Baccus, J. R., Baldwin, M. W., & Packer, D. J. (2004). Increasing implicit self-esteem through classical conditioning. Psychological Science, 15(7), 498-502.

Implicit self-esteem is the automatic, nonconscious aspect of self- esteem. This study demonstrated that implicit self-esteem can be increased using a computer game that repeatedly pairs self-relevant information with smiling faces. These findings, which are consistent with principles of classical conditioning, establish the associative and interpersonal nature of implicit self-esteem and demonstrate the potential benefit of applying basic learning principles in this domain.

Besheer, J., Palmatier, M. I., Metschke, D. M., & Bevins, R. A. (2004). Nicotine as a signal for the presence or absence of sucrose reward: a Pavlovian drug appetitive conditioning preparation in rats. Psychopharmacology, 172(1), 108-117.

Rationale. In Pavlovian conditioning research, nicotine is typically conceptualized as the unconditioned stimulus (US) that becomes associated with an exteroceptive conditioned stimulus (CS). This research has not explored the possibility that nicotine can also function as a CS. Objectives. The present research examined whether nicotine served as a CS for the presence (CS+) or absence (CS-) of sucrose and started defining its specificity. Methods and results. Rats trained in the CS+ condition had nicotine (0.4 mg/kg, base) paired intermittently with brief access to sucrose. Intermixed were saline sessions without sucrose. Nicotine acquired the ability to evoke goal tracking. This conditioned response (CR) decreased across extinction sessions. The CR was sensitive to nicotine dose (ED50=0.113 mg/kg) and administration to testing interval; 0-min and 100-min delays produced no CR. The CS properties were specific to nicotine in that amphetamine and bupropion substitution was incomplete. Rats in the CS- condition received similar discrimination training except that sucrose was paired with saline. Nicotine also served as a CS-; the saline state CS+ acquired control of goal tracking. Mecamylamine, but not hexamethonium, blocked nicotine's ability to serve as a CS+ and CS-, indicating a role for central nicotinic acetylcholine receptors. Conclusions. Nicotine served as a signal for the presence or absence of sucrose. The extinction, CS-, and substitution results eliminated a psychomotor stimulant account. The conceptualization of nicotine as a CS suggests novel empirical research in which a drug acquires additional inhibitory and/or excitatory value based on other outcomes present during its effects.

Donahoe, J. W., & Vegas, R. (2004). Pavlovian conditioning: The CS-UR relation. Journal of Experimental Psychology- Animal Behavior Processes, 30(1), 17-33.

A new Pavlovian procedure used fluid-elicited throat-movement responses of the pigeon (N = 66) to study the effects on conditioning of the temporal relation of the conditioned stimulus (CS) to the unconditioned stimulus-unconditioned response (US-UR). Because the throat-movement response has a substantial latency and duration, the relation of the CS to the US and UR could be independently evaluated. Four experiments indicated that, operationally, the relation of the CS to the UR-not to the US-is critical for conditioning in this preparation. The conventional emphasis on CS-US relations is based on procedures that confound the occurrence of the US with the UR and that foster generalization decrement between training and testing. The authors indicate how several conditioning phenomena may be reinterpreted in terms of CS-UR relations.

Herbert, J. S., Eckerman, C. O., Goldstein, R. F., & Stanton, M. E. (2004). Contrasts in infant classical eyeblink conditioning as a function of premature birth. Infancy, 5(3), 367-383.

The impact of premature birth on associative learning was evaluated using simple delay eyeblink conditioning in which a tone conditional stimulus was paired with an air puff unconditional stimulus. Fourteen preterm (28-31 weeks gestation) and 11 full-term infants completed at least 3 conditioning sessions, I week apart, at 5 months of age (corrected age). Preterm and full-term groups demonstrated associative learning, as confirmed by comparison with an unpaired control group. Preterm infants, however, exhibited more variability in their learning rates. The majority of full- term infants and half the preterm infants exhibited rapid acquisition and gradual extinction of conditional responding. A greater proportion of preterm than full-term infants failed to acquire conditional responding within 2 training sessions. Differences in associative learning rates were not the result of differences in arousal or attentional processes. Diversity in acquisition rates exposed an increased risk for disrupted infant learning due to premature birth.

