Domino Causality

Domino Causality+ sets the guiding principles in the search for innovative drugs. We only can improve productivity by constant attention to the entire line of causality, of the domino chain. Merely optimizing or improving any single link is not helpful.

Dr. Moriarity, a metaphysician, sets up fifty numbered dominoes standing in a straight line with their dots facing the same way on a table in a room, but puts a blind in front of the dominoes so that only numbers one and fifty are visible. You enter the room, and observe that domino number one and domino number fifty are lying flat with their tops pointing in the same direction… Does this mean that either domino caused the other to fall? Not necessarily ... Dr. Moriarty could have pushed over only dominoes number one and fifty, or bumped the table in a way that only these two dominoes fell, or that all the dominoes fell at once. It is essential to remove the blind and look at the intervening dominoes... Do their positions suggest they fell in sequence rather than being bumped or shaken? Did any reliable observers hear the telltale sound of dominoes slapping one another in sequence? From the positions of all the dominoes, can we eliminate rival causal mechanisms, such as earthquakes and wind, as well as human intervention? If the dominoes fell in sequence, can we tell by looking at whether the dots are face up whether the direction of the sequence was from number one to number fifty or the reverse? Bennett, George (1997). Process Tracing in Case Study Research

Such inquiries help narrow the list of potential causes, but even if the experiment is repeated, it will be difficult to resolve fully the problem of equifinality, or of similar outcomes occurring through different causal processes, and to eliminate all potential rival explanations but one, especially when human agents are involved who may be doing their best to conceal causal processes.

The domino metaphor illustrates the potential complexity of choosing from alternative causal paths. If we extend the metaphor to many lines of dominoes, with many potential starting points, intersections, and diverting branches, and possibly several lines intersecting with the final domino in question, the potential complexity of causal mechanisms is apparent. A single domino may set off many branches, one or more of which may reach the final domino, or there may be many different dominoes that begin chains toward the final domino, perhaps with no one of these chains being necessary but each of them being sufficient to knock it over...

Domino Causality is an organizing principle. It provides a compelling image around which all parties in the drug development effort organize their evidence. Team members see and understand how their focused efforts contribute to the overall chain. It lays out the goals at a level of detail that is actionable for each team member.

The mere exercise of conceiving the domino chain increases the team’s tolerance for ambiguity+; for working with provisional results. This is a good thing for R&D effectiveness. Discussions revolve around the end to end domino chain and how to best remove individual blinds, and not on why any individual contribution is more important for the overall chain. When everyone does this the roadmap gradually comes into focus; the shortest path to the finish line becomes clear.

Further Reading