Psy190 General Psychology

PSY190 General Psychology

Introduction What did you see? What does it mean?

SENSORY SYSTEMS The stimulus is modified by an accessory structure

(ex: lens of the eye, ear) Transduction, the transformation of incoming energy into neural activity, takes place at the sensory receptors. Receptors stimulate sensory neuron activity, which carries messages (except smell) to the thalamus and then to the cerebral cortex. Refer to Figure 4.1

Changes in stimuli produce the greatest receptor

response; stimuli that remain at a constant level produce adaptation.

HEARING

A reaction to wave Auditory system consists of ears, parts of the brain

and various connecting neural pathways. Hearing system: Transmission: amplifies and passes sound wave to

receptors Transduction: converts sound energy to neural activity

The sound wave causes the movement of basilar

membrane, which stimulates the hair cells, which transduce the vibrations into changes in neural firing patterns.

VISION

Visible light is electromagnetic radiation that has a

wavelength from about 400 to 750 nanometers. Visual system consists of eyes, parts of the brain and pathways connecting them. Visual system: image forming and transduction system Visual transduction, the conversion of light energy into neural activity, takes place in the photoreceptors of the retina. Two photoreceptors:

Rods: sensitive to light  Cone: detect color, active in bright light 

THE CHEMICAL SENSES: SMELL AND TASTE Olfaction, or smell, occurs when airborne

chemicals are detected by receptor cells in the upper part of the nose. Axons from the nose travel to the olfactory bulb,

and from there axons spread to many areas of the brain, especially to the amygdala.

Gustation detects chemicals that come into

contact with taste receptors in papillae on the tongue. Each taste bud in the papillae responds best to

one or two of tastes but weakly to the others.

Touch and Temperature Stimulus and Receptors for Touch. There are many types of receptors in or somewhere near the skin that respond to mechanical deformation of the skin. Temperature. Some skin receptors are sensitive to warmth (warm

fibers) and cold (cold fibers). Many receptors that respond to temperature also respond to touch.

Pain Pain as an Information Sense. Painful stimuli cause the release of chemicals, causing pain nerves

to fire. A-delta fibers- carry sharp, pricking pan sensations C fibers- carry long-lasting, dull aches & burning sensations Gate control theory- a gate in the spinal cord can either let pain impulses travel upward to the brain or block their progress.  Input from skin sense can take over the pathway used by pain

impulses 

ex: rubbing skin around a wound reduces pain

 Brain block incoming pain signals at spinal cord synapses

Perception It is the process through which people take raw

sensations from the environment and interpret them, using knowledge, experience, and understanding of the world, so that the sensations become meaningful experiences. Major functions of the perceptual system: Determining which part of the sensory environment to

attend to Localizing or determining where objects are Recognizing or determining what objects are Abstracting the critical information from objects Keeping the appearance of objects constant

THREE APPROACHES TO PERCEPTION Constructivist- the perceptual system uses fragments of

sensory information to construct an image of reality. Influenced by our experiences, expectations and inferences (ex:

half of a person behind a desk)

Computational- neural activity transforms sensory stimulation

into our experience of reality. Focuses on nervous system’s manipulations of incoming signals

Ecological- perceive most clues from the environment directly,

without interpretation.

PSYCHOPHYSICS Psychophysics is the study of the relationship

between the physical energy of the environmental stimuli and the psychological experience that those stimuli produce. Absolute threshold is the minimum amount of

energy that can be detected 50 percent of the time. Ex: 1 teaspoon of sugar in 2 gallons of water

Basic Processes in Perceptual Organization The task of determining what edges & other

stimuli go together to form an object.

Figure-Ground Organization: assign some stimuli

to the foreground (figure) and some to the meaningless background (ground).

 Can’t see figure and ground at the same time  Figure 5.7

Grouping: We see a figure via principles of

grouping.

 Tend to group certain elements together  principles of grouping:  proximity, similarity, continuity, closure, common region, common fate, synchrony, and connectedness.  Figure 5.8

Basic Processes in Perceptual Organization (con’t) Explanations: The likelihood principle: We tend to perceive objects in the way that experience

tells us is the most likely arrangement.

The simplicity principle: We organize stimulus information into the simplest possible perception. Reduces the amount of information that have to process

Perception of Location and Distance Two-Dimensional Location- determine where the

object is Visual location Auditory localization

Depth Perception: Ability to perceive distance Stimulus depth cues include: interposition, relative size, height in the visual field, texture gradients, linear perspective, clarity, color, and shadows.

Perception of Location and Distance (con’t) Depth cues from moving objects include motion parallax Different rate of movement provide information about the relative distance of those objects near objects seem to move faster Ex: nearer objects outside a moving car move faster Cues based on properties of the visual system. binocular disparity- a depth cue based on the difference between two retinal images of the world.

Perception of Motion Our brain decides whether something is moving by

evaluating movement cues in the retinal image, eye and head movement, and vestibular and tactile cues. Looming is the rapid expansion in the size of an image on the retina. Object looms->interpret it as an approaching stimulus.

Stroboscopic motion is an illusion in which we perceive

continual movement from a series of separate still images moving across the retina. It enables us to perceive movement in films and videos.

Perceptual Constancy

ability to perceive sameness even when the image

on the retina changes. Size Constancy. Our perception of an object’s size is based on the size of our retinal image and how far away we think the object is. Knowledge & experience tell us objects don’t

suddenly change size

Shape Constancy. The brain automatically puts

together information about retinal images and distance as movement occurs. Brightness Constancy. How bright we perceive an object to be is based on real-world knowledge and on the brightness of that object relative to its background.

RECOGNIZING THE PERCEPTUAL WORLD Top-down Processing use knowledge in making inferences to recognize objects (ex: cheeseng in lecture) our knowledge, motivations, and expectations influence perception. (ex: mistake another lecturer) Bottom-up Processing analyze stimuli into basic features Ex: cheeseng in Bali Island Network Processing (PDP) the extensive interaction and communication among the various feature analyzers The stimuli excite other’s correct interpretation (R->P)

ATTENTION Attention is the process of directing and focusing

certain psychological resources, usually by voluntary control, to enhance perception, performance, and mental experience. Attention improves mental processing, requires effort, and has limited resources. Directing Attention-the tendency to focus on some

stimuli in the environment while ignoring others Ignoring Information-actively ignoring stimuli  Ex: ignore the air cond’s sound

Divided Attention-between two practiced or automatic

tasks

 Ex: Do assignment while listen to radio  Different types of attention

Tutorial Question Mary was waiting for her father at a bus

station after class. Suddenly a speedy car went out of control and crashed into the station. Luckily, Mary was able to run away from the station. Explain how do the following sensation and perception enable Mary to do so. Perception of location and distance Perception of motion Attention