These are the descriptions of the Reserved and Libidinous sexual perks,
Reserved: You start with a lower Libido, and you gain less Libido when items and events would increase it.
Libidinous: You start with a higher Libido, and it increases more readily when events and items would increase it.
Tested Libido gains with Ice Wine and Lustful Liquor and these are the results,
So while the descriptions only mention you gaining less or more Libido with items that would increase it, these perks are also making you lose less or more with items that would decrease it.
Also for some reason, with the Reserved perk, you can only ever decrease Libido to 1 after increasing it past the 0 you start with.
Reserved: You start with a lower Libido, and you gain less Libido when items and events would increase it.
Libidinous: You start with a higher Libido, and it increases more readily when events and items would increase it.
Tested Libido gains with Ice Wine and Lustful Liquor and these are the results,
| Perk | Lustful Liquor, Libido Gain | Ice Wine, Libido Loss |
| None | +5 | -8 |
| Libidinous | +7.5 | -12 |
| Reserved | +2.5 | -4 |
So while the descriptions only mention you gaining less or more Libido with items that would increase it, these perks are also making you lose less or more with items that would decrease it.
Also for some reason, with the Reserved perk, you can only ever decrease Libido to 1 after increasing it past the 0 you start with.