Sensations come first then perception.
Sensations vs. perception
- Sensation: stimulus detection.
- From environment stimuli -> nerve impulses.
- Perception: making of what the senses tell us.
- Giving meaning to the sensory information.
- Sensory receptors (receive input) -> transduction -> analysis of
-> reconstruction into neural representation -> comparison with
others -> recognition and interpretation.
- Absolute threshold: lowest level of detection 50% of the time.
- Interspecies variation.
- Lower absolute threshold (more sensitive); higher absolute threshold
- Lots of individual variation in detection
Different decision criterion.
Signal detection theory.
To ignore, or not to ignore
- Difference threshold.
Just noticeable difference.
Proportional between size of the stimuli.
- Sensory adaptation: picking information relevant to remember.
Most of the time good.
- Hue changes
- Saturation changes
- Brightness changes
How we see
- Light reflects and object, waves come into your eye, through Pupil, to
- Retina: contains the rods and cones. The Fovea contains only cones.
Blind spot where no information is received.
- Rods and cones: neurones that change the waves.
- Back of eye, photoreceptor, bipolar ganglion, light waves.
- How many? Rods 120-125 million; Cones 7-8 million Dark adaptations
- Photo receptors
- Cones can renew their intensity quicker than rods.
- Selectively fire
- Respond to specific characteristics of visual stimuli
- Discovered by Hubel & Wiesel.
Auditory System: What we hear
- Loudness: Intensity of wave’s physical pressure.
- Measured in decibels (dB)
- Pitch: frequence of the sound wave.
- How rapidly the air vibrates.
- Number of sound waves (cycles) per second
- Measured in Hertz (Hz)
How we hear
Ear drum -> oval window -> cochlea -> basilar and tectorial
membrane -> hair cells in organ of corti -> neurotransmitters to
- Conduction deafness – mechanical issues
- Nerve deafness – receptor or auditory nerve issues
- Other causes?
What we taste
Tongue has receptors for: taste, touch temperature.
- 500 – 10 000 buds.
- Genetic diffs in taste.
- Also culture and learning.
- Takes place in the pores of your tongue.
- Sweet and fatty – high calorie (good)
- Bitter – poisonous (bad)
- Genetic differences in taste responses. - Supertasters (25% of Americans)
Broccoli, caffeine and saccharin bitter, high sensitivity to sweet
salty and spicy.
- Have more taste buds.
- Olfactory receptors are like neurotransmitter binding sites on
- Send messages to the olfactory bulb (forebrain)
- Hot new research area – pheromones!