Abstract
In two experiments, we examined the conditions under which signaling an unconditioned stimulus (US) with a nominal conditioned stimulus (CS) interferes with the conditioning of situational cues in defensive freezing in the rat. Subjects received footshock USs that were (1) either signaled or unsignaled and (2) either varied or fixed in their temporal location within the conditioning session. Experiment 1, with only one trial per session, yielded no evidence that signaling affected pretrial freezing using either a fixed or variable interval between placement in the context and shock onset. In a test in which no CSs or footshocks were presented, groups that previously had received footshock at a fixed temporal location showed greatest freezing at around that same time. For groups that had received footshocks at various times, freezing declined across the test session. Experiment 2 showed overshadowing of pretrial freezing after more extensive conditioning with many trials per session, but only if the intershock intervals were variable rather than fixed.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
Ayres, J. J. B. (1966). Conditioned suppression and the information hypothesis.Journal of Comparative & Physiological Psychology,62, 21–25.
Baker, A. G., Mercier, P., Gabel, J., &Baker, P. A. (1981). Contextual conditioning and the US preexposure effect in conditioned fear.Journal of Experimental Psychology: Animal Behavior Processes,7, 109–128.
Balsam, P. D., &Gibbon, J. (1988). Formation of tone-US associations does not interfere with the formation of context-US associations in pigeons.Journal of Experimental Psychology: Animal Behavior Processes,14, 401–412.
Balsam, P. D., &Tomie, A. (1985).Context and learning. Hillsdale, NJ: Erlbaum.
Fanselow, M. S. (1982). The postshock activity burst.Animal Learning & Behavior,10, 448–454.
Gibbon, J., &Balsam, P. (1981). Spreading association in time. In C. M. Locurto, H. S. Terrace, & J. Gibbon (Eds.),Autoshaping and conditioning theory (pp. 219–253). New York: Academic Press.
Goddard, M. J. (1995). Acquisition of US-no US associations in Pavlovian conditioning.Learning & Motivation,26, 264–277.
Jackson, R. L., &Minor, T. R. (1988). Effects of signaling inescapable shock on subsequent escape learning: Implications for theories of coping and “learned helplessness.”Journal of Experimental Psychology: Animal Behavior Processes,14, 390–400.
Jenkins, H. M., Barnes, R. A., &Barrera, F. J. (1981). Why autoshaping depends on trial spacing. In C. M. Locurto, H. S. Terrace, á J. Gibbon (Eds.),Autoshaping and conditioning theory (pp. 255–284). New York: Academic Press.
Kehoe, E. J. (1983). CS-US contiguity and CS intensity in conditioning of the rabbit’s nictitating membrane response to serial compound stimuli.Journal of Experimental Psychology: Animal Behavior Processes,9, 307–319.
Maes, J. H. R., &LoLordo, V. M. (1996). The effect of a discrete signal on context conditioning: Assessment by preference and freezing tests.Learning & Motivation,27, 428–450.
Maes, J. H. R., &Vossen, J. M. H. (1992). One-trial aversive conditioning to contextual cues: Effects of time of shock presentation on freezing during conditioning and testing.Bulletin of the Psychonomic Society,30, 403–406.
Maier, S. F., &Keith, J. R. (1987). Shock signals and the development of stress-induced analgesia.Journal of Experimental Psychology: Animal Behavior Processes,13, 226–238.
Marlin, N. A. (1981). Contextual associations in trace conditioning.Animal Learning & Behavior,9, 519–523.
McAllister, W. R., McAllister, D. E., Weldin, G. H., &Cohen, J.M. (1974). Intertrial interval effects in classically conditioning fear to a discrete conditioned stimulus and to situational cues.Journal of Comparative & Physiological Psychology,87, 582–590.
Miller, R. R., &Schachtman, T. R. (1985). The several roles of context at the time of retrieval. In P. D. Balsam & A. Tomie (Eds.),Context and learning (pp. 167–194). Hillsdale, NJ: Erlbaum.
Odling-Smee, F. J. (1975a). Background stimuli and the interstimulus interval during Pavlovian conditioning.Quarterly Journal of Experimental Psychology,27, 387–392.
Odling-Smee, F. J. (1975b). The role of background stimuli during Pavlovian conditioning.Quarterly Journal of Experimental Psychology,27, 201–209.
Odling-Smee, F. J. (1978a). The overshadowing of background stimuli by an informative CS in aversive Pavlovian conditioning with rats.Animal Learning & Behavior,6, 43–51.
Odling-Smee, F. J. (1978b). The overshadowing of background stimuli: Some effects of varying amounts of training and UCS intensity.Quarterly Journal of Experimental Psychology,30, 737–746.
Rescorla, R. A., &Wagner, A. R. (1972). A theory of Pavlovian conditioning: Variations in the effectiveness of reinforcement and nonreinforcement. In A. H. Black & W. F. Prokasy (Eds.),Classical conditioning II: Current research and theory (pp. 105–132). New York: Appleton-Century-Crofts.
Wagner, A. R., &Rescorla, R. A. (1972). Inhibition in Pavlovian conditioning: Application of a theory. In R. A. Boakes & M. S. Halliday (Eds.),Inhibition and learning (pp. 301–336). London: Academic Press.
Williams, D. A., Frame, K. A., &LoLordo, V. M. (1992). Discrete signals for the unconditioned stimulus fail to overshadow contextual or temporal conditioning.Journal of Experimental Psychology: Animal Behavior Processes,18, 41–55.
Williams, D. A., &LoLordo, V. M. (1995). Time cues block the CS, but the CS does not block time cues.Quarterly Journal of Experimental Psychology,48B, 97–116.
Author information
Authors and Affiliations
Corresponding author
Additional information
This work was supported by grants from the Natural Sciences and Engineering Council of Canada.
Rights and permissions
About this article
Cite this article
Lolordo, V.M., Williams, D.A. & Mcphee, J.E. Overshadowing of situational cues with variable but not fixed intertrial intervals. Animal Learning & Behavior 29, 143–152 (2001). https://doi.org/10.3758/BF03192823
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.3758/BF03192823