PSYC304 Week 6 Notes

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PSCY304 | LESSON 6: SELECTIVE ADAPTATION Introduction We all live in an environment that offers stimuli to all of our senses, things we taste, smell, see, hear, and touch. In this lesson you will learn about how we focus on some stimuli more than others. Our senses can also change their sensitivity when exposed to extremes by becoming more or less sensitive. We can also fill-in-the-gaps to perceive an object as constant even though the stimuli change. This lesson focuses on the relationship between the information available to our senses and the way the brain processes this information to create a meaningful experience and even change how our receptors react to the stimuli. Topics to be covered include:  Sensory interaction  Selective attention  Sensory adaptation  Perceptual constancy and deception Sensory Interaction Are you aware of just one sense at a time? When you sit down to a delicious meal, you smell enticing aromas, you see the colorful food. You do not have to actively think “I want to smell this.” Our individual senses react to the chemicals released by the steak and to the rays of light reflecting off the food, but we react to how these are processed by the perceptual system and how our brain combines the sensory information with prior experience. If you love to eat grilled steak, your brain converts the chemicals in the air and the rays of light into joyful anticipation that the meal will taste delicious. This automatic processing of the information from multiple senses is called sensory interaction . When you look at the face of a loved one, you are not just sensing a pattern of colors and shapes. Your brain puts those colors and shapes together with prior knowledge and you identify the image as someone you love. Selective Attention Have you ever been at a social event or a restaurant where many people are talking and yet you can focus on your conversation with your friends? You are able to focus on hearing your friends and tune out the other conversations in the room. Selective attention allows us to focus on one stimulus and ignore others (Baron, 2003). However, we are not completely focused on your friends. If yet another friend came in to the restaurant and called your name, you would probably notice even if your back was to the door where they entered. Saylor Academy (2012) calls this the cocktail party phenomenon . While we are using selective attention to listen to our friends, your perceptual systems are still monitoring the environment. This is a valuable survival trait. If

a new sound meant a dangerous predator approaching, your perception system would alert you to the danger. That said, sometimes we do completely tune out the world. How many times have you gone up to a friend using their cell phone and started talking to them without getting a response? Distracted walking accidents are increasing at alarming rates. According to the National Safety Council (n.d.), the number of pedestrian fatalities rose by nine percent from 2015 to 2016 due in part to phone users selectively attending their phones. Sensory Adaptation Your body can change the sensitivity of your senses to persistent stimuli. Sensory adaptation , also called selective adaption , is a change in the response to one type of stimuli due to its persistence (Wallach, Eytan, Marom, & Meir, 2008). For instance, if a teacher uses yellow highlighting to emphasize important information in the notes posted on the course website, you would give those parts extra attention. However, if the teacher highlights an entire document in yellow, the yellow loses its ability to inspire an extra effort. Let’s look at some examples of sensory adaptation (Sahyouni, 2013). 1/5  Ears Have you ever walked into a room such as this nightclub where the music was very loud? After you have been there for a while, it does not seem as loud to you. When exposed to a high intensity sound, muscles of the inner ear contract making the ear less sensitive to sound. When you leave the room and go somewhere quieter, at first you might have trouble hearing your friends when they speak due to this decrease in sensitivity. Unless you did permanent damage to your hearing (which is entirely possible even from one exposure), the inner ear muscles relax making your ears more sensitive to sound. Then you can easily hear your friends talk again. 2/5  Nose You will learn more about your chemical senses in Lesson 7, but you already are familiar with being able to smell odors. If you use perfume, you smell it when you put it on, but later you cannot detect it. You probably know smokers who are not aware that they and their home smells like cigarette smoke. It is not that the odor goes away quickly. When molecules of perfume or cigarette smoke enter the nose, there are neurons that have odor receptors to detect the chemical stimulus. Then the neurons send an electrical signal to the brain that an odor was detected. After just a few breaths, the chemical sense system responds less to the odor. 3/5  Vestibular

The vestibular system is often called the sixth sense. Along with proprioception (perception of our body’s position) and kinesthesia (our perception of how our body moves through space), it allows us to know if we are standing up or lying down, even if blindfolded (Lumen, n.d.). According to Saylor Academy (2012), in an experiment subjects wore virtual reality goggles that skewed their view, showing their reversed so that everything was upside down or tilted at an angle. The subject’s brain adjusted and soon the subject perceived the view as right-side-up even though the goggles showed them the room upside down. Balance is a rather complex ability that comes from a combination of what we see, what we touch (proprioception), input from our muscles and joints, and the vestibular system. The vestibular system gives us a sense of motion, equilibrium and spatial orientation using input from the vestibular apparatus, part of the inner ear (Vestibular Disorders Association, n.d.). 4/5  Sight You are probably already familiar with visual sensory adaptation. If you wake up in a dark room and open your eyes, your pupils dilate so that more light can reach the retina. Not only that, but your rods and cones also become more sensitive to light. If you then go outside on a sunny day, your pupils contract to decrease the amount of light that reaches the retina. 5/5  Touch Have you ever jumped into a pool or lake and thought the water was far too cold? However, after just a moment you no longer feel so cold because your brain stops paying attention to the temperature of the water. Selective Adaptation Why does our body change its sensitivity to a continued stimulus? Scientists believe the ability to ignore unchanging stimuli allows our brains to focus on new important changes in our environment that might require our attention. Sensory adaptation does not happen in response to every stimulus. Consider this man walking down a path. If he stops and stares at a tree, the image does not fade away due to sensory adaptation. Why not? Do you remember from Lesson 4 how our eyes are constantly moving to look at different parts of an image in tiny movements called saccades? According to Saylor Academy (2012), these eye movements result in the light rays coming to our retina are ever-changing and our brain considers these changing images to be new information. You can take this selective attention test by watching the video: Selective Attention Test . Perceptual Constancy One of the important functions of our perceptual system is to recognize an experience even when the stimuli are different. You can recognize your coffee cup if you see it from above, from the

side, from the bottom, or from other angles. “The ability to perceive a stimulus as constant despite changes in sensation is known as perceptual constancy (Saylor Academy, 2012, ch. 4.5). You also have perceptual constancy with the relative difference of colors. If you have black coffee in a white cup in your kitchen and then walk into a dimly lit room, both the coffee and the cup will seem dimmer, but the cup will continue to be perceived as brighter than the coffee. However, our perceptions can be deceived. How and why they are deceived gives us insight into how our perceptual system interprets information provided by our senses. Perceptual Deception 1/7  Which is brighter, square A or square B? Watch this video to see if were correct at: Lightness Constancy Test . If the video does not convince you, cover up most of the image with your hands so that you only see squares A and B so as to compare them. In general with the images in this slideshow, the height/width ratio of your computer screen may distort some of the illusions and make them ineffective. 2/7

 When you look at the top three lines, which shaft is the longest? It turns out that your brain is deceived. When you look at the bottom three lines, it shows that all the shafts have the same length. This is known as the Müller-Lyer illusion (Saylor Academy, 2013). This deception is thought to be related to our brains perceiving the arrows as three-dimensional views of a box. The upper arrow is perceived to be an outside edge of the box. The middle arrow is perceived to be an inside edge of the box. The brain assumes the outside edge to be closer than the inside edge. Our experience with how an object looks smaller when it is farther away leads us to believe that the inside edge (the middle arrow) is the longer arrow. 3/7 

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