MCQs in Surgery (part -1)

MCQs in Surgery

#Muscles which primarily responsible for rectal continence?
• (1.) Ext.spincter .
• (2.) Int. sphincter
• (3.) Puborectalis
• (4.) sacrococcoygenous

#Commonest complication of immunosuppresion is :
• (1.) Malignancy (2.) Graft rejection (3.) Infection (4.) Thrombocytopenia

#Highest chance of success in renal transplant is seen when the donor is the:
(1.) Identical twin (2.)Father (3.) Mother (4.) Sister

• #Commonest type of cancer of the renal pelvis and upper ureter is :
• (a.) Transitional cell carcinoma
• (b.) Adenocarcinoma
• (c.) Squamous cell carcinoma
• (d.) Nephroblastoma

• #commonest site of intestinal atresia is in the:
• (a.) Duodenum 
• (b.) Jejunum
• (c.) Ileum
• (d.) Colon

• #Complication of Meckle’s diverticulum include:
• (a.) Hemorrhage
• (b.) Intussusception
• (c.) Strangulation
• (d.) All are correct

• #In Budd chiari syndrome , the occlusion is at the :
• (a.) IVC
• (b.)Renal vein
• (c.) Hepatic vein
• (d.) Splenic vein

• # lesion most likely to undergo malignancy :
• (a.) intradermal neavus
• (b.) Junctional neavi
• (c.) actinic dermatitis
• (d.) dermal neavi

• Features of hypovolemic shock are all except:
• (a.) oliguria
• (b.) bradycardia
• (c.) low BP
• (d.) acidosis

• # Carcinoma stomach is associated with blood group :
• (a.) A
• (b.) B
• (c.) AB
• (d.) O

• #cock’s peculiar tumor is:
• (a.) papilloma
• (b.) infected sebaceous cyst
• (c.) cylindroma
• (d.) squamous cell carcinoma

• # amoebic abscess ruptures most commonly into …….cavity:
• Pleural
• Peritoneal
• Pericardial
• The lumen of the intestine
• Right lung

• # Best diagnostic aid in blunt trauma abdomen is :
• CT scan
• 4 quadrant aspiration
• Peritoneal lavage
• Ultrasound


• # Best positioning for self palpation of breast in women is :
• Sitting
• Standing
• Leaning forward
• Lying down

• # Structures preserved in funtional radical dissection of the neck :
• Internal jugular vein
• Sternomastoid
• Lymph nodes
• Accesory nerve 

• # Earliest sign of deep vein thrombosis is :
• Calf tenderness
• Rise in temperature
• Swelling of calf muscles
• Homan’s sign


• # Hemoblia is characterized by except:
• Jaundice
• Malena
• Biliary colic
• Fever 

• # Ectopic testis is found in all locations except:
• Lumbar
• Perineal
• Intra abdominal
• Inguinal

• # Management of an open wound seen 12 hrs after injury:
• Suturing
• Debridement and suture 
• Secondary suturing
• Heal by granulation

• #Toxic megacolon is seen in:
• Carcinoma colon
• Gastocolic fistula
• Ulcerative colitis
• Carcinoid
• All of the above


• #complication of total parenteral nutrition include:
• Hyperglycemia
• Hyperosmotic dehydration
• Hypokalaemia
• Azotemia
• All of the above 



• # In portal hypertension, the sites of portosystemic anastamosis include:
• Lower end of esophagus
• Around umbilicus
• Extraperitoneal surgace of abdominal organs
• Lower third of rectum and anal canal
• All of the above

• # Commonest posterior mediastinal tumor is:
• Lung cyst
• Neurofibroma
• Dermoid
• Thyroid
• Thymic tumor

• #prognosis for carcinoma rectum is best assessed by :
• Site of tumor
• Histological grading
• Size of tumors
• Duration of the symtoms

• # A 80 years old man has a foci of adenocarcinoma in the prostate. The next treatment is:
• Palliative radiotherapy
• Chemotherapy
• Prostatectomy
• No treatment is required

