You can clad your roof in solar panels, bike to work and recycle or compost all your waste, but your environmental cred might still amount to nothing if you let Fluffy roam free.
That's been suggested by a new study that lends more credence to calls for action over wandering domestic cats.
The US research found bird lovers who let their pet cats out of the house were judged to be less concerned about the environment by other members of the bird-watching community on social media.
That was the case even if the property owner was otherwise employing all of the same sustainable practices as those keeping cats indoors.
"We thought this was a very interesting opportunity to study group norm violations," said study author Hwanseok Song, a doctoral student at Cornell University.
"What happens within this community when they see one of their members violate an important group norm?
"Do people notice cues that a member within their community is letting their cat outdoors?
"Do these people who notice those cues actually use that information to make judgments on that group-norm violator?"
Song and his collaborators used Habitat Network, a socially-networked US mapping application that allowed users to create and share virtual maps of their properties that highlight their sustainability efforts, essentially a show-and-tell for good conservation practices.
They created two identical profiles of a pro-environmental property with a small lawn, low chemical usage and solar panels.
The only difference between the profiles: one version had an icon and an image indicating an indoor pet cat and the other an outdoor pet cat.
Outdoor cats were a divisive issue for many nature lovers because of the threat they pose to wildlife, particularly birds.
Here in New Zealand, domestic cats alone kill at least 18.7m animals a year - including 1.1m native birds, according to Forest & Bird.
Habitat Network users were asked to rate each property owner's level of sustainability.
The researchers found participants who didn't own cats negatively judged property owners with an outdoor cat and even considered them significantly less likely to engage in a variety of pro-environmental behaviours - even though the maps made it clear these property owners had invested in solar power and used few chemicals on their lawns.
"Everything else in this map is pretty much signaling that this is a person already quite committed to sustainability cause," Song said.
"It usually takes a strong environmental commitment to install a solar panel.
"These findings say a lot about how we make judgments of others who are either violating, or complying with, these sometimes-parochial norms."
Explained: Brain sparks before bungee courage
If you've ever bungee-jumped, you'll know the feeling: that moment of terrified hesitation on the platform before you take the plunge.
But something else happens in your brain during the build-up.
Researchers have looked at the science around "readiness potential" using a 192m bungee jump as their laboratory.
Readiness potential might be described as an electrical shift in the brain that indicates an upcoming act of will, taking place even before it registers in our consciousness.
The phenomenon was first described in 1964 by scientists who measured the brain waves of a test person over hundreds of finger movements and under strict laboratory conditions.
Despite numerous studies, it's never been measured in a real-life situation - although for good reason.
Since the voltage shift is in the range of only a few millionths of a volt, only measurements under laboratory conditions have been considered possible.
To advance the development of brain-machine interfaces, a team of German scientists researchers sought to find out whether the readiness potential could be assessed in everyday environments.
They were also interested in whether the willpower necessary for initiating an act would influence the characteristics of the brain potential.
For their study, two semi-professional cliff divers agreed to have their brain waves recorded before jumping from the second tallest bungee jumping platform in Europe, the 192m Europa Bridge near Innsbruck in Austria.
After only a few jumps, the researchers were able to measure the readiness potential beyond any doubt.
"Once again, the current experiment shows that the boundaries of the possible are shifting and that neurotechnology might soon be part of our everyday life," said study co-author Dr Surjo R Soekadar, a psychiatrist and neuroscientist at the University of Tubingen.
Great friends think alike
"Friendship is born at that moment when one person says to another: 'What! You too? I thought I was the only one.'."
That's how famed fantasy writer CS Lewis put it.
But now researchers have shown how there's quite a bit of science behind those ties that bind.
The team from Dartmouth University in the US found friends have similar neural responses to real-world stimuli - and these similarities could even be used to predict who your friends are.
They found that you can predict who people are friends with just by looking at how their brains respond to video clips.
Friends had the most similar neural activity patterns, followed by friends-of-friends who, in turn, had more similar neural activity than people three degrees removed, or, if you will, friends-of-friends-of-friends.
Their new study was the first of its kind to examine the connections between the neural activity of people within a real-world social network, as they responded to real-world stimuli, which in this case was watching the same set of videos.
"Neural responses to dynamic, naturalistic stimuli, like videos, can give us a window into people's unconstrained, spontaneous thought processes as they unfold," lead author Dr Carolyn Parkinson said.
"Our results suggest that friends process the world around them in exceptionally similar ways."
The study analysed the friendships or social ties within a cohort of nearly 280 graduate students.
The researchers estimated the social distance between pairs of individuals based on mutually reported social ties.
Forty-two of the students were asked to watch a range of videos while their neural activity was recorded in a functional magnetic resonance imaging (fMRI) scanner.
The videos spanned a range of topics and genres, including politics, science, comedy and music videos, for which a range of responses was expected.
Each participant watched the same videos in the same order, with the same instructions.
The researchers then compared the neural responses pairwise across the set of students to determine if pairs of students who were friends had more similar brain activity than pairs further removed from each other in their social network.
The findings revealed that neural response similarity was strongest among friends, and this pattern appeared to manifest across brain regions involved in emotional responding, directing one's attention and high-level reasoning.
Even when the researchers controlled for variables, including left-handed- or right-handedness, age, gender, ethnicity, and nationality, the similarity in neural activity among friends was still evident.
The team also found that fMRI response similarities could be used to predict not only if a pair were friends but also the social distance between the two.
"We are a social species and live our lives connected to everybody else," co-author Dr Thalia Wheatley added.
"If we want to understand how the human brain works, then we need to understand how brains work in combination - how minds shape each other."