Sensation• Sensation - the activation of receptors in the various sense organs.• Sensory receptors - specialized forms of neurons.• Sense organs: • Eyes – Visual Sensation • Ears – Auditory Sensation • Nose- Olfactory Sensation • Skin – Tactile Sensation • Taste buds (tongue) – Gustatory Sensation
So where do vision and hearing (& the other senses)• The Brain!happen?• The physical energy in the environment is detected by the eyes, ears, etc. but we can‘t see, hear, etc. until the brain interprets them— i.e., makes sense of them. So in a way, we see, hear, smell, etc. in our brains!
Transduction• Transforming signals into neural impulses.• Information goes from the senses to the thalamus , then Remember Ethan in Sky High. He to the various areas changes his body to slime. Solid form to liquid form. Change from in the brain. one form of energy to another. Transduction is transforming physical energy into neural impulses
Sensory Thresholds• Just noticeable difference or the difference threshold) - the smallest difference between two stimuli that is detectable 50 percent of the time.
Sensory Thresholds• Absolute threshold - the smallest amount of energy needed for a person to consciously detect a stimulus 50 percent of the time it is present.
Subliminal Sensation• Subliminal stimuli - stimuli that are below the level of conscious awareness. • Just strong enough to activate the sensory receptors but not strong enough for people to be consciously aware of them. • Limin - ―threshold‖ • Sublimin - ―below the threshold.‖• Subliminal perception – process by why subliminal stimuli act upon the unconscious mind, influencing behavior.
Perception of Minimal Stimuli• Subliminal Perception • The concept of subliminal perception is well known to the general public. • Subliminal perception is the idea that a stimulus can influence behavior even when it is so weak or brief that we do not perceive it consciously. • There is concern that subliminal perception can powerfully manipulate human behavior.
Perception of Minimal Stimuli• What does ―subliminal‖ mean? • When the term ―subliminal‖ is used, it refers to the quality of being ―below the (sensory) threshold.‖ • Scientists use it to indicate that the stimulus was not consciously detected in a given presentation. • Because the only way to know if a stimulus has been detected is to ask, it is very difficult to interpret the results of research on subliminal stimuli.
Perception of Minimal Stimuli• What subliminal perception cannot do • Claims that subliminal stimuli in advertisements can make people buy things are unsupportable. • This claim has been tested repeatedly and no evidence has been found. • Advertisements in American culture have little need of subliminal stimuli. They are overtly and effectively manipulative.
Perception of Minimal Stimuli• What subliminal perception cannot do • Messages in music (recorded backwards or superimposed) cannot make people do anything, evil or otherwise. • This claim has also been repeatedly tested under controlled conditions. • No one listening to the messages can discern these messages. • No one‘s behavior has been changed after listening to music containing messages.
Perception of Minimal Stimuli• What subliminal perception cannot do • Subliminal audiotapes just don‘t work • Claims that addictions can be overcome, self- esteem can be improved, and general self- improvement can be achieved through the use of subliminal audiotapes are also unsupported. • Any results achieved through the use of these tapes can be attributed to the placebo effect or to the individual user‘s motivation to improve.
Perception of Minimal Stimuli• What subliminal perception can do • Some subtle effects on subsequent perception and emotion have been supported • ―Priming‖ individuals to see an object in subsequent presentations has been achieved through repeated presentations (Bar & Biederman, 1998) • Emotional states can be influenced by subliminal presentation of messages that may be perceived as emotionally loaded (Masling et al., 1991)
Perception of Minimal Stimuli• Subliminal perception • The fact that subliminal perception can influence behavior at all is interesting. • But the effects overall are much smaller than people hope or fear.
Habituation and Sensory Adaptation• Habituation - tendency of the brain to stop attending to constant, unchanging information.• Sensory adaptation - tendency of sensory receptor cells to become less responsive to a stimulus that is unchanging.
Somesthetic Senses• Somesthetic senses - the body senses consisting of the skin senses, the kinesthetic sense, and the vestibular senses. • ―Soma‖ – body • ―Esthetic‖ - feeling1. Skin senses - the sensations of touch, pressure, temperature, and pain. • Sensory receptors in the skin • Gate-control theory - pain signals must pass through a ―gate‖ located in the spinal cord.
