Editing Nautilus (section)

===Brain and intelligence===
{{Main|Cephalopod intelligence}}
Nautiluses are much closer to the first cephalopods that appeared about 500 million years ago than the early modern cephalopods that appeared maybe 100 million years later ([[ammonoids]] and [[coleoids]]). They have a seemingly simple [[brain]], not the large complex brains of [[octopus]], [[cuttlefish]] and [[squid]], and had long been assumed to lack intelligence. But the cephalopod nervous system is quite different from that of other animals, and recent experiments have shown not only memory, but a changing response to the same event over time.<ref name="callaway">{{cite magazine|url=https://www.newscientist.com/article/dn14033-simpleminded-nautilus-reveals-flash-of-memory.html|title=Simple-Minded Nautilus Shows Flash of Memory|author=Ewen Callaway|date=2 June 2008|magazine=New Scientist|access-date=7 March 2012}}</ref><ref name="phillips">{{cite journal|url=http://jeb.biologists.org/content/211/12/iii.full.pdf#page=1&view=FitH |archive-url=https://web.archive.org/web/20121029181222/http://jeb.biologists.org/content/211/12/iii.full.pdf |archive-date=2012-10-29 |url-status=live|title=Living Fossil Memories|author=Kathryn Phillips|date=15 June 2008|page=iii|volume=211|doi=10.1242/jeb.020370 |journal= Journal of Experimental Biology|issue=12|s2cid=84279320|doi-access=free|bibcode=2008JExpB.211Y...3P }}</ref><ref name="crook"/>

In a study in 2008, a group of nautiluses (''N. pompilius'') were given food as a bright blue light flashed until they began to associate the light with food, extending their tentacles every time the blue light was flashed. The blue light was again flashed without the food 3 minutes, 30 minutes, 1 hour, 6 hours, 12 hours, and 24 hours later. The nautiluses continued to respond excitedly to the blue light for up to 30 minutes after the experiment. An hour later they showed no reaction to the blue light. However, between 6 and 12 hours after the training, they again responded to the blue light, but more tentatively. The researchers concluded that nautiluses had memory capabilities similar to the "[[short-term memory|short-term]]" and "[[long-term memory|long-term memories]]" of the more advanced cephalopods, despite having different brain structures.<ref name="callaway" /><ref name="phillips" /><ref name="crook"/> However, the long-term memory capability of nautiluses was much shorter than that of other cephalopods. The nautiluses completely forgot the earlier training 24 hours later, in contrast to octopuses, for example, which can remember conditioning for weeks afterwards. However, this may be simply the result of the [[classical conditioning|conditioning]] procedure being suboptimal for sustaining long-term memories in nautiluses. Nevertheless, the study showed that scientists had previously underestimated the memory capabilities of nautiluses.<ref name="crook">{{cite journal|author1=Robyn Crook  |author2=Jennifer Basil |name-list-style=amp |year=2008|title=A biphasic memory curve in the chambered nautilus, ''Nautilus pompilius'' L. (Cephalopoda: Nautiloidea) |journal=The Journal of Experimental Biology|volume=211|pages=1992–1998|doi=10.1242/jeb.018531 |url=http://jeb.biologists.org/content/211/12/1992.full.pdf#page=1&view=FitH |archive-url=https://web.archive.org/web/20110817221242/http://jeb.biologists.org/content/211/12/1992.full.pdf |archive-date=2011-08-17 |url-status=live|issue=12 |pmid=18515730|s2cid=6305526 |doi-access=free|bibcode=2008JExpB.211.1992C }}</ref>