• # acute urinary retension in a male child may be due to:
• Prostatic enlargement
• Urethral stricute
• Hysteria
• Meatal ulcer with scabbing

• # line of surgical division of the lobes of the liver is :
• Falciform ligament to the diaphragm
• Gallbladder bed IVC
• Gall bladder bed on the it.crus of diaphragm
• One inch to the left of falciform ligament to the IVC

• # rare complication of ulcerative colitis:
• Psudopolypi
• Carcinoma
• Toxic dilatation
• Massive hemorrhage

• # commonest site of peptic ulcer perforation:
• Anterior aspect of the first part of duodenum 
• Posterior aspect of the first part of duodenum
• Greater curvature of the stomach
• Lesser curvature of  the stomach
• Anterior aspect of the second part of duodenum

• # bronchogenic carcinoma which produce paraneoplastic syndrome:
• Squamous cell carcinoma
• Oat cell carcinoma
• Adeno carcinoma
• Large cell carcinoma

• #Commonest site of branchial cyst :
• Lower 1/3 of sternomastoid on anterior border
• Lower 1/3 of sternomastoid on posterior border
• Upper 1/3 of sternomastoid on anterior border
• Upper 1/3 of sternomastoid on posterior border

• # treatment of zollinger ellison syndrome :
• Total gastrectomy with removal of tumor
• Partial gastrectomy
• Excision of tumor alone
• H2 receptor antagonist

• # lymph node which is to be first involved in carcinoma breast:
• Pectoral group
• Internal mammary
• Apical
• Central
• Supra clavicular

# warthins tumor is:
Malignant neoplasm
Rapidly growing
Gives a hot pertechnetate scan 
Cold pertechnetate scan


• #Commonest site of amoebiasis in the gut:
• Ileum
• Caecum
• Ascending colon
• Transverse colon
• Sigmoid colon

• # earliest symptoms of carcinoma rectum:
• Pain
• Alternation of bowel habit
• Bleeding PR
• Tenesmus


• # commonest site of carcinoma tongue:
• Apical
• Lateral borders
• Dorsum
• Posterior 1/3
• Faucio lingual


• # Dentigerous cyst arises from:
• An unerupted tooth
• Apex of an infected tooth
• Nasopalatine cyst
• Solitary bone cyst
• Multi locular keratocytes


• # Curlings ulcer is seen in :
• Burns patients
• Patients with head injuries
• Zollinger Ellison Syndrome
• Analgesic drug abuse

• # Commonest cause of A-V fistula is :
• Congenital
• Traumatic
• Surgical creation
• Tumor erosion

• # slidding constituent of large direct hernia is:
• Bladder
• Sigmoid colon
• Caecum
• appendix

• # treatment of choice for subgaleal hematoma:
• Incision and evaucation
• Needle aspiration
• Antibiotics and then drain
• Conservative 

• # which one is not Ranson’s prognostic criteria in acute pancreatitis ?
• Age over 55 years
• Blood glucose more than 200 mgs%
• WBC more than 16000/mm3
• Serum calcium more than 8 mg% 


• # which suphonamide is used for the treatment of ulcerative colitis?
• Sulphamethiazide
• Sulphathalazole
• Sulphaguanidine
• Salazopyrin


• # which is not true regarding varicocele?
• Testicular veins involved
• More common on the right side
• May be the first feature of renal tumor
• Feels like a bag of worms

• # Regarding Hashimotos thyroiditis which is false:
• Auto immune thyroiditis
• Plasma cell and lymphocytic infiltration
• Hypothyroid state
• Hypoparathyroid state 

• # signs of cerebral compression are all except:
• Bradycardia
• Hypotension
• Papilloedema
• Vomiting
• Deterioration of the level of consciousness

• # barium meal picture of carcinoma stomach is:
• Filling defect
• Loss of rugosity
• Small capacity of stomach
• Delayed emptying of barium
• All of the above

• # Most common site of carcinoma stomach is:
• Prepyloric
• Body of stomach
• Fundus
• Lesser curvature

• # Retromammary abcess arises from :
• Tuberculous rib
• Infected hematoma
• Chronic empysema
• All of the above

