The memory performance level of each of the fly lines carrying a mutant trbl allele was significantly reduced compared to wild type CS. Flies that were trans-heterozygous for the trbl gene trbl3-54/trbl1119 performed significantly lower than CS and flies with only one copy of a mutant allele (left-most comparisons H(3, N=910) = 53.32, p < 0.001, Kruskal-Wallis ANOVA test with multiple comparisons (p<0.05 = *, p<0.01 = **, and p<0.001 = ***)). The reduction in memory performance found with flies carrying only a single mutant trbl allele was not increased with the trans-heterozygote trbl3-54/trbl3519 (right-most comparisons H(3,N=750) = 32.67, p < 0.001 Kruskal-Wallis ANOVA test with multiple comparisons (p<0.01 = ** and p<0.001 = ***)). The values represent means and the error bars are SEMs.