Previous studies show that reading sentences about actions leads to specific motor activity associated with actually performing those actions. We investigate how sign language input may modulate motor activation, using British Sign Language (BSL) materials, some of which explicitly encode direction of motion, vs. written English, where motion is only implied. We find no evidence of action simulation in BSL comprehension, but replicate effects of action simulation in comprehension of written English. The results suggest that the perception of motor articulation in the language input interferes with mental simulation involving the motor system.