Startle produces early response latencies that are distinct from stimulus intensity effects
- 317 Downloads
Recent experiments pairing a startling stimulus with a simple reaction time (RT) task have shown that when participants are startled, a prepared movement was initiated earlier in comparison to voluntary initiation. It has been argued that the startle acts to trigger the response involuntarily. However, an alternative explanation is that the decrease in RT may be due to stimulus intensity effects, not involuntary triggering. Thus the aim of the current investigation was to determine if RT simply declined in a linear fashion with increasing stimulus intensity, or if there was a point at which RT dramatically decreased. In the present experiment participants completed 50 active wrist extension trials to a target in response to an auditory stimulus of varying stimulus intensity (83–123 dB). The presented data show that RTs associated with a startle response are separate from stimulus intensity facilitated responses. Furthermore, this startle facilitation is more highly associated with sternocleidomastoid electromyographic (EMG) activity, rather than the EMG from the widely used startle response indicator muscle orbicularis oculi.
KeywordsStartle Electromyography Reaction time Orbicularis oculi Sternocleidomastoid
This work was supported by a grant from the Natural Sciences and Engineering Research Council of Canada awarded to I.M.F. and a Michael Smith Foundation for Health Research scholarship awarded to A.N.C.
- Davis M (1984) The mammalian startle response. In: Eaton RC (ed) Neural mechanisms of startle behavior. Plenum, New York, pp 287–351Google Scholar
- Luce RD (1986) Response times: their role in inferring elementary mental organization. Oxford University Press, New YorkGoogle Scholar
- National Institute for Occupational Safety and Health (NIOSH) (1998) Publication No. 98–126: criteria for a recommended standard. CDC, CincinnatiGoogle Scholar
- Wadman WJ, Denier van der Gon JJ, Geuze RH, Mol CR (1979) Control of fast goal-directed arm movements. J Hum Mov Stud 5:3–17Google Scholar
- Woodworth RS (1938) Experimental psychology. Henry Holt, New YorkGoogle Scholar