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Perception & Human Factors

"We shall understand accidents when we understand human nature"
- Kay (Accidents: Some facts and theories, 1971.)

Human Factors is defined as "the application of scientific data to make the world compatible with human abilities, fitting the product to the sensory, information processing, and motor attributes of the user." It is an area of applied psychology that arose 60 years ago in the aviation industry. Until then, accidents were almost invariably attributed to mechanical fault, to weather or to human error. Careful analyses began to show poor design caused many accidents; there was a mismatch between humans and design. One the earliest, and most influential examples (Fitts, P.M., & Jones, R.E. 1947a, Analysis Of Factors Contributing To 460 “Pilot Error” Experiences In Operating Aircraft Controls, Report No. TSEAA-694-12).was the common pilot error of grabbing the wrong lever and raising the landing gear rather than lowering the flaps. The two controls looked and felt the same and were located next to one another. In modern human factors terms, pulling the wrong lever is an "active error" while the control design was a "latent failure," or an "error trap." Note than in human factors, "human error" refers does not equate to blame. In fact, the concept of blame has no place in human factors. Human factors is a method of reducing accidents by studying human abilities, limitations and predispositions and then by designing artifacts and environments that fitted the human. This approach is often termed "user centered design."

Human factors is not engineering. It may be used by engineers at times, but the underlying science is purely psychology, mixed with some physiology and the occasional kinesthesiology. The largest professional human factors organization in America is the Human Factors & Ergonomic society. Human factors uses scientific knowledge of human capabilities, such perception and attention, memory and behavior, to understand how people interact with the world. This can mean interactions with buildings, computers, medical or other electronic devices, vehicles or other technology. Human factors helps design better environments and analyzes the source of error and accident in existing ones. It is widely applicable, since human error occurs at some point in most of our interactions with the world.

Almost all human interactions with the world involve visual perception. Most everyday activities, driving, reading, watching TV, operating a computer or medical device, deciding which brand of soap to buy, etc., involve the human ability to see, to recognize and to decide whether two things appear the same or different, and then to make a decision and to respond. Understanding how this happens is often the key to analyzing human choice and behavior and to understanding accident and trademark confusion.

Many studies have purported to show that human error is the most common accident cause:
  • In the first major study, "The Origin of Accidents" (1928), Herbert Heinrich examined 75,000 industrial accidents and attributed 88% to "unsafe human acts."
  • Former National Transportation Board Chair Jim Hill has testified before a congressional committee that human error causes 70% of accidents in all walks of life.
  • A Boeing study of major worldwide airline crashes found that 71.7% were due to human error.
  • Reason (Human Error, 1992), studied 180 nuclear power plants in 1983 and 1984 and concluded that human error was 52% of the root causes.
  • Rasmussen et. al. (New Technologies and Error, 1987) found that 88% of all occupational accidents are caused primarily by individual workers.
  • Wood et al. (CSERIAC, 1994) concluded that over 70% of operating room anesthetic incidents involve human error.
  • According to the most complete surveys, over 90% of all highway accidents are caused fully or in part by human error. And of these, 90% are caused by perceptual error and 10% by response error. In short, perception is a factor in over 80% of all highway accidents. Most of this error is due to perceptual and attentional failure or to inadequate highway visibility conditions. Moreover, visibility of warning labels, usability of computer/medical devices, legibility of instructions, placement of signs and warnings, recognition of people and objects, etc are all ultimately an issue in visual perception.

These percentages are amazingly large, but hide one important fact - that accidents attributed to human error are often really caused by a poorly designed system, product or environment. The role of the human factors expert is to determine the contributions of the individual and the circumstances.  

Many people have heard the term "human factors" but are unsure what it means. Here is list of articles which provide a general overview of perception and human factors. They should be useful in gaining understanding of how human factors people think and analyze the huge number of accidents which involve human behavior. We also provide seminars on most of these topics

Personal Injury: Road Accidents
  • Is The Moth-Effect Real?
  • Human Error in Road Accidents
  • Reaction Time
  • Let's Get Real About Perception-Reaction Time
  • Why PRT Is Not Like Gravity
  • Vision in Older Drivers
  • Weather and Accidents: Rain & Fog
  • Accidents At Rail-Highway Crossings
  • Seeing Pedestrians At Night
  • Underride Accidents
  • Rear End Collision: Looming
  • Night Vision
  • Distracted Pedestrians
  • Failure To See
  • Perception-Reaction Time (PRT) Programs
  • Twilight (3.2 lux) As A visibility Criterion
  • Human Error And Fault Tolerance
  • Why Pedestrians Die
  • Bicyclists! Read This To Save Your Life
  • Personal Injury: Warnings & Product Defects
  • Warnings and Warning Labels
  • Warning Effectiveness Checklist
  • The Psychology of Warnings
  • Drugs, Adverse Effects & Warnings
  • Are Warnings Effective?
  • Human Error Vs. Design Error
  • Product Misuse And "Affordances"
  • Safety Hierarchy: Design Vs. Warning
  • Thinking Like A Human Factors Expert
  • Personal Injury: Other
  • Diving Accidents in Pools
  • Falls Down Steps
  • Medical Error
  • Computer & Medical Error
  • Nursing Error
  • Criminal & Police
  • Errors in Eyewitness Identifications
  • Perceptual Error in Police Shootings
  • Eyewitness Memory Is Unreliable
  • Human Factors In Forensic Evidence
  • Intellectual Property
  • "Any Fool Can See The Trademarks Are Different"
  • Measuring Confusion For Intellectual Property
  • Color in Trademark and Tradedress Disputes
  • Color Functionality: A Case Example
  • Visual Human Factors
  • 33 Reasons For Not Seeing
  • Seeing Color
  • Determining Visibility
  • "Inattentional Blindness" & Conspicuity
  • Computer animation has perceptual limitations
  • Photographs vs. Reality
  • The Six Laws Of Attention
  • What is "inattention?"

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