ARCHAEOLOGICAL VISION AT ÇATALHÖYÜK
MICHAEL ASHLEY-LOPEZ
There is little debate that vision plays a critical role in archaeological fieldwork. Nonetheless, vision is but one tool employed during an excavation. All of the senses are employed in fieldwork and some would argue that feel and gut instinct (experience) is more important than seeing. Further, optical vision - light entering the eye and our ability to process this information - is merely a small part of 'seeing' - seeing is a recursive process that involves memory, perception and emotion. It is my hope that by focusing on the visual, I may articulate the role of vision in archaeology, both from the perspective of archaeologists and fieldwork in the present to viewers and viewing conditions in the past.
This season, I conducted a systematic vision testing program of members of the Çatalhöyük teams. Tests were conducted over a series of days and at several times each day, under different lighting conditions. The objective was to reveal what conditions, if any, affect the archaeologists' ability to use their eyes as investigative tools and to explore ways to improve the viewing conditions at the site. Experimental glasses were employed and testing took place both under the existing shelters and under full sun and cloudy conditions. Preliminary results show that there are several simple, cheap and effective ways to improve field vision at the site.
Introduction
My interest in Çatalhöyük has always been in the visual, be it painted walls or simply how to document the archaeological record. Optical vision is often taken for granted in archaeology and 'normalized', as if it is assumed that we all see the same things the same way, although clearly this is not the case. Thus, this year I turned my attention toward the archaeologists and 'seeing' in archaeology, for the express aim of exploring practical ergonomic issues - from the extraordinarily bright working conditions under the exposed Anatolian sun to the comparatively low-contrast shelters and off-site work areas.
I conducted a series of vision test of members (I prefer 'member' to 'subject') of the Çatalhöyük teams in their working areas. Tests were administered over a series of days and at several times each day, under different lighting conditions. A lot of time was spent observing and documenting the archaeological process in action. Particular attention was paid to the changing lighting conditions, as well as to the field conditions and disposition of the team members. Additionally, some members were interviewed about their ideas on vision in archaeology, present and past.
I focused my study on five areas of the site:
- BACH: Under shelter compared to North shelter and exposed lighting.
- TP (Posnan): Summit area compared to North shelter and exposed working conditions.
- South: Preliminary testing in area where new South shelter will be placed this year.
- Flotation Area: Under shelter and under exposed sun conditions.
- Sorting (Heavy Residue) Area: Under normal working conditions and shrouded conditions to reduce ambient glare from compound.
All told, about 50 members were tested, three times per session - left eye, right eye, both eyes - and for an average of three sessions, approximately 450 tests.
Testing procedure:
The test employed for this study is the Pelli-Robson contrast sensitivity test. This test is a poster made up of triplets of letters that gradually change from black letters on white (high contrast) to very light grey letters on white (low contrast). Under controlled, clinical viewing conditions, this test is used to diagnose certain eye diseases and degrading contrast sensitivity in individuals.
Figure 19: Michael Ashley-Lopez testing Katy in the flotation area
Contrast sensitivity is a good marker for assessing vision in archaeology due to the repetitive nature of the work. Prolonged periods of working under the same lighting conditions while looking at a similar color matrix leads to a desensitization to the stimulus through adaptation. In other words, you become less sensitive to subtle differences in the viewed material, be it under bright sunlight or shelter.
Due to time constraints in the field and the desire to test as many people as possible under different viewing conditions, I needed to limit the testing 'battery' to one easy-to-perform test. The PRCS test takes less than five minutes to administer on both eyes.
This test of letters is recognizable by all members in the testing group. Contrast sensitivity tests can also take the form of gradients that would be more difficult to explain to non-English speakers, although they have many benefits over letter tests.
Under exposed conditions, members were tested with their naked eyes several times per day. Members were also tested wearing one of two pairs of glasses. These glasses block 100% ultraviolet (UV), dramatically reduce glare and a large amount of ambient light. One pair was tinted amber (warm) and the other was grey (cool). Members would wear the glasses for a minimum of ten minutes to allow their eyes to accommodate and then the test was re-administered.
