From the article:
To obtain more rigorous data on the connection, Nave, Nadler, and their colleagues conducted two randomized controlled studies in which 643 healthy men received an application of testosterone gel or a placebo and completed questionnaires and behavioral tasks that measured cognitive empathy. Participants were then shown a photo of an actor’s eyes and asked to select the emotional state that best described their expression. All participants also had their 2D:4D ratio [ratio of the length of the participant’s second finger to their fourth finger; proxy for sensitivity to testosterone] measured.
While the testosterone gel did increase participants' levels of the hormone, the researchers found no evidence that testosterone administration affected performance on tests of cognitive empathy [capacity to read the emotions of others]. They also found no relationship between participants' performance on the tests and their 2D:4D ratio.
“The results are plain,” says Nave. “However, it’s important to note that the absence of evidence is not evidence of absence. We found that there is no evidence to support this effect of testosterone, but that doesn’t rule out any possible effects. From what we know, though, it seems that if testosterone does have an influence, the effect is complex, not linear. Reality is typically not that simple.”