Potentiation of taste by another taste during compound aversion learning

Nostalgia enhances route learning in a virtual environment

Salient landmarks enhance route learning. We hypothesised that semantically salient nostalgic landmarks would improve route learning compared to non-nostalgic landmarks. In two experiments, participants learned a route through a computer-generated maze using directional arrows and wall-mounted pictures. On the test trial, the arrows were removed, and participants completed the maze using only the pictures. In the nostalgia condition, pictures were of popular music artists and TV characters from 5 to 10 years ago. In the control condition, they were recent pictures of these same artists and characters. In Experiment 1, in the test trial, participants in the nostalgia condition completed the maze faster than controls. Experiment 2 conceptually replicated these findings and extended them by exploring boundary conditions. Participants had to learn two mazes sequentially. In Maze 1, we placed nostalgic/control landmarks only at non-decision points (whereas we placed them at decision points in Experiment 1). In Maze 2, we placed nostalgic/control landmarks at decision points during acquisition but removed them in the test trial (whereas they were present in the test trial in Experiment 1). In both mazes, participants in the nostalgia (compared to control) condition completed the test trial faster.

A Proximal Perspective on Disgust

The functional basis of disgust in disease avoidance is widely accepted; however, there is disagreement over what disgust is. This is a significant problem, as basic questions about disgust require knowing if single/multiple forms/processes exist. We address this issue with a new model with one form of disgust generated by multiple processes: (a) pure disgust experienced during gastrointestinal illness; (b) somatosensory disgust elicited by specific cues that activate the pure disgust state; (c) anticipatory disgust elicited by associations between distance cues for somatosensory disgust and requiring threat evaluation; (d) simulated disgusts elicited by imagining somatosensory and anticipatory disgust and frequently involving other emotions. Different contamination processes interlink (a–d). The implications of our model for fundamental questions about disgust (e.g., emotion status; continuation into animals) are examined.

CS-US interval determines the transition from overshadowing to potentiation with flavor compounds

The present series of five flavor aversion experiments with rat subjects examined compound conditioning at varying CS-US intervals. Using a taste-taste design, Experiments 1A and 1B demonstrated overshadowing at a 0-min CS-US interval and potentiation at a 120-min CS-US interval, and these effects occurred with both tastes of the compound. Experiment 2 showed that the aversion to a single element is reduced when the CS-US interval is increased to 120 min, but the aversion for a compound taste is not. Experiments 3A and 3B explored odor + taste compound conditioning; the results demonstrated odor potentiation across the trace interval and a transition from taste overshadowing to taste potentiation. Collectively, the data show that the change from overshadowing to potentiation was not due to changes in the aversions produced by compound conditioning but, instead, was due to a more rapid loss of conditionability across a trace interval prior to the US in single-element conditioning. These experiments suggest that following compound conditioning, the aversion to each element represents generalization decrement from the configured compound, but the designation of overshadowing or potentiation actually depends on the status of conditioning in the single-element control.

Potentiation and overshadowing between landmarks and environmental geometric cues

Rats were required in three experiments to find one of two submerged platforms that were situated in the same pair of diagonally opposite corners of a rectangular grey swimming pool. The experimental groups were trained with landmarks, comprising A4 cards attached to the walls, located in the corners containing the platforms. For the control groups, the landmarks were situated in the corners containing the platforms for half of the trials, and in the other corners for the remaining trials. Learning about the positions of the platforms with reference to the shape of the pool was overshadowed in the experimental groups when the landmarks were white, and enhanced when the landmarks were black. A fourth experiment assessed whether geometric cues influenced the control acquired by the landmarks. As in the previous experiments, the presence of the geometric cues overshadowed learning about the landmarks when they were white, but enhanced learning when the landmarks were black.

Enclosure shape influences cue competition effects and goal location learning

In virtual-environment spatial-learning procedures, Experiment 1 investigated blocking of learning about distal landmarks beyond the walls of an enclosure following preliminary training to find a goal using local landmarks within the enclosure. Separate sets of blocking and control groups searched within enclosures that, in plan view, formed either a square or a circle. Blocking was apparent when training and testing occurred in the circular but not the square enclosure. In Experiment 2, preliminary training to find a goal using local landmarks blocked spatial learning based on a circular enclosure divided into four differently coloured sections. The results are discussed in relation to theories of incidental versus error-correcting learning linked to different types of spatial cue.

