Sensation and Perception

Sensation

• Sensory receptors and the nervous system receive and represent stimulus energies from the environment.
• Sensory organs like the nose and eyes bring in information including smells, colors, and visual details.

Perception

• The process of organizing and interpreting sensory information, that enables recognition of meaningful events and objects.
• The brain makes sense of sensory information, and relates it to familiar things.

Transduction

• Conversion of one form of energy into another, such as light waves into neural impulses.
• Step 1: Sensory receptors receive stimulus.
• Step 2: Sensory receptors transform stimulus.
• Step 3: The brain delivers neurological signals for interpretation.

Absolute Threshold

• The minimum stimulation needed to detect a particular stimulus 50% of the time.

Difference Threshold

• The minimum difference between two stimuli required for detection 50% of the time.
• This is also the just noticeable difference (JND).

Weber's Law

• To tell the difference between degrees of stimulation, two stimuli must differ by a constant minimum percentage.
• The intensity of two lights must differ by 8% to notice a change.
• Two objects must differ in weight by 2% to notice a change.
• Two tones must differ in frequency by 0.3% to notice a change.

Bottom-Up Processing

• Starts with sensory input in which the brain attempts to understand and make sense of new information.

Top-Down Processing

• Is guided by experience and higher-level processes, forming perceptions based on what is expected or previously known.

Eye Anatomy

• The cornea is the clear, protective outer layer that light passes through first.
• The pupil is a small adjustable opening in the center of the eye through which light passes.
• The iris is a ring of muscle tissue that forms the colored portion of the eye around the pupil, by controlling the size of the pupil opening.
• The lens is a transparent structure behind the pupil that changes shape to focus images on the retina.
• Accommodation refers to the process of the lens changing its curvature and thickness to focus. Myopia (nearsightedness) can be corrected with lenses or surgery; hyperopia (farsightedness) is when the lens focuses light past the retina.
• The retina is the light-sensitive inner surface of the eye, containing receptor rods and cones plus layers of neurons that begin the processing of visual information.

Rods

• Retinal photoreceptors detect black, white, and gray, and are sensitive to movement.
• Rods are necessary for peripheral and twilight vision, when cones don't respond.

Cones

• Retinal photoreceptors that are concentrated near the center of the retina, and function in daylight and in well-lit conditions.
• Cones detect fine detail and create color sensations.

Young-Helmholtz Trichromatic (Three-Color) Theory

• The retina contains three different types of color receptors (cones).
• One cone is most sensitive to red, one to green, and one to blue.
• When stimulated in combination, these cones can produce the perception of any color.

Hering Opponent-Process Theory

• Cone photoreceptors are paired together such as (red-green, blue-yellow, white-black), to enable color vision.
• Activation of one color of the pair inhibits activation of the other.
• Some cells are stimulated by green and inhibited by red; others are stimulated by red and inhibited by green.

Audition

• The sense or act of hearing.

Taste (Gustation)

• On the top and sides of the tongue are 200 or more taste buds.
• Each taste bud contains a pore that catches food chemicals.

Smell (Olfaction)

• You can smell something when molecules of a substance in the air reach a tiny cluster of receptor cells at the top of each nasal cavity.

Taste Sensations

• Sweet indicates energy source.
• Salty signals sodium essential to physiological processes.
• Sour indicates potentially toxic acid.
• Bitter indicates potential poisons.
• Umami indicates proteins to grow and repair tissue.

Research on smell

• Foul smells lead to harsher judgments of immoral acts.
• Fishy smells lead to more suspicion.
• Citrus scent of cleaning products leads to less littering.

Kinesthetic Sense

• Position and motion detectors in muscles, tendons, and joints sense the position and movement of body parts.

Vestibular Sense

• Fluid-filled semicircular canals and a pair of calcium crystal-filled vestibular sacs located in the ears monitor the head's and body's movements.

Sensory Interaction

• The senses can influence each other.
• Smell has an impact on taste.
• The ability to detect various tastes is altered when closing the nose.
• Visual images are better when accompanied by noise.
• Soft sounds are better if paired with a visual cue.

