Transsituational negative contrast

Rats were shifted from 32% sucrose solution in one apparatus to a 4% sucrose solution in a different apparatus, and the performance of these animals was compared to rats that received the 4% solution in both situations. Transsituational negative contrast effects were found in both consummatory and instrumental measures of behavior and, in addition, these contrast effects were found to have some elements in common with both successive and simultaneous contrast effects, but were identical to neither.     

Incentive contrast: A review of behavioral changes following shifts in reward

The literature relevant to incentive contrast effects is reviewed, with emphasis on the data published since the reviews by Black (1968) and Dunham (1968). Contrary to the evidence available for the earlier reviews, the current literature indicates that positive contrast is a reliable phenomenon. Its occurrence is facilitated by use of a constant delay of reward, use of a long runway, or possibly by a shift while a negative contrast effect, resulting from a previous shift, is still present in the animals’ behavior. Positive contrast also occurs in consummatory behavior when sucrose or saccharin solutions are shifted. Conditions that are ineffective in producing positive contrast are reviewed, as are the effects of numerous variables on both successive and simultaneous contrast. In addition, positive and negative contrast effects resulting from shifts in delay or percentage of reward, contrast resulting from shifts in sucrose, saccharin, or ethanol solutions, contrast in choice behavior, and transsituational contrast are reviewed. The relationship of the data to several theoretical interpretations of contrast is also considered.     

Anticipatory contrast: Within-subjects analysis

Contrast in consummatory behavior occurs readily when a less preferred substance follows a preferred substance. A previous experiment indicated that contrast in consummatory behavior may also develop when a less preferred substance precedes a preferred substance in brief daily exposures. In the present experiment, the same animals sometimes received 0.15% saccharin followed, 15 sec later, by 32% sucrose (.15–32) and sometimes received 0.15% saccharin followed by the same 0.15% saccharin solution (.15-.15). One solution pair was given each day, and the two conditions, .15–32 and .15-.15, occurred in alternation across days. The two different solution conditions were correlated with different cues. Saccharin intake from the first tube was lower when the second tube contained 32% sucrose than when it contained .15% saccharin, both in original discrimination training and following a reversal of the cue-solution pairings. These results support the conclusion that contrast in this situation is based on the anticipation of the impending 32% sucrose each day, rather than on a retrograde comparison with the 32% sucrose received the previous day. These data are considered in terms of Pavlovian conditioning outcomes when the CS is a stimulus with hedonic value.     

Reward devaluation disrupts latent inhibition in fear conditioning

Three experiments explored the link between reward shifts and latent inhibition (LI). Using consummatory procedures, rewards were either downshifted from 32% to 4% sucrose (Experiments 1–2), or upshifted from 4% to 32% sucrose (Experiment 3). In both cases, appropriate unshifted controls were also included. LI was implemented in terms of fear conditioning involving a single tone-shock pairing after extensive tone-only preexposure. Nonpreexposed controls were also included. Experiment 1 demonstrated a typical LI effect (i.e., disruption of fear conditioning after preexposure to the tone) in animals previously exposed only to 4% sucrose. However, the LI effect was eliminated by preexposure to a 32%-to-4% sucrose devaluation. Experiment 2 replicated this effect when the LI protocol was administered immediately after the reward devaluation event. However, LI was restored when preexposure was administered after a 60-min retention interval. Finally, Experiment 3 showed that a reward upshift did not affect LI. These results point to a significant role of negative emotion related to reward devaluation in the enhancement of stimulus processing despite extensive nonreinforced preexposure experience.     

Chlordiazepoxide and the determinants of negative contrast

Previous experiments have shown that the negative contrast effect in consummatory behavior that occurs when rats are shifted from 32% to 4% sucrose is alleviated by the tranquilizer chlordiazepoxide (CDP). However, in these experiments, CDP was effective on the second postshift day but not on the first postshift day. The three experiments described in this paper suggest that this differential effectiveness of CDP is not due to the difference in preshift-postshift retention intervals on Day 1 (24 h) and Day 2 (48 h), but is due instead to the necessity of some degree of experience (about 5 min) with the postshift solution. These results, combined with those of an earlier study which showed elevated corticosterone in shifted animals on the second postshift day but not on the first postshift day, suggest that negative contrast may be a dynamic process, involving sequential processes of detection, evaluation, and conflict over the postshift period. It was further suggested that CDP becomes effective in moderating contrast only when the conflict stage is reached.     

