Fact or fiction: home underdogs pack a mean bite, often winning straight up against visiting favorites? Through three weeks of the NFL season, it is apparent that football fans like to bet on teams who are underdogs at home by three or four points.

Home-field advantage is usually the most logical reason for betting home dogs, as teams traditionally play better at home, and the game will usually turn out to be close as the home team is spurred on by their fans. Home teams typically get three points on the point spread just for home-field advantage.

This trend was especially prevalent last season, when a lot of teams, who were out of the postseason hunt and had nothing to play for, pulled off some upsets against playoff-bound teams (for example, Miami's 21-0 shutout of New England on December 10, 2006).

So far this season, the home dog has been in vogue only a couple of times. The first occurrence was in Green Bay as the Packers were 3-point underdogs at home against the Philadelphia Eagles in their season opener, and came away with a 16-13 win over the Eagles at Lambeau Field.

This is a good example of home-field advantage because Lambeau Field is known for having some of the rowdiest fans in football, so any time the Packers are underdogs at home, it would be wise to consider a wager on Brett Favre and the boys. Of course, they needed some lousy special teams play by Philly to win, but no matter.

Arizona also pulled this off in Week 2, when they were 2.5-point home underdogs against the Seattle Seahawks, and they came away with a 23-20 win over their division rivals.

The Cardinals have long been one of the league's laughingstocks, but a powerful albeit young offense and an improving defense have given their fans and backers hope for the upcoming season. A 2.5-point spread is a tricky factor to consider as the field goal often comes into play late in many games.

In upcoming Week 4 action, there are some instances where this could happen again, so pay attention if you like to bet home dogs. San Francisco is currently a 1-point underdog as they host the Seahawks, and the 49ers are playing well this season as another up-and-coming team.

The Giants are 2.5-point underdogs at home against the Eagles, and it should be safe to assume the Eagles will not have another 56-point outburst like they did last week against Detroit.

You can see which home underdogs the experts at PointSpread.com are betting this week by clicking the buy picks links in the right navigation of the home page. You can also find NFL home underdogs in the matchups section here.