Under both capitalism and socialism, labor incentives depend on whether workers can appropriate the marginal returns to their effort. In capitalism, part of the product of labor is extracted by private owners as profit. In socialism, a larger share of the product is typically collectivized.
In socialism, a larger share of the product is typically collectivized and redistributed through the state or society as a whole. From an incentive-theoretic perspective, when individuals receive a smaller direct return from additional effort, their motivation to work may decline.
Therefore, the problem of weak labor incentives is not unique to capitalism; it can also arise in socialism when the worker is not the residual claimant of the product of labor.
Even in social-democratic societies, this issue can still emerge: highly educated and productive individuals may face substantial taxation and redistribution, which can reduce the direct rewards of their labor by transferring part of the value they create to those who contribute less economically, whether due to lower skills, lower productivity, or social disadvantage.