How do sensations become perceptions

When people have not been in a room for a while, the lights go out. However, once someone walks into the room, the lights go back on.

For this to happen, the sensor has a threshold for motion that must be crossed before it turns the lights back on. So, dust floating in the room should not make the lights go on, but a person walking in should. For example, when you pick up a 5 lb weight, and then a 10 pound weight, you can feel a big difference between the two. However, when you pick up lbs, and then lbs, it is much more difficult to feel the difference.

Additionally, both sensory and decision making processes are influenced by many more factors than just intensity. Involves higher mental processes. You set criterion based on expectations and consequences of inaccuracy.

For example - at a party, you order a pizza But when you first order the pizza, you know it won't be there in 2 minutes, so you don't really pay attention for the doorbell. As the time for the pizza to arrive approaches, however, your criterion changes A the visual system works on sensing and perceiving light waves.

Light waves vary in their length and amplitude:. The functioning of the retina is similar to the spinal cord - both act as a highway for information to travel on.

Dilates and Constricts. This is why it is more difficult to see colors in low light. The cones are mostly in and around the fovea but decrease as you go out. C Seeing In Color - we can see many colors, but only have 3 types of cones that receive information about color.

We have cones that pick up light waves for red, green, and blue. The ratio of each each color to the other then determines the exact color that we see. Each receptor can only work with one color at a time so the opponent color in the pair is blocked out. Please look for the one in your book and give it a try. People just assume that because we see colors, that they actually exist in the world. In other words, that when they see the color red, that red is a real, physical, tangible, "thing".

In addition, our perceptions are affected by a number of factors, including beliefs, values, prejudices, culture, and life experiences. Both light and sound can be described in terms of wave forms with physical characteristics like amplitude, wavelength, and timbre. Wavelength and frequency are inversely related so that longer waves have lower frequencies, and shorter waves have higher frequencies.

Light waves cross the cornea and enter the eye at the pupil. The fovea contains cones that possess high levels of visual acuity and operate best in bright light conditions. Rods are located throughout the retina and operate best under dim light conditions.

Visual information leaves the eye via the optic nerve. Information from each visual field is sent to the opposite side of the brain at the optic chiasm.

Another example of modern research on unconscious processes is research on priming. Priming generally relies on supraliminal stimuli, which means that the messaging may occur out of awareness, but it is still perceived, unlike subliminal messaging. Supraliminal messages are be perceived by the conscious mind.

For example, in one study, shoppers listened to either French or German music the supraliminal messaging while buying wine, and sales originating from either country were higher when music from that same country was played overhead. These lists contained words commonly associated with the elderly e.

The remaining participants received a language task in which the critical words were replaced by words not related to the elderly. After participants had finished they were told the experiment was over, but they were secretly monitored to see how long they took to walk to the nearest elevator.

The primed participants took significantly longer. That is, after being exposed to words typically associated with being old, they behaved in line with the stereotype of old people: being slow.

Such priming effects have been shown in other domains as well. For example, Dijksterhuis and van Knippenberg demonstrated that priming can improve intellectual performance. They asked their participants to answer 42 general knowledge questions taken from the game Trivial Pursuit. Both of these studies have had difficult times replicating, so it is worth noting that the conclusions reached may not be as powerful as originally reported.

Absolute thresholds are generally measured under incredibly controlled conditions in situations that are optimal for sensitivity. Sometimes, we are more interested in how much difference in stimuli is required to detect a difference between them. This is known as the just noticeable difference jnd or difference threshold. Unlike the absolute threshold, the difference threshold changes depending on the stimulus intensity. As an example, imagine yourself in a very dark movie theater.

If an audience member were to receive a text message on her cell phone which caused her screen to light up, chances are that many people would notice the change in illumination in the theater.

However, if the same thing happened in a brightly lit arena during a basketball game, very few people would notice. The cell phone brightness does not change, but its ability to be detected as a change in illumination varies dramatically between the two contexts.

It is the idea that bigger stimuli require larger differences to be noticed. For example, it will be much harder for your friend to reliably tell the difference between 10 and 11 lbs. Think about a time when you failed to notice something around you because your attention was focused elsewhere.

While our sensory receptors are constantly collecting information from the environment, it is ultimately how we interpret that information that affects how we interact with the world. Perception refers to the way sensory information is organized, interpreted, and consciously experienced. Perception involves both bottom-up and top-down processing.

