PSYC 1000 Lecture Notes - Lecture 9: Detection Theory, Electric Light, Absolute Threshold
14 Dec 2016
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Sensation, perception and consciousness (part 1)
Introduction to Psychology PSYC*1000-01 Lecture 09
October 6th 2016
Module(s) 4.1 & 4.2
1. What’s the differene etween sensation and pereption?
• Sensation: The detection of physical energy by our sensory organs, which is then relayed to the brain -
Light waves (eyes), sound waves (ears), pressure (skin), chemicals (tongue) and airborne chemicals
(nose)
• Perception: The brain makes sense out of the raw sensory input from the sensory organs
How do we make sense of the world? What are you seeing?
• Top-down processing: using models, ideas, and expectations to interpret sensory information (Is that
something you have seen before?)
• Bottom-up processing: taking sensory information and then assembling and integrating it (what are
you seeing?)
From sensory organs to the brain
• Reception: the stimulation of sensory receptor cells by energy (sound, light, heat, etc)
• Transduction: transforming this cell stimulation into neural impulses
• Transmission: delivering this neural information to the brain to be processed
Can you tell something is going on?
• Light bulb is slowly turned on the absolute threshold if the point of energy that we are able to see the
light bulb is on
• Absolute threshold: the minimum level of stimulus intensity needed to detect a stimulus half the time
• Subliminal: below our threshold for being able to consciously detect a stimulus, but still registered by
the sensory organ
• Difference threshold refers to the minimum difference (in colour, temperature, etc) for a person to be
able to detect the difference half the time
What’s Weer’s law?
• For two stimuli to be perceived as different they must differ by a constant minimum percentage and
not a constant amount
• e.g., 1/100th of the weight, not 2 ounces or grammes
Is detection is only a question of receptors?
• Signal detection theory aims to explain whether or not we detect a stimulus, particularly with
background noise
• It suggests that detection depends on psychological factors such as alertness, expectations, motivation,
as well as sensory experience
• Thus detection is impacted by both sensation (bottom up) and perception (top-down)
3. How do we organize objects?
Gestalt principles
• Gestalt psychology tries to understand the laws of our ability to acquire and maintain meaningful
perceptions in an apparently chaotic world.
• Law of Pragnanz: We perceive objects in our environment in their simplest form
• 1. Proximity: Objects physically close to each other tend to be perceived as unified wholes
• 2. Similarity: Objects similar to each other tend to be perceived as unified wholes
• 3. Continuity: We still perceive objects as wholes even if other block part of them
• 4. Closure: Parts are combined to create wholes
• 5. Symmetry: We perceive objects that are symmetrically arranged as wholes
• 6. Figure-ground: Figure is the centre of our attention, we ignore the background.
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Sensation: the detection of physical energy by our sensory organs, which is then relayed to the brain - Light waves (eyes), sound waves (ears), pressure (skin), chemicals (tongue) and airborne chemicals (nose) Perception: the brain makes sense out of the raw sensory input from the sensory organs. Top-down processing: using models, ideas, and expectations to interpret sensory information (is that something you have seen before?: bottom-up processing: taking sensory information and then assembling and integrating it (what are you seeing?) From sensory organs to the brain: reception: the stimulation of sensory receptor cells by energy (sound, light, heat, etc) Transduction: transforming this cell stimulation into neural impulses. Transmission: delivering this neural information to the brain to be processed. For two stimuli to be perceived as different they must differ by a constant minimum percentage and not a constant amount e. g. , 1/100th of the weight, not 2 ounces or grammes.
