... the "Prank" ? Reverse Psychology & Impulsiveness

[Matt]

No: HPFGUIDX 99929

--- Pippin wrote:
> I have no problem believing that Sirius, loathing 
> Snape, acted on a murderous whim and told Snape what 
> to do. What I can't credit is that Snape, loathing 
> Sirius, acted on a whim and did it. 
> .......
> Snape, unlike Bertha, is usually careful and assesses 
> the risks in advance. Otherwise he'd have been 
> terminated with extreme prejudice a long time ago. 
> If Snape finds himself in unexpected hot water, it's 
> because he underestimates the risks that others are 
> willing to take...for Sirius to use the Shrieking 
> Shack as a refuge, or for James and Sirius to hex 
> him in front of witnesses, or for Harry and his 
> friends to attack him, for example. 

I largely agree with your analysis of adult Snape, but am not sure how
valid it is to project all of that cautiousness back onto 15-year-old
Snape.  Even adult Snape sometimes lets his emotions get the better of
him where Harry is concerned (the sputtering scene in PA, the temper
tantrum at the end of the "Worst Memory" scene in OP).  Place him back
in the throes of adolescence, and confront him with the direct objects
of his hatred (the Marauders) rather than the projected one (Harry),
and I could see him getting carried away by an impulse.  

Amber's speculation at the beginning of this thread about Snape having
some self-destructive impulses is also worth considering.  We don't
see those impulses in the adult Snape, but we certainly have enough
background to understand how he could have felt that way at 15.  Being
an unpopular, bad-looking, bullied kid with a tough family life does
not do quite as much for your self-esteem as being a Professor and
Head of House at Hogwarts at the age of 35.  If Snape was a bit
self-destructive (even far short of suicidal), and a bit impulsive
where the Marauders were concerned, I can see him rushing into
something -- possibly at a more careful pace (giving James time to
catch up to him), but without any really sober reflection.

-- Matt