Embodied Cognition

• The influence of bodily sensations, gestures, and other states on cognitive preferences and judgements.
• Holding a warm drink leads people to rate someone more warmly, feel closer to them, and behave more generously.
• Experiencing the cold shoulder makes people judge the room to be colder.
• Sitting at a wobbly desk and chair makes relationships seem less stable.

Synesthesia

• In a few select individuals, the brain circuits for two or more senses become joined.
• When the stimulation of one sense (such as hearing sound) triggers an experience of another, it is called synesthesia.
• Synesthetes may hear music as colors or experience numbers as tastes.

Perceptual Set

• A mental predisposition to perceive one thing and not another.

Priming and Perceptual Set

• Subjects are more likely to see an old woman instead of a young woman when primed with cues.

Selective Attention

• The tendency to focus on just a particular stimulus among the many that are being received.

Cocktail Party Effect

• Focus on one particular voice (that person who called your name) amidst the crazy loudness of all those other voices.
• Is a great example of selective attention.

Research on Car Accidents

• fMRI scans show a 37% decrease in brain activity in areas vital to driving when a driver is listening to a conversation.
• Cell phone users are four times more at risk of a car crash.
• 28% of traffic accidents occur when drivers are chatting on cell phones or texting.
• Using a cell phone carries a risk four times higher than normal or equal to the risk of drunk driving.

Selective Inattention

• At the level of conscious awareness, the salient objects available to be sensed are missed when focusing on one set of stimuli.

Inattentional Blindness

• Refers to the failure to see visible objects when attention is directed elsewhere.

Change Blindness:

• Failure to notice changes in the environment.

Subliminal Stimuli

• Stimuli that are not detectable 50% of the time.
• Are below ones absolute threshold.
• May not be consciously noticed if they are weak.

Priming

• Activation, often unconsciously, of certain associations predisposes memory, perception, or response.

Sensory Adaptation

• Diminished sensitivity to stimuli as a consequence of constant stimulation.
• Once noticing and evaluating a new stimuli as non-threatening, one might pay less attention to it.
• Attention is saved and directed for new incoming stimuli, or changes in the existing stimuli.

Gestalt Psychologists

• People tend to organize clusters of sensations into a gestalt, a German word meaning a form or a whole.
• Perception depends on organization; the whole exceeds the sum of its parts.

Necker Cube

• Excellent vehicle that helps in understanding the distinction between sensation and perception. Only the visual stimuli are the blue wedges (sensation).
• The circles, lines, and cube are all the products of the mind and not on the page (perception).

Figure-Ground

• The organization of the visual field into objects such that they stand out from their surroundings.

Gestalt Grouping Principles

• Mind brings order and structure to stimuli by following certain rules for grouping. These rules which are applied even by infants.
• These explain how the perceived whole differs from the sum of the individual parts.

Proximity

• A Gestalt law of grouping that states figures that are nearby are grouped together.

Continuity

• The Gestalt law that entails smooth, continuous patterns are perceived rather than discontinuous ones.

Closure

• A Gestalt law of grouping stating gaps are filled in to create a complete, whole object.

Depth Perception

• Is the ability to see objects in three dimensions although the images that strike the retina are two- dimensional. It allows to judge distance.
• Eleanor Gibson and Richard Walk designed a series of experiments in their Cornell University laboratory with a visual cliff.

Visual Cliff Experiment

• 6 to 14-month-old infants were placed on the edge of the "cliff" and coaxed by their mothers to crawl out onto the glass. Infants refused to do so, indicating that they could perceive depth.

Binocular Cues

• Depth cues, such as retinal disparity and convergence, that depend on the use of two eyes.
• These help in judging distance when an object becomes closer or farther.

Linear Perspective

• Parallel lines appear to meet in the distance. The sharper the angle of convergence, the greater the perceived distance.

Visual Illusions

• Occur when the principles of perception cause the eye to interpret visual input incorrectly.

The Ames Room

• A distorted room, designed and constructed by Adelbert Ames, appears to have a normal rectangular shape when viewed through a peephole with one eye.
• The girl in the right corner appears to be very large because she is perceived to be at the same distance as the girl in the left corner.
• The room however, is distorted, and is not a normal, evenly rectangular shape.

Explore sensation, perception, transduction, and thresholds. Learn how our senses receive and interpret stimuli, transforming them into meaningful experiences. Understand the processes from sensory input to brain interpretation.