Schneider, C., Palomba, D., & Flor, H. (2004). Pavlovian conditioning of muscular responses in chronic pain patients: central and peripheral correlates. Pain, 112(3), 239-247.

A differential conditioning design using an aversive slide as conditioned stimulus (CS+) that was followed by an intracutaneous electric stimulus to the left index finger as unconditioned stimulus (US) and a pleasant slide that was not followed by shock (CS-) were used to test the hypothesis of enhanced aversive conditioning of muscular responses in chronic back pain patients (CBP). Heart rate, skin conductance levels, and integrated surface electromyograms (EMG) from the left and right m. flexor digitorum, the right m. trapezius, and bilaterally from the m. orbicularis oculi were recorded. The electroencephalogram (EEG) was measured from nine electrode positions. The CBP patients showed an enhanced muscular response of the left forearm (where the US was applied) to the CS+ already in the preconditioning phase. During acquisition both the left forearm and the right trapezius of the patients but not the controls displayed enhanced muscular responding to the CS+. During extinction the CBP patients' muscular responses to both CS+ and CS- were elevated. The contingent negative variation of the EEG differentiated between CS+ and CS- in the healthy controls but not the chronic pain patients. These data confirm the hypothesis of enhanced muscular responding in chronic pain patients and suggest a dissociation of muscular and central processes during aversive conditioning in the patients that might contribute to the chronicity problem. (C) 2004 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

Stockhorst, U., Mahl, N., Krueger, M., Huenig, A., Schottenfeld-Naor, Y., Huebinger, A., Berresheim, H. W., Steingrueber, H. J., & Scherbaum, W. A. (2004). Classical conditioning and conditionability of insulin and glucose effects in healthy humans. Physiology & Behavior, 81(3), 375-388. gif html version of this paper (ATHENS username and password needed for access outside the College)

We examined whether the effects of intravenously injected insulin and glucose (the physiological endogenous insulin production stimulus) could be classically conditioned in healthy humans. We expected a conditioned blood glucose decrease to a conditioned stimulus (CS) previously paired with insulin and an, albeit lower, blood glucose decrease to a CS paired with glucose injection. In addition, we analyzed glucoregulatory hormone and symptom conditionability. Thirty healthy males were divided into three groups and were given the CS and an intravenous injection of either insulin (0.05 IU/kg) in Group 1, glucose (15%, 0.5 g/kg) in Group 2, or placebo [physiological saline (0.9%)] in Group 3 during the acquisition phase on 4 days. All participants were given the olfactory CS (rosewood-peppermint smell) and placebo injection on Day 5 (test). On Day 5, the total blood glucose decrease tended to be higher in Group I than in Group 3 (P less than.10), especially at CS presentation (P less than.10) and previous unconditioned hypoglycemia time-point (P less than.05). The conditioned blood glucose decrease was statistically nonsignificant in Group 2, but shortly after CS presentation, insulin level and blood glucose changes were negatively correlated in Groups I and 2 in contrast to positive correlation in Group 3. Furthermore, Group I showed an increase in noradrenaline (P less than.05), a temporarily delayed increase in growth hormone (GH; P less than.05), and an increase of autonomic and neuroglycopenic symptoms, reaching a medium and small effect size, respectively. Group 2 responded with an increase in cortisol (P less than.01) and neuroglycopenic symptoms (P less than.05) at the time-point of the previous unconditioned blood glucose minimum. To conclude, the effects of exogenously applied insulin can be conditioned in a reliable way. In correspondence with the lower intensity of the unconditioned stimulus (US), conditioning effects with glucose-and, thus, endogenously produced insulin- are weaker but also reflect the actions of central insulin. Future studies will examine the diverse actions of insulin within the brain further. (C) 2004 Elsevier Inc. All rights reserved.

Change in blood glucose levels on day 5, when all groups received the CS (rosewood-peppermint smell) and a saline injection