Trying to figure out effect size for the following information:

CONTROL GROUP:

The results from the pre-test (M = 4.67 = ,SD= 0.58) and post-test (M= 4.67,SD= 0.58) scores of the control group indicate that providing a myth with the correlating fact will not decrease the belief in the myth,t(4) = 3.1,p= .5

EXPERIMENTAL GROUP:

The results from the pre-test (M=4 ,SD= 0) and post-test (M=4.67 ,SD= 0.58) scores of the experimental group indicate that providing a myth with the correlating fact will not decrease the belief in the myth,t(4) = 3.1,p= 0.09

The effect size I am getting for control group is 0 and -3.27 for experimental. Can you also clarify what the findings mean?