Response patterning in goldfish: single alternation in a Pavlovian aversive paradigm

Single alternation behavior was studied in a Pavlovian aversive shuttle-response situation using goldfish. Independent groups of fish were given either a fixed interval between alternating reinforced (R) and nonreinforced (N) trials or were given differential temporal information between trials. Although all groups exhibited higher response probabilities on reinforced than on nonreinforced trials, goldfish receiving a short interval (10 s) following R trials and a long interval (60 s) following N trials (R10N60) demonstrated significantly superior alternation performance compared with subjects receiving a fixed intertrial interval (R35N35) or a long interval following R trials and a short interval following N trials (R60N10). The alternation performance exhibited by the R10N60 group was shown to be equivalent to that of subjects receiving standard color discrimination training. However, the alternation performance in group R35N35 showed a great deal of within-subject variability and raises questions concerning the elusive nature of alternation using Pavlovian conditioning procedures.     

The effect of an aversive event on the return of fear

An experiment on the return-of-fear (ROF) was carried out on 40 snake- or spider-phobic subjects in order to determine whether an arousing event that occurs shortly before retest influences the magnitude of the ROF. Additionally, we attempted to produce a reinstatement of fear by introducing an unrelated aversive event (shock) after the fear had been reduced. The arousal manipulation successfully increased subjective arousal but not heartrate responsiveness. The increases in subjective arousal were not followed by increases in ROF, and the attempt to produce a reinstatement of fear did not succeed. A significant correlation between speed of fear-reduction and ROF was obtained.     

Modification of escape responding in humans by increasing the magnitude of an aversive event

Escape responding of humans on an avoidance-escape schedule was replaced by avoidance responding by increasing the magnitude of the aversive stimulus. The aversive stimulus consisted of a point loss period. The shift from escape to avoidance responding was effected under a condition of response cost.     

Reflexive fighting in response to aversive stimulation

Reflexive fighting was elicited between paired rats as a reflex reaction to electric shock prior to any specific conditioning. Such fighting was fairly stereotyped and easily differentiated from the rats' usual behavior. The strength of this reflex was not attributable to any apparent operant reinforcement. Elicitation of fighting was a direct function of the enclosed floor area and a nonmonotonic function of the shock intensity.

Failure to scramble the polarity of the electrified grid produced inconsistent fighting. Under optimal conditions fighting was consistently elicited by shock regardless of the rat's sex, strain, previous familiarity with each other, or the number present during shock. Repeated shock presentations did not produce an appreciable decrease in fighting until signs of physical debility appeared. Although shock did not cause a rat to attack inanimate objects, it did produce attack movements toward other small animals. Failure of guinea pigs to defend themselves revealed that the elicitation of fighting from the rat does not require reciprocal attack. Paired hamsters showed fighting reactions similar to those of the rats, whereas guinea pigs failed to fight. Electrode shock and a heated floor elicited fighting between the rats, but intense noise and a cooled floor did not.

     

Noncontingent access to preferred sensory stimuli as a treatment for automatically reinforced stereotypy

Researchers have previously suggested that interventions designed to decrease stereotypic behavior are most effective when they include access to stimuli that are matched to the specific sensory consequences hypothesized to maintain the stereotypy. In an attempt to replicate this finding, we used stimulus preference assessments and a reversal design to evaluate the effectiveness of noncontingent access to highly preferred stimuli that were matched to the specific sensory consequences hypothesized to be maintaining the stereotypic behavior of an individual with developmental disabilities. The participant was also given noncontingent access to a highly preferred edible stimulus as a control condition. Results indicated that noncontingent access to a matched sensory stimulus produced consistent decreases in aberrant behavior while access to a highly preferred edible stimulus did not. Copyright © 2005 John Wiley & Sons, Ltd.     

