ERGONOMICS FINAL REVIEWER PERCEPTUAL AND COGNITIVE Cognitive ergonomics – interaction between human and system that considers the human abilities and limitations - application and psychology to work Perception – based on how we interpret all these different sensations Three (3) Perception Process: 1. Selection – is your decision on what you want to focus to 2. Organization – choosing on what kind of reaction we are going to make depending on the situation. 3. Interpretation – categorizing the effects from the first two stages. VISUAL DISPLAYS – device with a screen that displays characters Visual - something that appeals to the sight Display - to put / spread before the view; a public showing of objects of interest. Factors influencing visual display effectiveness A. Physical location 1. positioning of a visual 2. Location of a display 3. the size of the informational content and the time course of the signal. B. Display Arrangements C. Lighting Conditions D. Static versus dynamic displays E. Display coding 2. Color and Contrast – There are actually two color systems: one which deals with emitted light and one which deals with reflected light. - colors of light that we perceive can be produced by combinations of the three primary colors: Red, Green, and Blue Subtractive Color - pertains to an illuminated object that reflect lights, but does not produce its own Additive Color - pertains to self-luminous light sources 3. CIE (Color Matching) – the Commission Internationale de l’Eclairage (CIE) developed a light measurement standard 4. Color displays –more appealing to the eye than monochrome displays *Color Coding – help us see patterns and distinguish one area from another 5. Pre-attentive Processing (Parallel Processing and Pattern Recognition) 6. Text & Character Attributes • Contrast - Brightness contrast between character and background. • Size - Height, height-to-width ratio, strokewidth-to-height ratio, character spacing, word/item spacing, and line spacing. • Font - Character shape, presence or absence of serifs. • Color - Choices for text, background, color-coding. HUMAN FACTORS ASPECTS OF VISUAL DISPLAY DESIGN Selecting the appropriate character and text attributes depends on: 1. Human visual system – is sensitive only to a small portion of the electromagnetic spectrum • User Population - Who will use the display? • Display Application - How will the display be used • Environment - Will the display be used in an office environment, an air traffic control tower, aircraft cockpit, maintenance area, or equipment shelter? 7. Symbols and Icons – • Icon - identified without text or labeling. • Symbol - no physical resemblance to what it represents. Its meaning must be learned. • Computer Icon - usually placed within a border that may or may not contain a label. Auditory Presentation Avoid extreme auditory dimensions - if sound is too loud or there will be a "startle response". β Signal/noise ratio - establish intensity relative to ambient noise levels to avoid masking. β Variable Signal - works best to attract attention by minimizing perceptual adaptation to monotones and increasing the delectability of the signal, e.g. Beep! Beep! Beep! is better than "Beeeeeeep"! β Don’t overload the auditory channel – consider the effect of the auditory information on the whole system AUDITORY DISPLAYS –used to orient attention to events outside the user's field of view Warning Signals - Auditory displays are useful for signaling alarms General Principles 1. Compatibility - Make use of pre-existing stimulus-response relationships 2. Orienting reflex - is a basic reflex to turn to the source of a sound (stimulus), 3. Learned - Examples are sirens which are learned to be associated with an emergency. 4. Approximation - Complex messages should be presented in two stage signals: a. Attention Demanding Signal - to capture attention. b. Designation Signal - with precise message information. 5. Dissociability - Auditory signal must be discernible from other noise, e.g. when several phones ring in an office it's difficult to tell which is ringing. 