CPR (Cardiopulmonary Resuscitation)

CPR( Cardiopulmonary Resuscitation

Summary:
(1.) Look for safety
(2.) Check for response
(3.) Call for help
(4.) Airway
(5.)Breathing
(6.) Check Carotid Pulse
(7.) Chest Compression
(8.) Defibrillation
(9.) Medication

-chest compression:The low half of the victim’s sternum
Depress the sternum 1/2 to 2 inches ( 4to 5 cm )
Allow the chest to return to its  normal position
Compression and chest recoil/relaxation times should be approximately equal
To limit interruptions to no longer than 10 seconds
-If the patient is adult the ratio should be 30:2 .It means that you have to give the victim 2 complete breathings and 30 chest compressions.
 -If the victim is Children and infants, the ration should be: 15:2
-Every 30 compressions should be followed by 2 complete breathings .
-You should check if there is carotid pulse after 2-3 cycles.
- You should keep on repeating the cycle until carotid pulse is seen.

-defribrillator:Sophisticated, reliable computerized devices
Use voice and visual prompts to guide lay rescuers and healthcare provider to safely defibrillate VF SCA
AEDs are of no value for arrest not caused by VF/pulseless VT, and they are not effective for treatment of nonshockable rhythms
-Drugs used in CPR:
Atropine – can be injected bolus, max 3 mg to block vagal tone, which plays significant role in some cases of cardiac arrest
Adrenaline – large doses have been withdrawn from the algorithm.  The recommended dose is 1 mg in each 3-5 min.
Vasopresine – in some cases 40 U can replace adrenaline
Amiodarone  - should be included in algorithm
Lidocaine – should be used only in ventricular fibrillation

Hydrocephalus

Hydrocephalus

                                            Summary:

-excessive accumulation of CSF in the brain resulting into ventricular widening

-Types:

congenital and  acquired;

communicating and non- communicating (obstructive) hydrocephalus. One of he common cause of hydrocephalus is aqueductal stenosis(non-communicating)

hydrocephalus ex-vacuo and normal pressure hydrocephalus

-1 in every 500 children

-the infant skull can expand to accommodate the buildup of CSF so can tolerate hydrocephalus better than adults

-symptoms: increase in head circumference( in children), vomiting,sleepiness, irritability, downward deviation of eyes( sunsetting), seizures ,papilledema, double vision ,urinary incontinence, lethargy, drowsiness, memory loss.

-symptoms of normal pressure hydrocephalus: gait problem, urinary incontinence and dementia.( very confused with Alzheimer’s disease, parkinson’s disease and creutzfeldt-jakob disease)

-CT or MRI for diagnosis

-Treatment: surgical insertion of a shunt system

    In few patients( third ventriculostomy)

-Complication of a shunt system:

Mechanical failure, infections, obstructions, need to lengthen or replace the catheter,

overdraining: causes ventricles to collapse,subdural hematoma, slit ventricle syndrome

Underdraining: symtoms persists

Prognosis:

Fully recovered in some patients whereas reoccur in other patients. Complicated by other health conditions

 

Sensation and Perception

Contents

•              A brief introduction of Medical Psychology

•              Three stages of recognizing the world: sensing, identifying & recognizing

•              Sensing: Definition of sensation & perception; Classification, biological basis of sensation; Sensibility: absolute & difference threshold; Adaptation

•              Principles of perceptual organization

•              Perceptual identification & recognition

•              Illusion

What is Psychology

Ø Psych- : soul

Ø A branch of science for just more than 100 years

Ø To research and reveal the mechanism of mental phenomena    

ü Mental process: cognition, emotion, and behaviors

ü Personality: temperament, character, et al.

What is Medical Psychology?

Ø Not a common term throughout the whole world

Ø American Psychological Association (APA):

ü A branch of psychology that integrates somatic and psychotherapeutic modalities into the management of mental illness and emotional, cognitive, behavioral and substance use disorders.

