Visual Occlusion Instrument
Accession Number: 2014.ep.4
The instrument consists of two components: a Head Assembly which is connected by a long electrical wire to a main Control Unit.
The Head Assembly is a flexible visor of wood laminate with an ?aluminum frontispiece. It has two rectangular eye slots with two wooden shutters painted black. Four small metal bolts control the movement of the shutters. The visor is rounded at the temple and each arm has a space that is most likely intended to accommodate a bolt or other fastener for a helmet or similar apparatus. Electrical wiring behind the frontispiece and above the eye slots collects in a long electrical wire that extends from the arm of the left eye slot to the main Control Unit.
The Control Unit is a large metal box. It is unpainted and grey in colour. The box consists of a front panel with controls, a hinged top panel with vents, and a back panel with vents and a wide slat at its base for wiring. The sides of the box each have a handle of the same metal.
The front panel has been attached to the box with metal screws and projects forward from rest of the box. The square hole to which it was bolted does not share its dimensions suggesting that the front panel was not made to fit.
The bottom left corner of the front panel has three features (from left to right): a red indicator light, an “on/off” toggle switch, and a knob marked “Fuse” with an arrow indicating a counter-clockwise direction. An attached plaque in the upper centre bears a manufacturer’s name and is etched with the instrument’s name and an order number. The right side of the front panel has two slide switches and eight rotating dials. These are separated roughly into three rows and three columns: a column under the label “Left” corresponding to the left-eye shutter on the Head Assembly, a ‘shared’ column, then a “Right” column corresponding to the right shutter.
The two switches centred at the top can move to the “Off”, “Run”, or “On” positions. On each side of this switch is a dial labelled “On Off Ratio” with settings numbered clockwise from 1-10 on a black, circular face. In the centre of the row below, there is a dial labelled “Phase” and on each side is a dial labelled “Frequency”. All 3 dials in this row have metallic, square faces with settings numbering clockwise from 1-10. Below, the dial at the centre of the row switches from “Sync.” on the left to “Ind.” on the right. On each side is a dial labelled “Freq. Range” which moves from settings numbered 1-3 clockwise.
The slatted top panel lifts on hinges. Inside the metal box has an ?electrical board at its bottom. The board holds five (?ten) transformers, five capacitors, and fifteen vacuum tubes, all of varying sizes and makes. Manufacturers include: Hammond Manufacturing LTD. for transformers, Mallory for capacitors, and Raytheon, Marconi, GE, and Westinghouse for vacuum tubes.
Typewritten labels were pasted on the electrical board beside most vacuum tube places indicating the voltage and model required (e.g. “V8 2D21” next to a Marconi vacuum tube).
The back of the board sports two electrical wires through the slat in the back panel of the box. The wire closest to the left connects to the Head Assembly, while the central wire ends in a black, three-pronged, North American wall plug.
Steel, Aluminum, Glass, Wood, Plastic, ?Other MetalsA small plaque on the Control Unit’s front panel reads: “George Kelk LTD. Toronto Canada”. The instrument’s name “Light Shutter” is etched below on the same plaque and below that next to the word “Order” is etched “P-42”. All other markings on the Control Unit refer to the dials and are described in detail under the “Description” field. On the electrical board, most capacitors, vacuum tubes, and transformers have manufacturer’s markings. These are described under the “Description” field. Typewritten labels have been pasted to the electrical board indicating the necessary voltage and model of most vacuum tubes.
A small plaque on the Control Unit’s front panel reads: “George Kelk LTD. Toronto Canada”. The instrument’s name “Light Shutter” is etched below on the same plaque and below that next to the word “Order” is etched “P-42”.
All other markings on the Control Unit’s front panel refer to the dials and are described under the “Description” field.
On the electrical board, most capacitors, vacuum tubes, and transformers have manufacturer’s markings. These are described under the “Description” field.
Typewritten labels have been pasted to the electrical board indicating the necessary voltage and model of most vacuum tubes.
Control Unit: Height = 27.6, Width = 54, Length = 39; Head Assembly: Height = 9.7, Width = 7.2, Length = 22.8
The instrument’s technical function is described in two typewritten pages in its accompanying folder. The dials and switches on the Control Unit determine the frequency at which the eye shutters on the Head Assembly cover the eye slots. They can also determine whether both shutters will fall at the same time or whether the experimenter will control each shutter independently.
