Drinking while thirsty can lead to conditioned increases in consumption.

A within-subject design was used to test whether repeatedly drinking a novel-flavoured and coloured drink while thirsty would influence subsequent liking for or consumption of that drink, compared to a different flavoured and coloured drink repeatedly consumed while less thirsty. Each participant was given 300 ml of one flavoured drink (H) after consuming a high salt meal (5.27 g of salt), and 300 ml of another flavoured drink (L) after consuming a low salt meal (1.27 g of salt). Participants had 4 sessions with each meal-type/drink combination, in an intermixed order. Pre- and post-training assessments of the drinks were conducted to determine the impact of the training regime on pleasantness and perceived thirst-quenching effect of the drinks. The final session included a choice test, and ad libitum access to the chosen drink, after either a high or low salt meal. In this final choice session, people drank almost twice as much H as L; however, there were no differential effects of past training on rated liking or choice. The increased consumption of H might reflect greater liking for H which was not detected by the rating scales; or it might reflect the learning of greater "conditioned thirst" in response to the flavour of H.

No evidence for latent learning of liking for flavours conditioned by caffeine.

RATIONALE: The ability of caffeine to condition liking for flavours depends on the caffeine deprivation status of subjects; however, it is not known if a latent liking for a flavour can be acquired in an undeprived state, which subsequently emerges when consumers are caffeine deprived. OBJECTIVES: To determine if exposure of undeprived caffeine consumers to a novel drink containing caffeine leads to increased liking for this drink when they are subsequently tested when caffeine-deprived. METHODS: In a double-blind placebo controlled study, four groups of 13 moderate caffeine consumers evaluated a novel flavoured drink on 5 days. The test group consumed this drink with 100 mg caffeine when undeprived on days 1-4, and in a deprived state on day 5. Three control groups had the same conditions on all 5 days, with an undeprived group receiving the caffeinated drink, and two deprived groups receiving the drink with caffeine or placebo. RESULTS: The pleasantness of the drink did not change over the 4 training days in the test group, and did not alter when this group was tested when caffeine-deprived. At no stage did these ratings differ between the test and undeprived control groups. Pleasantness increased significantly over the 5 days in the deprived group who received caffeine, and decreased in the deprived group who received placebo. CONCLUSIONS: These results suggest that repeated pairing of a novel flavour with the effects of caffeine in subjects who are not caffeine deprived does not lead to an emergent liking for that flavour when subsequently tested caffeine-deprived. However, the pleasantness of the same caffeinated drink increased if it was consumed when caffeine deprived.

Expression of flavour preferences conditioned by caffeine is dependent on caffeine deprivation state.

RATIONALE: The acquisition of a caffeine conditioned flavour preference depends on the caffeine deprivation status of subjects during conditioning. It is not known if the expression of an established flavour preference is also state-dependent. OBJECTIVES: To determine if the expression of a flavour preference conditioned by caffeine is dependent on the level of deprivation at the time of testing. METHODS: In a double-blind placebo controlled study, 44 subjects were given 4 days exposure to a novel flavoured drink following overnight abstinence from caffeine. Half the subjects received caffeine (100 mg) in the drink, while the remainder had placebo (maltodextrin, 100 mg). Subjects rated the pleasantness of the drink each time. On a fifth (test) day, the subjects were given additional caffeine (100 mg) or placebo 2 h before consuming and rating the pleasantness of the drink. RESULTS: Pleasantness ratings for the novel drink increased over the 4 conditioning days in subjects receiving caffeine, but decreased in those given placebo. On day 5, subjects who were trained and tested in the same caffeine deprivation state expressed pleasantness ratings similar to those for the final training day. In contrast, subjects who were trained and tested in different states expressed pleasantness ratings that were significantly different from those of the final training day. CONCLUSIONS: These results suggest that the expression of caffeine conditioned flavour preferences are acutely sensitive to current motivational state, and a number of possible explanations are discussed.

The effects of a low dose of caffeine on cognitive performance.

There is little evidence concerning the effects of caffeine in doses typical of one cup of tea. The present study investigated the effect of 60 mg caffeine, consumed in either tea or hot water, on performance on a subset of the CANTAB test battery. Eight males participated in a practice session and four test sessions. In each test session, the participant consumed a different hot beverage and then, over approximately 90 min, completed nine tests from the CANTAB battery. The four beverages were created by crossing beverage identity (tea or hot water) and caffeine dose (0 or 60 mg). Significant speeding of reaction time by caffeine consumption was found in pattern recognition, delayed match to sample, and match to sample visual search. The effect on reaction time of 60 mg caffeine can be detected, and may be evident within minutes of consumption. Objective reports of immediate beneficial effects of consumption, most research has postponed measurement to coincide with peak plasma caffeine levels (Blanchard and Sawers 1983). The intention of the present study was to investigate the effects of consuming a single cup of tea on a variety of cognitive tests. Testing began immediately after consumption and lasted approximately 80 min.

The effect of intertrial food presentations on anticipatory goal-tracking in the rat.