Ø In China:

ü An interdisciplinary science of Psychology & Medical Science; Applying psychological principles to medical practice

Main fields of Medical Psychology

•              Mental factors and health

ü    Relationship between emotion and health

ü    Relationship between personality and health

•              Stress and health; psychosomatic diseases

•              Mental assessment & mental measurements

•              Abnormal psychology and Psychotherapy

•              About general diseases:

ü    Common mental responses to diseases

ü    Doctor-patient relationship & communication

It is not the cat in your house!

Ø Newborn calves are not afraid of tigers.

SENSATION & PERCEPTION
HOW THE WORLD ENTERS THE MIND?

How the world enters the mind?

3 stages

Sensation,

Ø The process by which stimulation of sensory receptors produces neural impulses that represent experiences inside or outside the body.

Ø The awareness of properties of an object or event when a sensory receptor is stimulated.

Perception,

The set of processes that organize information in the sensory image and interpret that information as having been produced by objects or events in the external world.

SENSATIONS

STAGE Ⅰ: SENSING

Classification of Sensation

•                 External sensations: perceiving and reflecting information of things or events in external world. According to sense organs:

ü   Vision, Hearing, Smell, Taste, and Skin senses (tactile, pressure, warmth, pain)

•                 Internal sensations: perceiving and reflecting information of body itself.

ü Kinesthetic Sense & Vestibular Sense

pathway of Sensation

General physiological pathway of sensation

SOME COMMON SENSATIONS

1. Vision

Ø Adequate stimulus: visible lights (wavelength 380-780nm)

Ø Sense Organ: eyes

Ø Receptors: rods and cones at retina

Ø Afferent nerve: optic nerve

Ø Central Nervous System: visual cortex of brain  

2. Hearing

Ø Adequate stimulus: audible sounds (wave frequency 16-20000Hz)

Ø Sense Organ: ears

Ø Receptors: hair cells at cochlea 

Ø Afferent nerve: auditory nerve

Ø Central Nervous System: auditory cortex of brain

3. Smell

Stimuli: Odors

Ø Sense organ: nose

Ø Receptors: olfactory cilia

Ø Afferent nerve: olfactory nerve

ü CNS: olfactory bulb

ü Olfactory neurons, unlike most neurons, are constantly dying and being replaced

4. Taste

Ø The surface of the tongue is covered with papillae

Ø Taste buds(Taste-receptor cells

ü Taste buds may be damaged by alcohol, smoke, and acids, but the taste system is the most resistant to damage of all sensory systems, as taste receptors are replaced every few days, even more often than smell receptors.

Basic taste

Ø Four Taste Sensations: sweet, salty, sour, bitter

ü Most sensitive to bitter, least sensitive to sweet

Ø Umami Possible fifth taste sensation; “savory” or “meaty” ；brothy  taste； monosodium glutamate 

5. Touch and Skin Senses

Ø Cutaneous senses: pressure, cold, and warmth

Ø Meissner corpuscles  respond best when something rubs against the skin

Ø Merkel disks  are most active when a small object exerts steady pressure on the skin; refined tactile sense  

Ø The skin has separate receptors for hot and cold

6. The Vestibular Senses
 

Ø To tell how the body is oriented in the world with respect to gravity through tiny hairs in fluid-filled sacs and canals in the inner ear

Motion Sickness   

Ø Directly related to vestibular system.

Ø Symptoms: Dizziness, fatigue, nausea, vomiting

Ø Sensory Conflict Theory: Motion sickness occurs because vestibular system sensations do not match sensations from the eyes and body. 

Ø Medications, relaxation, and lying down might help.

7. The Kinesthetic Senses
 

ØThe kinesthetic sense provides constant sensory feedback about what the body is doing during motor activities.

ØTwo sources of kinesthetic information:

üreceptors in the joints  

üreceptors in muscles and tendons

The Kinesthetic Senses

Ø Receptors in the joints respond to pressures that accompany different  positions of the limbs and to pressure changes that accompany movements

Ø Receptors in the muscles and tendons respond to changes in tension that accompany muscle shortening and lengthening

8. Pain  

Ø Pain is critical to survival. People with insensitivity to pain often become scarred and their limbs deformed from injuries that could have been prevented had they been sensitive to pain.

