Sec Delay Research Articles

Visual orientation in children's discrimination learning under constant, variable, and covariable delay of reinforcement

Sixty-four first-grade children learned a two-choice, simultaneous discrimination under one of four conditions of delayed reinforcement: (a) constant 2-sec delay; (b) constant 16-sec delay; (c) 2- and 30-sec variable delay; and (d) 2- and 30-sec covariable delay. The response measures consisted of acquisition data, visual orienting responses (eye movements), starting speeds, and response speeds. The results indicated that (a) constant 16-sec delay produced poorer discrimination performance than constant 2-sec delay; (b) constant 16-sec delay resulted in more visual orienting than constant 2-sec delay; (c) discrimination performance under covariable delay was superior to performance under constant 16-sec delay; and (d) differences in starting speeds between learners and nonlearners were not correlated with differences in the number of orienting responses. Alternative interpretations of delayed reinforcement effects were discussed.

Discrimination facilitation as a function of differential choice-point delay

Sixty rats experienced differential delay contingencies to ascertain how cue visibility related to choice-point delay in a black-white discrimination problem. Ss experiencing no delay at the choice point took longer to learn the discrimination than Ss experiencing cue visibility during an enforced choice-point delay. Cue visibility during the whole 4-sec delay period, first half of the delay period, and last half of the delay period, produced similar learning rates. The data indicate that the delay vs “;stirred-up”; state controversy is more complex than would be suggested by an analysis based on cue visibility time or “;stirred-up”; state of an animal.

Some preliminary observations on the role of the telencephalon in food-reinforced behaviour in the goldfish, Carassius auratus

Summary o 1. The failure in acquisition and retrieval of shock avoidance tasks in forebrainless fish is not due to a lessened sensitivity to shock, or to failure to manifest signs of fear. 2. Normal and forebrainless fish show similar speeds of feeding, and the hunger drive is comparable. 3. The ability to learn a simple simultaneous vertical v. horizontal discrimination is not interfered with by the removal of the forebrain. The introduction of a 5-sec delay between response and reward causes extinction of the discrimination in the operated, but not in the normal fish. 4. Use of an operant feeding situation, involving an inbuilt delay, shows that the forebrainless fish also acquire an association more slowly than normals if delay is involved. Nevertheless, a stable association can be formed, and after more training the trained forebrainless fish show a feeding rate equal to that of the normal fish. The removal of the forebrain thus has no gross effect on feeding rate. 5. The hypothesis of the teleost forebrain as a primitive holding or attention centre is considered in the light of the available evidence.

Delayed response in blind cats before and after prefrontal ablation

Eleven cats were blinded by bilateral section of the optic nerve and trained on delayed response (DR) after 70 days' postoperative recovery. Six learned DR as well as normal cats; the remaining 5 animals either did not learn to approach the correct feeder, signalled by a continuous auditory cue, or failed to maintain correct approach behavior when a brief delay intervened between stimulus offset and response. Comparable failures were not observed in intact cats. The blind cats which met criterion on 30 sec delay were subjected to the bilateral ablation of the proreal and anterior orbital gyri. They showed the same deficits in postoperative retention of DR as sighted cats with these cortical lesions. This experiment demonstrates [1] that vision is necessary for immediate or delayed auditory localization by some cats, and [2] that prefrontal decortication has an equivalent effect on DR retention by cats that learned DR with or without vision.

Intertrial reward (ITR) and delay of reward: Effects on resistance to extinction

Six groups of rats (N =10) were trained to traverse a straight runway. Two of the groups were trained under regular consistent- and partial- reward procedures, i.e., RRRRR and RNRNR. Two additional groups were trained under the partial reward schedule above but, in addition, received ITR(r), i.e., RNrRNrR. One such group received ITR after a wait of 15 sec in the Intertrial interval box, another after a wait of 30 sec. The remaining two groups were trained under either 15-see or 30-sec partial delay of reward, i.e., RDRDR. The results of an extinction phase showed that ITR and delayed reward are not identical processes. ITR was found to decrease resistance to extinction only in the 30-sec wait condition.

Contrast effects and delay of reward in the double alleyway

Four groups of albino rats received a factorial arrangement of contrasting rewards in G1 (2 or 8 pellets) and G2 (2 or 8 pellets) of a double alleyway. After 63 trials, each group was divided into two equal groups and shifted to either a 15-sec or 0-sec delay of G1 reward. During preshift trials, a “depression” effect occurred in A1. During postshift trials, delay of G1 reward inhibited A1 speeds but had no effect on A2 speeds. The results were interpreted as supporting the notion that the double alleyway may be considered as a differential conditioning situation. The postshift A2 speed data were interpreted within the framework of frustration theory.

