Taste preferences as a function of food deprivation during original taste exposure

It has been reported previously that rats prefer a flavor they consumed under high deprivation to a flavor they consumed under low deprivation (Revusky, 1967). Here it was found that this preference occurs only if nutritive solutions are used and the flavors are given preceding and following eating. If flavors are given separately from the daily feeding, rats prefer the flavor given under low deprivation, whether or not a nutritive solution is used (Experiment 3). If flavors are given before and after the daily feeding, rats prefer the flavor they had under high deprivation (before feeding) more if sucrose solutions are used than if saccharin solutions are used and more on a high-deprivation test than on a low-deprivation test (Experiments 1 and 2). It was concluded that the “incentive value” of consumption is not necessarily higher under high deprivation than under low deprivation. The preference for the low-deprivation flavor obtained here may reflect a greater proportional rewarding effect of consumption under low deprivation or may reflect an aversion to the flavor consumed under high deprivation. Perhaps a small taste of flavor under high deprivation initiates responses of digestion that are unsatisfied and thus aversive, and the more so the higher the deprivation level.     

Cross-modal transfer as a function of initial training level in classical conditioning with the rabbit

Initial reinforced training with a conditioned stimulus (CSA) from one sensory modality subsequently facilitates the rate of acquisition of the rabbit’s nictitating membrane response to a second conditioned stimulus (CSB) from a different sensory modality. In Experiment 1, the level of transfer was a direct function of the number of CSA-US pairings (0, 15, 30, 60, and 120). In Experiment 2, cross-modal transfer appeared to be maximal after initial training was conducted to a performance criterion as small as two CRs to CSA. The results are discussed with respect to theories of transfer, particularly a layered network model of conditioning that suggests that CR acquisition to each CS depends on two sequentially organized associations, one unique to the CS and one that is common to all associations involving the target response system.     

Savings in classical conditioning in the rabbit as a function of extended extinction

In the present experiments, savings phenomena following a limited amount of initial acquisition and extended extinction were examined. Experiments 1 and 2 compared rates of reacquisition following brief acquisition and various amounts of extinction in conditioning of the rabbit’s nictitating membrane and heart rate response, respectively. Experiment 3 compared rates of acquisition to a novel stimulus (e.g., light) following brief acquisition and various amounts of extinction to another stimulus (e.g., tone). In addition, in Experiment 3 recovery of responding to the extinguished stimulus during acquisition to the novel, cross-modal stimulus was examined. Experiments 1, 2, and 3 demonstrated that with a limited number of acquisition trials (1) there was a graded reduction in the rate of reacquisition as a function of the number of extinction trials in both conditioning preparations, (2) there was a graded reduction in the rate of cross-modal acquisition as a function of the number of extinction trials, but (3), in Experiment 3, recovery of responding to the extinguished stimulus during cross-modal training of the novel stimulus appeared uniformly robust even in the face of extended extinction.     

Postdiscrimination generalization as a function of interresponse time

Following 20 sessions of variable-interval 20-sec reinforcement in the presence of a single 45-deg line-tilt stimulus, three pigeons were trained to discriminate between line tilts of 45 deg correlated with variable-interval 20-sec reinforcement and line tilts of 15 deg correlated with extinction. A generalization test along the line-tilt dimension was administered following a criterion discrimination performance. Gradients derived in terms of relative frequency of response as a function of line tilt indicated strong external stimulus control and exhibited clear peak shift. From the interresponse time (IRT) distributions generated for responding to each test stimulus, probability of response conditional upon IRT (IRTs/Op) was derived as a joint function of line tilt and IRT. The IRTs/Op functions for responses following IRTs in 0.2-sec-wide classes from 0.2 to 1.0 sec and for responses following IRTs in the interval of 1.0 to 2.0 sec were similar to the relative generalization gradients and also exhibited peak shift. Few IRTs were greater than 2.0 sec. External stimulus control was established over responses terminating IRTs both longer and shorter than 1.0 sec.     

Tracking of the expected time to reinforcement in temporal conditioning procedures

In one experiment, the rate and pattern of responding (head entry into the food cup) under different distributions of intervals between food deliveries were examined. Separate groups of rats received fixed-time (45, 90, 180, or 360 sec), random-time (45, 90, 180, or 360 sec), or tandem fixed-time (45 or 90 sec) random-time (45 or 90 sec) schedules of reinforcement. Schedule type affected the pattern of responding as a function of time, whereas mean interval duration affected the mean rate of responding. Responses occurred in bouts with characteristics that were invariant across conditions. Packet theory, which assumes that the momentary probability of bout occurrence is negatively related to the conditional expected time remaining until the next reinforcer, accurately predicted global and local measures of responding. The success of the model advances the prediction of multiple measures of responding across different types of time-based schedules.     

