Unit 3: Sensation & Perception

Sensation

The process of the sensory organs transforming physical energy into neurological impulses the brain interprets as the five senses of vision, smell, taste, touch, and hearing.

Perception

The process of selecting, organizing, and interpreting sensations. Our version of reality.

Bottom-Up Processing

Analysis of the stimulus begins with the sense receptors and works up to the level of the brain and mind.

Top-Down Processing

Informational processing guided by higher-level mental processes as we construct perceptions, drawing on our experience and expectation.

Psychophysics

A study of the relationship between physical characteristics of stimuli and out psychological experience with them. Physical to Psychological World. Examples: light to brightness, sound to volume, pressure to weight, and sugar to sweet.

Absolute Threshold

Minimum stimulation needed to detect a particular stimulus 50% of the time. Stimulus intensity is in lumens.

Signal Detection Theory

Predicts how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise). Assumes that there is no single absolute threshold. Depends on the quality of the stimulus, the environment, and the person who is detecting.

Subliminal (Threshold)

When stimuli are below one's absolute threshold for conscious awareness.

Difference Threshold

Minimum difference between two stimuli required for detection 50% of the time. Just noticeable difference (JND)

Weber's Law

Two stimuli must differ by a constant minimum PERCENTAGE (rather than a constant amount), to be perceived a different. light intensity- 8%, weight-2%, tone frequency-0.3%.

Sensory Adaptation

Diminishing sensitivity to unchanging stimulus. After constant exposure to stimulus, nerve cells fire less frequently. Our eyes are always moving.

Perceptions

Organized by meaning - as the world is useful to us.

Selective Attention

At any given moment we focus our awareness on a limited aspect of all we experience. Our 5 senses take in 11 million bits info/second, and only consciously process 40! Examples: Cocktail Party Effect - Attending selectively to 1 voice among many. Cell phones and driving - slower response to traffic signals.

Visual Capture

If sense are in conflict, we have a tendency to allow visual images to dominate our perception (trust our vision the most).

Gestalt

The different ways individuals group stimuli together in order to make a whole that makes sense to them. These principles are divided up into five categories: proximity, similarity, continuity, connectedness, and closure.

Figure-ground

The organization of the visual field by separating an object (figure) from its surroundings (ground).

Grouping

Organize things into meaningful form. Basic rules for grouping stimuli together:

Proximity

Tendency to group nearby things together

Similarity

Tendency to group similar things

Continuity

Tendency to see smooth continuous patterns

Connectedness

Tendency to want to see complete images

Closure

Tendency to automatically fill in gaps

Depth Perception

Our ability to perceive objects in 3 dimensions and to judge distance.

Visual Cliff

A test given to infants to see if they have developed depth perception. A space that looks like a cliff but is really just a trick of the eye.

Binocular Cues: Retinal Disparity

Images from the two eyes differ.

Binocular Cues: Convergence

Neuromuscular are caused by eyes greater inward turn when viewing a near object.

Monocular Cues: Relative Size

If two objects are similar in size, we perceive the one that casts a smaller retinal image to be farther away.

Monocular Cues: Interposition

Objects that occlude (block) other objects tend to be perceived as closer.

Monocular Cues: Relative Height

We perceive objects that are higher in our field of vision to be farther away than those that are lower.

Monocular Cues: Relative Motion

Objects closer to a fixation point move faster and in opposing direction to those objects that are farther away from a fixation point, moving slower and in the same direction.

Monocular Cues: Linear Perspective

Parallel lines, such as railroad tracks, appear to converge in the distance. The more the lines converge in the distance, the greater their perceived distance.

Monocular Cues: Light and Shadow

Nearby objects reflect more light into one eye than more distant objects. Given 2 identical objects, the dimmer one appears to be farther away.

Relative Clarity

A monocular cue for perceiving depth; hazy objects are farther away than sharp, clear objects.

Texture Gradient

Gradual change from coarse, distinct texture to fine, indistinct texture signals increasing distance.

Phi Phenomenon

When 2 adjacent lights blink on and off in quick succession, we perceive a single light moving back and forth (traffic arrows; stop-the-light game in arcades).

Perceptual Constancy

Perceiving objects as unchanging even as illumination and retinal images change.

Perceptual Adaptation

Visual ability to adjust to an artificially displaced visual field. Example: prism glasses.

Perceptual Set

A mental predisposition to perceive one thing and not another.

Context Effects

Context instilled by culture also alters perception.

Human Factor Psychologists

They design things to fit natural perceptions. "Curse of knowledge". Can help avoid frustration and danger. Example: airlines - now call out altitude as descend.

Extrasensory Perception (ESP)

Perception without sensory input. A large percentage of scientists do not believe in ESP.

Claims of ESP: Telepathy

Mind-to-mid communication. One person sending thoughts and the other reading them.

Claims of ESP: Clairvoyance

perception of remote events, such as sensing a friend's house on fire.

Claims of ESP: Precognition

Perceiving future events, such as a political leader's death.

Claims of ESP: Parapsychology

The systematic study of alleged psychological phenomena involving the transfer of information or energy that cannot be explained in terms of presently known scientific data or laws.