Week 5 Flashcards
Explain psychophysics
Psychophysics describes the relationship between the physical energy in the environment and the psychological experience of that energy.
What is the absolute threshold
The absolute threshold is the smallest amount of physical energy a sensory system can detect.
What is the difference threshold
The smallest difference between stimuli that we can detect is called the difference threshold, or the just-noticeable difference (JND).
Describe Webers Law
the smallest detectable difference in stimulus energy is a constant fraction of the intensity of the stimulus. JND = KI, where K is the constant fraction and I is the intensity.
Describe Magnitude estimation
Magnitude estimation is how our perception of stimulus intensity is related to the actual strength of the stimulus. The perception of magnitude is not absolute but relative. Our experience of one stimulus depends on its relationship to others.
Describe Fechner’s Law
Fechner’s law says that constant increases in physical energy will produce smaller increases in perceived magnitude. For example, it only takes a small increase in volume to make a soft sound seem twice as loud, but it will take an incredible increase in volume to make a rock band seem twice as loud. This assumption applies to most, but not all stimuli.
Describe Stevens’s power law
Stevens’s power law for magnitude estimation works for a wider array of stimuli. It includes a factor that takes into account the differential sensitivity of various sensory systems.
Describe Signal detection theory
is a mathematical model of how a person’s sensitivity and response criterion combine to determine decisions about whether a near-threshold stimulus has occurred.
Describe the computational model
tries to determine the computations that a computer would have to perform to solve perceptual problems to explain how complex computations of the nervous system turn raw sensory stimulation into a representation of the world. The computational approach focuses on the nervous system’s manipulations of incoming signals.
Describe constructivist approach
argues that perceptual systems construct a representation of reality from fragments of sensory information. This representation is strongly influenced by learning, expectations, and inferences from past experiences, including culture.
Describe ecological approach
most perceptual experience comes directly from the environment rather than from interpretations or expectations. Stimuli directly give most of the information needed to make sense of the world.
Explain Perceptual organisation
is the task performed by the perceptual system to determine what stimuli go together to form an object. Your perceptual system can organise unconnected elements into objects by creating imaginary connecting lines called subjective contours.
Explain figure-ground discrimination
When faced with complex stimuli, perceptual systems automatically pick out certain features, objects, or sounds to emphasise. This is called figure-ground discrimination. Figure is the emphasised features, and ground is the less meaningful background.
Explain grouping
Perceptual systems group certain elements in the environment together, more or less automatically. Gestalt psychologists argue that people perceive sights and sounds as organised wholes. Gestalt principles that describe these grouping tendencies are:
Proximity:
the closer the objects or events are to one another, the more likely they are to be perceived as belonging together
Similarity:
similar elements are perceived to be part of a group.
Continuity:
sensations that appear to create a continuous form are perceived as belonging together.
Closure:
people tend to fill in missing contours to form a complete object.
Texture:
stimuli that have the same texture (for example, oriented along the same directions) tend to be grouped together.
Simplicity:
people group stimuli to provide the simplest interpretation of the world.
Common fate:
objects that are moving in the same direction at the same speed are perceived as a group.
Explain ocular accommodation
he muscles surrounding the lens either tighten (to make the lens more curved for focusing on close objects) or relax (to flatten the lens for focusing on more distant objects). Information from the muscles is relayed to the brain and helps create distance perception.
Explain Eye convergence
involves each eye rotating inward to project the image of an object on each retina. Information about the rotation goes to the brain and the greater the rotation, the closer the object is perceived to be.
Explain Retinal disparity
(binocular disparity), the difference between the two retinal images of an object (one from each eye), provides distance cues. This difference decreases with increasing distances. Depth can be created by showing each eye a separate photograph of a scene, each taken from a slightly different angle.
