'Long-latency' responses occurring with startle in the conscious monkey.

A monkey was noted to have an intermittent startle response to tendon tapping and vibration of proximal arm muscles. The latency of the first phase of this response, averaging 34 ms in triceps (and of average duration 49 ms), was similar to that described for the long-latency reflex response to muscle stretch in the same muscles. Unrecognised startle responses could explain some of the reported differences in long-latency reflexes in proximal and distal muscles.