Bottom-up processing refers to the fact that perceptions are built from sensory input. On the other hand, how we interpret those sensations is influenced by our available knowledge, our experiences, and our thoughts. This is called top-down processing. Look at the shape in Figure 3 below.

Seen alone, your brain engages in bottom-up processing. Sensations allow us to see a red burner, but perceptions entail the understanding and representation of the characteristic hot.

Also, a sensation would be hearing a loud, shrill tone, whereas a perception would be the classification and understanding of that sounds as a fire alarm. Throughout this chapter sensations and perceptions will be discussed as separate events, whereas in reality, sensations and perceptions can be more accurately thought of as occurring along a continued where boundaries are more fluent between where a sensation ends and a perception begins.

You have probably known since elementary school that we have five senses: vision, hearing audition , smell olfaction , taste gustation , and touch somatosensation. It turns out that this notion of five senses is extremely oversimplified.

We also have sensory systems that provide information about balance the vestibular sense , body position and movement proprioception and kinesthesia , pain nociception , and temperature thermoception , and each one of these sensory systems has different receptors tuned to transduce different stimuli.

The vision system absorbs light using rod and cone receptors located at the back of the eyes, sound is translated via tiny hair like receptors known as cilia inside the inner ear, smell and taste work together most of the time to absorb chemicals found in airborne particles and food via chemically sensitive cilia in the nasal cavity and clusters of chemical receptors on the tongue.

Touch is particularly interesting because it is made up of responses from many different types of receptors found within the skin that send signals to the central nervous system in response to temperature, pressure, vibration, and disruption of the skin such as stretching and tearing. The sensitivity of a given sensory system to the relevant stimuli can be expressed as an absolute threshold. Another way to think about this is by asking how dim can a light be or how soft can a sound be and still be detected half of the time.

The sensitivity of our sensory receptors can be quite amazing. Under quiet conditions, the hair cells the receptor cells of the inner ear can detect the tick of a clock 20 feet away Galanter, Additionally, one teaspoon of sugar can be tasted within two gallons of water, and the human olfactory system can detect the scent of one drop of perfume throughout a six room apartment. It is also possible for us to get messages that are presented below the threshold for conscious awareness—these are called subliminal messages.

A stimulus reaches a physiological threshold when it is strong enough to excite sensory receptors and send nerve impulses to the brain: This is an absolute threshold. A message below that threshold is said to be subliminal: The message is processed, but we are not consciously aware of it. Over the years, there has been a great deal of speculation about the use of subliminal messages in advertising, rock music, and self-help audio programs to influence consumer behavior.

Research has demonstrated in laboratory settings, people can process and respond to information outside of awareness. This demonstrates that although we may not be aware of the stimuli presented to us, we are processing it on a neural level, and also that although subliminal priming usually is not strong enough to force unwanted purchases, it may influence our perceptions of things we encounter in the environment following the subliminal priming.

Absolute thresholds are generally measured under incredibly controlled conditions in situations that are optimal for sensitivity.

Sometimes, we are more interested in how much difference in stimuli is required to detect a difference between them. This is known as the just noticeable difference JND, mentioned briefly in the above study comparing color perceptions of Chinese and Dutch participants or difference threshold.

Unlike the absolute threshold, the difference threshold changes depending on the stimulus intensity. As an example, imagine yourself in a very dark movie theater. If an audience member were to receive a text message on her cell phone which caused her screen to light up, chances are that many people would notice the change in illumination in the theater. However, if the same thing happened in a brightly lit arena during a basketball game, very few people would notice.

The cell phone brightness does not change, but its ability to be detected as a change in illumination varies dramatically between the two contexts. Webers Law : Each of the various senses has its own constant ratios determining difference thresholds. Webers ideas about difference thresholds influenced concepts of signal detection theory which state that our abilities to detect a stimulus depends on sensory factors like the intensity of the stimulus, or the presences of other stimuli being processed as well as our psychological state you are sleepy because you stayed up studying the previous night.

Human factors engineers who design control consoles for planes and cars use signal detection theory all the time in order to asses situations pilots or drivers may experience such as difficulty in seeing and interpreting controls on extremely bright days. While our sensory receptors are constantly collecting information from the environment, it is ultimately how we interpret that information that affects how we interact with the world.