sensation thresholds and the eye. the five senses??
TRANSCRIPT
Sensation
Thresholds and the Eye
The Five Senses??
Basic Principles
Sensation – process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment
Perception – process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events
A Demonstration of Perception
A Demonstration of Perception
Types of Processing
Bottom-up Processing – analysis that begins with the sensory receptors and works up to the brain’s integration of sensory information
Top-down Processing – information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations.
Top-Down vs. Bottom-Up
Thresholds
Psychophysics – the study of relationships between the physical characteristics of stimuli and our psychological experience of them.
Absolute Threshold – the minimum stimulation needed to detect a particular stimulus 50 percent of the time (school test for hearing)
Thresholds (cont’d)
Signal Detection Theory – A theory predicting how and when we detect the presence of a faint stimulus (the signal) amid background stimulation (noise). Assumes there is no single absolute threshold and that detection depends partly on a person’s experience, expectations, motivation, and level of fatigue.
Examples of Signal-Detection Theory New mothers and newborns Wartime vs. peacetime Life or death consequences (radar
detection, ICU nurses, air traffic controllers, airport )
Signal Detection Theory Correctly identifies stimulus as absent
Response
Yes
Response
No
Signal
Present
Hit Miss
Signal
Absent
False Alarm Correct Negative
Thresholds (cont’d)
Subliminal – any signal below absolute threshold for conscious awareness (by definition you will detect it some percent of the time)
Priming – the activation, often unconsciously, of certain associations, thus predisposing one’s perception, memory, or response.
Thresholds (cont’d)
Difference Threshold – the minimum difference a person can detect between two stimuli (50% of the time). This is experienced as a “just noticeable difference” or JND.
Thresholds (cont’d)
Let’s do a demonstration. I need a volunteer! Weber’s Law – to perceive a difference,
two stimuli must differ by a constant minimum percentage (rather than a constant amount).
Sensory Adaptation Sensory Adaptation – diminished
sensitivity as a consequence of constant stimulation. (cold swimming pools and hot showers….)
Our perceptions are organized by the meanings our minds impose.
Sensory adaptation reduces sensitivity, but it enables us to focus on informative changes in our environment without being distracted by constant stimulation.
The Eye
Eye Movements
Eye Movements
Eye Movements
Eye Movements
Eye Movements