Human memory capacity is many orders of magnitude more impressive than previously realised, psychologists have shown (the study can be accessed for free).
Timothy Brady and colleagues presented 14 participants with 2,500 mundane objects, presented one at a time for three seconds each. The whole study phase took over five and a half hours. The participants’ motivation was maintained by asking them to look out for repeats. Ten minutes after the study phase, the participants showed astonishing accuracy when they were presented with three hundred pairs of objects, one at a time, and tasked with identifying which of the objects in each pair they’d been shown earlier (try out the task).
“These results indicate a massive capacity-memory system, in terms of both the quantity and fidelity of the visual information that can be remembered,” the researchers said.
Landmark studies in the 1970s showed that after viewing tens of thousands of scenes, people could afterwards say which of two images they’d seen before with high accuracy. However, the original scenes were paired with completely different scenes (e.g. a wedding versus a beach), leading many commentators to argue that these results only said something about our ability to remember the gist of what we’ve seen.
By contrast, during the test phase of this new study, the original images were paired up with three different types of memory foil: an object from a completely different category than all previously seen objects; a physically similar object from a previously seen object category; and finally, an object identical to one seen earlier, but in a different state or pose (for example, a side-cabinet with one of its doors open rather than closed). This latter condition particularly was designed to test the participants’ memory for visual detail, not just gist. Remarkably, accuracy was found to be 92 per cent, 88 per cent, and 87 per cent, respectively across these foil types.
The researchers said these accuracy levels mean they have yet to find the upper limit of visual long term memory. “Here we raise only the lower bound of what is possible,” they said, “by showing that visual long-term memory representations can contain not only gist information but also details sufficient to discriminate between exemplars and states.”
T. F. Brady, T. Konkle, G. A. Alvarez, A. Oliva (2008). Visual long-term memory has a massive storage capacity for object details Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0803390105