Kathleen Vohs and Jonathan Schooler had one group of students read passages that asserted and otherwise promoted the view that free will is an illusion, while the control group read neutral material. The former group was then found to express weaker belief in free will on a Free Will and Determinism Scale, and were more likely to cheat on a mathematics task than were those in the control group. In a companion experiment, a group of participants exposed to statements of behavioral determinism more often engaged in deceptive behavior equivalent to stealing (in which they allowed the researchers to pay them for correct answers they didn't give on a mathematical task) compared to participants exposed to neutral statements or statements endorsing free will.
Baumeister, Masicampo and DeWall built upon these findings, showing that students exposed to material advocating determinism were subsequently less likely to agree to lend help to someone else (even in minor ways, e.g., allowing a classmate to use one's cell phone), were less likely to actually volunteer to help someone in need (even by doing easy work such as stuffing envelopes), and, most disturbingly, were more likely to engage in acts of aggression against innocent people than were their peers who had been exposed to messages that were either neutral or endorsed free will.
These findings are not really surprising. The authors cite other evidence and provide a brief account for why disbelief in one's freedom to choose one's actions correlates with engaging in undesirable antisocial behavior. Vohs and Schooler:
It is well established that changing people’s sense of responsibility can change their behavior. For example, invoking a sense of personal accountability causes people to modify their behavior to better align with their attitudes (Harmon-Jones & Mills, 1999). Believing that outcomes are based on an inborn trait, rather than effort, also influences behavior. For instance, Mueller and Dweck (1998) observed 10-year-old children who were told that they had been successful on an initial task either as the result of their intelligence or through their hard work. In a second round, all the children encountered a task that was well beyond their performance level (i.e., they failed at it). When the children were given yet a third task, those who thought their earlier success was due to their intelligence put forth less effort and reported lower enjoyment than those who thought their initial success was due to their own effort. The authors concluded that the former children’s belief that their performance was linked to their intelligence indicated to them that achieving a high score on the difficult problems in the second round was beyond their ability. Hence, faring poorly (on an admittedly difficult task) indicated to children in the intelligence condition that they were simply not smart enough for the task, which in turn led them to stop trying to perform well and to like the task less.
If reducing people’s sense of control also reduces the amount of effort they put toward improving their performance, then advocating a deterministic worldview that dismisses individual causation may similarly promote undesirable behavior.
Baumeister, Masicampo and DeWall further discuss why belief in free will seems to promote socially desirable behavior:
. . . Vohs and Schooler (2008) proposed that disbelief in free will serves as a subtle cue that exerting volition is futile and thereby gives people permission not to bother. The idea of not bothering to exert volition appeals to people insofar as volition in the form of self-control and choice requires exertion and depletes energy (Baumeister, Bratslavsky, Muraven, & Tice, 1998; Gailliot et al., 2007; Vohs et al., 2008). In a sense, then, making people disbelieve in free will may serve as a nonconscious prime to act in relatively automatic ways, which would thus include enacting impulses rather than exerting control and restraint.
We examined two related possibilities, as well. One was that inducing belief in free will stimulates a conscious feeling of being active and energetic, thereby making people feel like they want to exert control. Another is that belief in free will supports (and disbelief undermines) a sense of personal responsibility and accountability. Feelings of responsibility and accountability may make people feel that they ought to behave in socially desirable ways, such as performing prosocial acts of helping and restraining antisocial impulses to aggress against others. The deterministic belief essentially says that the person could not act otherwise, which resembles a standard form of excuse (“I couldn’t help it”) and thus might encourage people to act in short-sighted, impulsive, selfish ways.