Sensation & Perception - Chapter 5 Flashcards
What is Sensation and Perception?
SENSATION
-Stimulation of the sense organs
PERCEPTION
-The selection, organization, and interpretation of sensory input
What is Psychophysics?
-The study of how physical stimuli are translated into psychological experiences
(Gustav Fechner)
- Sensation begins with a STIMULUS (any detectable input from the environment
- In order for something to be detected, it must reach our ABSOLUTE THRESHOLD (Minimum amount of stimulation that an organism can detect.) Detected right 50% of the time
The JND and Weber’s Law
The JND (Just Noticable Difference) is the smallest difference in the amount of stimulation that a specific sense can detect (difference threshold)
WEBERS LAW
The size of the JND is a constant proportion of the size of the initial stimulus
WEBERS FRACTION
The constant proportion mentioned above. Weber fractions differ depending on sensory input
(Fraction to detect differences in weight is 1/50)
Psychophysical Scaling
Everything is relative in perception - we can’t measure things using absolute scales
This is because of FECHNERS LAW, which states that subjective sensation is proportional to the logarithm of the stimulus intensity
(Constant increments in stimulus intensity produce smaller and smaller increases in the perceived magnitude of sensation
Signal Detection
The signal-detection theory proposes that the detection of stimuli involves decision processes as well as sensory processes, which are both influenced by a variety of factor besides stimulus intensity
What is Subliminal Perception?
the registration of sensory input without conscious awareness
ex. lipton iced tea experiment
Sensory Adaptation
A gradual decline in sensitivity due to prolonged stimulation. (Wearing a watch and clothes, you dont feel it after a while)
Adaptive process - keeps us attuned to the changes in our environment rather than the constants
The Stimulus: Sound
- Sound waves are vibrations of molecules that ravel through a medium, such as air
- Move at a fraction of the speed of light
- Characterized by their AMPLITUDE, their WAVELENGTH, and PURITY
Human Hearing Capacities
Wavelengths of sound are described in terms of their FREQUENCY, which is measured in cycles per second or HERTZ (HZ) (Pitch depends mainly on frequency)
- Humans can hear sounds ranging from a low of 20-Hz to a high of about 20,000-Hz
- Amplitude of a sound wave is measured in DECIBELS (dB). In general, the greater the amplitude of a sound wave, the louder it will be perceived.
- A general rule is that perceived loudness doubles about every 6-10dB.
- Even brief exposure to sounds > 120 dB can be painful and cause damage to your auditory system.
- We have the lowest absolute threshold for sound amplitude when sounds are in the 2000-Hz range
Sensory Processing in the Ear
THREE MAJOR PARTS OF THE EAR
- Outer ear
- Middle ear
- Inner ear
-Sound is conducted differently in each section
Theories of Hearing
Two main theories of pitch perception
PLACE THEORY
-Holds that perception of pitch corresponds to the vibration of different portions, or places, along the basilar membrane.
FREQUENCY THEORY
-Holds that perception of pitch corresponds to the rate, or frequency, at which the entire basilar membrane vibrates
- While both theories have been proven to have some flaws, they essentially are BOTH correct
- Current thinking is that pitch perception depends both on the place and frequency coding of vibrations
- Low freq tones appear to be translated into pitch through frequency coding
- High freq pure tones appear to rely on place coding
- Complex tones depending on complex combinations of place and frequency coding
Auditory Localization
- Locating the source of a sound in space
- Ears being set apart in humans help auditory localization
- Two cues are particularly important: SOUND INTENSITY (loudness), and the timing of sounds arriving at each ear
Deafness
- 1 in 1000 people are deaf
- Several causes of deafness, some genetic others derive from disease, injury, or exposure to loud noise
TWO MAJOR TYPES OF DEAFNESS ARE
- CONDUCTIVE DEAFNESS
- NERVE DEAFNESS
- noise induced hearing loss is a big problem in our society
- Some age-related hearing loss is normal
Music and Its Effects
Sacks (2007)
-Showed that the brains of musicians are identifiable in that they have larger MOTOR, AUDITORY, and VISUOSPATIAL areas of the CEREBELLUM than the brains of non-musicians
- Some links between music training and some language abilities
- Been suggested that music can enhance our spatial abilities (MOZART EFFECT)
The Gustatory System
Sensory system for taste
- Physical stimuli for the sense of taste are chemical substances that are soluble
- Gustatory receptors are clusters of taste cells found in the taste buds that line the tranches around tiny bumps on the tongue
FOUR PRIMARY TASTES
- Sweet, 2. Sour, 3. Bitter, 4. Salty
SOMETIMES A FIFTH 5. Umami
Perception of Taste
Perceptions of taste quality appear to depend on the complex patterns of neural activity initiated by taste receptors
- Some basic taste preferences appear to be innate and automatically regulated by physiological mechanisms
- But, overall, taste preferences are largely learned
- People cary in their sensitivity to certain tastes
NONTASTERS vs SUPERTASTERS vs MEDIUM TASTERS
(Variations in sensitivity mean that when two people taste the same food, they will not have the same sensory experience)
-Taste sensitivity influences people’s eating habits
(Supertasters generally have better health habits than non-tasters
-Women more likely to be supertasters than men
Perception of Flavour
Perception of taste is different than taste
-Flavour is a combination of taste, smell, and the tactile sensation of food in one’s mouth (odours very imp to the perception of flavour)
The Olfactory System
Smell
- Humans usually characterized as being relatively insensitive to smell
- Physical stimuli are chemical substances - volatile ones that are carried in the air
- Receptors for smell are OLFACTORY CILIA, hair-like structures located in the upper portion of the nasal passages
Buck & Axel (1991) clarified the mechanisms involved in odour recognition
-Found a gene set consisting of 1000 different genes that affec tthe operation of our olfactory receptor cells
- Odours cant be classified as neatly as tastes
- Humans have about 350 different types of olfactory receptors
- Sense of smell shows sensory adaption (Perceived strength of an odour usually fades to less than half its original strength within four minutes)
- Humans can distinguish among about 10,000 different odours
- Females tend to be somewhat more accurate than males on odour recognition tasks
Chemical Communication
PHEROMONES: chemical messages, typicallly imperceptible, that can be sent by one organism and received by another member of the same species.
-Humans give off, and are susceptible to, other humans’ pheromones
Touch
- Physical stimuli for touch are mechanical, thermal,and chemical energy that impinge on the skin
- These stimuli can produce perceptions of tactile stimulation (the pressure of touch against the skin), warmth, cold, and pain
- Human skin is saturated with at least 6-types of sensory receptors
Feeling Pressure
- Tactile localization very precise (for ex, a mosquito biting you)
- Sensory adaptation occurs with our perception of pressure, just like our other senses
- Nerve cells that carry information about tactile stimulation are routed through the spinal cord to the brainstem
- Tactile pathway then projects through the thalamus onto the somatosensory cortex