Anxiolytic-like effect of ejaculation upon frustration

In three experiments, we studied the consequences of ejaculation upon the frustrative or contrast response of male rats exposed to reward downshift situations (i.e., surprising changes from 32% to 4% sucrose solutions). Similar to what has been found after treatment with anxiolytic agents, consummatory suppression was partially reversed by previous ejaculations in a second postshift trial (Experiments 2 and 3), such a result not having been obtained in a first postshift trial (Experiment 1). Moreover, the effect of ejaculations upon males' behavior during a second postshift trial was transitory, disappearing when assessed during the third and fourth postshift trials (Experiment 3). These results are in accordance with both Amsel's (1958, 1992) frustration theory and Flaherty's (1996) multistage hypothesis of successive negative contrast; the diverse factors that are known to modulate contrast effects are considered, including an interpretation of the present data in terms of the anxiolytic-like effect of the ejaculation.     

Apparent disinhibition of successive but not of simultaneous negative contrast

In a series of three experiments, rats shifted from a 32% to a 4% sucrose solution, after 10 days’ exposure to the 32% solution, exhibited a negative contrast effect in lick rate. In each experiment, shifted rats that received a novel stimulus (tone) during the postshift period exhibited a higher lick rate (smaller contrast effect) than shifted subjects not receiving the tone. This increase in lick rate resembles Pavlovian disinhibition and is interpreted as supporting an inhibitory view of successive negative contrast effects. Control conditions included in Experiments 2 and 3 favored the disinhibition interpretation of the effect of the tone, as opposed to a rate-dependency hypothesis or to the nonspecific energization of behavior. In Experiments 4–6, the tone was introduced coincident with the occurrence of a simultaneous negative contrast effect. Rather than disinhibition, a decrease in licking occurred. These results were discussed in terms of differences between successive and simultaneous contrast.     

Successive negative contrast in the consummatory responding of didelphid marsupials

In a consummatory experiment patterned after previous work with rats and goldfish, successive negative incentive contrast was sought in didelphid marsupials of two species (Lutreolina crassicaudata andDidelphis albiventris). Half of the subjects of each species were trained from the outset with a 32% sucrose solution and shifted occasionally to a 4% sucrose solution; the rest, which served as controls, were trained only with the 4% solution. The positive results obtained (less response to the 4% solution in the shifted subjects than in the controls) fit the hypothesis, based on comparative work with descendants of older vertebrate lines, that the mechanism of successive negative incentive contrast evolved in a common reptilian ancestor of birds and mammals.     

Preweanling handling influences open-field behavior,but not negative contrast or sucrose neophobia

Handling of preweanlings (Days 2–15) had substantial effects on the open-field behavior of rats when tested as adults. In general, handled rats reared more, ambulated more, and defecated less than nonhandled rats. However, the handling manipulation had no effect on the degree of negative contrast that occurred when rats were shifted from 32% to 4% sucrose. Experiments 2 and 3 showed that preweaning handling did not influence sucrose neophobia in two different test situations. These data, in conjunction with those of other studies, suggest that preweaning handling may have powerful but limited effects on adult behavior, and that these effects are probably not best characterized in terms of global concepts such as emotionality.     

Proactive interference of open field on consummatory successive negative contrast

Reactivity to a reward is affected by prior experience with the different reinforcer values of that reward, a phenomenon known as incentive relativity, which can be studied using the consummatory succesive negative contrast (cSNC) paradigm, in which the performance of animals that receive a 4 % sucrose solution after trials on which they were exposed to 32 % sucrose is compared with that of subjects that always receive the 4 % sucrose solution. The exploration of a novel open field can enhance or block the acquisition of associative and nonassociative memories. The effect of open field on cSNC has not yet been explored. The main result of the present study was that open-field exposure significantly modified the expression of cSNC. Exposure to an open field 1 h but not immediately before the downshift interfered with the expression of cSNC. These animals drank more of the downshifted reward than did controls that were not exposed to the apparatus, and this behavior persisted for up to three recovery trials. This phenomenon was observed even when the animals were given a more protracted preshift phase and when the discrepancy between the preshift and shift incentive values of sucrose were increased. An open field also interfered with incentive downshift when open-field exposure occurred 6 h before the downshift, and repeated exposure to the apparatus did not deteriorate this effect. The present study adds to a growing body of literature that indicates that open-field exploration can interfere with memory formation.     

