Sensation & Perception

Basics Sensation & Perception rat eht saw tac ehT rat eht saw tac ehT Sensation - The stimulation of sensory receptors, & transmission of sensory information to the Central Nervous System. Sensation is the stimulation of sensory receptors, & transmission of sensory information to the Central Nervous System.(Central Nervous System being the spinal cord & brain) Sensory receptors located in places like the eyes & ears & elsewhere in the body. The stimulation of senses is automatic. All incoming sensation must be interpreted by the brain. As a result, often we see what we want to see and hear what we want to hear or vise versa. So sensation is not merely a physical event, it can be very psychological. HERE IS AN EXAMPLE of making something what is, isn’t. Read the following sentence from right to left, once , without stopping. Don’t read it again. If we would have read it the right way it wouldn’t have made sense to us. What started out as light energy, and going from there to the brain, has been given a meaning not contained in the actual source of the light energy. This is called. . . Click for yellow papered text and have a student read the two paragraphs – Tell then this is an example of perception over sensation. rat eht saw tac ehT rat eht saw tac ehT rat eht saw tac ehT

Basics Perception- The psychological process by which we interpret sensory info. Perception is the psychological process by which we interpret sensory information. Imagine your at one end of a football field. There are players close to you, while other player are at the other end of the field. Those players who are far away look small compare to those players whore are close to you. You still know that the players at the far end are really not tiny. ---How do you know? Whether you think it or not, it’s from experience. Experience that you gained as a child or even an infant. --Perception reflects learning expectations, and attitudes. Both are influenced by absolute threshold, difference threshold, signal detection theory & sensory adaptation. *Click for an audio story about a person who regained his sight – but had to learn perception

Basics Radio Story starts now Perception- The psychological process by which we interpret sensory info.

Basics Absolute threshold - The weakest amount of stimulus that can be sensed. Thresholds vary between individuals & other organisms. Absolute Threshold - The weakest amount of stimulus that can be sensed. Thresholds vary between individuals & other organisms. Hearing tested - You sit there waiting for beeps - then you hear one, raise your hand etc. While you were waiting, the tester was trying different beeps. You simply didn’t hear the beeps before. The point in which you heard the first beep is Absolute threshold. Absolute thresholds for humans have been determined for the senses of vision, hearing, smell and touch. dogs’ absolute threshold for certain sounds is different from that of a human. Examples: Taste - 1 teaspoon of sugar dissolved 2 gal. of water Sight - Picture a candle at night, you slowly back up What’s the the threshold? the point last seen (30 miles) For us to function in the world, we need absolute thresholds low enough to see, hear etc what is going on in the world, but not so low that we can see, hear, sell etc EVERYTHING. We would have sensory overload. Difference threshold - The minimum amount of difference that can be distinguished between two stimuli.

Basics • Difference threshold - The minimum amount of difference that can be distinguished between two stimuli. Difference Threshold - We also need to be able to detect small differences between stimuli - what makes stimulus different from another. The minimum amount of difference that can be detected between two stimuli is known as the difference threshold. Difference Threshold - The minimum amount of difference that can be distinguished between two stimuli. Click for each square. Each square moves to a little darker blue. The point(or square) at which we notice the squares getting darker is the difference threshold. Difference threshold - The minimum amount of difference that can be distinguished between two stimuli.

Basics • Signal detection theory - distinguishing sensory stimuli that takes into account the setting -physical state, mood, & expectations (parents hearing a faint newborn whimper over louder sounds) Signal Detection Theory - We focus on whatever we consider important. Talking to someone at a loud party, reading with all the other distractions, pain may seem to disappear when we forget about the pain, or concentrating on doing something else. Signal detection theorist seek to understand why people respond differently to the same stimuli, and why the same person’s reactions vary as circumstances change. Example: Exhausted parents can hear a faint newborn whimper, but fail to hear louder unimportant sounds.

Basics Click to show the size of the pupil get larger – our eyes adapt to changing stimuli – light stimuli Sensory adaptation - Process by which becoming more sensitive to weak stimuli, & less sensitive to unchanging stimuli. Examples: Bart’s smelly room. You walk into his room and it stinks, but after a few minutes, you barely notice the smell. Eyes adapting to light and dark. Living in the city and become unaware of the sounds of traffic. You jump into the pool, it’s freezing, but after a while, you get used to it. After constant exposure to stimulus, our nerve cells fire less frequently. Sensory receptors begin to fatigue. - Allows us to ignore unimportant sensory changes, and notice the important ones. • Sensory adaptation - Process by which becoming more sensitive to weak stimuli, & less sensitive to unchanging stimuli. (Bart’s smelly room)