INTRODUCTION TO PSYCHOLOGY

Perception

Perception

“Perception refers to the interpretation of what we take in through our senses. In terms of optical illusions this means our eyes.”

Simply put, our brains are tricked into seeing something which may or may not be real.

According to Alan Saks and Gary Johns, there are three components to perception.[9]

•The Perceiver, the person who becomes aware about something and comes to a final understanding. There are 3 factors that can influence his or her perceptions: experience, motivational state and finally emotional state. In different motivational or emotional states, the perceiver will react to or perceive something in different ways. Also in different situations he or she might employ a "perceptual defence" where they tend to "see what they want to see".

•The Target. This is the person who is being perceived or judged. "Ambiguity or lack of information about a target leads to a greater need for interpretation and addition."

•The Situation also greatly influences perceptions because different situations may call for additional information about the target.

Factors that Influence

Perception The Object of Perception:

some things in our environment tend to attract attention

Backgrounds and Surroundingsour surroundings at the moment of perception will affect our perceptions

The Perceiverwe each bring unique experiences and personal points of view to each situation

Weber’s Law• Computes the Just

Noticeable Difference.

• The change needed is proportional to the original intensity of the stimulus.

• The more intense the stimulus the more change is needed to notice the difference.

Perceptual Ideas

Signal Detection theory• Absolute thresholds

are not really absolute.

• Things like motivation or physical state can effect what we sense.

• False Positives• False Negatives

Top-Down Processing• We perceive by filling

the gaps in what we sense.

• I _ant ch_co_ate ic_ cr_am.

• Based on our experiences and schemas.

• If you see many old men in glasses, you are more apt to process a picture of an old man (even when you may be in error).

Bottom-Up Processing

• Also called feature analysis.

• We use the features on the object itself to build a perception.

• Takes longer that top-down but is more accurate.

Figure Ground Relationship

Our first perceptual decision is what is the image is the figure and what is the background.

Gestalt Psychology• Gestalt psychologists focused on how we GROUP objects together.

• We innately look at things in groups and not as isolated elements.

• Proximity (group objects that are close together as being part of same group)

• Similarity (objects similar in appearance are perceived as being part of same group)

• Continuity (objects that form a continuous form are perceived as same group)

• Closure (like top-down processing…we fill gaps in if we can recognize it)

In order to make sense of our world our brains try to see patterns or shapes that are recognizable. This principle is called

“grouping”.

http://www.keele.ac.uk/depts/aa/widening/uniworld/webclub/rs/optical.htm

The mind forms shapes that don't exist

Constancy

• Objects change in our eyes constantly as we or they move….but we are able to maintain content perception

• Shape Constancy• Size Constancy• Brightness

Constancy

Perceived Motion

• Stroboscopic effect (flip book effect)

• Phi phenomenon • Autokinetic Effect

(if people stare at a white spotlight in a dark room, it appears to move.)

Parallel Lines? 

Embedded Images

2 dimensional chalk drawing

• When you look at the top figure, your visual system will organize the elements into a box. The box will reverse, as in the Necker Cube illusion. The elements in the bottom figure have terminations and do not readily group into a box figure that shows reversals

                             

The shades of red are identical

The difference in the appearance is related to the influence of the

backgrounds.

Compare the shades of red…

When you look at the figure you will see either a vase or two faces. If you continue to look, the figure will appear to shift to the alternative organization

Old Woman or Young Girl?

Any movement you see is an illusion!

Straight Lines?

http://www.at-bristol.org.uk/Optical/Hermann_main.htm

                                                                                                                                      

Hermann Grid

Impossible Triangleand Trident

What is wrong with this sign?