Broadhurst compared the twins' voice onset times to each other, hypothesizing that Niki, the gay twin, would have a longer voice onset time than Sammy, the straight twin.

She found the opposite − Niki actually had the shorter voice onset time. That's not all. Broadhurst also compared how each twin spoke when talking with straight people versus gay people.

Voice Onset Time (VOT): The interval between the release of a stop consonant and the onset of vocal fold vibration, serving as a key acoustic cue in voicing distinctions.

Then they tested the birds' perception of speech sounds that varied in two cues: voice onset time and the frequency of the first formant (formants are resonating frequencies of the vocal tract).