Visual Metaphors #1: Time and Causality

Most failures, most success. (Tom Peters‘ Irreducibles)

It seems that although most of my beliefs about the visual display of facts aren’t exactly widespread, there are co-conspirators. In the april issue of Juan C. Dürsteler’s newsletter on information visualization, he extends a rather unusual criticism of the widespread time axis:

Time, nevertheless is not well represented by a line since it isn’t a spatial dimension and, moreover, it’s irreversible. Paradoxically, the widest used metaphor is that of the line.

This is obviously a claim too bold, and the rebuttal by Stephen Few is entirely justified. Still, it might be quite rewarding to check visual data displays with this question in mind:

Do linear plots of time suggest either reversibility or causal disjunction where those states can really not be assumed?

It is probably easy to find examples where this is the case. In a previous post, I commented on continuous scales of text, such as in a recent visualization of the digg social news site. In that case, the timeline may suggest that future stores somehow have an effect on older ones, which of course breaks the logic of one-directional progress of time.


So in the case of a simple line graph, the error that Dürsteler points out would look something like this (fig1):

Assuming the situation of someone thinking at the point in time marked “now”,

we can assume that the data recorded before that moment, that to the left of the line (a), has some sort of influence on his thoughts.

we can however not assume any influence of anything that happens afterwards, such as (b).

Maybe time will deliver some better case scenarios. Does any reader have suggestions for a case in which time as a one-directional axis is misinterpreted so that faux causalities arise?


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