External cue control of DRL performance in rats with septal lesions

Abstract Septally-lesioned, thalamically-lesioned, and normal animals were trained to bar-press on a DRL-20 schedule for food reinforcement. For half of the animals, a cue light signalled the end of the required delay during the first half of training. The light cue conditions were reversed for all animals in the last half of training. All animals decreased their rate of response during training, regardless of the presence or absence of the cue light. However, the septal animals, in contrast to the normal and thalamic animals, increased their reinforcement frequency only when the cue light was used. In addition, when the cue light was used, all animals had a bimodal distribution of inter-response times, with one mode at the shortest recorded delay and a mode at the 20-sec delay interval. When the cue light was not used, the thalamic and normal animals again had a bimodal distribution, while the septal animals had a unimodal distribution with the mode located at the shortest recorded delays. The results suggested that the cue light functioned as a discriminative cue for bar-pressing and secondly, as a reinforcing stimulus for behaviors which mediated the required delay. It was concluded that the septal deficit on DRL schedules results from a failure to utilize response-produced, proprioceptive stimuli as cues for bar-pressing.

Item priority in free recall

In multiple-trial free recall there is a tendency for newly learned items, i.e., items recalled for the first time, to be recalled prior to those which had recalled on previous trials (old items). Two mechanisms have been offered to account for this effect, (a) a subject strategy to recall new items first and (b) the operation of a serial-position bias in favor of “new” items. These explanations were contrasted in this study by comparing priority effects obtained under a condition that produces a strong position bias (0-sec delay between presentation and recall) with one that results in a greatly reduced bias (30-sec delay). Two groups (0 and 30 sec) learned two successive lists of words for four trials each. The results supported the positionbias explanation since significant priority effects were only obtained for the 0-sec group.

Effects of within-chain response delay upon post-delay operant performance

Operant responding of rats was delayed by withholding the response levers between the two components of a response chain. Latency and rate of responding in the second component were facilitated by a 10 sec delay with respect to a 4 sec delay. When the delay was increased to 50 sec. the facilitation of latency declined whereas the facilitation of response rate increased.

Effect of delay of escape reward and response compatibility on human reaction time.

The gradient of escape reward under compatible and incompatible responses performed during delay of reward by human subjects was studied. A discrimination jump reaction time task was used; escape was from aversive noise. Subjects practised the same jump response and one of two delay responses on pre‐reward discrimination trials and were told that the pre‐reward jump response was the escape response on noise trials. During noise trials reward followed the escape response by 0, 0·4, 4·0 or 8·0 sec. A no‐noise control group for each kind of delay response was included. The jump speeds for both kinds of delay responses were the same for pre‐reward trials and also for reward trials for zero delay. For reward trials the delay groups with the incompatible response were slower than the compatible response group counterparts on all but 8·0 sec delay. The no‐noise controls did not improve. Extinction was immediate for all reward groups.

Effects of combined lesions of frontal granular cortex and caudate nucleus in the neonatal monkey

Combined bilateral lesions of frontal granular cortex and caudate nucleus were produced in 7 monkeys between the 2nd and 56th postnatal day. When comparisons were made with 4 monkeys which had previously sustained bilateral resections of frontal granular cortex alone at comparable ages, it was found that the frontal-caudates, in contrast to the frontals, displayed failure to thrive, somato-motor and growth deficiencies, postoperative seizures and later cognitive impairments. When tested at the 7th postoperative month, 2 of the 3 surviving frontal-caudates could not perform a delayed response task beyond a minimal (0 sec) delay interval. It was concluded that early reflexive and somato-motor function is principally mediated by subcortical systems but that some degree of representation also exists at cortical levels. In contrast to neocortex, the caudate nucleus appears to be involved in a neural system responsible for the retention of delayed response capacity following early brain injury.

Punishment following escape and avoidance training

Rats were trained in a runway for five days with a 0, 1, 2, or 4- sec delay between grid drop and shock onset followed by four days of extinction with punishment. The 0- sec (escape) Ss showed less resistance to extinction and slower running during extinction.

The effects of long-term training with delayed reward and delay-box confinement on instrumental performance

Thirty-five rats were trained for 36 days (6 trials/day) in a runway with 20 sec delay (D) or no delay (ND). Each training group was divided in extinction into 20 sec delay-box confinement (D) or no confinement (ND). Extinction lasted for 12 days (6 trials/day). Despite the long term training the D Ss were still running slower at the end of training. The D Ss were also far more variable than the ND Ss. Resistance to extinction varied inversely with duration of confinement in extinction. Increases in confinement from training to extinction produced faster extinction; decreases produced slower extinction.

