Journal Club: Cockatoos crack complex locks to get the nut
SUMMARY: Confirming what many companion parrot owners already know, ten cockatoos demonstrated their strategic and spatial reasoning abilities by opening a series of five locks in sequence to obtain a reward -- without prior training.
"Muppet", a goffin's cockatoo, Cacatua goffiniana, solves the bolt-type lock on a puzzle box. doi:10.1371/journal.pone.0068979.s001
Image: Alice Auersperg/University of Vienna.
Confirming what many companion parrot owners already know, ten cockatoos demonstrated their strategic and spatial reasoning abilities for scientists by opening a complex series of five locks in sequence to obtain a reward -- without prior training. Further, the cockatoos then applied their knowledge to open the locks after their specific order was changed. These findings suggest that cockatoos are capable of persistently working towards a particular goal and they are sharp-eyed observers who can determine how physical objects interact with each other. They can then flexibly apply their knowledge from previous tasks to solving the job at hand instead of merely reproducing a learned series of motions.
Not long ago, I told you about a clever cockatoo, Figaro, who spontaneously designed tools to fetch a cashew nut that was just out of his reach. This was remarkable because cockatoos are not known to manufacture their own tools in the wild.
Figaro is a captive-bred hand-fed Tanimbar corella, Cacatua goffiniana, more commonly known in the pet trade as the Goffin's cockatoo. This near-endangered species is endemic to the Tanimbar Islands archipelago in Indonesia, where they live in dry tropical forests in flocks of 10 to 100 individuals.
Figaro lives with a flock of 14 Goffin's cockatoos in a large indoor-outdoor aviary at the University of Vienna in Austria (meet the flock, below):
The Goffin Lab's flock of cockatoos. The group consists mainly of subjects hatched between 2010 and 2011. Four animals are young adults (hatched between 2006 and 2007).
These cockatoos have highly conspicuous, complex and structured exploratory behaviours that are providing cognitive scientists with a window into their learning processes.
The stepwise multi-lock puzzle box challenge
As companion parrot owners can tell you, cockatoos are master locksmiths, often learning within just a few days how to open locks on their cages. But what happens when a Goffin's cockatoo is confronted with a series of locks, each one blocking access to the next in the sequence?
Such multiple-step problems that must be solved in a specific stepwise sequence are challenging because there is no immediate reward for completing just one step in the process. Later steps in the sequence also lack reinforcement value because earlier sequential steps must be completed first, but the reward can only be obtained after the last step in the sequence has been successfully completed.
When confronted with such a complex problem, will the parrot open all the locks, or will she get bored with the problem and eat her breakfast instead? Just how determined, persistent and creative are these birds when confronted with a novel problem such as this?
These are some of the questions asked by Alice Auersperg, who works in the Department of Cognitive Biology at the University of Vienna, and the international team of scientists and cockatoos that she assembled.
To learn more about these questions, the human team members designed a puzzle box and baited it with a portion of a cashew nut (the cockatoos' favourite food) that was visible behind a transparent door secured with five different interlocking devices. Each lock jammed access to the next lock in the series so all the locks could be opened only in a specific sequence (see "constellation 1", figure 1A; larger view):
Figure 1. A & B. Basic configurations. A) basic task configuration for acquisition & transfer test 1, 3 and 4. L5) pin; L4) screw; L3) bolt; L2) wheel; L1) bar. B) configuration for TT 2. The position of all locks except ‘bar’ has been altered. doi:10.1371/journal.pone.0068979.s001
To open the door of the puzzle box and retrieve the cashew nut, the parrots had to successfully solve five different mechanical locks as follows: remove a pin (L5), then a screw (L4), then a bolt (L3), then turn a wheel 90 degrees (L2) and then finally pull a latch sideways (L1, figure 2; larger view):
Figure 2. Actions required for removing each individual lock (L1-L5): 1. Grab the pin by the top ring and pull up; 2. Unscrew the screw with 25-30 consecutive up-and-down movements with beak or claw; 3. Insert beak under the lower end of the bolt and push it through the fixation ring; 4. Twist the wheel 90° and then pull it towards your body through the T-bar using either beak or claw; 5. push the bar through its fixation.
Image: Alice Auersperg/University of Vienna.