Pain mechanisms

Ø The network of pain receptors is a fine mesh that covers the entire body. Some receptors respond only to temperature, while others respond to chemical or mechanical stimuli.

Ø Pain impulses start at the spinal cord, are relayed to the thalamus, and then to the cerebral cortex

Psychology of Pain

Ø Important factors affecting determining how much pain is experienced:

ü Emotional responses, context factors, and subjective interpretation

Ø Psychological processes influencing pain responses:

ü Hypnosis  , deep relaxation, and thought distraction.

The Gate-control theory
 

Ø Cells in the spinal cord act as neurological gates, interrupting and blocking some pain signals and letting others through to the brain. The brain and receptors in the skin send messages to the spinal cord to open or close the gates.

MEASUREMENT OF SENSIBILITY
 

Sensibility of sense organs

Ø Threshold:

ü Absolute threshold  

ü Difference threshold  

Absolute threshold,  

Ø The smallest, weakest stimulus energy that the organism   can detect

Ø Operationally defined as the stimulus level at which a sensory input is detected half of the time

Absolute thresholds of some sensations

Difference threshold,  

Ø The smallest physical difference between two stimuli that can still be recognized as a difference

Ø Operationally defined as the point at which the stimuli are recognized as different half of the time

Just Noticeable Difference, JND
 

Ø The difference threshold value:

ü The smallest amount of change in a stimulus that can be detected half the time

Weber’s Law

Ø JND is proportional to the magnitude of the stimulus.

 

Ø The JND between stimuli(⊿ I) is a constant fraction (K)of the intensity of the standard stimulus(I)

ü The larger the stimulus the larger the change must be to be noticed.

Response Bias

Ø The systematic tendency for an observer to favor responding in a particular way that is unrelated to the qualities of the sensory stimulus.

ü e.g., tending to say “yes” or “no” all of the time.

Ø There are at least three sources of response bias: Desire, Expectation & Habit.

 

Signal Detection Theory, SDT.  

Ø A systematic approach to the problem of response bias

Ø Focuses on the process of making a judgment about the presence or absence of a stimulus, especially in uncertain situation.  

The four possible types of response in SDT

SDT & Payoff Matrix  

Ø Payoff Matrix: the combination of rewards and penalties for correct and incorrect decisions. If the Payoff Matrix changes, then the person’s pattern of responses will also change.

ü One dollar for each Hit and no penalty for a False Alarm: it is in one's best interest to say that the stimulus was present whenever there is uncertainty.

ü Losing two dollars for each False Alarm: it is better for the observer to be cautious in saying that a stimulus occurred.

SDT

Ø Unlike classical psychophysics which conceptualized a single absolute threshold, SDT identifies two distinct processes in sensory detection:

ü Sensory Processes: reflecting an observer’s sensitivity to the stimulus

ü Decision Processes: reflecting an observer’s response bias to the stimulus

Adaptation  : Sensitivity changing

Ø Entering a room full of fragrant orchids and getting used to the sweet smell.

ü Associating with people of noble character accustoms one to good ways.

Ø Staying in a fish market and getting used to the stink.

ü Long exposure to bad surroundings or bad company accustoms one to evil ways.

Adaptation   

ØSensory Adaptation is the diminishing responsiveness of sensory systems to prolonged stimulus input.

üSensory systems are more sensitive to change in stimulus input than to steady input.

Dark & Light Adaptation

Ø Increased retinal sensitivity to light after entering the dark

Ø Similar to going from daylight into a dark movie theater

Adaptation ranks

ØFrom easy to difficult:

üWarmth

üTouch & pressure

üSmell

üHearing

üPain 

PERCEPTUAL ORGANIZATION
 

STAGE Ⅱ: ORGANIZING

Perceptual organization

ØPerceptual organization refers to the internal representation of an object.

