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

Outline Introduction Experiment Discussion

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.

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)

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.

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.

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.

– 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)

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.

– 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 7 contacts + 1 contact Constant state 8 contacts 1 new contact in 1 old contact out

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.

– 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.

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 1 st = 2 nd ; 2 nd > 3 rd ; 3 rd > 4 th The bearing and speed are the most difficult types of changes to detect. Change detection with respect to these contacts degraded over time.

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 3 rd and 4 th quarters are overloaded or not? The cautions for new interface designs.