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INTRODUCTION TO PSYCHOLOGY Sensation & Perception
Sensation & Perception •We understand the world through our senses, our “windows” on the world•Our reality, in fact, is dependent upon two basic processes: –Sensation:Gathering information –Perception: Interpreting information
An Example of Misperception
Sensation & Perception •How the Physical World Relates to the Psychological World •How We See and How We Hear •How We Make Sense of What We See
How the Physical Relates to the Psychological World The Detection Question The Difference Question The Scaling Question
The Questions 1. The detectionquestion is concerned with the limits on our ability to detect very faint signals –How intense does a light have to be for us to see it? –How intense does a sound have to be for us to hear it?
The Questions 2. The differencequestion is concerned with limits on our detection abilities, but in this case with our ability to detect very small differences between stimuli –What is the smallest difference in brightness between two lights that we can see? –What is the smallest difference in loudness between two sounds that we can hear?
The Questions 3. The scalingquestion is concerned with how we perceive the magnitudes (intensities) of clearly detectable stimuli –What is the relationship between the actual physical intensities of stimuli and our psychological perceptions of these intensities?
The Detection Question •Absolute thresholdis the minimum amount of energy in a sensory stimulus that is detected 50% of the time •Subliminal stimulusis one that is detected only up to 49% of the time –Any effects of subliminal persuasion are short-lived with no long-term consequences on our behavior
Theoretical and Observed Absolute Thresholds
Four Possible Outcomes in a Signal Detection Study Present Absent “Yes”Hit False Alarm “No”Miss Correct Rejection Observer’s Response Signal
The Difference Question •A difference thresholdis the minimum difference between two stimuli that is detected 50% of the time •Weber’s Law says that for each type of sensory judgment, the difference threshold is a constant fraction of the standard stimulus value used to measure it
The Scaling Question •Sensory adaptationis the disappearance to repetitive or unchanging stimuli –This sensory adaptation has survival value, as it is more important to detect new stimuli (which may signal danger) than constant stimuli
How We See and Hear How the Eye Works How We See Color How the Ear Works How We Distinguish Pitch
Physical Characteristics of Light and Sound Waves •Wavelengthrefers to the distance in one cycle of a wave, from one crest to the next –With respect to vision, humans can