This is a surprisingly difficult question to answer. And it is an even more difficult one to quantify.

Think about it — you know what Neptune is, but you have never seen it. You have never touched it, or used it in any way. It doesn’t have any function at all for you. But you would still say that you know what it is. Is it because you can hold a picture of it in your mind? Then what about things like valor or honesty? You can picture people doing those things, but you cannot actually picture those things.

Fortunately, neuroscience can give us some tiny insights into the philosophical question of what it means to know what something is. A recent article concentrated on this question on a much smaller scale and sought to determine what kind of knowledge is activated when a concept is brought to mind. Here is how it worked.

Participants were first given a similarity judgment task — they were shown two different pictures of knots and asked to say whether or not the two pictures were of the same knot (if they were, they were taken from different angles). None of the participants had any sort of extensive experience with knot-tying. The researchers took baseline fMRI readings from this task.

Next, the participants learned 30 different knots in different ways. For the first set of 10 knots, the participants learned the name of the knot — they saw a video of the knot being rotated in space along with the name of the knot.

The next 10 knots they learned to tie by watching a video of the knot being tied. Finally, they learned the names and how to tie the last 10 knots. Now each participant had sensorimotor experience for 10 knots, linguistic experience for 10 more, and both types of experience for a further 10. There were also 10 more knots used in the test phase that the participants had never seen before.

The test phase consisted of the same distinction task as the experiment started with. Now, however, neuroimaging comparisons were made between the knots for which participants possessed different kinds of knowledge.

From the “tying” condition, researchers discovered that participants showed increased activation in the interparietal sulcus (IPS), which is traditionally associated with tool use, suggesting a sort of “pragmatic” knowledge representation. In contrast, the knots in the “naming” condition showed very little increased activation in the expected, linguistically oriented areas of the brain.

The authors offer a few possible explanations for this distribution of activity, and point out several factors that may have limited their ability to detect a linguistic component of object representation in the brain. One interesting point they bring up is that the name of the knot has no semantic value; it is simply a label — and previous experiments have shown that a descriptive, semantically valuable label is more likely to create a neurological response.

Anyway, the experiment provides some really great evidence for embodied cognition and the effect that it has on object knowledge; even when the participants were not asked to retrieve any functional or procedural information about the knots, they still activated areas of the IPS, suggesting that this sort of information is automatically activated when an object is perceived and recognized.

So, in the fashion of journalists who over-interpret and sensationalize scientific results, I will say that this proves that you do not really know what Neptune is.

What are your thoughts? I am interested to hear any alternative theories on why the linguistic parts of the brain were not activated to the expected levels.

References

Cross ES, Cohen NR, Hamilton AF, Ramsey R, Wolford G, & Grafton ST (2012). Physical experience leads to enhanced object perception in parietal cortex: insights from knot tying. Neuropsychologia, 50 (14), 3207-17 PMID: 23022108

Image via PeterPhoto123 / Shutterstock.