Many high-profile instances of police brutality over the past year could have been avoided by addressing law enforcement culture, training, and supervision—and an overhaul of police institutions is crucial to prevent more of those cases, a new study released Thursday concluded.

The Police Executive Research Forum (PERF), a nonprofit policy organization based in Washington, D.C., analyzed a number of cases in which officers used excessive force as a first-resort means of addressing situations and found that, in departments throughout the country, police do not receive adequate training in communication, crisis intervention, and nonviolent deescalation of crises.

Rather, a pervasive culture of aggression and competition encourages officers to react with force, even when suspects are unarmed, which has caused “missed opportunities to ratchet down the encounter, to slow things down, to call in additional resources,” PERF executive director Chuck Wexler wrote in a summary of the report, Re-Engineering Training On Police Use of Force (pdf).

“Sometimes there is a feeling of competitiveness about it,” he wrote. “If an officer slows a situation down and calls for assistance, there is sometimes a feeling that other responding officers will think, ‘What, you couldn’t handle this yourself?'”

Deescalating tension or calling in additional resources, in fact, is often perceived as being “antithetical” to police culture.