This paper describes two experimental protocols for direct comparison on human and machine phonetic discrimination performance in continuous speech. These protocols attempt to isolate phonetic discrimination while controlling for language and segmentation biases. Results of two human experiments are described including comparisons with automatic phonetic recognition baselines. Our experiments suggest that in conversational telephone speech, human performance on these tasks exceeds that of machines by 15%. Furthermore, in a related controlled language model control experiment, human subjects were better able to correctly predict words in conversational speech by 45%.