Roles of visual and taste cues in ingestional neophobia: Response latency effects in chicks (Gallus domesticus)

Latency measures of starting to drink and of consummatory behavior were used to investigate ingestional neophobia to novel visual and novel taste cues in chicks. In Experiment 1 (N = 36), latencies to start drinking were reliably shorter to ingesta that appeared familiar from previous rearing or preexposure procedures. After drinking started, consummatory responding occurred reliably more rapidly to familiar taste cues than to novel ones. However, the presence of familiar visual cues reliably facilitated consumption of a novel taste. Experiments 2 and 3 (Ns = 144 and 180) were performed to evaluate, respectively, whether the ingestional effects of taste stimulus intensity, 0%–6% vinegar, and of visual stimulus intensity, 0%–1.0% concentrations of red food-coloring in water, changed during ontogeny for chicks 3, 5, and 7 days old. In Experiment 2, reliable direct effects of taste concentration on consummatory response latencies occurred immediately in 7-day-olds but were delayed in 3-day-olds. In Experiment 3, each age group immediately showed reliably slower starting and consummatory response times, the higher the concentration of red food-coloring. Intake performance in both experiments was consistent with the latency data. Experiments 1–3 showed that visual and taste cues of ingesta separately influenced approach and consummatory behaviors of the ingestive response sequence and that these influences depend on ontogenetic events.     

Anticipatory contrast as a function of access time and spatial location

Intake of a 0.15% saccharin solution was suppressed when it was followed by a 32% sucrose solution in brief daily pairings. With equal access durations to the two solutions, intervals of intermediate duration (2 or 3 min) produced a larger contrast than more extreme intervals (1 or 10 min). There was no evidence of inhibition of delay with the 10-min interval (Experiments 1A and 1B). When access times were asymmetrical, longer access time to the first solution reduced contrast, whereas longer access time to the second solution enhanced contrast (Experiment 2). Contrast was greater when the two solutions were presented at consistent and separate spatial locations than when location was changed randomly or when both solutions were presented in sequence at the same location. However, a degree of contrast occurred in all conditions (Experiment 3). Experiment 4, conducted with the solutions in opposite arms of a T-maze, showed that anticipatory approach to the location correlated with the 32% sucrose solution developed prior to lick suppression on the saccharin solution. However, within daily sessions, there was a reliable increase in contrast without correlated changes in anticipatory-approach behavior. Access-time effects were attributed to altered reward values, whereas spatial-separation effects suggest that goal-directed responses contribute to, but do not cause, anticipatory contrast.     

Effect of taste context and ambient context changes on successive negative contrast

Rats shifted from 32% sucrose to 4% sucrose lick less than rats that experience oniy the 4% solution. Previous experiments have found this negative contrast effect to be reduced (“disinhibited”) by the addition of a novel tone in the postshift period. In Experiment 1 of this paper, the negative contrast effect was enhanced when a novel flavor was added to the sucrose solution in the postshift period. In Experiments 2–4, changes in the ambient context, even changes sufficient to produce disruptions in licking, did not alter the degree of negative contrast. Tiese results suggest that (1) rats compare rewards across substantially different contexts, (2) contrast may serve to enhance taste neophobia, and (3) a disinhibitory effect may be confined to the presentation of punctate, nontaste, novel stimuli within a familiar context.     

Effects of sucrose concentrations on single-alternation performance in rats

In Experiment 1, rats received single-alternation training with 32% or 4% sucrose reward (Phase 1) followed by a shift in reward from 32% to 4%, and vice versa (Phase 2). In Phase 1, high reward facilitated alternation performance over low reward. In Phase 2, performance on rewarded trials increased as reward increased but was unchanged as reward decreased. Performance on nonrewarded trials showed negligible effects of shifts in reward. In Experiment 2, rats received goalbox placements with 32% or 4% sucrose alternated with nonreward in Phase 1; and in Phase 2, they received alternation runway training with the same or the opposite reward from that of placements. Performance on rewarded trials was faster, the higher the reward in runway training; performance on nonrewarded trials was slower, the higher the reward in placements. In Experiment 3, Phase 1 provided placements with 64%, 32%, 16%, or 4% sucrose or dry mash alternated with nonreward; Phase 2 provided alternation runway training with dry mash reward. Alternation prerformance developed more rapidly, the higher the sucrose concentration in placements. Only 64% sucrose produced performance superior to that for dry-mash placements.     

Correlation of corticosterone elevation and negative contrast varies as a function of postshift day

In three experiments, rats shifted from 32% to 4% sucrose consumed less of the 4% sucrose than did rats that had received only the 4% solution. Experiment 1 showed that this negative contrast effect was not accompanied by a corticosterone elevation on the first day subsequent to the shift. Experiments 2 and 2a showed that corticosterone levels were substantially elevated on the 2nd postshift day and that there was a tendency for degree of elevation in corticosterone to be related to degree of lick suppression. These results are discussed in terms of other data suggesting that anxiolytic drugs and disinhibitory stimuli are more effective in alleviating contrast on the 2nd postshift day than on the 1st postshift day. It is suggested that, in the present paradigm, reaction to stimulus change may be the primary determinant of contrast on the 1st postshift day, but emotional processes related to reward loss and/or conflict develop by the 2nd postshift day.     

