A couple of scientists walked into a bar and … began posing moral quandaries. When they presented bar-goers with a version of the classic “trolley problem”—would you push a man in front of a train, killing him in order to save five track workers?—they found that the drunker people got, the more likely they were to say they’d push the man.  Alcohol, the researchers observed, can make us more utilitarian in our reasoning.
It can also make us less charitable. In one study, researchers offered people 20 euros and gave them a chance to donate some or all of the money to Doctors Without Borders. Compared with sober subjects, those who’d downed an alcoholic peach drink were significantly less likely to donate. 
But as anyone who’s slurringly professed his affection for another knows, we’re not always heartless when under the influence. Indeed, one study found that alcohol alters the “bystander effect,” whereby people are more reluctant to help a person in need if others are present. When an experimenter dropped a jar of items in front of several people, those who’d been drinking were quicker to offer aid than those who were sober. The study’s authors suggested that this might be because alcohol lessens social inhibitions. 
It inflates egos, too. In one experiment, the drunker bar patrons were, the more attractive they considered themselves.  And the mere belief that we’ve been drinking can be enough to cause this ego boost: People who were told they’d consumed an alcoholic drink considered themselves more attractive, bright, original, and funny than did those who thought they’d had a nonalcoholic drink—whether or not either drink was actually alcoholic. Another experiment found that sober people find us more appealing when we’re a bit buzzed: Individuals who’d consumed the equivalent of a large glass of wine were deemed more attractive than sober people. (The effect evaporated when people consumed more than one drink.) 
Our appreciation for others also increases after a drink or two. Participants in one study who imbibed a fruity vodka drink found minimally to moderately attractive faces significantly more beautiful than did those who’d consumed an alcohol-free drink.  This might be because we’re less able to distinguish symmetrical faces from asymmetrical ones when we’ve been drinking,  and symmetry is known to be an important component of attractiveness.
Humans aren’t alone in becoming less discriminating after drinking—fruit flies that have been chronically exposed to alcohol are more impulsive about mate selection when under the influence.  As animal as this tendency is, it may not be a problem so long as we keep sipping. One forthcoming study found that unhappy couples got along better and were more able to solve conflicts after a few vodka-cranberry drinks.  Which is to say, alcohol might help you not just find a mate, but keep one.
 Duke and Bègue, “The Drunk Utilitarian” (Cognition, Jan. 2015)
 Corazzini et al., “Economic Behavior Under the Influence of Alcohol” (PLOS One, April 2015)
 Van Bommel et al., “Booze, Bars, and Bystander Behavior” (Frontiers in Psychology, Feb. 2016)
 Bègue et al., “Beauty Is in the Eye of the Beer Holder” (British Journal of Psychology, May 2013)
 Abbeele et al., “Increased Facial Attractiveness Following Moderate, but Not High, Alcohol Consumption” (Alcohol and Alcoholism, May 2015)
 Chen et al., “The Moderating Effect of Stimulus Attractiveness on the Effect of Alcohol Consumption on Attractiveness Ratings” (Alcohol and Alcoholism, Sept./Oct. 2014)
 Souto et al., “Alcohol Intoxication Reduces Detection of Asymmetry” (Perception, June 2008)
 Han et al., “Recurring Ethanol Exposure Induces Disinhibited Courtship in Drosophila” (PLOS One, Jan. 2008)
 Fairbairn and Testa, “Relationship Quality and Alcohol-Related Social Reinforcement During Couples Interaction” (Clinical Psychological Science, forthcoming)