Air Carrier Captain reported during taxi from the ramp at IAH airport another aircraft taxied right across their path resulting in the captain taking evasive action to avoid a collision.

Narrative

Cleared to taxi for departure from spot B; SC; then RA to spot 1. Approaching the RA bridge; Ramp called us; then told us to continue taxi to spot 1. I had already slowed my taxi a little because I saw another air carrier coming out of either spot J or H; and I thought the controller was going to tell us to follow that plane. When he said to continue; I assumed the other air carrier was cleared to taxi on the RB bridge (I did not hear the other air carrier's initial taxi clearance). When I realized that the other air carrier; was shooting right out in front of us; I hit the brakes to avoid a collision. The other air carrier proceeded across the RA bridge then transitioned back to the RB taxiway on the other side. I asked the ramp controller why he sent two aircraft to the RA bridge at the same time; and he never gave a good answer. I'm not sure if the other air carrier mistakenly went to the RA bridge when he was told to cross the RB bridge or if Ramp control made the mistake of allowing us to both taxi to the same place at the same time.