6. Parsimony – short message 7. Invariance - to avoid confusion Auditory Processing – how the brain perceives and interprets sound information Step 1: Auditory Awareness a) Auditory Awareness - the ability to detect sound b) Sound Localization - the ability to locate the sound source c) Auditory Attention/Auditory Figure-Ground the ability to attend to important auditory information including attending in the midst of competing background noise. Step 2: Auditory Discrimination a) Auditory Discrimination of Environmental Sounds - the ability to detect differences between sounds in the environment b) Auditory Discrimination of Suprasegmentals - the ability to detect differences in nonphoneme aspects of speech including rate, intensity, duration, pitch, and overall prosody c) Auditory Discrimination of Segmentals - the ability to detect differences between specific speech sounds. Step 3: Auditory Identification a) Auditory Identification (Auditory Association) - the ability to attach meaning to sounds and speech b) Auditory Feedback/Self-Monitoring - the ability to change speech production based on information you get from hearing yourself speak c) Phonological Awareness (Auditory Analysis) - the ability to identify, blend, segment, and manipulate oral language structure Step 4: Auditory Comprehension a) Auditory Comprehension - the ability to understand longer auditory messages b) Auditory Closure - the ability to make sense of auditory messages when a piece of auditory information is missing; filling in the blanks 3. Relearning- assess the time saved while learning material again. Three (3) types of Human Memory 1. Sensory Memory- It acts through the five senses of sight, hearing, smell, taste and touch 2. Short term Memory- temporary recall of the information which is being processed at any point in time, and has been referred to as “the brains past-it note. 3. Long term Memory- Intended for storage of information over a long period of time Types of Long-term Memory: 1. Declarative Memory (Explicit Memory) – memory of factual information, general knowledge, data, and events • Episodic Memory – memories of personal experiences • Semantic Memory – general factual information 2. Procedural Memory (Implicit Memory) – memory of how to perform a task c) Auditory Memory - the ability to retain auditory information d) Linguistic Auditory Processing - the ability to interpret, retain, organize, and manipulate spoken language for higher level learning and communication. MEMORY, ATTENTION AND MENTAL WORKLOADS Memory – picked up by one or more senses Memory is built and retrieved in three different ways: 1. Recall- person retrieves information learned earlier. 2. Recognition- person has to only identify the previous learned information. Attention –focuses an individual's awareness - complex cognitive function Types of Attention 1. Selective Attention- select from the various factors to focus on only the one you want. 2. Sustained Attention- focus on one specific task for a continuous amount of time without being distracted. 3. Alternating Attention- allows you to shift your focus of attention and move between tasks having different cognitive requirement. 4. Divided Attention- process two or more responses. It is often referred to as multitasking. Mental workload –amount of cognitive work required for a person to complete a certain task over time Mental –relating to the total emotional Workload –amount of work Measurement of Workload 1. Self-assessment measures - subjective or self-report measures 2. Task performance measures - based upon the assumption that the mental workload of an operator influences system performance. 3. Physiological measures - take the physiological responses of the operator's body into account. Environmental Factors and Their Applications Physical Environment: Noise, Illumination, Temperature, Vibration and Job Design Noise Pollution Regulation – To assure that all companies must maintain a proper and healthy environment Physical environment – refers to the factors that directly affects the human body Audiometric testing – It is done by trained technicians to detect any hearing loss - can increase or decrease the productivity NOISE Noise – unwanted sound Sound –produced by vibrating objects Four Major Properties of Noise a) Frequency (Hz) – The number of waves that pass a fixed place b) Sound Pressure (dB) –The difference between the instantaneous pressure and the static pressure of the medium. c) Sound Power (watt) – The rate at which sound energy is emitted d) Time Distribution – A measure of how much time the matter spends in it Illumination Illumination – act of placing light on an object Two Types of Illumination 1. Natural Light – Light received on Earth from the sun 2. Artificial Light –any light source that is produced by electrical means Daylight Can Be Divided into Two Components a) Sunlight is light received at Earth’s surface, directly from the sun. b) Skylight is light from the sun received at Earth’s surface after scattering in the atmosphere Three Classes of Illumination π· = πΆ1/ π2 + β― + πΆπ/ ππ ; X 100 Incandescent lamps – Produce light by heating a filament. Incandescent lamps can operate directly from mains electricity. D – Dose C - Actual Exposure Time T – Allowable Exposure Time Discharge lamps – Produce light by an electric discharge in a gas. Noise Safety Formula (HLP) Types of Hearing Protection a) Ear Plugs – made of foam, rubber or plastic b) Ear Muffs – cover the whole ear and are preferred by some people c) Ear Caps – good for occasional use or for people who find earplugs uncomfortable NRR(Noise Reduction Rating)– is found on the earmuff or earplug package Solid state lamps – Produce light by the passage of an electric current through a semiconductor The Wavelengths of The Light The wavelength is (λ) unit (nm or nanometer) is related to the frequency (f) unit (Hz or Hertz). π c=π∗λ c = 300,000 km/s or 3 x 10^8 m/s Lighting Conditions That Can Cause Discomfort Flicker – achieved by high frequency operation Glare – to have too much light Visual discomfort – can occur when your eyes start to feel tired Raynaud’s Phenomenon – A disorder of the blood cells Extreme Heat Health Effects TEMPERATURE - measure of warmth or coldness of an object Thermal Comfort – feels neither too cold nor too warm Environmental Factors 1. Air temperature – Temperature of the air surrounding the body 2. Radiant Temperature – Heat that radiates from a warm object 3. Air velocity – speed of air moving across the employee 4. Humidity –the resulting amount of water evaporated in the air Relative humidity – is the ratio between the actual amount of water vapor in the air Personal Factors 1. Clothing Insulation – Clothing is both a potential cause of thermal discomfort 2. Metabolic heat – Also called “Work Rate”. The more physical work we do, the more heat we produce Extreme Cold Health Effects Hypothermia – A common cold injury associated with low body heat Frostbite – when your skin's exposed to the cold Trench foot – Long immersion of foot under the water. Cold-induced of hives – Reddish and itching of face Chilblains – small and itchy swelling on the skin Heat Stroke. The most serious heat-related illness Heat Exhaustion. Often a precursor to heat stroke Heat Cramps. Caused by the body's depleted salt and water levels from excessive sweating Heat Rash. Skin irritation caused by excessive sweating Fainting. A sudden loss of consciousness HUMIDEX 1. Dry bulb temperature – also known as normal temperature is an indicator of heat content and measure of how dry is the air. 2. Wet Bulb Temperature – is a measure of how much moisture is present in the air. VIBRATION Vibration or oscillation – means quickly moving back and forth Two Types of Vibration Whole body vibration (WBV) –when the body is supported on a surface that is vibrating ο· ο· Visual impairment – a decreased ability to see, fixable by usual means, such as glasses Motion sickness – common problem in people traveling by car Hand-arm vibration – vibration transmitted to the hand and arm during the operation of handheld power tools ο· White finger - is discoloration of the extremities Vibration magnitude – is the frequency weighted acceleration value measured in m/s2 Vibration meter – used to measure vibration Vibration Frequency – expressed in cycles per second using the SI unit hertz (Hz) Vibration Direction – The responses of the body to motion differ according to the direction of the motion Vibration Duration – duration of exposure JOB DESIGN Job design – involves systematic attempt to organize tasks Four Approaches to Job Design 1. The Mechanistic Job Design Approach – stems from the scientific management school of thought & time and motion study 2. The Motivational Job Design Approach – stems from the work in job enrichment and enlargement 3. The Biological Job Design Approach – derived from the sciences of biomechanics, work physiology 4. The Perceptual/Motor Job Design Approach – main contributors are the human factors engineering guidelines Job simplification – breaking the job into easier sub-parts Job enlargement – combines into one job with two or more tasks Job Rotation – practice of moving employees between different tasks to promote experience and variety Job enrichment – giving workers more control over how their job is performed (Frederick Herzberg) Benefits of Job Design 1. Employee Input – Employees have the option to vary tasks as per their personal and social needs 2. Employee Training – Training is an integral part of job design 3. Work / Rest Schedules – clearly defining the number of hours an individual has to spend in his/her job. 4. Adjustments –aligning the manpower requirements for the same.
