array [] vs {}

Hi,
I am attempting to use arrays in a db for the first time and am having
strife:
[] notation work only on non-empty initialized arrays. Is this
a feature/bug I should know about? For example:

create table test (
myname varchar(50),
myarray int[]
);

INSERT INTO test (myname) values ('bobo');

UPDATE test SET myarray[1] = 5;

SELECT * FROM TEST;
myname | myarray
--------+---------
bobo |
(1 row)

-- An empty array column is not what I'd expect
-- but curly brackets work

UPDATE test SET myarray = '{5}';

SELECT * FROM TEST;
myname | myarray
--------+---------
bobo | {5}
(1 row)

-- However If I revert to [] notation I can do as I please:

UPDATE test SET myarray[2] = 50;
SELECT * FROM TEST;
myname | myarray
--------+---------
bobo | {5,50}
(1 row)

- [] works as expected?

Any tips for getting myarray[1] to behave?

Sean