Because the MBR demonstrates a particular sensitivity to the temporal relationship between the reflexogenic and the modifying stimulus, and because there is evidence to suggest that individual differences exist in blink reflex modification (Schwarzkopf, McCoy, Smith, & Boutros, 1993), the current studies investigated the potential of the MBR as a measure of individual differences in speed of processing.
In Study 1 the temporal relationship (SOA) between a modifying tone of 60 ms duration and a reflexogenic glabellar tap was varied.
Measurement of the characteristics of the modifying tone, and of the SOAs between the tone and reflexogenic tap, was carried out prior to testing using a Bruel and Kjaer sound-level meter and a cathode-ray oscilloscope.
These results clearly demonstrate that the presence of the tone facilitated both the latency and amplitude of the blink reflex and that the effects varied, as expected, with the experimental manipulation of SOA between the onset of the modifying tone and the reflexogenic tap.
Before examining the relationship between individual differences in the MBR and processing speed (as indexed by Ravens and IT), any possible relationship between individual differences in the latency of the unmodified blink reflex (which reflects the simple low-level processing of the reflexogenic tap stimulus) and processing speed was investigated.
These results again demonstrate that the tone modified both latency and amplitude of the blink reflex and that effects varied with the experimental manipulation of SOA between the reflexogenic tap and the modifying tone.
The latency of the unmodified blink reflex, which reflects the simple low-level processing of the reflexogenic tap stimulus (no influence of the tone) was again examined for any relationship with intelligence and processing speed.