Potentiation, overshadowing, and blocking of spatial learning based on the shape of the environment

Rats were trained in Experiment 1 to find a submerged platform in 1 corner of either a rectangular or a kite-shaped pool. When the walls creating this corner were a different color than the opposite walls, then learning about the shape of the pool was potentiated in the kite but not in the rectangle. Experiments 2-4 revealed that learning about the rectangle can be overshadowed and blocked when information about the wall color indicates the location of the platform. The results mimic findings that have been obtained with Pavlovian conditioning, and they challenge the claim that learning about the shape of the environment takes places in a dedicated geometric module.

The interaction between response effects during the acquisition of response priming

In three experiments we investigated the role of associative learning in the acquisition of response priming by effect stimuli, by examining their interaction during response-effect learning. Having replicated the ability of visual effect stimuli to prime their associated responses, we paired a response with a compound consisting of visual and auditory effects before assessing the ability of the auditory effect stimulus to prime the response. This priming was reduced if the visual stimulus had been pre-trained as an effect of the response. By contrast, priming by the visual effect stimulus was potentiated when the auditory effect had been pre-trained. We interpret these interactions in terms of contemporary associative learning theory derived from studies of conditioning.

Limitations on representation-mediated potentiation of flavour or odour aversions

Odour aversion learning is often potentiated in the presence of flavour stimuli. Establishment of an aversion to an odour is greater when an odour + flavour compound is paired with illness than when the odour alone is paired with illness. Holland (1983) showed that under some circumstances auditory or olfactory stimuli previously paired with flavours may also potentiate odour aversion learning. The present experiments examined limitations on this representation-mediated potentiation of aversion learning. The results indicated that conditioned stimuli (CSs) that activate representations of potentiating cues are themselves immune to potentiation by other CS-activated representations, but remain susceptible to potentiation by their real stimulus associates.

Spatial learning based on the shape of the environment is influenced by properties of the objects forming the shape

In 3 experiments rats had to find a submerged platform that was located in a corner of a kite-shaped pool. The color of the walls creating this corner provided an additional cue for finding the platform in the shape + color condition but not the shape-only condition. During tests in a pool with walls of a uniform color but no platform, more time was spent in the corner where the platform was originally located after training in the shape + color than in the shape-only condition. The results challenge theories that assume either that learning about the shape of the environment takes place in a dedicated module or that cues compete for the control they acquire over behavior.

Odor of taste stimuli in conditioned "taste" aversion learning

The present research addresses whether rats can express odor aversions to the odor of taste stimuli. In Experiment 1, saccharin or salt were either mixed in distilled water, so the rats could taste and smell them, or presented on disks attached to the tubes' metal spouts so the rats could only smell them. Aversions were established to taste stimuli under both conditions. The results of Experiment 2 indicate that conditioning was to the odor of the tastes when they were presented on disks in Experiment 1, hence both taste and odor aversions were established by means of "taste" stimuli. Taste aversion learning thus may more properly be termed flavor aversion learning, with flavor referring to both taste and odor components.

Starch-based conditioned flavor preferences in rats: influence of taste, calories and CS-US delay

Six experiments examined the rat's preference for flavors associated with hydrolysed starch (Polycose) solutions. Hungry rats developed a preference for a flavor (CS+) mixed into a saccharin-sweetened 16% Polycose solution over a flavor (CS-) mixed in saccharin-water. The addition of acarbose, a drug which inhibits starch digestion, to the Polycose solution blocked the flavor preference. This finding indicates that it is the postingestive rather than the taste properties of Polycose that condition flavor preferences. Rats also developed a preference for a CS+ flavor that preceded the ingestion of a Polycose solution by 10 min. This flavor conditioning, however, was not obtained in all experiments. Some CS flavors may be more effective than others in producing conditioned flavor preferences over a delay. Preference conditioning over a delay was facilitated when the rats had previously learned that the taste of the US (Polycose) was not associated with rapid caloric repletion; this was accomplished by giving the rats prior exposure to a Polycose + acarbose solution. Rats with such pre-exposure learned to prefer a CS + flavor that preceded by 10 to 60 min the consumption of a Polycose solution (without acarbose). The results demonstrate that calorie-based flavor preferences can be conditioned over a delay, but conditioning is influenced by the nature of the CS and US stimuli used.