Does owning a firearm influence your behavior in any way?

Following any gun-related tragedy, a recurring question emerges: Could the incident have been prevented if the individual had not possessed a firearm? Would Mindy McCready have still taken the life of her dog and then her own? Would Olympian Oscar Pistorius have shot his girlfriend? While we can't reverse time to know how these events would have unfolded without firearms, we can examine existing research on how gun ownership shapes human behavior.

Proponents of gun rights often claim they own firearms for recreational purposes, such as hunting or target shooting, or for self-defense against criminals [source: Bushman]. They argue that gun ownership in the U.S. has reached an all-time high, and coincidentally, the murder rate has decreased by 49 percent since 1991 [source: National Rifle Association].

Advocates for gun control contend that reducing the number of guns would lead to fewer fatalities, and while knives can still be dangerous, they don't cause as many deaths as firearms [source: Anderson]. According to the 2012 General Social Survey, gun ownership in households has dropped to a 35-year low, now at 34 percent, compared to 43 percent in the 1990s. This suggests that the link between gun ownership and a decrease in crime may not hold [source: Tavernise and Gebeloff]. The gap in these findings could be due to the fact that although fewer households own firearms, those that do typically own more than before.

The influence of gun ownership on behavior is a complex subject. However, research indicates that simply owning a firearm or even just observing one can alter the way people act.

There is a concept known as the "weapons effect," first explored in 1967. Researchers Leonard Berkowitz and Anthony LePage discovered that the mere presence of guns in a room led individuals to act more aggressively, such as delivering stronger electric shocks to other participants. A 1975 study showed that drivers tended to act more aggressively when following a truck that had a gun displayed in a rack, compared to one without a gun. Despite logic suggesting caution around vehicles displaying firearms, humans have an inherent ability to quickly identify danger, such as recognizing weapons and snakes. Studies indicate that weapons activate the same part of our brain responsible for responding to danger and aggression [source: Bushman]. Another 2006 study revealed that men who interacted with guns experienced an increase in testosterone and aggression [source: Klinesmith].

Guns and Suicide

When considering gun violence, one might envision a criminal using a 9 mm pistol against a victim or a homeowner defending himself with a shotgun. However, the majority of gun-related deaths in the U.S. are not the result of violent crimes, but rather suicides committed with firearms [source: Sapien]. In 2011, the most recent year for which data is available, 19,766 people in the U.S. took their own lives using a gun, while 11,101 people were killed in homicides involving firearms [source: Hoyert and Xu].

In the case of Mindy McCready, it's easy to argue that if she hadn't had access to a firearm, she may have found another way to end her life. Police also discovered bottles of prescription drugs in her home [source: People Magazine].

There is, however, a link between gun ownership and suicide. A 2004 CDC survey on gun violence, published in the American Journal of Epidemiology, revealed that gun owners who took their own lives were more likely to use their firearms than other methods like pills. A 1992 study included in the CDC survey found that individuals with a gun in their home were five times more likely to commit suicide. Additionally, a large-scale national study in 2003 showed that having access to a firearm made a person over three times more likely to die by suicide compared to those without guns in their homes [source: Dahlberg, Ikeda and Kresnow].

Why does this happen? Experts suggest that suicide is often an impulsive decision, usually occurring during moments of intense crisis. Between 85 and 90 percent of individuals who use guns to attempt suicide die, which is a significantly higher rate than with other methods. It’s believed that if people didn't have access to firearms in those vulnerable moments, they may have survived. In fact, the Israeli Defense Force found that by prohibiting soldiers from taking their weapons home over the weekend, it reduced the suicide rate by 40 percent [source: Neyfakh].

Guns and Homicide

It’s clear that owning a firearm increases the risk of self-harm, but what about the potential for harm to others?

Much of the government-backed research on gun violence originates from the 1990s, as in 1996, the National Rifle Association successfully lobbied Congress to reduce funding for such studies. Before that, however, the CDC found that having a firearm in the home made homicide about three times more likely for family members living there [source: Sapien]. This aligns with a 1992 study that showed violent family disputes were three times more likely to result in death when a firearm was involved, compared to other weapons [source: Saltzman].

Many homicides are not the result of careful planning. Instead, they often stem from arguments between friends or family members, possibly about money or infidelity, which escalate into violence. Introducing a firearm into such situations significantly increases the likelihood of a fatal outcome, much more so than using a baseball bat or a knife.

However, researchers point out that while there is a correlation between firearms in the home and homicide, it is not as strong as the connection between firearms and suicide. Most murder victims are not shot in their own homes, unless they are women, children, or the elderly. Additionally, households with firearms might have a higher involvement in criminal activity. A frequently cited study of 400 homicide victims killed in their homes found that half were shot, and in most cases, the victim knew the perpetrator. Forced entry was uncommon, occurring only 14% of the time. In this study, 36% of the households owned firearms, compared to 23% of control households [source: Hemenway].

Changes in behavior also manifest on the streets. A 2009 study examining 677 shootings in Philadelphia over a period of two-and-a-half years found that individuals carrying firearms were 4.5 times more likely to be shot and 4.2 times more likely to be killed than unarmed individuals. The researchers believe that owning a gun may give individuals a sense of power, which could lead them to act impulsively or venture into dangerous situations they might typically avoid [sources: Callaway, Branas].