Ogni antibiotico è efficace in relazione a un determinato gruppo di microrganismi comprare doxycycline senza ricettain caso di infezioni oculari vengono scelte gocce ed unguenti.
mals for use as tools, without extensive prior
experience, is almost unknown. In experiments
Shaping of Hooks in New
by Povinelli [experiments 24 to 26 in (2
)], chim-panzees (Pan troglodytes
) repeatedly failed to
unbend piping and insert it through a hole toobtain an apple, unless they received explicitcoaching. Further experiments [exp. 27 in (2
Alex A.S.Weir, Jackie Chappell, Alex Kacelnik*
) have shown a similar lack of deliberate,specific tool modification in primates. There are,however, numerous suggestive field observa-
Many animals use tools, but their understand-
different from those previously reported and
) and one report of a male capuchin
ing of physical forces or causal relations is
would be unlikely to be effective with natural
monkey (Cebus apella
) unbending a piece of
). Primates are considered the
materials. She had little exposure to and no prior
wire to obtain honey (10
most versatile and complex tool users, but
training with pliant material, and we have never
Our finding, in a species so distantly related
observations of New Caledonian crows (Cor-
observed her to perform similar actions with
to humans and lacking symbolic language, rais-
) raise the possibility
either pliant or nonpliant objects. The behavior
es numerous questions about the kinds of un-
that these birds may rival nonhuman primates
probably has a developmental history that
derstanding of "folk physics" and causality
in tool-related cognitive capabilities.
includes experience with objects in their envi-
available to nonhumans, the conditions for
We report here an experiment inspired by
ronment ( just as infant humans learn about ev-
these abilities to evolve, and their associated
the observation that a captive female spontane-
neural adaptations. Comparisons between New
ously bent a piece of straight wire into a hook
Caledonian crows and their relatives, as well as
and successfully used it to lift a bucket contain-
between other cognitively exceptional birds and
ing food from a vertical pipe (Fig. 1A). This
their relatives (11
), offer a unique natural ex-
occurred on the fifth trial of an experiment in
periment to examine hypotheses about the eco-
which the crows had to choose between a
logical and neural preconditions for complex
hooked and a straight wire and only after the
cognition to evolve. It is not yet known if New
hooked wire had been removed by the other
Caledonian crows are also exceptional in cog-
subject (a male). The animals had prior experi-
nitively demanding tasks not involving tools.
ence with the apparatus, but their only previousexperience with pliant material was 1 hour of
References and Notes
free manipulation with flexible pipe-cleaners a
1. S. Chevalier-Skolnikoff, Behav. Brain Sci. 12
, 561 (1989).
2. D. J. Povinelli, Folk Physics for Apes
year before this experiment, and they were not
Press, Oxford, 2000).
familiar with wire (6
3. G. R. Hunt, Nature 379
, 249 (1996).
To investigate the importance of this ob-
4. G. R. Hunt, Proc. R. Soc. Lond. Ser. B Biol. Sci. 267
servation, we conducted several new trials in
5. J. Chappell, A. Kacelnik, Anim. Cogn. 5
, 71 (2002).
which we placed a single straight piece of
6. The female subject waswild-caught asa juvenile in
garden wire (0.8 mm in diameter, 90 mm
March 2000 and hasbeen in our laboratory ever
since. The male subject was in a zoo in New
long) on top of the tube and did not intervene
Caledonia for over 10 yearsuntil he wasmoved to
until either of the birds obtained the food (a
our laboratory, also in March 2000 (it is not known
valid trial) or dropped the wire irretrievably
when or how he wascaught). See (5
) for further
details of subjects, history, and housing conditions.
into the tube (an invalid trial).
7. The male rarely attempted thistask and never bent
Out of 10 valid trials (interspersed with
the wire. He observed the female bending the wire
seven invalid ones), the female bent the wire
and stole the food from her in three trials. The birds
are tested together because they are highly social
and used it to retrieve the food nine times, and
and, when separated, are less motivated to partici-
Bending wire into hooksby a captive New
the male retrieved the food once with the
pate in experiments.
Caledonian crow. (A
) The female New Caledonian
straight wire (7
). To bend the wire, she first
8. E. Visalberghi, Int. J. Primatol. 18
, 811 (1997).
crow extracting the bucket containing meat using
wedged one end of it in sticky tape (available
9. M. Tomasello, J. Call, Primate Cognition
a piece of wire she had just bent. This is a photo
Press, New York, 1997).
around the bottom of the tube and the side of
taken after the experiment wascompleted, but
10. J. R. Anderson, M. C. Henneman, Mammalia 58
the plastic tray containing the apparatus) or held
the hook and posture depicted are typical of
it in her feet at a location 3 m from the food,
experimental trials. (B
) Outline tracingsof all the
11. I. M. Pepperberg, The Alex Studies: Cognitive and
bent wires, with the end inserted into the tube
Communicative Abilities of Grey Parrots
where there was no tape. She then pulled the
Univ. Press, Cambridge, MA, 1999).
facing right. Numbersrefer to trial number. The
other end orthogonally with her beak (see Mov-
12. We thank D. Wilson for technical assistance, the
wire bent in trial 8 was not successfully used to
ie S1), resulting in a bend with an angle of 74 ⫾
Wissenschaftskolleg zu Berlin for a research fellow-
retrieve the bucket (it wasdropped into the tube).
ship to A.K., and Joan Silk for comments on the
30° (mean ⫾ SE) (see Fig. 1B for individual
Because of experimenter error, the wire in trial 10
manuscript. The work was funded by a grant from the
tool shapes). She started to bend the wire 35 ⫾
was2 cm longer than the wire in the other trials.
Leverhulme Trust to A.K. and a scholarship from the
8 s after the start of each trial and used the
Scale bar, 5 cm.
Wellcome Trust to A.A.S.W.
resulting hook 6 ⫾ 2 s later. In all cases but one,
Supporting Online Material
she tried with the straight wire (for 15 ⫾ 4 s)
eryday physics from their manipulative experi-
before starting to make the hook. In all valid
ence), but she had no model to imitate and, to
trials, the birds retrieved the food within 2 min.
our knowledge, no opportunity for hook-making
Thus, at least one of our birds is capable of
to emerge by chance shaping or reinforcement
novel tool modification for a specific task. In the
of randomly generated behavior. She had seen
Department of Zoology, South ParksRoad, Oxford
wild, New Caledonian crows make at least two
and used supplied wire hooks before but had not
OX1 3PS, UK.
sorts of hook tools using distinct techniques (3
seen the process of bending.
*To whom correspondence should be addressed.
), but the method used by our female crow is
Purposeful modification of objects by ani-
www.sciencemag.org SCIENCE VOL 297 9 AUGUST 2002
A Study of Online SocialNetworks in Mauritius: Impact on Secondary Education Assoc. Prof. Kavi Khedo Mr. S.M.R.A. ElaheebocusMr. R. Suntoo Ms. A. Mocktoolah February 2015 Funded by the Mauritius Research Council Under the Unsolicited Research Grant Scheme Agenda} Online Social Networks } Aim of the Project
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