Making safe: The dirty history of a bomb disposal robot

In the Ulster Museum’s new gallery The Troubles and Beyond, the central display showcases a Wheelbarrow bomb disposal robot. This machine was invented by the British Army in Northern Ireland in 1972 and used by officers of the 321 Explosive Ordinance Disposal Squadron (321EOD) to defuse car bombs planted by the Irish Republican Army (IRA). This article offers an alternative history of that machine – a dirtier history – that critically assesses its role during the Troubles. Centrally, the article contests the British Army’s preferred account of this machine as a ‘game-changing’ technological innovation in counterinsurgency, and their understanding of themselves as benign peacekeepers. Rather than figure the Wheelbarrow robot as an unreadable ‘black box’ used instrumentally by the superior human operators of 321EOD, this article seeks to foreground the unruly transfers of agency between the machine and its operators as they tested and experimented in the exceptional colonial laboratory of Northern Ireland. The article further explores the machine’s failures during bomb disposal episodes, the collateral damage that resulted, and the multiple and often unruly reactions of local populations who watched the Wheelbarrow robot at work. Providing a ‘dirty history’ of the Wheelbarrow robot is an effort to demonstrate that war can never be fully cleaned up, either through militarized mythologies of technological innovation or hopeful museum displays.

Object Substitution: A New Form of Masking in Unattended Visual Locations

Can four dots that surround, but do not touch, a target shape act as a mask to reduce target discriminability? Although existing theories of metacontrast and pattern masking say “no,” we report this occurs when targets appear in unpredictable locations. In three experiments, a four-dot mask was compared with a standard metacontrast mask that surrounded the target. Although accuracy was predictably different for the two masks at a central display location in Experiment I, both masks had similar strong effects on accuracy in parafoveal locations. Experiment 2 revealed that both four-dot and metacontrast masking were insensitive to contour proximity in parafoveal display locations, and Experiment 3 showed that four-dot masking could occur even at a central location if attention was distributed among several targets. We propose that targets in unattended locations are coded with low spotiotemporal resolution, leaving them vulnerable to substitution by the four dots when attention is directed to them.

The Effects of Visual Depth and Eccentricity on Manual Bias, Induced Motion, and Vection

The relationship between the effects of visual-surround roll motion on compensatory manual tracking of a central display and the perceptual phenomena of induced motion and vection were investigated. To determine if manual-control biases generated in the direction of surround rotation compensate primarily for the perceived counterrotation of the central display (‘induced motion’) or the perceived counterrotation of the entire body (‘vection’), the depth and eccentricity of the visual surround were varied. In the first experiment, twelve subjects attempted to keep an unstable central display level while viewing rotating visual surrounds in three depth planes: near (∼20 cm in front of the central display), coplanar, and far (∼21 cm behind the central display). In the second experiment, twelve additional subjects viewed a rotating surround that was presented either in the full visual field (0–110 deg) or in central and peripheral regions of similar width. Manual-control biases and induced motion were shown to be closely related to one another and strongly influenced both by central and by peripheral surround motion at or beyond the plane of fixation. Vection, on the other hand, was shown to be much more dependent on peripheral visual inputs.

Linear Vection in the Central Visual Field Facilitated by Kinetic Depth Cues

Illusory self-motion (vection) is thought to be determined by motion in the peripheral visual field, whereas stimulation of more central retinal areas results in object-motion perception. Recent data suggest that vection can be produced by stimulation of the central visual field provided it is configured as a more distant surface. In this study vection strength (tracking speed, onset latency, and the percentage of trials where vection was experienced) and the direction of self-motion produced by displays moving in the central visual field were investigated. Apparent depth, introduced by using kinetic occlusion information, influenced vection strength. Central displays perceived to be in the background elicited stronger vection than identical displays appearing in the foreground. Further, increasing the eccentricity of these displays from the central retina diminished vection strength. If the central and peripheral displays were moved in opposite directions, vection strength was unaffected, and the direction of vection was determined by motion of the central display on almost half of the trials when the centre was far. Near centres produced fewer centre-consistent responses. A complete understanding of linear vection requires that factors such as display size, retinal locus, and apparent depth plane are considered.

Circular Vection as a Function of the Relative Sizes, Distances, and Positions of Two Competing Visual Displays

In studies where it is reported that illusory self-rotation (circular vection) is induced more by peripheral displays than by central displays, eccentricity may have been confounded with perceived relative distance and area. Experiments are reported in which the direction and magnitude of vection induced by a central display in the presence of a surround display were measured. The displays varied in relative distance and area and were presented in isolation, with one moving and one stationary display, or with both moving in opposite directions. A more distant display had more influence over vection than a near display. A central display induced vection if seen in isolation or through a ‘window’ in a stationary surrounding display. Motion of a more distant central display weakened vection induced by a nearer surrounding display moving the other way. When the two displays had the same area their effects almost cancelled. A moving central display nearer than a textured stationary surround produced vection in the same direction as the moving stimulus. This phenomenon is termed ‘contrast-motion vection’ because it is probably due to illusory motion of the surround induced by motion of the centre. Unequivocal statements about the dominance of an eccentric display over a central display cannot be made without considering the relative distances and sizes of the displays and the motion contrast between them.