Exam 1 Ch. 1-5

Top-Down

(knowledge-based processing) Processing that starts with the analysis of high-level information, such as the knowledge a person brings to a situation. Also called knowledge-based processing. Distinguished from bottom-up, or data-based processing, which is based on incoming data.

Grand Mother Cell

A highly specific type of neuron that fires in response to a specific stimulus, such as a person's grandmother.

Palmer (1975) showed observers a kitchen scene

An example of how a scene schema can influence perception is an experiment by Stephen Palmer (1975), which used stimuli like the picture in Figure 5.36. Palmer first presented a context scene such as the one on the left and then briefly flashed one of the target pictures on the right. When Palmer asked observers to identify the object in the target picture, they correctly identified an object like the loaf of bread (which is appropriate to the kitchen scene) 80 percent of the time, but correctly identified the mailbox or the drum (two objects that don't fit into the scene) only 40 percent of the time. Apparently, Palmer's observers were using their knowledge about kitchens to help them perceive the briefly flashed loaf of bread.

Gestalt principles

Having questioned the idea that perceptions are created by adding up sensations, the Gestalt psychologists proposed that perception depends on a number of principles of perceptual organization, which determine how elements in a scene become grouped together. The starting points for the principles of organization are things that usually occur in the environment. Principles that describe how elements in a scene become grouped together. Many of these principles were originally proposed by the Gestalt psychologists, but new principles have also been proposed by recent researchers.

The steps of the perceptual process

Information about the stimulus in the environment (the distal stimulus; Step 1) hits the receptors, resulting in the proximal stimulus (Step 2), which is a representation of the stimulus on the retina. Receptor processes (Step 3) include transduction and the shaping of perception by the properties of the receptors. Neural processing (Step 4) involves interactions between the electrical signals traveling in networks of neurons. Finally, the behavioral responses—perception, recognition, and action—are generated (Steps 5-7).

five "global image features

Information that may enable observers to rapidly perceive the gist of a scene. Features associated with specific types of scenes include degree of naturalness, degree of openness, degree of roughness, degree of expansion, and color.

Bottom-up

Processing that is based on the information on the receptors. Also called data-based processing.

Five Questions About the Perceptual World

Question 1: What Is the Perceptual Magnitude of a Stimulus? Question 2: What Is the Identity of the Stimulus? Question 3: How Quickly Can I React to It? Question 4: How Can I Describe What Is Out There? Question 5: How Can I Interact With It?

Question 1: What Is the Perceptual Magnitude of a Stimulus?

Technique: Magnitude Estimation Things are big and small (an elephant; a bug), loud and soft (rock music; a whisper), intense and just perceptible (sunlight; a dim star), overpowering and faint (heavy pollution; a faint smell). Fechner was not only interested in measuring thresholds using the classical psychophysical methods; he was also interested in determining the relationship between physical stimuli (like rock music and a whisper) and the perception of their magnitude (like perceiving one to be loud and the other soft). Fechner created a mathematical formula relating physical stimuli and perception; modern psychologists have modified Fechner's equation based on a method not available in Fechner's time called magnitude estimation (Stevens, 1957, 1961).

Question 4: How Can I Describe What Is Out There?

Technique: Phenomenological Report Look around. Describe what you see. You could name the objects you recognize, or you could describe the pattern of lights and darks and colors, or how things are arranged in space, or that two objects appear to be the same or different sizes or colors. Describing what is out there is called phenomenological report. For example, do you see a vase or two faces in Figure 1.21? We will see in Chapter 5 that displays like this are used to study how people perceive objects in front of backgrounds. Phenomenological reports are important because they define the perceptual phenomena we want to explain, and once a phenomenon is identified, we can then study it using other methods.

Question 5: How Can I Interact With It?

Technique: Physical Tasks and Judgments All of the other questions have focused on different ways of measuring what we perceive. This last question is concerned not with perception but with actions that follow perception (Step 7 of the perceptual process). Many perceptual researchers believe that one of the primary functions of perception is to enable us to take action within our environment

Question 3: How Quickly Can I React to It?

Technique: Reaction Time The speed with which we react to something can be determined by measuring reaction time—the time between presentation of a stimulus and the person's reaction to it. An example of a reaction time experiment is to ask participants to keep their eyes fixed on the + in the display in Figure 1.20a and pay attention to location A on the left rectangle. Because the participant is looking at the + but paying attention to the top of the left rectangle, this task resembles what happens when you are looking in one direction but are paying attention to something off to the side.

Question 2: What Is the Identity of the Stimulus?

Technique: Recognition Testing When you name things, you are categorizing them. The process of categorizing, which is called recognition, is measured in many different types of perceptual experiments. One application is testing the ability of people with brain damage. As we saw earlier in this chapter, Dr. P.'s brain damage led him to have trouble recognizing common objects, like a glove. The recognition ability of people with brain damage is tested by asking them to name objects or pictures of objects.

Structuralism

The approach to psychology, prominent in the late 19th and early 20th centuries, that postulated that perceptions result from the summation of many elementary sensations. The Gestalt approach to perception was, in part, a reaction to structuralism.

the "light-from-above" assumption

The assumption that light usually comes from above, which influences our perception of form in some situations.

Viewpoint invariance

The condition in which object properties don't change when viewed from different angles. Responsible for our ability to recognize objects when viewed from different angles.

Classical psychophysical methods

The methods of limits, adjustment, and constant stimuli, described by Fechner, that are used for measuring thresholds.

the blind spot

The small area where the optic nerve leaves the back of the eye. There are no visual receptors in this area, so small images falling directly on the blind spot cannot be seen.

States of an axon

There are variations on this basic neuron structure: Some neurons have long axons; others have short axons or none at all. Especially important for perception are sensory receptors (see Figure 1.5), which are neurons specialized to respond to environmental stimuli.

The process of transforming energy - Transduction

Transduction is the transformation of one form of energy into another form of energy (see Chapter 1). Visual transduction occurs in photoreceptors (the rods and cones) and transforms light into electricity. The starting point for understanding how the rods and cones create electricity are the millions of molecules of a light-sensitive visual pigment that are contained in the outer segments of the photoreceptors. Visual pigments have two parts: a long protein called opsin and a much smaller light-sensitive component called retinal.

retinal damages and vision problems

retinitis pigmentosa, which led to Larry Hester's blindness, is a degeneration of the retina that is passed from one generation to the next (although not always affecting everyone in a family). This condition first attacks the peripheral rod receptors and results in poor vision in the peripheral visual field (Figure 3.5b). Eventually, in severe cases, the foveal cone receptors are also attacked, resulting in complete blindness.

difference threshold

the smallest difference between two stimuli that enables us to tell the difference between them.

Absolute threshold

the smallest stimulus level that can just be detected. In the grating acuity example, this threshold was the smallest line width that can be detected.