Effects of stimulus intensity on response acquisition and generalization in a behavioral task with humans

Abstract

We reviewed the literature on the relationship between conditioned stimulus (CS) intensity and conditioned response (CR) strength. Overall, studies indicate that both variables are positively related, however, such a relation has seldom been found in humans, especially when between-subjects designs are used. Moreover, in humans, the effect has only been investigated using auditory CSs in galvanic skin response and eyelid conditioning procedures. By using a videogame task, we assessed the relationship between CS intensity and the CR along two conditioning phases in human participants. In phase 1, participants were trained to respond to a light that signaled an imminent spaceship attack. The light could be bright or dim (between-groups). In phase 2, the alternate stimulus was used. The intensity had no effect on phase 1 but had a small effect in phase 2, after participants had the opportunity to compare both stimulus intensities. An assessment of the shift that occurred between phases showed a slight generalization decrement only in the bright-to-dim group, allowing some room for improvement during phase 2 in that group. The absence of a decrement with the stimulus shift in the dim-to-bright group could be ascribed to the bright stimulus having energizing properties that compensate for the decrement.