SENSATION AND PERCEPTION We make sense of our world by both taking in (sensation) and processing (perception) sensory input. Sensation: the process by which our sensory receptors and nervous system receive stimulus energies from the environment Perception: the process of organizing and interpreting sensory information, allowing us to recognize objects and events

SENSATION AND PERCEPTION People who suffer from visual agnosia – an inability to recognize objects through sight – have functioning visual sensation, but the process of perception is impaired

THRESHOLDS Psychophysics: the study of the relationship between physical stimuli and our psychological experience of them → this process involves: 1. receiving sensory stimulation 2. transforming it into neural impulses 3. delivering neural info. to the brain

THRESHOLDS What is the minimum amount of stimulus necessary for detection? Where is the threshold? → the absolute threshold is the minimum stimulation needed to detect a particular stimulus 50% of the time

THRESHOLDS → Difference threshold/just noticeable difference (JND): the minimum difference between two stimuli required for detection 50% of the time * Weber’s Law states that for two stimuli to be perceived as different, they must differ by a constant minimum %, not amount (example: two weights must differ by 2%, lights by 8%, tones by 0.3%)

SIGNAL DETECTION THEORY Signal Detection Theory assumes there is no single absolute threshold, that detection of a stimulus depends on a person’s experience, expectations, motivation, and alertness → SDT considers the level of ‘noise’ – irrelevant stimuli – in the system: more noise = more difficulty in picking up weak signal

SIGNAL DETECTION THEORY → SDT measures ‘detectability’: the probability, based on multiple factors, that a stimulus will be detected 1. Hit: present and detected 2. Miss: present and not detected 3. False Alarm: detected, but not present 4. Correct Rejections: not detected, not present

SUBLIMINAL PERCEPTION Subliminal: below one’s absolute threshold for conscious awareness → can we unconsciously sense subliminal stimuli? YES! → can these stimuli affect our behavior? Not much, the effects are subtle and fleeting * priming: the unconscious activation of associations predisposing one’s perception/memory

SENSORY ADAPTATION Why do we initially notice a new stimulus and gradually become less and less aware of it? → sensory adaptation refers to diminished sensitivity as a consequence of constant stimulation, allowing us to focus on informative changes in our environment → same but different: habituation refers to a decreasing response to a stimulus with repeated exposure to it