Signal-controlled responding

Pigeons' key pecks were reinforced with grain, then extinguished. An 8-second tone preceded the availability of peck-dependent grain 1 second after tone offset. When a tone signalled grain and an 8-second clicking sound did not, three pigeons pecked during a high percentage of tone periods, but they pecked during a low percentage of click periods. When the roles of the tone and clicking sound were reversed, performance reversed. For other birds, when a key peck during the tone cancelled the availability of grain (omission procedure), the tendency to key peck during the tone decreased some, but still remained high. A third group of pigeons received the omission procedure with the addition that the tone could not end unless 2 seconds had elapsed without a key peck. The pigeons continued to respond in a high percentage of tone periods. The experiments favor an explanation based on the pairing of the tone with a reinforced response, such as Pavlovian conditioning.     

Reflex augmentation of a tap-elicited eyeblink: the effects of tone frequency and tap intensity

The amplitude of the human eyeblink elicited by a mild tap between the eyebrows can be increased if a brief tone is presented simultaneously with the tap. In two experiments we examined how this reflex augmentation effect varies with changes in the frequency characteristics of the tone and with changes in the intensity of the tap. We also examined how these effects change in the course of development. For newborn infants and for adults, fixed intensity tones with frequencies of either 1, 2, or 4 kHz produced equivalent amounts of reflex augmentation. Furthermore, while blink amplitude was an increasing function of tap intensity in both populations, the amount of reflex augmentation engendered by a simultaneously presented tone was independent of the intensity of the tap.     

The effects of stimulus movement and attention on peripheral stimulus localization by 8- to 26-week-old infants

This study examined the effect of stimulus movement on localization probability and latency during attention and inattention. Forty infants, 10 each at 8, 14, 20, and 26 weeks of age were presented with a central stimulus. Then, a peripheral stimulus was presented (static or dynamic checkerboard). Stimulus movement did not affect localization probability. Infants localized the dynamic peripheral stimulus more quickly than the static peripheral stimulus when there was no focal stimulus. Focal stimulus attention attenuated this difference in localization latency between static and dynamic stimuli. Signal detection analysis showed that sensitivity to the peripheral stimulus increased over this age range along with a decrease in the bias against responding. The effects of attention were on response bias rather than stimulus sensitivity. These results imply attention affected the localization response to the peripheral stimulus but did not affect the sensitivity of the sensory and perceptual pathways to peripheral stimuli.     

Reversibility of single-incentive selective associations.

Rats were trained to press a lever in the presence of a tone-light compound stimulus and not to press in its absence. In each of two experiments, schedules were designed to make the compound a conditioned punisher for one group and a conditioned reinforcer for the other. In Experiment 1, one group's responding produced food in the presence of the compound but not in its absence. The other group's responding terminated the compound stimulus, and food was presented only in its absence. When tone and light were later presented separately, light controlled more responding than did tone in the former group, but tone gained substantial control in the latter. The same effects were also observed within subjects when the training schedules were switched over groups. In Experiment 2, two groups avoided shock in the presence of the compound stimulus. In the absence of the compound, one group was not shocked, and the other received both response-independent and response-produced shock. When tone and light were presented separately, the former group's responding was mainly controlled by tone, but the latter group's responding was almost exclusively controlled by light. These effects were also observed within subjects when the training schedules were switched over groups. Thus, these single-incentive selective association effects (appetitive in Experiment 1 and aversive in Experiment 2) were completely reversible. The schedules in which the compound should have been a conditioned reinforcer consistently produced visual control, and auditory control increased when the compound should have become a conditioned punisher. Currently accepted accounts of selective associations based on affinities between shock and auditory stimuli and between food and visual stimuli (i.e., stimulus-reinforcer interactions) do not adequately address these results. The contingencies of reinforcement most recently associated with the compound and with its absence, rather than the nature of the reinforcer, determined whether auditory or visual stimulus control developed.     

Comparison of infant and adult P300 from auditory stimuli.

Event-related brain potentials (ERPs) using auditory stimuli were recorded from 5- to 10-month-old infants and normal young adults with a passive tone sequence paradigm. A P3 (P300) component was obtained which demonstrated the same central-parietal maximum scalp distribution for both subject groups. P3 amplitude was smaller and its peak latency longer for infants compared to those of the adults across all electrode sites. P3 measures remained stable across stimulus trials indicating that ERP habituation was not occurring. Evaluation of individual subjects suggests that the P3 can be elicited from infants with auditory stimuli in a manner similar to that from adults and may serve as a useful index for the assessment of cognitive function in infants.     

