  The assertion that there is an intrinsic excess of binaries with mass ratios
q \simeq 1 - the twin hypothesis - is investigated. A strong version of this
hypothesis (H_s), due to Lucy & Ricco (1979) and Tokovinin (2000), refers to a
narrow peak in the distribution function psi(q) for q \ga 0.95. A weak version
(H_w), due to Halbwachs et al. (2003), refers to a broad peak for q \ga 0.8.
Current data on SB2's is analysed and H_s is found to be statistically
significant for a sample restricted to orbits of high precision. But claims
that H_s is significant for binaries with special characteristics are not
confirmed since the sample sizes are well below the minimum required for a
reliable test. With regard to H_w, additional observational evidence is not
presented, but evidence to the contrary in the form of Hogeveen's (1992b) model
of biased sampling with psi \propto q^{-2} is criticized. Specifically, his
success in thus fitting catalogued data depends on implausible assumptions
about the research methodologies of binary-star spectroscopists.
