Ison J R, Zuckerman M, Russo J M
J Exp Psychol Anim Behav Process. 1975 Oct;1(4):318-25. doi: 10.1037//0097-7403.1.4.318.
Startle reactions are inhibited if their elicitation is preceded by weak neutral stimuli at lead times of fractions of a second, or by intense startle-eliciting stimuli at lead times of up to several seconds. In three experiments (a) two weak stimuli, (b) one weak stimulus and one intense stimulus, or (c) two strong stimuli were given in combination. In all three conditions the combination provided more response inhibition than did either stimulus alone. Conditions 1 and 2 gave combination effects in which the inhibited proportion of the response was described by the rule for compounding the probabilities of independent events, indicating that the stimuli had noncompetitive independent access to the inhibitory machinery. The rule over-estimated the effect of the compound in Condition c, suggesting the presence of some other summative process, perhaps involving the prolongation of the refractory period.
如果在惊跳反应引发前的几分之一秒的提前期给予微弱的中性刺激，或者在长达几秒的提前期给予强烈的惊跳引发刺激，惊跳反应就会受到抑制。在三个实验中，（a）组合给予两个微弱刺激，（b）组合给予一个微弱刺激和一个强烈刺激，或者（c）组合给予两个强烈刺激。在所有这三种情况下，组合刺激比单独的任何一种刺激都能提供更多的反应抑制。条件1和条件2产生了组合效应，其中反应的被抑制比例由独立事件概率复合规则来描述，这表明刺激对抑制机制有非竞争性的独立作用途径。该规则高估了条件c中复合刺激的效应，这表明存在一些其他的累加过程，可能涉及不应期的延长。