Selective Attention

Ø The mind has a limited capacity to process information. The brain’s limited processing capacity makes it impossible to attend to everything and makes the filtering of information to the brain necessary

Ø Filter Theory of Attention: filtering occurs early in the process, before the input’s meaning is assessed

Dealing with
information not attended to

Ø Information that is not attended to will not make its presence known, unless it is very distinct or personally relevant.

Ø The cocktail party phenomenon;

ü When an individual hears their own name mentioned across a noisy room although the individual is participating in an unrelated conversation. Thus, even information to which an individual is not attending is processed to some extent.

Organizational Processes

ØPutting sensory information together to give the perception of coherence.

ØWhat a person experiences as a result of these processes is called a percept

 

Figure & Ground

Ø Figure: an object in the foreground of the visual field

Ø Ground : the background against which the object is seen

 

Gestalt Principles
of
Perceptual Grouping
 

Gestalt psychology,  

ØA theory of mind and brain that proposes that the operational principle of the brain is holistic, parallel, and analog, with self-organizing tendencies; or, that the whole is different than the sum of its parts.

The Gestalt effect

ØThe Gestalt effect refers to the form-forming capability of our senses, particularly with respect to the visual recognition of figures and whole forms instead of just a collection of simple lines and curves.

1. The Law of Proximity

ØAll else being equal, the nearest elements are grouped together

 

2. The Law of Similarity

Ø All else being equal, the most similar elements are grouped together

 

3. The law of closure

4. The law of good continuation
 

5. The Law of Pragnanz

Ø a general law that states that individuals perceive the simplest organization that fits the stimulus pattern

6. The Law of Common Fate
 

ØAll else being equal, elements moving in the same direction and at the same rate of speed are grouped together

Perceptual Constancies

ØPerceptual constancy refers to the tendency to see the world as invariant, constant, and stable, DESPITE changes in the stimulation of sensory receptors

üSize, shape , lightness, color, distance, and location constancy

Size and shape constancy

Ø Size constancy refers to the ability to perceive the true size of an object despite variations in the size of its retinal image

Ø Shape constancy refers to the ability to perceive correctly an object’s actual shape, even when the object is slanted away from the viewer, making the shape of the retinal image substantially different from that of the object itself

Shape constancy

Ø When a door is open, its image actually forms a trapezoid. Shape constancy is indicated by the fact that it is still perceived as a rectangle.

Size constancy

Square A is exactly the same color as square B. No kidding.

TWO TYPES OF PERCEPTIONS

1. Motion Perception

Ø Motion perception requires comparison across different fixations of the world and is dependent on reference frame

Ø Induced motion  occurs when a stationary object appears to be moving because a reference frame to which it is being compared is moving.

ü There is a tendency for the visual system to take a larger, surrounding figure as the reference frame for a smaller figure inside it.

Phi phenomenon

Ø The simplest form of apparent motion is the phi phenomenon, which occurs when two stationary spots of light are turned on and off alternately very quickly. It appears that a single light is moving back and forth between the two spots of light.

Phi phenomenon

Ø Temporal interval between fluorescent lamp a and b:

ü Shorter than 30ms (milliseconds), a and b emerging at the same time

ü Longer than 200ms, b after a

ü 60ms or so, a light moves from a to b

Illusory Motion:
stroboscopic movement

ØFrom still images, the brain perceives fluid motion.

üA movie or television: no actual motion occurs on the screen.

How does movie works?

Ø A motion picture is a series of still pictures flashed very rapidly on the screen, at the rate of 24 frames per second. Each picture varies slightly from the one preceding it. Similarly, when you watch television, you are seeing a series of 30 still images per second.

2. Depth Perception
 

Ø Depth perception requires that the visual system extract three-dimensional representations from two-dimensional information

Ø Vision relies on depth cues that allow the interpretation of sensory input

 

MONOCULAR CUES

Depth cues

Motion parallax

Ø When an observer moves, the apparent relative motion of several stationary objects against a background gives hints about their relative distance.

Ø This effect can be seen clearly when driving in a car nearby things pass quickly, while far off objects appear stationary.

Depth from motion,   

Ø A form of depth from motion, kinetic depth perception, is determined by dynamically changing object size.

