By the way, Martin
says, in Octopus: Physiology and Behaviour of an Advanced
Invertebrate (Springer, 1978) that contrary to popular report,
octopuses cannot learn to open jars:
Crabs can be wrested from containers (Pieron, 1911; Schiller, 1948;
Cousteau and Diole, 1973) but the results appear to be achieved by
chance and there is little indication that the octopus can learn to
deal with the situation more efficiently with practice. The animal
approaches and struggles with the apparatus until something happens;
if it learns any-thing as a result of its experience it is only to
be more persistent and vigorous.
There may have been further developments since 1978, of course.