Anticipation of incentive gain

In four experiments, the once daily availability of saccharin (.15%) preceded the availability of sucrose (32% or 2%). Experiment 1 showed that the intake of saccharin was reduced when it preceded 32% sucrose but not when it preceded 2% sucrose, as compared with saccharin-alone conditions. Experiment 2 showed that less saccharin was consumed when the saccharin preceded sucrose by 5 min than when there was a 30-min intersolution interval. Experiment 3 replicated this finding and showed that the presentation of the two solutions through the same or different access holes in the apparatus was not relevant to the result. Experiment 4 showed that there was an inverse relationship between saccharin intake and the length of the intersolution interval in the range of 1 to 30 min. These data were interpreted to indicate that the animals learn the predictive relationship between the saccharin and sucrose solutions and that the intake of the saccharin is reduced by an anticipatory contrast mechanism—a mechanism that may have restricted temporal parameters.     

Microstructural analysis of negative anticipatory contrast: A reconsideration of the devaluation account

An animal’s appetitive behavior is not a fixed response to current stimulation but can be affected by the anticipation of future events. For example, rats regularly given access to a moderately valued solution followed by a higher value solution (e.g., 4 % sucrose → 32 % sucrose) consume less of the initial solution than in control conditions where the initial solution is not followed by a higher value solution (e.g., 4 % sucrose → 4 % sucrose). Previous analyses have suggested that this negative anticipatory contrast effect does not depend on the “expectation” of a valuable stimulus producing a functional devaluation of a currently available stimulus of lesser value. In a within-subjects anticipatory contrast procedure, this study revealed that both consumption and the mean size of licking clusters were smaller for a 4 % sucrose solution on days when it preceded 32 % sucrose than on days when 4 % preceded 4 %. Since lick cluster size typically bears a positive monotonic relationship with the concentration of palatable solutions, this reduction is indicative of a decrease in the palatability/hedonic value of the solution subject to contrast. As such, we provide direct evidence that negative anticipatory contrast does produce a functional devaluation of the solution, thus challenging prevailing theoretical assumptions.     

Effects of sequences of sucrose reward magnitudes with short ITIs in rats

Two experiments assessed the role of aftereffect learning in rats rewarded with sucrose solutions. In Experiment 1, rats were trained in a single straight runway for two trials on each of 18 days, each trial terminating with either large (20% scurose) or small (3% sucrose) reward. The ITI was 3–5 min. The sequence of daily rewards for each of four groups was small-small (SS), small-large, (SL), large-small (LS), or large-large (LL). Response patterning and a simultaneous negative contrast effect were observed in LS and SL relative to the consistently rewarded controls. During 10 massed extinction trials, resistance to extinction was greatest for Group SL, followed in order by Groups SS, LL, and LS. Experiment 2 examined single alternation of large and small rewards administered for 10 trials on each of 31 days with an ITI of 60 sec. Reward for one group was 20% or 3% sucrose while another received 1 or 10 45-mg Noyes pellets. Appropriate patterning developed only in the food-pellet rewarded animals. The overall results suggest that sucrose rewards may produce high-amplitude and long-duration aftereffects which interfere with learning in designs employing several massed daily trials, but which may facilitate learning—relative to food-pellet rewards—with longer intertrial intervals and fewer daily trials.     

Frustration and sexual behavior in male rats

Frustration is an emotional state produced by the surprising omission in quantity and/or quality of an appetitive reinforcer. The aversive properties of stressors, such as electric shocks, produce responses similar to those elicited by a state of frustration. In this set of three experiments, we assessed the effects of water immersion (WIM, in Experiment 1)—that is, a physical stressor—and first (in Experiments 1 and 2) and second trials of a consummatory extinction (cE; i.e., a surprising reward omission; in Experiment 3) on the sexual behavior of male rats, as compared with nonstressed animals. The results showed a sexual deficit in the animals subjected to either WIM or cE, relative to control subjects, although these experimental conditions differed in the component of the male sexual response that was affected. The present results accord with the fear = frustration hypothesis, and with Amsel’s frustration theory.     

Positive and negative contrast effects obtained following shifts in liquid sucrose reward in thirsty rats

In a repeated shifts experiment four independent groups of thirsty rats received the following treatments: LSLS, LLLS, SSLS, and SSSS, with each letter denoting the magnitude (large or small) of sucrose reward received in each of the four phases of the experiment. While no negative contrast effect (NCE) was obtained in Phase 2, a very reliable positive contrast effect (PCE) was found in Phase 3. Moreover, a significant NCE was obtained in Phase 4. The results were explained in terms of the relative rather than absolute effects of reinforcement.