Ø As objects in motion become smaller, they appear to recede into the distance or move farther away; objects in motion that appear to be getting larger seem to be coming closer.

Perspective ,  

Ø The property of parallel lines converging at infinity allows us to reconstruct the relative distance of two parts of an object, or of landscape features.

ü Relative size: An automobile that is close to us looks larger than one that is far away.

Aerial perspective

Ø Due to light scattering by the atmosphere, objects that are a great distance away have lower luminance contrast  and lower color saturation

ü As the distance between an object and a viewer increases, the contrast between the object and its background decreases. The contrast of any markings or details on the object also decreases. The colors of the object also become less saturated and shift towards blue

Occlusion  

Ø Occlusion (blocking the sight) of objects by others is also a clue which provides information about relative distance.

Texture gradient

Ø Suppose you are standing on a gravel road.

ü The gravel near you can be clearly seen in terms of shape, size and color.

ü As your vision shifts towards the distant road the texture cannot be clearly differentiated.

BINOCULAR CUES

Depth cues

Retinal disparity

Ø If an object is far away, the disparity of that image falling on both retinas will be small.

Ø If the object is close or near, the disparity will be large.

Ø It is stereopsis that tricks people into thinking they perceive depth when viewing 3D movies and stereoscopic photos.

Convergence

Ø Also an oculomotor cue

Ø By virtue of stereopsis the two eye balls focus on the same object. In doing so they converge. The convergence will stretch the extraocular muscles. Kinesthetic sensations from these extraocular muscles help in depth/distance perception.

Ø The angle of convergence is larger when the eye is fixating on far away objects.

IDENTIFICATION & RECOGNITION PROCESSES

Stage Ⅲ: Identifying & Recognizing

Bottom-Up Process

Ø Also called data-driven processing.

Ø Bottom-up processing is taking sensory data into the system and sending it upward for extraction and analysis of relevant information.

ü It is anchored in empirical reality and deals with bits of information and the transformation of concrete, physical features of stimuli into abstract representations.

Bottom-top process

Top-down process

Ø Also called hypothesis-driven processing.

Ø Top-down processing is when past experiences, knowledge, motivations, cultural background, and expectations affect perception, as higher mental functioning influences how objects and events are understood.

 

Ø An example of top-down processing: Even though the second letter in each word is ambiguous, top down processing allows for easy disambiguation based on the context.

THE INFLUENCE
OF
CONTEXTS & EXPECTATIONS
 Expectations,  

ØObject identification is a constructive, interpretive process.

ØExpectations can influence hypotheses about what is out there in the world and can influence what is actually perceived.

 

 

Context,  

Ø It takes longer to recognize an object when it is seen in the wrong context, not in a familiar place

 

 

An explanation: Set  

Ø Set is a temporary readiness to perceive or react to a stimulus in a particular way. There are three types of sets: motor, mental, and perceptual.

ü A perceptual set is a readiness to detect a particular stimulus in a given context

ü A mental set is a readiness to deal with a situation, such as a problem-solving task or game, in a way determined by learned rules, instructions, expectations, or habitual tendencies.

ü A motor set is a readiness to make a quick, prepared response

 

Illusions & Hallucination

ØIllusion: Misleading or distorted perceptions of stimuli that actually exists

ØHallucination: When people perceive objects or events that have no external basis in reality

 

Final Lessons

Ø A perceptual experience in response to a stimulus event is determined not only by the stimulus but also by the person experiencing it.

Ø  In addition to sensation, final perception depends on past experience, expectations, wants, goals, values, and imagination.

 

Final lessons

Ø A proper balance of top-down and bottom-up processing achieves the basic goal of perception: to experience what is out there in a way that maximally serves your needs as a biological and social being, moving about and adapting to your physical and social environment.

Summary

•                 Terms: Psychology & Medical Psychology; sensation and perception; absolute and difference threshold; response bias

•                 Some common sensations and two kinds of perceptions

•                 Principles of perceptual organizations

•                 Two types of identifying and recognizing processes: bottom-top & top-down processes