Four experiments examined the sensitivity of anticipatory goal-tracking in the rat to stimulus-food contingency. Contingency was manipulated by varying the probability of food delivery in the absence of a food-tray-light or clicker conditional stimulus (CS), while holding constant the probability of food coincident with the CS. CS control of anticipatory food tray investigation was examined after a period of context extinction in all experiments. Acquisition of stimulus control was undermined by the scheduling of intertrial food deliveries (Experiment 1). The rate of intertrial food deliveries influenced subsequent acquisition of CS control when all intertrial food deliveries were omitted (Experiment 2). When intertrial food deliveries were added to the training regimen subsequent to acquisition of CS control, that control was impaired (Experiments 3 and 4).

Response specificity in animal timing.

The stimuli that control responding in the peak procedure were investigated by training rats, in separate sessions, to make two different responses for food reinforcement. During one type of session, lever pressing was normally reinforced 32 s after the onset of a light. During the other type of session, chain pulling was normally reinforced either 8 s after the onset of one auditory cue or 128 s after the onset of a different auditory cue. For both types of sessions, only the appropriate manipulandum was available, and 20% of the trials lasted 240 s and involved no response-contingent consequences. Rats were then tested with the auditory cues in the presence of the lever and the light in the presence of the chain. If the time of reinforcement associated with each stimulus was learned, response rates should peak at these times during transfer testing. However, if a specific response pattern was learned for each stimulus, little transfer should occur. The results did not clearly support either prediction, leading to the conclusion that both a representation of the time of reinforcement and the rat's own behavior may control responding in this situation.

Social blockade of taste-aversion learning in Norway rats (Rattus norvegicus): is it a social phenomenon?

In Experiment 1, hooded rats (Rattus norvegicus) were exposed to a novel diet in a food dish or on a conspecific; they were allowed to consume the same diet and then were injected with a toxin LiCl. Later both groups ate more of the novel diet than animals that had not been exposed, and the conspecific-exposed group ate more than the dish-exposed group. Reducing aversion learning by exposure on a conspecific is known as social blockade. We examined if this effect is because a conspecific intensifies dietary cues and thereby increases latent inhibition. Experiment 2 failed to show that diet on a conspecific is a more effective conditioned stimulus for taste-aversion learning than diet in a dish, and Experiment 3 showed that diet in a dish is an effective overshadowing stimulus in aversion learning but diet on a conspecific is not. These results suggest that social blockade cannot readily be assimilated to a latent-inhibition model and may be a distinctly social form of learning.

Analysis of the unique cue in configural discriminations.

Four experiments used an autoshaping procedure with pigeons to investigate the basis of configural discriminations. The elements of both a negative patterning (A+, B+, AB-) and a conditional discrimination (AC+, BD+, AD-, BC-) were paired, in a second-order procedure with two new key lights, X and Y. Responding was then tested to X and Y presented in compound with each other and with A and B. The pattern of responding to compounds containing X and Y was like the pattern of responding to compounds containing their associates, A and B. This suggests that A and B can be replaced by their associates without disrupting responding to their compounds. Because X and Y are physically different from A and B, this in turn suggests that any unique cue controlling responding to their compounds does not depend on the physical presence of the component stimuli. Instead the unique stimulus appears to arise from the joint activation of memory representations.

Effect of signaling intertrial unconditioned stimuli in autoshaping.

Context-unconditioned-stimulus (US) associations have been suggested as the mediator of the response decrement that occurs when extra USs are added to the intertrial intervals (ITIs) of an otherwise standard Pavlovian conditioning situation. The present autoshaping experiments were concerned with the effect of signaling those extra USs, since such signaling might be expected to lessen their ability to condition the context. Experiments 1 and 2 showed that signaling the ITI USs did reduce their detrimental effects on responding to the conditioned stimulus (CS). To determine whether that reduction was due to an impact of signaling on the target-CS-US association or on performance to the target-CS, Experiment 3 examined responding to differentially trained CSs in a common context, as well as responding to identically trained CSs in differentially trained contexts. Whether the CS was tested in a context of relatively high or low associative strength, more responding occurred to the CS trained with signaled, as compared with unsignaled, ITI USs; further, there was more responding to that CS in the more highly valued context. The pattern of results suggests that contextual value does interact with CS-US learning and may also affect performance to the CS.

Potentiation rather than overshadowing in flavor-aversion learning: an analysis in terms of within-compound associations.

Five experiments investigated the development of aversions to stimuli with strong odor components. Those odors were presented simultaneously with tastes are followed by lithium chloride. Contrary to expectations derived from previous investigations of compound conditioning, the presence of a taste stimulus at the time of conditioning was found to potentiate rather than overshadow the resulting odor aversions. Explanations in terms of either the taste's unconditioned aversiveness or nonassociative effects were found to be inadequate. An alternative interpretation attributing potentiation to the summed effects of within-compound odor-taste associations and odor-unconditioned stimulus associations was suggested. In agreement with such an interpretation, evidence of odor-taste associations was found in this situation. Furthermore, continued aversiveness of the taste was necessary for potentiation of the odor aversion to occur. An account of potentiation in terms of within-compound associations makes the phenomenon compatible with modern theories of Pavlovian associations.