Sensation & Perception

Sensation:
The activation of the sense organs by a source of physical energy.

Perception:
The sorting out, Interpretation, analysis, and integration of stimuli involving the sense organs and brain.

Sensation And Perception:
Sensations can be defined as the passive process of bringing information from the outside world into the body and to the brain. The process is passive in the sense that we do not have to be consciously engaging in a "sensing" process.Perception can be defined as the active process of selecting, organizing, and interpreting the information brought to the brain by the senses.


How they work Together:


1)Sensation Occurs:

a) sensory organs absorb energy from a physical stimulus in the environment.
b) sensory receptors convert this energy into neural impulses and send them to the brain.

2)Perception follows:

a) the brain organizes the information and translates it into something meaningful.
b) But what does "meaningful" mean? How do we know what information is important and should be focused on?

1)Selective Attention:

Process of discriminating between what is important & is irrelevant (Seems redundant: selective-attention?), and is influenced by motivation.


For example: students in class should focus on what the teachers are saying and the overheads being presented. Students walking by the classroom may focus on people in the room, who is the teacher, etc., and not the same thing the students in the class.


2)Perceptual Expectancy:
how we perceive the world is a function of our past experiences, culture, and biological makeup.For example, as an American, when I look at a highway, I expect to see cars, trucks, etc, NOT airplanes. But someone from a different country with different experiences and history may not have any idea what to expect and thus be surprised when they see cars go driving by.
Another example - you may look at a painting and not really understand the message the artist is trying to convey. But, if someone tells you about it, you might begin to see things in the painting that you were unable to see before.


All Of this called Psychophysics


Psychophysics:
Psychophysics can be defined as, the study of how physical stimuli are translated into psychological experience.


In order to measure these events psychologist used THRESHOLDS.

1)THRESHOLDS- A dividing line between what has detectable energy and what has not.
For example - many classrooms have automatic light sensors. 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.


2)DIFFERENCE THRESHOLDS- the minimum amount of stimulus intensity change needed to produce a noticeable changed.
the greater the intensity (ex., weight) of a stimulus, the greater the change needed to produce a noticeable change. 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 100 lbs, and then 105 lbs, it is much more difficult to feel the difference.


3)Signal Detection Theory- detection of a stimulus involves some decision making process as well as a sensory process. Additionally, both sensory and decision making processes are influenced by many more factors than just intensity.
a) Noise - how much outside interference exists.
b) Criterion - the level of assurance that you decide must be met before you take action. Involves higher mental processes. You set criterion based on expectations and consequences of inaccuracy.


For example - at a party, you order a pizza...you need to pay attention so that you will be able to detect the appropriate signal (doorbell), especially since there is a lot of noise at the party. 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...you become more focused on the doorbell and less on extraneous noise.