Sensation and Perception Year 11 Psychology CCGS 2015.

Sensation v Perception example 1 Look at this image. What do you SEE: What do you PERCEIVE: Sensation = Detecting stimuli input and sending it to the brain Perception = Transferring sensory information into meaning Everyone's sensation is the same, but perception can be different

(your brain thinks that it is in the shadow, so it interprets it as being lighter than it really is, your brain recognizes the checkerboard pattern and knows that it goes dark-light-dark, so it assumes that square B should be lighter than it really is).

Sensation – thresholds For a stimulus to be sensed it must have sufficient energy to be detected. Absolute threshold Smallest amount of energy that can be detected half of the time. Only half of the time because the minimum energy strength varies between people and time. Difference Threshold. Smallest possible difference between two stimuli that can be detected half of the time.

Webers Law. Ernst Weber noted that for people to really perceive a difference, the stimuli must differ by a constant "proportion" not a constant "amount". POPCORN VIDEO.

Perception or sensation? The body’s initial detection and conversion of stimulus energy is referred to as sensation The active process of organising and interpreting sensory stimuli to be a mental representation of the world is perception

BOTTOM UP THEORIES Emphasis the richness of the information entering the eye and the way that perception can occur from using all the information available. Gibson believes perception occurs directly from sensation, feature detection theories examine the processes involved with assembling perception from sensations.

Top Down Theories Stress the factors in the construction of reality that go beyond the information received from the senses. Gregorys theory and perceptual set theory regard perception as a very active process, whereby the individuals past knowledge, expectations and stereotypes seek out sensory data to “complete the picture”

Visual Perception – Illusions & Distortions Visual illusion experienced when our perception of a stimulus is inconsistent with the reality of the object Past experiences leads you to build up expectations about how you will perceive/respond to a certain stimuli = perceptual expectancy

Muller-Lyer Illusion Consists of 2 lines of equal length, each with different shaped ends One line has arrowheads at each end of the line Other line has feathertails at end of each line When we look at it We think that the feathertail line looks longer than arrowhead line Reality = both lines are exactly the same!

Muller-Lyer Illusion Explanation Eye movement theories suggest illusion occurs because the eyes look in the wrong place Eyes drawn past the line with feathertails to make the line look longer Line with arrowheads – eyes are drawn within the lines  line smaller

Ames Room Illusion Constructed to look like a rectangular room  dimensions aren’t normal When viewer looks through a peephole with one eyes, they see a room consistent with their expectations of a normal rectangular room Viewer observes a person as either shrinking or growing as they walk from one of side of room to other

Ames Room Illusion Room is not actually rectangular in shape  trapezium! Back wall is positioned on an oblique angle 2 back corners cast the same-sized image on the retina which is perceived to be the same distance away Distorted windows and flooring