Magnitude of fear as a function of expected time to all aversive event

Three rats were trained to press a lever on a random-interval 1min schedule of food reinforcement. In successive phases of the experiment, electric shocks were superimposed at 1-min fixed intervals, 2-min fixed intervals, or at 1-min random intervals. In the fixed-interval conditions, there was a steep gradient of reduction in response rate as the time for the next shock approached; in the random-interval condition, the response rate following a shock was relatively constant. The present method appears to be adequate to monitor the instantaneous level of fear. The results suggest that animals were timing in units proportional to the fixed interval and that aversive events which occur randomly in time are perceived as phenomenologically random by the rat.     

Cross-modal transfer as a function of similarities between training tasks in classical conditioning of the rabbit

The present experiments examined transfer of training from visual to auditory sensory modalities in classical conditioning of the rabbit’s nictitating membrane response. Experiment 1 examined transfer from initial training with a single visual CS to subsequent auditory discrimination training, and Experiment 2 examined transfer from visual discrimination training to auditory discrimination training. The major findings were that (1) initial conditioning of a visual CS facilitated the overall rate of CR acquisition to the auditory CSs separate from the requirements for discrimination learning (Experiments 1 and 2), and (2) initial visual discrimination training facilitated auditory discrimination learning (Experiment 2). Thus, the animals appeared to encode separately both contiguous CS-US relations and CS+ versus CS? relations during initial visual training. The results are discussed with respect to theories of extradimensional transfer.     

Resistance to discrimination and subsequent resistance to extinction as a function of the sequence of partial S+ reward in differential conditioning

The effects of transitions from nonrewarded (N) to rewarded (R) trials (N-R transitions) on discriminative behavior in differential conditioning and subsequent resistance to extinction were investigated in two experiments. In Experiment 1, groups given N-R transitions within S+ were more resistant to discrimination (ran fast in S?) and extinction than were groups given a partial reinforcement (PRF) schedule in S+ devoid of N-R transitions. Experiment 2 indicated that N-R transitions that occur when an N trial in S? is followed by an R trial in S+ are as effective in increasing resistance to discrimination, but not resistance to extinction, as are N-R transitions that occur within S+. The sequential effects obtained here were highly similar to those in conventional PRF and support the view that differential conditioning and PRF are highly interrelated phenomena. The results are discussed in terms of the extension of sequential theory to differential conditioning and the importance of internal reward-produced cues in discrimination learning.     

Utilization and dominance of spatially separated cues as a function of water deprivation

Utilization and dominance of physically separate redundant-relevant cues were measured in albino rats under moderate (18 h/day) or high (23.5 h/day) water deprivation. Cues were located on goal doors (brightness) and the floor (texture) in a two-choice discrimination apparatus. Three experiments were carried out with the following paradigms: incidental cue, redundant-relevant cue discrimination, and optional shift discrimination. Deprivation did not affect rate of acquisition of initial discrimination or cue dominance. Cue utilization, however, was inversely related to deprivation in redundant-relevant cue and optional shift discrimination tasks. These effects were limited, however. Over-training on the redundant-relevant cue task eliminated the effect. Within the optional shift situation, only animals that initially acquired a texture cue discrimination were affected by deprivation. Other factors affecting cue utilization in these experiments were also described and discussed.     

Resistance to extinction of a learned taste aversion varies with time of conditioning

Sixteen rats were maintained out of doors in cages with natural light, temperature, and social stimulation for 3 months. Subsequently, by pairing the taste of sucrose with IP injections of LiCl, the rats were conditioned to avoid sucrose. Each of four groups of rats received the CS-US pairing at a different time of day. Times of conditioning were 6 a.m., 12 a.m., 6 p.m. and 12 p.m. EST. A two-bottle preference test between 4% sucrose solution and tap water was initiated 24-h after conditioning. Daily measurements of preference were continued for 16 consecutive days. Results indicated that, although all groups initially exhibited equivalent sucrose aversions, the groups conditioned at 12 a.m. and 6 p.m. extinguished within 12 days while the 6 a.m. and 12 p.m. groups continued to manifest profound aversions for sucrose throughout the 16 test days.     

