A scientifically useful comparison of Semax and Selank starts with the experiments, not a list of desired effects. Both names appear in nervous-system research, but distinct sequences and research traditions do not establish that one is better for attention, anxiety or learning.

For Semax, an original study examined BDNF expression in rat brain. For Selank, investigators studied changes in genes associated with neurotransmission in an animal model. Semax stimulates BDNF expression in rat brain Selank and genes involved in GABAergic neurotransmission These are mechanistic observations. They do not amount to a randomized comparison of cognitive or anxiety outcomes in people.

The measurements themselves require care. Messenger RNA, protein abundance, receptor function and behavior are related but separate levels of evidence. A change at one level cannot simply be relabeled as improvement at another. Brain region, timing and experimental context can also change the interpretation of a molecular signal.

A meaningful human comparison would define the clinical question and use appropriate validated outcomes. Treatment of a diagnosed anxiety disorder is different from enhancement in healthy volunteers. Short-term performance on one test is different from sustained improvement in daily functioning. Blinding, an adequate comparator and systematic adverse-event collection would be essential.

This article therefore offers no winner and no combination strategy. It separates the types of questions that have been investigated from the claims that remain unestablished by the cited sources. Before publication, a specialist should examine the full human literature, language limitations, regulatory status and formulation identity. Until then, labels such as cognitive enhancer or proven anxiolytic should not stand in for a precise account of what a study actually measured.