Successive Negative Contrast Effect Research Articles

Successive Negative Contrast Effects for Activity-Conditioned Goldfish (Carassiusauratus) as a Function of Housing Conditions

Young goldfish were individually housed in large containers (Part 1), individually housed in small containers (Part 2), or housed in large containers in groups of five (Part 3). The fish were run in sets of five fish (five fish simultaneously in an activity-conditioning chamber). Thus, the fish had to compete for the large or small US that was dropped in the water following a 10-sec. CS (light). Fish in each part comprised groups LS (large US in the first phase of training and small US in the second phase of training), LL, SL and SS. All LS groups showed downward shifts in activity and negative contras effects (lower activity levels than SS control fish). None of the SL groups produced complete upward shifts in activity. Group-housed fish in Part 3 showed larger increases in activity to the CS than individually housed fish in Parts 1 and 2.

Negative contrast as a function of reinforcement location and consistent vs. varied reward magnitude

Subsequent to receiving small reward magnitude in the straight runway during Stage 1, rats were given consistently large magnitude of reward or varied large and small reward during placement trials (Stage 2) in a housing cage or in the goalbox. During Stage 3, only animals receiving consistently large magnitude of reward in goalbox placement trials showed a successive negative contrast effect. The results were supportive of frustration theory.

Successive reductions of liquid and solid sucrose rewards

Successive reductions in sucrose rewards are examined in two analogous runway experiments. In Experiment 1, rats were trained for 24 preshift days with 1 ml of either 30% or 3% sucrose solution as reward. Training trials were administered two per day with an intertrial interval (ITI) of 3-5 min. During 2 postshift days, all animals received 20 trials (10 per day with the same ITI) with the 3% reward. Experiment 2 employed essentially the same procedure, except the rewards were either eight or two Noyes sucrose (92.4%) pellets in preshift. Postshift was to the two-pellet reward. The data suggested a successive negative contrast effect (SuNCE) in Experiment 2 with solid pellets, but not in Experiment 1 with liquid solutions. The findings are briefly considered in light of the sequential and frustration accounts of the SuNCE.

Effects of changing alley color on the successive negative contrast effect

In Phase 1, four groups of rats received either large or small food reward in a black or white straight alley. In Phase 2 all rats received small food reward in the white alley. Rats that had received large reward in Phase 1 ran more slowly in Phase 2 to small reward than did rats that received small reward in both phases (successive negative contrast effect, or NCE). There was a temporary decrement in running speed for both groups that experienced a change in alley color, but the size of the NCE was not reduced by the change in alley color. It was suggested that the NCE can be used to measure the strength of connection between a particular cue and reward expectancies in instrumental learning situations. Within this context, the present results suggest that, under the conditions employed in this experiment, alley color was not strongly associated with reward expectancies.

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 Effects with Goldfish (Carassius Auratus)

Goldfish were trained with large (10 pellets of freeze-dried tubifex worms) or small (1 pellet) reward as the appetitive Us in a forward classical conditioning situation. Activity (Cr) was recorded during each 9.5-sec. Cs-Us interval. The fish experienced 5 days of training with 20 trials per day. One-quarter of the classically conditioned fish with a given Us magnitude were shifted to the opposite Us after the third day of training, and one-quarter were shifted in the middle of the fourth day of training. Fish that were downward-shifted (3 or 3.5 days of training) produced negative contrast effects; that is, they became significantly less active during Cs presentations than fish maintained on the small Us in both phases of the study. Downward shifts were not as rapid as downward shifts obtained with rats in instrumental learning situations. Upward-shifted fish (3 or 3.5 days of training) increased activity, but did not attain the activity level of fish maintained on the large Us in both phases of the study.

Partial reward, the negative contrast effect, and incentive averaging

A total of 169 rats, distributed across six experiments, received training in a straight runway with a 5-min intertrial interval. A variety of shifts in reward schedules, to and from partial reward, were employed to assess the effects of partial reward on the successive negative contrast effect. The results were seen as supportive of an incentive averaging approach to partial reinforcement.

The effect of prior reward magnitude on the successive negative contrast effect

Separate groups (N = 10) of albino rats received nondifferential large (L), nondifferential small (S), or no reward training prior to differential reward training (Groups L-LS, S-LS, and LS, respectively) in a nonchoice brightness discrimination apparatus. A fourth condition received small reward in each discriminandum throughout training. Results suggested that the extent of simultaneous negative contrast was greater for Group L-LS than for Group S-LS and clearly indicated that the development of discrimination and negative contrast effects was retarded for the prior reward conditions relative to the standard differential conditioning group (LS).

Effects of varied preshift reward magnitude on successive negative contrast effects in rats.

Effects of varied preshift reward magnitude on successive negative contrast effects in rats.

Simultaneous and successive contrast with delay of reward

In Experiment I, rats showed no evidence of a successive negative contrast effect (NCE) when shifted from immediate reward to a 15-sec delay of reward. Experiment II provided a direct comparison of NCE in both successive and simultaneous paradigms. As in Experiment I, there was no evidence of a successive NCE, but a reliable simultaneous NCE was observed. These results add support for the view that simultaneous and successive NCEs are not due to a single, common process.

Percentage body weight and the successive negative contrast effect in rats

In two runway experiments employing rats the successive negative contrast effect was evaluated for animals maintained at high or low body weights. In both experiments the effects on performance of shifting reward magnitude were independent of body weight. These results contrast with those of previous studies in which the successive negative contrast effect occurred only under low body weight. It was suggested that when conditions are maximal or near maximal for production of the successive negative contrast effect, as they were here but not in previous investigations, body weight will not influence the size of this effect.

Stimuli and incentives as determinants of the successive negative contrast effect

Seventy-two rats received 10 preshift and 7 postshift instrumental conditioning trials in a straight runway. The preshift magnitudes of intertrial reinforcement and runway reward were factorially manipulated, while all Ss received a small ITR and runway reward in the postshift period. Both reductions in ITR and runway reward magnitude produced negative contrast effects.

Successive negative contrast effect: Intertrial interval, type of shift, and four sources of generalization decrement.

Successive negative contrast effect: Intertrial interval, type of shift, and four sources of generalization decrement.