Figure 20: Serdar tries out the grey ‘specs’
Members who worked under shelters, be it the BACH shelter, flotation or the sorting area, were tested under normal working conditions, again at several times per day (Fig. 19). Members who worked in exposed sun conditions (TP and South) were tested under full sun, cloudy conditions and also at several times during the work day (Fig. 20). Most members were also tested in the North shelter at the same time of day (around 2pm) to provide a 'normal' condition.
Results:
Preliminary results met common sense expectations - members performed best when the viewing conditions were optimal. Optimal viewing conditions vary from person to person, but all members benefited from the reduced glare, UV and ambient light exposure provided by the glasses, in many cases significantly. Even when the member reported that seeing 'seemed' better without the glasses - these particular pairs were quite dark and strongly tinted - they still performed better optically while wearing them, almost without exception.
The BACH tent appears to be the least pleasant visual area. Members consistently performed worse than when tested in the North tent and as a group did not perform as well as other members who were tested under exposed, bright sun conditions. This is a result of the shelter, not the members' abilities, for many of the BACH members were tested outdoors and/or with the glasses and performed as well as anyone on site. BACH team members consistently reported that it was 'clearer' and 'more comfortable' in the North shelter than in the BACH tent. I attribute this both to the material of the tent (white plastic vs. muslin that breaks up the ambient glare) and the open side flaps that place a bright glare spot in the peripheral vision of people working in the tent.
In the TP area, members generally performed well with the glasses and when tested in the North shelter and did worse under bright, exposed sun conditions. All members reported (not surprisingly) that it was more comfortable to work under the North shelter than under the direct sun. Near the end of the season, a temporary shelter was constructed over the TP area. All members of the TP team reported that it was easier to see under the temporary shelter, yet in spite of this they consistently performed worse when tested under the shelter than under exposed conditions. As with the BACH tent, the side glare seems to be the culprit.
In the South area, members were tested under direct sun, with glasses and in mixed lighting - overcast conditions. As with the TP area, members performed best with the glasses and the worst under flat, overcast conditions. Some members had strong preferences of one pair of glasses over the other, reporting a distinct favorite but not always for purely 'visual' reasons. One member found that the amber glasses made her feel even 'hotter' than normal, while another found the same pair made her feel more 'happy'. Both members performed better with them than without them. We will have to wait until next season to test members inside the new South area shelter, scheduled for completion by the end of this year.
This season, the flotation area was covered with a blue plastic tarp. In the past, the flotation area has been covered with a green plastic tarp, white cloth tarp or not at all. Members of the flotation team were tested under the tarp, under direct sun and with the glasses. All members performed best with the glasses under full sun than under the shelter. All members also performed better under full sun than under the shelter, but none would prefer to work without it.
The sorting area for heavy residue is located on the porch in the veranda, under shelter from the permanent awning. Sorting is a highly focused, repetitive task where performance is improved with experience. In the past, members of the sorting team performed would wear magnifying glass head gear to aid in viewing the small seeds and charcoal bits but with practice, all choose to forego this tool and prefer their naked eyes. As a group, the sorting team (women) had outstanding contrast sensitivity when tested in the work area. There is quite a lot of glare that comes off of the gravel floor of the compound and when the sorting area was shrouded from this glare, the members performed exceptionally better on the test. I will need to re-test them next year with a more refined chart with a higher threshold.
Future plans
The 2003 season promises to be very exciting at Çatalhöyük, with a larger than ever multi-national team and full-scale excavations occurring site-wide. The new South shelter will be complete and the West Mound, TP and the flotation area should also be sheltered. The North area will undergo a transformation as a 40x40 metre area begins to be unearthed.
I would like to continue and expand the vision study to include more members and the 'new' work areas on the mound. I plan to work with the lab areas and do a more thorough project in the experimental house. I began interviews this summer, but not as many as I would have liked so I will continue interviewing as well. I will probably switch to another contrast sensitivity test called the Ginsberg Functional Acuity Contrast Test that uses gratings instead of letters and is more sensitive in order to both double check borderline test areas and to achieve a 'finer grain' of acuity site wide.
You may contact me at mashley@uclink.berkeley.edu. A version of this report, complete with images is available at http://www.mactia.berkeley.edu/catal/experimentation/experimentation.html