The politics of researching global health politics Comment on “Knowledge, moral claims and the exercise of power in global health”

In this comment, I build on Shiffman’s call for the global health community to more deeply investigate structural and productive power. I highlight two challenges we must grapple with as social scientists carrying out the types of investigation that Shiffman proposes: the politics of challenging the powerful; and the need to investigate types of expertise that have traditionally been thought of as ‘outside’ global health. In doing so, I argue that moving forward with the agenda Shiffman sets out requires social scientists interested in the global politics of health to be reflexive about our own exercise of structural and productive power and the fact that researching global health politics is itself a political undertaking

Perception of scene-relative object movement: Optic flow parsing and the contribution of monocular depth cues

AbstractWe have recently suggested that the brain uses its sensitivity to optic flow in order to parse retinal motion into components arising due to self and object movement (e.g. Rushton, S. K., & Warren, P. A. (2005). Moving observers, 3D relative motion and the detection of object movement. Current Biology, 15, R542–R543). Here, we explore whether stereo disparity is necessary for flow parsing or whether other sources of depth information, which could theoretically constrain flow-field interpretation, are sufficient. Stationary observers viewed large field of view stimuli containing textured cubes, moving in a manner that was consistent with a complex observer movement through a stationary scene. Observers made speeded responses to report the perceived direction of movement of a probe object presented at different depths in the scene. Across conditions we varied the presence or absence of different binocular and monocular cues to depth order. In line with previous studies, results consistent with flow parsing (in terms of both perceived direction and response time) were found in the condition in which motion parallax and stereoscopic disparity were present. Observers were poorer at judging object movement when depth order was specified by parallax alone. However, as more monocular depth cues were added to the stimulus the results approached those found when the scene contained stereoscopic cues. We conclude that both monocular and binocular static depth information contribute to flow parsing. These findings are discussed in the context of potential architectures for a model of the flow parsing mechanism