The instrument was most likely used in connection with professor John W. Senders’ research concerning visual sampling and the reception of tachistoscopic information. Senders’ relevant research frequently focused on the visual perception of pilots and automobile drivers. In this video clip, Senders conducts an “experiment on the attention span needed for safe driving” with a visual occlusion device: http://www.youtube.com/watch?v=kOguslSPpqo
Unlike the device in the clip, the Visual Occlusion Instrument has a wall plug suggesting that it was intended for indoor use. It also has controls for eye shutters that move independently from one another. Despite these differences, the device in the video may indicate that the Visual Occlusion Instrument was similarly used by an experimenter to test a subject’s ability to process visual information through brief exposure.
As described in the “Condition Report”, the instrument is in poor condition. The rubber coating on the two main electrical wires is brittle and already cracked in places. The wire connecting to the Head Assembly has begun to fray leaving the wires exposed.
The electrical board is covered in thick dust and other small particles and it is scattered with mouse droppings.
Further damage is primarily cosmetic:
The previous repairs to the left “Off/Run/On” switch have left green tape visible and the switch is still loose; a piece has broken off of the right “Freq. Range” dial; there is residue from masking tape in the centre of the front panel; the top panel is dented in the centre; there are a few minor scuffs and scratches primarily on the front panel and right side of the Control Unit box; and there are chips and scratches on the shutters of the Head Assembly (one large chip on the right eye shutter).
Associated Instruments: ?Helmet
?George Kelk LTD. It may be that this manufacturer only made the Control Unit’s front panel with switches and the internal electrical board, but that the metal box to which it was bolted was manufactured elsewhere.
Date of Manufacture: ?1953-8
Prof. Paul Milgram, Engineering Psychology, U of T.
The instrument’s accompanying folder includes a packing slip dated 1958, as well as a full circuit diagram, graphs plotting shutter frequency, etc. The initial typewritten pages indicate how the machine works, but not what it was used for.
General research using the search terms “visual occlusion instrument” produced minimal results. The search “visual occlusion device” provided a link to the “PLATO Visual Occlusion Spectacles” from Translucent Technologies Inc. The spectacles are intended for researching tachistoscopic perceptions by allowing “an experimenter accurately to control the timing of presentation of visual information to an experimental subject”.
The search terms “visual occlusion instrument”, “visual occlusion device”, “visual occlusion”, “eye shutter” and “light shutter” produced no relevant results in the databases and trade catalogues listed in the Appendices of the UTSIC Instruction Manual.
Similarly, searches for “George Kelk LTD” produced no results in Makers Databases. The website for what is now KELK states that the company has been manufacturing “state-of-the-art electronic measurement equipment” since its establishment in 1953. http://www.kelk.com/
All subsequent research centered on a suggestion that the instrument may have been used in connection to the work of John W. Senders, Professor Emeritus of Industrial Engineering at the University of Toronto. (Note: it was also mentioned that Senders did not recall using this exact instrument). The “CV” section on Senders’ website lists “Papers, Reports and Publications” and provides links to selected articles. These works from the list were consulted:
1. “Tracking Performance on Combined Compensatory and Pursuit Tasks”
2. Senders, John W., Ilse B. Webb, and Charles A. Baker, “The Peripheral Viewing of Dials,” Journal of Applied Psychology, 39 (1955): 433-6.
(This article is fully cited because it mentions “tachistoscopic exposure” on page 433.)
3. “Man’s Capacity to use Information from Complex Displays”
4. “An Investigation of Visual Attention and Operator Workload Measurement”
5. “On the Distribution of Attention in a Dynamic Environment”
6. “A Queueing Model of Visual Sampling: Experimental Validation”
(Note: none of these articles name or describe the instrument)
Senders’ larger texts have not yet been consulted:
1. Eye Movements and the Higher Psychological Functions, ed. John W. Senders et al.
2. Senders, John W., Visual Sampling Processes.
3. Senders, John W., Jaime R. Carbonell, Jane L. Ward, Human Visual Sampling Processes: A simulation validation study.
It may be useful to contact the Center for the History of Psychology at the University of Akron about their collection of psychologists’ manuscripts. A list of their texts from John W. Senders can be found here: http://cdm15960.contentdm.oclc.org/cdm/singleitem/collection/p15960coll10/id/490
Other occlusion devices continue to be used to test driving performance as in this Technical Report from the UMTRI Human Factors group at the University of Michigan: http://www.umich.edu/~driving/publications/UMTRI-99-37.pdf
It was suggested that the instrument may have been used in connection with the research of John W. Senders, Professor Emeritus of Industrial Engineering at the University of Toronto. However, it was also mentioned that he does not recall using this exact instrument.
- Donated to UTSIC