Wild chimps observed drinking alcoholic sap

Just one more example of how much humans and chimpanzees have in common. Check out this podcast describing wild chimpanzees seen drinking fermented tree sap as well as the video below.

Supplement video uploaded by the study's authors (Hockings et al., Royal Society Open Science, 2015) on Youtube.


Scientific American

KJ Hockings, N Bryson-Morrison, S Carvalho, M Fujisawa, T Humle, WC McGrew, M Nakamura, G Ohashi, Y Yamanashi, G Yamakoshi, T Matsuzawa. Tools to tipple: ethanol ingestion by wild chimpanzees using leaf-sponges. Royal Society Open Science. DOI: 10.1098/rsos.150150 (Published 9 June 2015)


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Hypothesis: Drug-seeking behavior, as a specific type of pleasure-seeking behavior, is a viable test for the presence of self-aware consciousness in an animal. This is based on the straightforward assumption that a preference for a mind-altering substance over a placebo, demonstrates the existence of a mind that can be altered.

This could be tested with compounds that have similar molecular structures, but the control substance is not psychoactive and the test substance is. The smell and taste of the substance are confounds but there should be ways to mask them to a sufficient degree. A positive result would occur when an animal repeatedly ingests the psychoactive compound, and shows a marked preference for it as compared to the inactive compound. ("I like A more than B," and "I like A so much I'll have it again and again.")

If we wanted to take it a little further, we might introduce "side effects" in the form of additional ingredients that have unpleasant effects, for example peppers for a burning taste, or emetics to produce vomiting. Does the preference for active drug A continue even when A is spiked with hot pepper and an emetic but inactive placebo B is not? Alternately, "make 'em work for it," by requiring effort to obtain the psychoactive compound: does the preference continue?

I'm aware of studies showing that rats will press a button repeatedly to get a zap of electricity into the pleasure centers of their brains, even when doing so causes them to ignore the need for food. None the less it would be interesting to see what happens with various substances, including those that are nearly universally socially endorsed by humans (alcohol and caffeine).

Rats are much less inclined to get drug-addicted if they are placed in species-appropriate environments (large, complex, with safe spaces and the company of other rats) rather than stuck in a small cage with nothing to do but press the cocaine paddle. Self-medication in response to a life of misery is also evidence of consciousness.

This is wonderful research, I like it. Keep up.
Thank you.

Re. Jane @ 3:

Good point. The rat's environment was a huge confound. I feel like an idiot for not catching that.

We can still reasonably conclude that rats have self-aware consciousness because, as I said, you can't alter your mind unless you have a mind to alter.

However, the experiments in question need to be re-run, controlling for environment:

Control: Rats in the same types of cages as used in the original study.

Test: Rats in sensorily-enriched environments with other rats: current state-of-the-art humane accommodations as described in various literature (I read one of the papers but don't have time to look up the cite for it).

Hypothesis: rats in condition (b) will demonstrate significantly less addictive behavior than rats in condition (a). Operationalization: button-presses per rat per day, ratio scale, zero to maximum observed. Test: T-test, 2-tailed. Significance threshold: this is basically social sciences so let's start with p < .05 and see what happens.

Anyone out there who wants to try this?

The difficult part would be wiring their pleasure centers given that they can roam freely, but a wireless system may be possible. Otherwise use cocaine as you mentioned. For that matter it would be interesting to test a variety of substances to see how the use/abuse of each is altered by environment. Of particular interest, any narcotic analgesic associated with high abuse rates in humans. Implied inference: the reason people in ghettos tend to use narcotics is to relieve the pain of living in deprived environments.