作 者： Joseph DiVita et al. 報告者：李正彥 日 期： 2006/4/27

1. Verification of the Change Blindness Phenomenon While Managing Critical Events on a Combat Information Display 作　者：Joseph DiVita et al. 報告者：李正彥 日　期：2006/4/27

2. Outline • Introduction • Experiment • Discussion

3. Introduction • Change blindness: people can not detect changes in objects and scenes after their attention is momentarily diverted. (Simons & Levin, 1997) • Current study investigated the phenomenon in the context of tasks performed by naval command and control system personnel. • High-load in visual search, situation assessment, voice communications, and control-display manipulation tasks.

4. The paradigms of change blindness • Include changing objects in a visual display… • During a blank interval between 2 successive presentation. (Rensink et al., 1997) • While the observer blinks or makes a saccade during viewing. (Henderson & Hollingworth, 1999) • When a set of dot patterns is superimposed on the scene. (O’Regan et al., 1999) • During a cut in a motion picture scene. (Levin & Simon, 1997) • In the course of a real-world occlusion event. (Simons & Levin, 1998) • The change to more directly attend objects. (Ballard et al., 1995)

5. To detect a change, we must engage in a comparison process. • Original scene has been encoded in to working visual memory → inefficiency of the comparison process. • People prefer to minimize the use of working memory when performing simple natural tasks. • Attention is specifically required to perceive change. (Rensink et al., 1997) • The development of attention is generally believed to be a relatively slow, serial process.

6. Determine whether or not change blindness occurs during the course of activities performed by operators of naval CIC consoles. • 2 factors contribute to the change blindness effect: • The content • The amount of information • The problems of the procedure of prior studies: • The tasks for observers are vague. • The tasks are diversion in essence. • In this study, the change detection tasks are relatively specific and skilled. • The purposes of current study: • Ascertain the degree to which change blindness occurred • Note any pattern to the change blindness phenomenon in this applied setting.

7. Experiment • Method • 28 employees from the SPAWAR, all had 2~20 years of job experience. • Display: air traffic about military tactics. (Figure 1) • 2-dimentional, top-down view. • Participants were instructed to select a symbol (contact). • Information present in a CCRO • Participants determine whether the information in the CCRO was consistent with the contact’s amity category.

8. Four categories of attribute changes were tested in the aircraft monitoring task: • Course refers to the compass direction of the contact relative to true north. • Speed reflects how fast the aircraft is traveling. • Range is the distance from the aircraft to ownship. • Bearing is the compass direction of ownship to the aircraft. • The majority of these changes are not significant, but are considered critical. • 6 different ways that new contacts entered the airspace were identified and tested. (Table 2)

9. Procedure • 2 monitors • Left: tactical situation display and CCRO • Right: alerts and notifications • Introductory materials. • Task explanation. • Participants answered a series of questions to ensure that each of the contacts had been focused. • Participants had to respond to alerts and notification. • Participants were instructed to report the change by selecting the appropriate contact with the mouse. • The immediate feedback is given.

10. On critical trials, the tactical display was blanked and the operator was informed. • On the alert display, a significant change had taken place on the tactical display. • 8/20 trials noted by a superscript a in Table1 & 2. • In other 12/20 trials, the course change becomes arbitrary. Initial state Constant state + 1 contact 1 new contact in 1 old contact out 7 contacts 8 contacts

11. Results • Figure 2, the percentage of the trials it took participants to correctly identify a change is plotted as a function of the number of selections. • Participants required 2 or more selections to correctly identify the changed contact on 28.8% of the critical trials. • Random model A: the result did not support that the participants is randomly guessing from among the 8 contacts. • Random model B: the result did not support that the participants is randomly guessing from among the remaining 5 contacts. • Random model B: the result did not support that the participants is randomly guessing from among the remaining 6 contacts.

12. Figure 3, each category incurred some degree of change blindness. • Difficulty to detect • Bearing changes > course and new track changes. • Figure 4, the percentage of trials requiring 3 or more selections for correct change detection with or without tactical graphics present for the 8 conditions. • In 7/8 conditions, changes were more difficult to detect without the tactical graphics. • Across 8 conditions and for the 2 display types, 2 graphical display conditions significantly differed from each other. • Detecting a course change (ACC1) was more difficult in the absence of tactical background graphics.

13. Figure 5, the percentage of 3 or more selections for the remaining 12 conditions not deed sensitive to the background graphics. • No significant difference in display type. • Change detection was more difficult without the tactical graphics when a hostile aircraft decelerated to be in formation (ACS5). • Figure 6, total number of selections to detect changes in each quarter is plotted. • The difficulty of change detection • 1st = 2nd ; 2nd > 3rd ; 3rd > 4th • The bearing and speed are the most difficult types of changes to detect. • Change detection with respect to these contacts degraded over time.

14. Discussion • Change blindness occurs in the CIC environment and that in tactical situations entailing greater numbers of contacts of interest, the effect is more severe. • If the participant’s attention is not diverted → no change blindness occurs. • The task in experiment is not memory-on-demand. The information is sufficient to capture the course changes tested. • Whether the increased memory demands in the 3rd and 4th quarters are overloaded or not? • The cautions for new interface designs.