Role of nonreinforcement in the fixed-interval performance of pigeons

Fixed-interval (FI) schedules have been used extensively to study timing abilities. In FI schedules, animals typically show higher response rates immediately after nonreinforced (N) cycles rather than reinforced (R) cycles (the reinforcement-omission effect), and they exhibit the highest rate approximately at the time when the reinforcer is scheduled to occur (peak performance). The present experiments were designed to determine the extent to which factors other than timing contribute significantly to these two learning phenomena. Pigeons were trained in an FI 16-sec schedule in which half the cycles were R and half were N. When successive cycles were separated by a 2-sec interval, responding early in the FI interval was higher after an N cycle than after an R cycle. This reinforcement-omission effect was eliminated when the interval between cycles was increased to 12 sec, because of an increase in performance after R cycles. In addition, timing of the 16-sec interval was assessed by interpolating 32-sec test cycles (all N cycles) at two rates—either 1 test cycle every other session, or 25 test cycles per session. Peak performance, presumably indexing the animal’s ability to time the 16-sec interval, emerged only with 25 test cycles per day, but not with 1 test cycle every other day, despite extensive training with the target, 16-sec-long interval. These results suggest that transient demotivation and time-based discrimination contribute significantly to the reinforcement-omission effect and peak performance, respectively.     

Programming response duration in a precueing reaction time paradigm

To determine whether the duration of certain motor activities can be a prespecified dimension of the motor program, we studied the duration of a motor response and the hand to be used, in a precueing paradigm. The response to be produced (a press on a push-button) was either short or long and involved either the right or the left hand. In Experiment 1, 200 and 700 ms (Block 1) or 700 and 2,500 ms (Block 2) were respectively chosen as short and long durations. No RT difference between short and long appeared when response duration was certain. When response duration was uncertain, RTs were longer for long than for short responses. In addition, the RTs that preceded the 700-ms response were longer in Block 1 than in Block 2. These results suggest that response duration can be programmed up to 2,500 ms and that the relative duration of a response in a given range is more relevant for programming mechanisms than its absolute duration. In Experiment 2, uncertainty concerning the response was maintained constant in a similar precueing paradigm, in which only 700-and 2,500-ms response durations were considered. The RTs preceding a long duration were shorter when duration was certain than when neither side nor duration was certain. No RT difference appeared before the short response duration. This seems to confirm that duration can be programmed up to 2,500 ms and also suggests that the program elaborated for the short duration constitutes a common basis for short and long responses: When duration is uncertain, programming a long duration requires just an additional operation to complete the program corresponding to the short duration, which has already been selected by default.     

The role of nonreinforcement in the learning of honeybees

Two series of experiments with honeybees were designed to test the assumption that inhibition is generated by nonreinforcement as a function of the excitatory value of the context. In the first series (Experiments 1-3), summation tests with B were made after A+/C-/AB- as compared to A+/C-/CB- training, with precautions taken to minimize the possibility of a masking effect of excitatory within-compound conditioning on AB trials; responding to B did not vary with training procedure. In the second series (Experiments 4-5), retardation tests rather than summation tests were used, in the belief that they might be more sensitive; after A+/AB-/CD- training, acquisition in a B+/D- problem was found to be no less rapid than in a D+/B- problem. A third series of experiments (Experiments 6-9) was designed to test the more general assumption that the effectiveness of nonreinforcement increases with the excitatory value of the context; response to B was found to be no different after A+/B+/C- training followed by A+/AB- training than after A+/B+/C- training followed by A+/CB- training. The results are compatible with the view that the role of nonreinforcement in honeybees is not to generate inhibition, but only to reduce excitation in a manner independent of the excitatory value of the context.     

Auditory event related potentials during lexical categorization in the oddball paradigm.

Event related potentials (ERPs) and reaction times (RTs) were recorded from 18 subjects, performing lexical categorization of words and nonwords. Three sets of monosyllable utterances, differentiated in semantic and rhyming attributes, were presented using the "oddball paradigm." ERPs included a sustained negativity which began approximately 100 msec after stimulus onset and peaked at approximately 400 mses (SN4) poststimulus, in response to target as well as to nontarget word stimuli. Semantic effects on SN4 latency were observed only for target utterances. Nonmeaningful word targets were associated with longer SN4 peak latencies as well as slower RTs compared to meaningful word targets. It is suggested that these longer latencies are due to a longer time required for an exhaustive search in permanent memory before categorizing a stimulus as a nonmeaningful word.