1 SENG 412: Ergonomics Lecture 11. Midterm revision Announcement Midterm will take place: on Monday, June 25 th, 1:00-2:15 pm in ECS 116 (not our usual classroom!) 2 Readings required for exam Lecture slides: - Visual sensory systems; - Auditory, tactile and vestibular systems - Signal detection, discrimination, and absolute judgment - Cognition Textbook chapters: - 4. Visual sensory systems - 5. Auditory, tactile, and vestibular systems - 6. Cognition (stop at page 145).! Readings for Signal detection, discrimination, and absolute judgment are distributed in chapters 4 (pp. 83-89) and 5 (pp.102-103). Types of exam questions Application of human factors principles related to sensory systems, perception and cognition to a concrete situation Questions related directly to visual, auditory, and tactile perception. Insist on why s and how s. How to prepare for this exam: Do not simply memorize concepts. They will be stored only in your short-term memory! Reflective learning: Build connections between concepts. Active learning: Apply the concepts: find examples that illustrate the real-life manifestation of a concept 3 4 Visual sensory system The questions contained in this review are just examples of questions. A subset of these questions might or might not be part of the midterm. Some topics are not covered by this review, which is not intended to be exhaustive Answers to the questions will be discussed in class; they are not posted on slides. A research study has indicated that the small font size on prescription drug containers was making it difficult for some patients to read the dosage instructions. One hundred eighty patients whose average age was 70 were assessed to determine the point at which the patients would be unable to read the instructions without a magnifying glass. All of the patients had impaired eyesight in one or both eyes, although the level of impairment varied. Researchers permitted the patients to bring the prescription drug bottle as close to their faces as necessary in order to read the instructions. Patients who took longer than 30 seconds to find a readable position for the bottle were then classified as reading with great difficulty. What type of limitation of the visual sensory system causes this readability problem? Choose one of the limitations below and justify your choice. In your justification, include a brief definition of the chosen concept. - visual accommodation ability - visual acuity - contrast sensitivity 5 6
Visual sensory system In minimally invasive surgery, monocular camera conveys the site of operation to a TV monitor. This imposes severe restrictions on depth perception of the site of operation. What perceptual cue is unavailable for the endoscopic task? What perceptual cue(s) can a surgeon use for not getting lost during an endoscopic procedure? Visual sensory system Give one example of each: a visual stimulus which is processed via a long saccade; a visual stimulus which is processed via a short saccade 7 8 Visual sensory system Example of short questions (why s and how s): Why do we need a three-cone system instead of a single-cone system? The cone sensitivity graph might be helpful for finding the right answer. Visual sensory systems A general guideline for writing software manuals relates to the inclusion of entry points that are easy to locate by browsing. A good design scheme shows each text section name in boldface, arranges sections alphabetically, and puts the terms at the top of each page as headers. Find one element in this design scheme that supports bottom-up processing Find one element in this design scheme that supports top-down processing. 9 10 Visual sensory systems Which type of target-oriented visual search (serial or parallel) requires the use of memory? Explain why. You may use examples of visual searches in your explanation. Which type of target-oriented visual search (serial or parallel) requires attentional resources? Explain why. You may use examples of visual searches in your explanation. When designing a graphical user interface, what type of visual search (serial or parallel) is best suited for attention capture? What elements can you use for implementing your attention capture mechanism? Auditory sensory systems Find one major difference between visual and auditory alarms. What are the design implications of this difference? List and briefly describe two types of noise-induced hearing loss. Which subfield of ergonomics deals with such issues? 11 12