Alteration of flow dynamics in the carotid artery system of "stroke" patients. Clinical and arteriographic study.

Percutaneous retrograde arch aortography was performed in a series of 94 patients with symptoms suggesting cerebrovascular insufficiency. In 26 of these a major stenosis (greater than 50% reduction of measured luminal diameter) was present in the cervical carotid artery(s). In 75% of this subgroup an arleriographic flow pattern was seen which correlated closely with the lateralization of cerebral ischemic manifestations. This pattern consists of a 0.5 sec or greater delay in linear flow of contrast material through the stenosed carotid artery as compared with the contralateral one. Evidence is presented to support the assumption that such a finding reflects an actual diminution of volume blood flow and is the result of the stenosis demonstrated. Two control groups of 19 neurologically normal and 60 neurologically symptomatic patients without significant stenosis of larger cerebral vessels were studied by arteriography in an identical manner. No patient in either control group manifested a unilateral delay in linear flow. Provided artefact can be excluded, this sign is believed to be a valuable index of the clinical significance of cervical carotid artery stenosis.

DELAYED AUDITORY FEEDBACK WITH DIFFERENT DELAY TIMES AT EACH EAR.

Binaurally asynchronous delayed auditory feedback (DAF) was compared with synchronous DAF in 80 normal subjects. Asynchronous DAF (0.10 sec difference) did not yield results different from those obtained under synchronous DAF with a 0.20 sec delay interval, an interval characteristically resulting in maximum disruptions in speech.

EXTEROCEPTIVE CONTROL OF RESPONSE UNDER DELAYED REINFORCEMENT.

Three white rats, after 50 continuous reinforcements, were exposed successively, under dim illumination, to reinforcement delays of 1, 3, 5, 7.5, 10, 15, and 20 sec, with prolonged training at the 20-sec level. Behavior was maintained at each level, and an increase in interval was accompanied by an increase in post-reinforcement pause. Subsequently, under both 20- and 30-sec delays, the animals were tested during half of each daily session to determine the effect of introducing darkness during each delay interval. The result of this stimulus "support" was to regularize and increase response rate for each animal at both interval values.

Soft gamma rays from Eu152 and Eu154 following resonance neutron capture

Abstract The gamma-ray spectra up to 300 keV from the odd Eu152 and Eu154 have been measured with a NaI(Tl) scintillator following resonance neutron capture in the 0.33, 0.46, 1.06 and 2.46-eV resonances. Absolute intensities are reported for gamma rays of 95±4 keV from Eu152 and 74±4 and 95±4 keV from Eu154. The thermal capture spectrum of Eu was reinvestigated with a lead critical absorber, and the resulting value for the contribution of a prompt (⪷ 100-μ sec delay ) ≈ 74- keV gamma ray from Eu152 is ⪷ 0.5 photons per 100 captures in elemental Eu. This large discrepency with the results of Skliarevskii et al., using an unpulsed neutron source, might indicate a new delayed transition.

Interaction of fast neutrons with fluorine

Fluorine targets were irradiated with fast neutrons arising from D(d, n), Be(d, n) and T(d, n) reactions using the deuterons accelerated in a one million volt Cockroft-Walton accelerator. Resulting charged particle spectra and low energy gamma ray spectra were studied. Using 15 MeV neutrons, the charged particle spectrum showed a small hump at (10.6 ± 0.8) MeV which is consistent with a 10.5 MeV alpha group leading to the ground state of N 16 in F 19 (n,α)N 16 reaction. The gamma spectra showed mainly 110±8 keV and 195 ± 10 keV gamma rays. Relative intensities to these gamma rays at each of the neutron energies are given. Gamma rays of 300 keV and 390 keV energy that might arise in F 19(n, α)N 16 reaction were looked for but not observed. Upper limits on their intensities with respect to 110 keV gamma rays are given. No real coincidence effect was found between 110 keV and 195 keV gamma rays up to 10 μ sec delay.

Round-the-word signals at very low frequency

An experiment is described in which very low frequency signals transmitted on 18 kc by NSS are detected after traveling once around the world. A diurnal field-intensity variation was observed with the maximum intensity appearing at sunset at the sending and receiving locations. The signal delay times were measured with 0.1373±.0005 sec delay under normal ionospheric conditions and 0.1365±.0005 sec delay on a disturbed day.