Reanimating dead spiders to use them as robot claws, licking rocks, backwards talking and a toilet that scans "anal-prints": this year's Ig Nobel prizes again put a spotlight on the quirky side of science.

The 23rd edition of the annual awards, given out "for achievements that first make people laugh, then make them think", was broadcast in an online ceremony on Thursday evening US-time.

Real Nobel prize winners -- some wearing silly hats -- gave out the prizes and a $10 trillion bill in essentially worthless, inflation-ravaged Zimbabwean dollars.

Here are the 10 winners of this year's Ig Nobels, which are produced by the science humour magazine Annals of Improbable Research.

- Rock lickers -

The chemistry and geology Ig Nobel went to Jan Zalasiewicz, a geologist at the UK's University of Leicester, "for explaining why many scientists like to lick rocks".

Zalasiewicz told AFP he wrote his article "Eating Fossils" after discovering that "some 18th-century geologists used the taste of rocks to help identify them". This is "a skill we've now mostly lost", he lamented.

The geologist, normally known for more serious work on defining the Anthropocene era, said he was honoured to become an Ig Nobel laureate because the prizes "have become one of the grand traditions of science".

- Repeating a word to meaninglessness -

The literature Ig Nobel was awarded to an international team of researchers "for studying the sensations people feel when they repeat a single word many, many, many, many, many, many, many times".

The team looked into how repeating a word can create a sense of unfamiliarity with something familiar, a feeling called "jamais vu" -- the opposite of deja vu.

To accept the award, the researchers repeated the word "the" dozens and dozens of times, until it seemed to lose all meaning.

- Reanimated spider claw machine -

The mechanical engineering prize went to US researchers who re-animated dead wolf spiders to use them as mechanical gripping tools, similar to the claw machine game seen in arcades.

Over an extremely creepy video of spiders opening their legs and gripping things, the researchers from Rice University in Texas explained the field of "necrobotics", in which parts of animals are used as bits of robots.

- Toilet that scans 'anal-prints' -

Seung-min Park of Stanford University in the US was awarded the public health prize for inventing a toilet that can swiftly analyse human waste.

His "Stanford toilet" even has an "anal-print" sensor, which is similar to fingerprint ID on mobile phones -- except for anuses.

"Don't waste your waste," Park said on accepting the award.

- Backwards talkers -

The communication prize was given to the study of people who are very good at speaking backwards.

Of course, the award-winners accepted their prize by speaking backwards.

- Cadaver nose hair -

The medicine prize went to researchers who used cadavers to explore whether there is an equal number of hair in both nostrils.

The result? It differs for everyone, but on average, the cadavers had around 120 nose hairs in their left nostril and 112 in the right.

- Electric taste -

The nutrition prize went to Japan's Hiromi Nakamura and Homei Miyashita for developing electrified chopsticks and straws that can made food and drink taste saltier.

"Have you ever tried to lick a battery?" Miyashita asked the ceremony.

- Boring into boring -

The education prize went to a team of researchers for studying how teachers seeming bored can in turn bore their students.

"We found that if students thought that teachers were bored while teaching, they too felt more bored," prize-winner Christian Chan said, boringly.

- Looking up -

The psychology prize went to US researchers for their experiments observing how many people on a city street would stop and look up if they saw strangers craning their necks upwards.

The more people who were looking up, the more passers-by joined in, the researchers found.

- Anchovy sex -

The physics prize went to researchers who measured how much "ocean-water mixing is affected by the sexual activity of anchovies".

"I think there is a consensus that it doesn't matter -- but I kind of don't believe it," said Bieito Fernandez Castro, one of the prize winners.

The real Nobel prizes will be announced next month.