I think there are two takeaways from this experiment. One is not at all noteworthy and one is somewhat interesting but has limited applications. The uninteres

I think there are two takeaways from this experiment. One is not at all noteworthy and one is somewhat interesting but has limited applications. The uninteresting takeaway is that people note whether a photo is B&W/color and use that to help date the photo. Well, no kidding. We use a lot of contextual information to try to figure that out: not only B&W/color but also graininess, hair/clothing styles, architectural clues, etc. It should not be surprising that we do this. In fact, it would be surprising if we didn't do this. The slightly more interesting takeaway is that we're bad at it, likely because most people don't have an accurate idea about when color photography became mainstream, and possibly also because some people fail to realize that sometimes B&W is an artistic choice, rather than a technical limitation. As for what applications that might have ... well, I'm not sure. If it's extremely important (for, say, financial or political reasons) to accurately date a photo, my guess is that you'll bring an expert rather than a layman who knows to account for this. So really the only time I see the effect coming into play is when you have an armchair historian who doesn't know their own limitations.