A comparison of pecking generated by serial, delay, and trace autoshaping procedures

Pigeons were exposed to serial, delay, and trace autoshaping procedures. In Experiment I, all conditioned stimuli (CSs) were changes in illumination of the response key. The number of trials to acquisition of the keypeck increased from serial, to 4-sec delay, 8-sec delay, and 8-sec trace procedures, in that order. In Experiment II, which used a longer intertrial interval, trials to criterion increased from 8-sec delay, to 28-sec delay, 8-sec trace, and 28-sec trace procedures, in that order. In Experiment III, two groups received serial procedures in which the first CS was either a tone or a houselight, and the second was a keylight. The tone group acquired the key peck more rapidly than the houselight group. Early in conditioning in these experiments, and when the conditioned stimulus was a change in the keylight, there was a short latency to the onset of pecking and pecking was directed at the CS. After extensive conditioning, or when the CS was relatively diffuse, pecking still occurred, but had a longer latency and was not reliably directed toward the conditioned stimulus.     

Implicit semantic priming in Spanish-speaking children and adults: an auditory lexical decision task

Although receptive priming has long been used as a way to examine lexical access in adults, few studies have applied this method to children and rarely in an auditory modality. We compared auditory associative priming in children and adults. A testing battery and a Lexical Decision (LD) task was administered to 42 adults and 27 children (8;1-10; 11 years-old) from Spain. They listened to Spanish word pairs (semantically related/unrelated word pairs and word-pseudoword pairs), and tone pairs. Then participants pressed one key for word pairs, and another for pairs with a word and a pseudoword. They also had to press the two keys alternatively for tone pairs as a basic auditory control. Both groups of participants, children and adults, exhibited semantic priming, with significantly faster Reaction Times (RTs) to semantically related word pairs than to unrelated pairs and to the two word-pseudoword sets. The priming effect was twice as large in the adults compared to children, and the children (not the adults) were significantly slower in their response to word-pseudoword pairs than to the unrelated word pairs. Moreover, accuracy was somewhat higher in adults than children for each word pair type, but especially in the word-pseudoword pairs. As expected, children were significantly slower than adults in the RTs for all stimulus types, and their RTs decreased significantly from 8 to 10 years of age and they also decreased in relation to some of their language abilities development (e.g., relative clauses comprehension). In both age groups, the Reaction Time average for tone pairs was lower than for speech pairs, but only all adults obtained 100% accuracy (which was slightly lower in children). Auditory processing and semantic networks are still developing in 8-10 year old children.     

Implicit expectations influence target detection in children and adults

When a sound occurs at a predictable time, it gets processed more efficiently. Predictability of the temporal structure of acoustic inflow has been found to influence the P3b of event‐related potentials in young adults, such that highly predictable compared to less predictable input leads to earlier P3b peak latencies. In our study, we wanted to investigate the influence of predictability on target processing indexed by the P3b in children (10–12 years old) and young adults. To do that, we used an oddball paradigm with two conditions of predictability (high and low). In the High‐predictability condition, a high‐pitched target tone occurred most of the time in the fifth position of a five‐tone pattern (after four low‐pitched non‐target sounds), whereas in the Low‐predictability condition, no such rule was implemented. The target tone occurred randomly following 2, 3, 4, 5, or 6 non‐target tones. In both age groups, reaction time to predictable targets was faster than to non‐predictable targets. Remarkably, this effect was largest in children. Consistent with the behavioral responses, the onset latency of the P3b response elicited by targets in both groups was earlier in the predictable than the unpredictable conditions. However, only the children had significantly earlier peak latency responses for predictable targets. Our results demonstrate that target stimulus predictability increases processing speed in children and adults even when predictability was only implicitly derived by the stimulus statistics. Children did have larger effects of predictability, seeming to benefit more from predictability for target detection.     

The effect of reinforcement differences on choice and response distribution during stimulus compounding

In Experiments I and II, rats were trained to respond on one lever during light and another during tone. The absence of tone and light controlled response cessation. In the multiple schedule of Experiment I, all reinforcements were received for responding in tone or light; in the chain schedule of Experiment II, all reinforcements were received in no tone + no light for not responding. Experiment I subjects, for which tone and light were associated with response and reinforcement increase, responded significantly more to tone-plus-light than to tone or light alone (additive summation). Experiment II subjects, for which tone and light were associated with response increase and reinforcement decrease, responded comparably to tone, light, and tone + light. Thus, additive summation was observed when stimulus-response and stimulus-reinforcer associations in tone and light were both positive, but not when they were conflicting. All subjects in both experiments responded predominantly on the light-correlated lever during tone + light, even when light intensity was reduced in testing. Furthermore, when a light was presented to a subject engaged in tone-associated responding, all subjects immediately switched the locus of responding to the light-correlated lever. No change in locus occurred when a tone was presented to a subject engaged in light-associated responding, irrespective of the stimulus-reinforcer association conditioned to tone. The light-lever preference in tone + light indicates that the heightened responding observed in Experiment I was not the summation of tone-associated behavior with light-associated behavior. Rather, it appears to be the result of a facilitation of one operant (light-associated responding) by the reinforcement-associated cue for the other.     