Auditory sensory systems List two criteria for auditory alarm design that handle sound masking. Which properties of the sound masking phenomenon are addressed by these two criteria? Give one example where sound masking is useful. What properties of the soundmasking phenomenon are used in the design of a system for sound masking? Auditory sensory systems Give an example of task which would rely on accurate sound localization. Explain how sound localization depends on the frequency of the sound. 13 14 Auditory sensory systems Why do we need such a complicated system (outer ear, middle, ear, inner ear) for hearing? Sensory systems (general) After a sleep-deprived spring break in Daytona Beach, a group of four college students begin their trip back to their university. To return in time for Monday morning classes, they decide to drive at night. Joe finds himself fighting to stay awake on a boring stretch of the highway at 3:00 am. After setting the cruise control, Joe begins to fall asleep. The car slowly drifts towards the shoulder of the highway. The system monitoring Joe s alertness detects the onset of sleep and the drift of the vehicle. As a result of this detection, the system generates an alert that vibrates the seat by means of a virtual rumble strip. This warning wakes Joe and enables him to quickly steer back onto the road. What type of alarm does the system provide? Give a justification for using this type of alarm instead of alarms based on other sensory systems. 15 16 Signal detection theory Read carefully the 2 scenarios below. What elements to they have in common? Are these two scenarios appropriate for being analyzed with the SDT? Justify your answer. 1. A seismologist is trying to decide whether to predict that a large earthquake will occur during the next month. The evidence is complex. Many bits of data can be brought to bear on the decision, but they are ambiguous and sometimes contradictory: -records of earthquake activity in the distant past (some of which are not very accurate), -seismographic records from recent times (whose form is clear, but whose interpretation is not), and so forth. 2. A witness to a crime is asked to identify a suspect. Was this person present at the time of the crime or not? The witness tries to remember the event, but the memory is unclear. It was dark, many things happened at once, and they were stressful, confusing, and poorly seen. Moreover, the crime occurred some time ago, and the witness has been interviewed repeatedly and has talked to others about the even. 17 Signal detection theory Give one example of your own where the Signal Detection Theory is applicable. 18
Absolute judgment Why is an absolute judgment task more difficult than a signal discrimination task? Base your justification on one example. Signal detection theory How do we measure the sensitivity of a human operator for a specific signal to noise ratio? Draw one graphical representation of the noise and of the (signal + noise) distributions for : Low sensitivity High sensitivity 19 20 Signal detection theory The diagram below shows the effect of shifting the criterion on the hit and false alarms rate. Which case corresponds to the most liberal criterion? Which case corresponds to the most conservative criterion? Explain why. The surgeon performance on endoscopic procedures is significantly affected by the poor hand-eye coordination. What element on the Human Information Processing diagram is appropriate for modeling this issue? 1 2 3 21 22 During a typical conference session, questions from the audience are asked at the end of each oral presentation. The organizers of a Canadian Ergonomics conference have decided to try a new scheme. The audience was told to keep all their questions until the end of the session, when all presenters formed an ad-hoc discussion panel. What impact has the new design scheme on the human information processors in the audience? List and discuss at least one advantage (or disadvantage) of this new scheme over the traditional one. Human Information Processing Consider the following statement. People can t keep more than 7+/-2 letters in working memory. In what sense is the statement right, and in what sense is the statement wrong? 23 24
Human Information processing A baseball coach faced with an unusual situation requiring a rule interpretation might think like this: "I remember a similar situation in a professional baseball game... When was it...? Last year... Reds vs. Giants... It was a night game, and the Giants had runners on first and second, when a line drive bounced and hit the umpire... What was the call...? I think they gave the batter a single and let the runners advance one base... But I thought when the ball hit the umpire it remained in play... Now I remember! If the umpire is in front of the fielders, it's a dead ball and a single. If the umpire would have been behind the fielder, it would have remained in play..." What type of memory does he use for retrieving the information that he was looking for? Give a brief justification for your choice. Consider the following memory aid implemented as a highway sign: LEFT TURN 1 MILE AHEAD What type of memory is supported by this aid? Find an example of your own, preferably from software engineering, which provides the same type of memory aid for a different user task. 25 26 Describe the role of selective attention in Situation Awareness. What other elements of the Human Information Processing are used in Situation awareness? 27