Somesthetic Senses2. Kinestheticsense - sense of the location of body parts in relation to the ground and each other. • Proprioceptive receptors (proprioceptors)3. Vestibular senses - the sensations of movement, balance, and body position. Tells us where our body is oriented in space.
Vestibular Sense • Tells us where our body is oriented in space. • Our sense of balance. • Located in our semicircular canals in our ears.
Kinesthetic Sense• Tells us where our body parts are.• Receptors located in our muscles and joints.
Perception and Constancies• Perception - the method by which the sensations experienced at any given moment are interpreted and organized in some meaningful fashion.• Mental interpretation of sensation results in perception
Perception and ConstanciesPERCEPTION = SENSATION +MEANINGFULINTERPRETATIONEx: Smell we experience due to theburning of an object is sensation andunderstanding that the burning object isrubber is PERCEPTION
Sensation and PerceptionSensation: your window to the worldPerception: interpreting what comes in your window.
Perception and Constancies• Size constancy - the tendency to interpret an object as always being the same actual size, regardless of its distance.• Shape constancy - the tendency to interpret the shape of an object as being constant, even when its shape changes on the retina.• Brightness constancy – the tendency to perceive the apparent brightness of an object as the same even when the light conditions change.
Gestalt Principles• Figure–ground - the tendency to perceive objects, or figures, as existing on a background.• Reversible figures - visual illusions in which the figure and ground can be reversed.
The white and black stripes onthese zebras can be reversed –both can serve as either figure orground.
Some Laws of Perceptual Organization Gestalt Principles• Closure - the tendency to complete figures that are incomplete. Ex : While proof reading missing letters escape from our attention & our minds fill up the gap !
Laws of Perceptual Organization Gestalt Principles• Continuity - the tendency to perceive things as simply as possible with a continuous pattern rather than with a complex, broken- up pattern.( Organization of perception appears to be going infinitely in the same direction) Ex : Cinema scenes though not individually, when they run in a sequence at the rate of 15 frames per second, they appear to be one and continuous
Laws of Perceptual Organization Gestalt Principles• Pragnanz – Pragnanz means compact but significant. In perceiving we do not add the different sensations received and edit them so as to get at the meaningful interpretation of the object perceived. We always perceive anything as a whole configuration or pattern so that it is simple, meaningful and stable. Ex: On seeing a man riding a cycle, we do not perceive the cycle and the rider separately, it appears as a whole unit to us. The mental act of ‗organizing‘ takes place during perception Menu
Laws of Perceptual Organization• Similarity - the tendency to perceive things that look similar to each other as being part of the same group.• Proximity - the tendency to perceive objects that are close to each other as part of the same grouping. Menu
Depth Perception• Depth perception - the ability to perceive the world in three dimensions.• Studies of depth perception • Visual cliff experiment Menu
Perceptual Illusions• Illusions are wrong / mistaken perceptions• Our perceptions are not always true and accurate. Sometimes errors do creep in our perception when our mind wrongly interpret the sensory input, which is otherwise known as ILLUSION
Perceptual Illusions• Illusion of movement : Ex: A spot of light in dark appears to be moving around• Illusion of perceptive : Ex: Two parallel lines appears to meet at along distance
Perceptual Illusions• Müller-Lyer illusion - illusion of line length that is distorted by inward-turning or outward- turning corners on the ends of the lines, causing lines of equal length to appear to be different.• Moon illusion – the moon on the horizon appears to be larger than the moon in the sky. • Apparent distance hypothesis
Factors that Influence Perception• Perceptual set (perceptual expectancy) - the tendency to perceive things a certain way because previous experiences or expectations influence those perceptions.• Top-down processing - the use of preexisting knowledge to organize individual features into a unified whole.• Bottom-up processing - the analysis of the smaller features to build up to a complete perception.
Applying Psychology• Extrasensory Perception (ESP) - claim of perception that occurs without the use of normal sensory channels such as sight, hearing, touch, taste, or smell. • Telepathy - claimed ability to read another person‘s thoughts, or mind reading. • Clairvoyance - supposed ability to ―see‖ things that are not actually present. • Precognition - supposed ability to know something in advance of its occurrence or to predict a future event.• Parapsychology - the study of ESP, ghosts, and other subjects that do not normally fall into the realm of ordinary psychology.
The Doorway to Psychology You cannot know anything except through the senses – Anaxagoras 55