To test the birds, each one was individually placed on a table with the puzzle box in an isolated room. One observer remained in the room, wearing sunglasses and sitting in a chair behind the bird to avoid providing any physical cues. Each parrot was given up to five sessions consisting of as many as ten trials each, with each trial lasting no more than 20 minutes. If the cockatoo managed to get the reward before the trial time concluded, the bird received up to nine more trials. If the cockatoo did not get the reward within 20 minutes, the trial was terminated and a new session was given on the following day.
The ten parrots were each allowed to investigate the puzzle box and its locks with their beaks, tongues and feet. Astonishingly, one subadult male, Pipin, was especially adept at solving this challenge, spontaneously working out how to solve the puzzle box challenge in less than 2 hours. Seven of the ten cockatoos managed to figure out at least part of the solution during their allotted time trials, and five managed to open the puzzle box's lock sequence after either watching another bird complete the entire task or after incrementally learning how to solve each device.
This video captures some of the parrots' trials:
As the above video shows, the parrots were persistent and determined problem-solvers who rarely forgot how to solve a particular lock when confronted by it in future trials (this "cognitive ratchet" effect is fundamental to the evolution of cognition). Further, they solved one lock after another, even though they obtained the reward only after solving all five devices.
"The progress of the birds towards the solution is unaffected by the fact that the goal is very distant" temporally and spatially, said Alex Kacelnik, a professor of zoology at the University of Oxford, and co-author of the study.
In contrast, most multi-step challenges relied on tools in close temporal and spatial proximity.
"Except for tool sets in chimpanzees, five-step problems, each requiring different action patterns, without previous training (as in Pipin) has never been reported in animals", said the study's leader, Dr Auersperg, in a press release.
But even in multi-step challenges faced by great apes and corvids, the sequences rarely exceeded three steps.
The transfer of task-learning challenge
But how flexible was the parrots' knowledge of how to solve the puzzle box lock sequence? Did they memorise the entire process as a rigid series of tasks that had to be completed in the original order to obtain the reward, or would they recognise each lock as an individual entity that needed to be solved after the original sequence ("constellation 1") of tasks had been altered or destroyed? In short, were the cockatoos capable of applying their knowledge to the task at hand?
To answer these questions, the team ran another series of tests where the sequential order of the locks was jumbled (see "constellation 2", figure 1B; larger view), some locks were rendered nonfunctional or were missing altogether -- could the cockatoos still solve this challenge?
"We confronted our six test subjects with [the] so-called 'Transfer Tasks' in which parts of the sequence were rendered nonfunctional", said Dr Auersperg in a press release.
"We [also] removed single locks inside the structure to see whether the birds would ignore the now ineffective parts ... in the sequence."
This video shows some of the trials with jumbled, nonfunctional or missing locks:
This study revealed that the cockatoos could solve each lock even when it was in a different place within the sequence.
"When we scramble the order of the locks, they don't go to the one that was the first last time, they would go to the one that you need to tackle now after the changes, meaning that the content of what they learn is quite flexible", said Professor Kacelnik.
"They are not simply repeating what has been rewarded before, but they are creating a new series of actions ... without any practice."
The cockatoos' innate and physical exploratory behaviours were assets for this study.
"We believe that they are aided by species characteristics such as intense curiosity, haptic (tactile) exploration techniques and persistence: cockatoos explore surrounding objects with their bill, tongue and feet", said Auguste von Bayern, a co-author of the study who is at the Max Planck Institute for Ornithology in Seewiesen, Germany.
"A purely visual explorer may have never detected the movability of the locks."
Other parrots, particularly New Zealand's keas, also show similarly innovative and physical behaviours.
But we must be cautious when pondering how these parrots view the world around them.
"We cannot prove that the birds understand the physical structure of the problem as an adult human would", said Professor Kacelnik.
"But we can infer from their behaviour that they are sensitive to how objects act on each other, and that they can learn to progress towards a distant goal without being rewarded step by step."
Auersperg A.M.I., Kacelnik A., von Bayern A.M.P. & Marshall J.R. (2013). Explorative Learning and Functional Inferences on a Five-Step Means-Means-End Problem in Goffin's Cockatoos (Cacatua goffini), PLoS ONE, 8 (7) e68979. doi:10.1371/journal.pone.0068979.s001
Alice Auersperg, email [9 July 2013]
Alex Kacelnik, email [10 July 2013]
University of Vienna press release.
University of Oxford press release.
Polly gets his own cracker: clever cockatoo manufactures, uses tools -- the comments on this piece are also quite interesting.
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