Study time and test performance as a function of test expectations

Study time and test performance change as a function of subjects expecting either open questions or a multiple-choice test on the contents of a history text. After studying a first history text, the subjects immediately received a test consisting of either open questions or multiple-choice items. They were led to expect the same type of test on a second text. Study time on Text 2 was self-paced, and the type of test was either the expected or unexpected one (either open questions or a multiple-choice test). The main hypothesis was confirmed that subjects consider open questions a more demanding test than a multiple-choice test. Accordingly, subjects expecting open questions on Text 2 used more study time and performed better on both types of test than did subjects expecting a multiple-choice test. Internal analyses revealed that the differences on study time and test achievement between the two expectation conditions occurred only when the subjects were thoroughly acquainted with the processing requirements of the learning material and its expected test.     

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.     

Reward sequence and reinforcement level as determinants of S− behavior in differential conditioning

In two differential conditioning experiments, groups of 10 rats each differed with respect to average reward and schedule of reward received in S+. Nonreward (N) occurred on all S? trials. In both experiments, extinction of responding to S? (resistance to discrimination) was extensively regulated by reward sequence and was largely independent of average reward. In Experiment 1, resistance to discrimination was a function of transitions from N to rewarded (R) trials (N-R transitions). In Experiment 2, resistance to discrimination was increased by large reward on the R trial of N-R transitions and decreased by large reward on the R trial of R-N transitions. These schedule effects on resistance to discrimination parallel the effects of comparable schedules on resistance to extinction following partial reinforcement. The results are discussed in terms of sequential theory, reinforcement level theory, and their implications for various schedule manipulations that have previously shown S? behavior to be inversely related to average reward in S+.     

The effect of nonreinforced stimulus exposure on the strength of a conditioned taste aversion as a function of retention interval: Do latent inhibition and extinction involve a shared process?

Two experiments examined the effects of nonreinforced flavor exposure on the strength of a conditioned taste aversion. Rats were conditioned by pairing maple flavor with LiC1. Prior to or subsequent to this pairing, some animals received nonreinforced exposure to either maple or saccharin. In separate subjects, preference for maple was tested 1 or 21 days after the last training episode. In the first experiment, the nonreinforced stimulus exposure occurred before conditioning (latent inhibition, or LI, procedure); in the second experiment, the nonreinforced exposure occurred after conditioning (extinction, or EXT, training). In both experiments, nonreinforced exposure to maple or saccharin reduced the magnitude of a conditioned maple aversion when testing occurred soon after conditioning. When testing was delayed, however, the attenuation due to nonreinforced saccharin exposure dissipated, both with the LI procedure and with EXT. In contrast, the nonreinforced exposure to maple was found to attenuate conditioned reactions at both short and long retention intervals. The release from generalized LI and spontaneous recovery following generalized EXT training are discussed in terms of retrieval processing. The possibility that the same mechanism may underlie LI and EXT is considered.     

Mothers' stress and expectations as a function of time since child's cochlear implantation

This study examined stress, attitudes, and expectations among mothers of deaf children who underwent cochlear implantation (CI), as related to time elapsed since surgery. Participants were 64 mothers of such children at different points in the implantation process: candidates, 0-3 years postimplantation, and more than 3 years later. Expectations in communication and academic domains decreased as time since implantation passed. No differences emerged in stress levels between the 3 groups. Higher levels of mothers' and fathers' education correlated with lower stress levels. Older mothers expressed lower levels on the cohesion dimension of family functioning. Findings suggested the need to consider mothers' expectations in the rehabilitation process and to encourage mothers' realistic expectations with regard to the effects of CI.     

Variability of classification by the matching familiar figures test as a function of grade level medians

This study examined the variability of classification by the Matching Familiar Figures Test (MFF) as a function of grade level medians. The MFF was administered to 52 kindergarten and 60 first-grade children, and classification was completed using two sets of medians. The first procedure involved classification based on medians for response time and errors computed from the combined MFF scores of the kindergarten and first-grade children. The second procedure involved clmsification of the same children based on separate medians for each grade. A x² analysis indicated that MFF classification was highly dependent upon which sample medians were used; 18%(N = 20) of the sample failed to maintain the same classification across both procedures. Analysis also revealed that for the majority (65%) of the children change in classification was due to the change in the median error cutoff. The implications of these findings for future MFF research involving young children and the need for standardized norms for the MFF are discussed.