To ensure a heatmap does not “eliminate the element of time”, the heatmap could show later-looked-at spots with more desaturated colors.
Of course, this has the same problem as the main point – that you can’t tell whether a spot is medium-saturated because everyone looks at it in the middle of browsing or because some people see it at the beginning and others see it only at the end. Still, this problem, like the article’s, could be fixed by moultano’s suggestion of making a heatmap for the variance as well as the value.
Or you could sacrifice the display of time, and display variance as saturation – less-variant, more-sure spots would have more saturated colors. This would be easier to read than two separate heatmaps for value and variance.
Of course, this has the same problem as the main point – that you can’t tell whether a spot is medium-saturated because everyone looks at it in the middle of browsing or because some people see it at the beginning and others see it only at the end. Still, this problem, like the article’s, could be fixed by moultano’s suggestion of making a heatmap for the variance as well as the value.
Or you could sacrifice the display of time, and display variance as saturation – less-variant, more-sure spots would have more saturated colors. This would be easier to read than two separate heatmaps for value and variance.