Attitude certainly plays a big role.
I had a game where I was losing my lane, I was making mistakes, but I knew what I was doing wrong. I felt that if I changed my strat up I could comeback and gain leverage on my opponents. Meanwhile, my jungler, so ever observant, took every chance he got to flame me for whatever mishap I made. I ignored him cause I could tell this guy was just a tilter, as if he had to find any little outlet to shift the blame for his losing game. Ya know, the kind that believe they are above reproach.
Unfortunately, he also did this to my bot lane, who were just having a though time. Sadly, our ADC was getting tilted by our jungler's flaming. Eventually when the option to early surrender came around, the jungler didn't delay to initiate it, and basically everyone else followed suit. Everyone became disillusioned with the game, but even though we were losing, I felt like my team was just not working at 100% because they fell into a negative attitude. So I said no. Also, I was pretty mad with that fucking jungler. All he did was flame, and give everyone a hard time. I felt sorry for bot, but no way this fucker will get out without some sort of pay back.
Anyways, down the road, I decided to roam bot. I didn't do much, but whatever happened, it gave my ADC courage to fight and he performed in a stellar fashion, completely killing everyone in the lane. After that he took tower, and started roaming. Little by little, he started to gain traction and got pretty strong. The jungler, still only able to see down a narrow tunnel, decides to surrender again. This time, I was backed by the ADC, and we denied it. He said in chat "No. I think we can win this." I was pretty glad he said that, it felt like climbed out of his rut and was invigorated to play to the end.
Ultimately, we won! And no thanks to asshole jungler. Well, he got some kills, and probably drew attention away from the enemy. But, seriously, it sucks when people just get tilted and then just completely give up. They use the score as an excuse, and just place no faith into their teammates.
TL;DR -- Attitude has a strong influence on a game's outcome. Also fuck flamers that just bitch the whole game, and then demand others to surrender. When you start flaming, you become part of the reason the team is losing.