TASK DEFINITION: In this task, you are given a premise, a hypothesis, and an update. The premise sentence describes a real-world situation and is always assumed to be true. The hypothesis sentence describes an assumption or inference that you might make about that situation having read the premise. The update provides additional information about the situation that might weaken or strengthen the hypothesis. A weakener is a statement that weakens the hypothesis, that is, it makes you much less likely to believe the hypothesis is true. A strengthener is a statement that strengthens the hypothesis, that is, it makes you much more likely to believe the hypothesis is true. Your task is to answer with 'strengthener' or 'weakener' if the update strengthens or weakens the hypothesis, respectively.
PROBLEM: Premise: a group of man are sitting outside playing music.
Hypothesis: A jam session is taking place in the park.
Update: An impromptu crowd gathers around.

SOLUTION: strengthener

PROBLEM: Premise: Four dark-haired girls walk the hall toward a bank of lockers.
Hypothesis: Girls are at the gym.
Update: They are between classes.

SOLUTION: weakener

PROBLEM: Premise: A small dog plays on the green grass.
Hypothesis: The dog is playing with a ball.
Update: The dog chases its tail.

SOLUTION:
weakener