected by these factors.
Sensory Adaptation • When we acclimate or become accustomed to something. It’s reduced sensitivity to stimulation that results from repeated presentations of that stimulation. For example, if you rent a car that was previously used by a smoker, you might at first be overwhelmed by the smell of smoke, but after driving it for 30 minutes or so, you may not notice the smell.
Ernst Weber In the 1820s or 1830s Weber began studying the tactile senses, the two-point threshold and weight perception. He also found that the “just noticeable difference” of change in magnitude of a stimulus is proportional to the magnitude of the stimulus , rather than being an absolute value. Fechner explored this relation further in the 1850s and, integrating Weber's logarithmic relation between physical and psychological (or perceived) magnitudes. This new law became known as Fechner's Law, or the “Weber-Fechner Law” and formed the basis of Fechner's new science--psychophysics.
Investigative poioneers A German psychologist with a background in physics, who invented psychophysics. Fechner's goal was to develop scientific techniques that would measure the relationship between the mental activity of the mind and the physical behavior of the body, establishing experimental psychology as a field—especially exploration of mind/body relationships
David Hubel Professor of Neurobiology at Harvard University. His research led to the discovery of the method by which visual information is processed by the brain, and greater understanding of how that processing system develops in very early childhood. His findings have resulted in the realization that a condition called strabismus (also known as cross-eye) is best treated before the age of two, before the visual system is no longer able to adapt to the corrected eye position.
Torsten Wiesel greatly expanded the scientific knowledge of sensory processing– his studies showed how the visual system builds an image from simple stimuli into more complex representations. This Swedish neurophysiologist was awarded the Nobel prize in 1981 (together with David Hubel) for their discoveries concerning information processing in the visual system.