Behavioral thresholds for tones during infancy

An adaptive up-down tracking procedure was used in combination with a visually reinforced head turn response to examine auditory sensitivity for 500, 2000, and 8000-Hz tone bursts in infants 6 to 18 months of age. Six- and 10-month-old infants were tested with headphone presentation of stimuli, while 10-, 14, and 18-month-olds were tested in sound field. Infant threshold estimates for both headphone and sound field were within 15 dB of adult comparisons for all frequencies and age groups. Six-month-olds were significantly less sensitive to the 8000-Hz tone than to either of the lower frequency stimuli, but older infants demonstrated approximately equal sensitivity for all three frequencies tested.     

ADULTS LISTEN SELECTIVELY; INFANTS DO NOT

Abstract— Infants' auditory detection thresholds are higher than adult thresh olds. Since adults listen selectively for an expected test tone frequency, and selective listening improves their detection performance, one hypothesis about why infant thresholds are high is that infants do not listen selectively. This hypothesis was tested by obtaining listening bands from adults and from 7- to 9-month-old infants. The results replicate earlier findings that adults listen selectively but indicate that infants do not. Lack of selective listening likely contributes to infants' high thresholds. Further, the finding that infants and adults have different listening strategies has implications for infants' auditory perception in general.     

The Development of Infant Memory

Over the first year and a half of life, the duration of memory becomes progressively longer, the specificity of the cues required for recognition progressively decreases after short test delays, and the latency of priming progressively decreases to the adult level. The memory dissociations of very young infants on recognition and priming tasks, which presumably tap different memory systems, are also identical to those of adults. These parallels suggest that both memory systems are present very early in development instead of emerging hierarchically over the 1st year, as previously thought. Finally, even young infants can remember an event over the entire "infantile amnesia" period if they are periodically exposed to appropriate nonverbal reminders. In short, the same fundamental mechanisms appear to underlie memory processing in infants and adults.     

非条件刺激降低再评估对条件性恐惧消退的影响

诸多情绪障碍治疗的关键在于促进条件性恐惧反应的消退, 研究证明非条件刺激再评估能够引起恐惧反应的变化。本研究将非条件刺激降低再评估范式应用于消退训练, 以主观预期值、皮电反应作为恐惧反应指标, 考察恐惧习得后非条件刺激强度降低对条件性恐惧消退的影响, 并运用评价性条件作用探讨非条件刺激再评估的作用机制。结果表明：在消退阶段, 降低组对条件刺激的皮电反应显著低于控制组。同时评价性条件作用结果显示：经过非条件刺激再评估, 降低组较控制组对条件刺激的评价更为正性。说明非条件刺激降低再评估有效改变条件刺激的负性效价, 降低个体的恐惧反应、促进恐惧消退。     

Second-order autoshaped key pecking based on an auditory stimulus.

In Experiment 1, pigeons were exposed either to paired or to unpaired presentations of a tone and grain, and then to paired presentations of a keylight with the tone. Substantial second-order conditioned pecking to the keylight was produced in the birds that had received paired presentations of tone and grain. In Experiment 2, second-order pecking to the keylight increased in probability across four groups that had received, respectively, 20, 80, 140, or 200 paired presentations of tone and grain. In Experiment 3, the amount of pecking directed towards a keylight which predicted the first-order, tone CS was as substantial in birds without a prior history of key pecking as in birds with such a history. A further experiment failed to discover any significant differences in the levels of second-order pecking to a keylight paired with a first-order tone CS or with a first-order keylight CS. Thus, an auditory signal that does not itself support pecking may enable a localized visual stimulus to evoke key pecking.     

Modality-repetition and attentional effects on reflex blinking in infants and adults

The ability of a brief prepulse to inhibit reflexively elicited startle is a robust phenomenon in adults of several species but is weak or absent in infants. The possibility that afferent processing of the prepulse is inadequate in infants was tested by assessing the integrity of two other types of reflex modulation that occur in modality-specific paths, that is, attenuation by repetition of same-modality stimuli and enhancement by modality-selective attention. The reflex, measured by electromyographic activity of the muscle controlling blink, was elicited by intense light flashes or noise bursts preceded by brief acoustic or visual prepulses and delivered during attention-directing acoustic or visual foregrounds that evoked cardiac deceleration. Modality-repetition effects were evidenced by smaller peak blink magnitude and longer latency of blinking to same than to different modality pairs and did not differ as a function of age (4-month-old infants or college students). Attention effects were also seen in both infants and adults and, in accord with previous findings, were evident in magnitude for infants and latency for adults. Thus, immaturity in paths mediating these effects could not explain delayed development of prepulse inhibition. Other possibilities include delayed maturation of extrinsic inhibition or of transient-processing systems.     

Differential responding without differential reinforcement: Intensity difference, continuum position, and reinforcement density effects

The response rates of five groups of rats were observed during exposure to different intensities of a four kilohertz tone within a two-component multiple schedule of nondifferential reinforcement. Response rates were found to be higher during the multiple schedule component which contained the higher intensity tone. Larger differences in response rates between the two multiple schedule components occurred with greater intensity separations (30 versus 20 decibels). At the 30 decibel separation a low absolute magnitude produced larger response rate differences than a high absolute magnitude, while at the 20 decibel separation a high absolute magnitude produced larger response rate differences. Increases in reinforcement density were accompanied by decreases in response rate differences between high and low intensity components only when over-all response rates also increased.     

Tonal frequency shifts and gaps in acoustic stimulation as reflex-modifying events

When a relatively weak signal, such as a mild tone, precedes an intense reflex-eliciting stimulus by an appropriate interval (about 100 msec), the amplitude of the elicited reaction is often reduced. It was found that in student volunteers a brief gap in a steady pure tone that occurred 150 msec prior to a mild tap to the glabella (the flat region between the eyebrows) could inhibit the eyeblink elicited by the tap. It was also found that a shift in tonal frequency across a gap in a tone was more inhibitory than a gap with no frequency shift, but it was no more inhibitory than the onset of the short second tone alone. The final study determined the minimum amount of frequency shift required to produce an additional inhibitory effect above that of a gap alone. The findings are discussed in terms of various aspects of sensory processing.     

Alcoholism risk and the P300 event-related brain potential: modality, task, and gender effects

The P300 event related potential (ERP) was elicited from young adults at low- (LR) and high-risk (HR) for alcoholism (n = 24/risk group), with equal numbers of male and female subjects employed. The effects of stimulus modality, task difficulty, and gender were assessed with analogous auditory and visual paradigms (tone location/head rotation and tone matching/shape matching). Although task performance was generally comparable across risk groups, LR subjects produced smaller P300 amplitudes than HR subjects for the visual matching tasks. No consistent risk group P300 latency effects were obtained. Gender, task difficulty, and scalp topography differentially modulated the risk group outcomes across paradigms. These findings suggest that P300 amplitude reflects risk-for-alcoholism in male and female young adults, but the specific task conditions and electrode location affect the strength of risk group differences.     

Heart rate conditioning in the newborn infant

In an attempt to condition heart rate in newborns, 21 infants were assigned to Conditioning, Random Control, and Backward Conditioning Groups. During training trials, the Conditioning Group received an eight-second tone (CS), a six-second ISI, and a ten-second presentation of glucose via nipple (UCS) that overlapped the last two seconds of tone. The Random Control Group received tones at the same intertrial intervals as the Conditioning Group, but glucose varied randomly. The Backward Conditioning Group received glucose during the ten seconds immediately preceding tone onset. The response to both CS and UCS during base trials was HR acceleration. The response to tone habituated in all groups, but the acceleration to glucose was maintained throughout conditioning. Although no conditioned response to the tone developed over trials, a large HR deceleration appeared during extinction to the absence of the UCS in the Conditioning Group only. This deceleration was interpreted as an orienting response to the absence of an expected event.     

Control by the auditory or the visual element of a compound discriminative stimulus: effects of feedback.

Groups of pigeons were trained to depress a treadle in the presence of a compound stimulus consisting of a tone and a red houselight (a) to avoid electric shock, or (b) to obtain grain. Immediate, exteroceptive feedback was equated for avoidance and appetitive groups within an experiment, but varied across experiments from elevation of a nonilluminated feeder to darkening of the chamber, termination of the tone, and elevation of an illuminated feeder. Responding in the absence of the compound stimulus postponed its next occurrence. After performance had stabilized, the degree to which each element controlled treadle pressing was determined. Generally, in the appetitive tests, the red light controlled much more responding than did the tone, but in the avoidance tests, the tone controlled more responding than did the red light.