RESISTANCE TO CHANGE AND FREQUENCY OF RESPONSE‐DEPENDENT STIMULI UNCORRELATED WITH REINFORCEMENT

Stimuli uncorrelated with reinforcement have been shown to enhance response rates and resistance to disruption; however, the effects of different rates of stimulus presentations have not been assessed. In two experiments, we assessed the effects of adding different rates of response‐dependent brief stimuli uncorrelated with primary reinforcement on relative response rates and resistance to change. In both experiments, pigeons responded on variable‐interval 60‐s schedules of food reinforcement in two components of a multiple schedule, and brief response‐dependent keylight‐color changes were added to one or both components. Although relative response rates were not systematically affected in either experiment, relative resistance to presession feeding and extinction were. In Experiment 1, adding stimuli on a variable‐interval schedule to one component of a multiple schedule either at a low rate (1 per min) for one group or at a high rate (4 per min) for another group similarly increased resistance to disruption in the components with added stimuli. When high and low rates of stimuli were presented across components (i.e., within subjects) in Experiment 2, however, relative resistance to disruption was greater in the component presenting stimuli at a lower rate. These results suggest that stimuli uncorrelated with food reinforcement do not strengthen responding in the same way as primary reinforcers.     

EFFECTS OF POINT‐LOSS PUNISHERS ON HUMAN SIGNAL‐DETECTION PERFORMANCE

Three experiments using human participants varied the distribution of point‐gain reinforcers or point‐loss punishers in two‐alternative signal‐detection procedures. Experiment 1 varied the distribution of point‐gain reinforcers for correct responses (Group A) and point‐loss punishers for errors (Group B) across conditions. Response bias varied systematically as a function of the relative reinforcer or punisher frequencies. Experiment 2 arranged two conditions — one where an unequal ratio of reinforcement (5:1 or 1:5) was presented without punishment (R‐only), and another where the same reinforcer ratio was presented with an equal distribution of point‐loss punishers (R+P). Response bias was significantly greater in the R‐only condition than the R+P condition, supporting a subtractive model of punishment. Experiment 3 varied the distribution of point‐gain reinforcers for correct responses across four unequal reinforcer ratios (5:1, 2:1, 1:2, 1:5) both without (R‐only) and with (R+P) an equal distribution of point‐loss punishers for errors. Response bias varied systematically with changes in relative reinforcer frequency for both R‐only and R+P conditions, with 5 out of 8 participants showing increases in sensitivity estimates from R‐only to R+P conditions. Overall, the results indicated that punishers have similar but opposite effects to reinforcers in detection procedures and that combined reinforcer and punisher effects might be better modeled by a subtractive punishment model than an additive punishment model, consistent with research using concurrent‐schedule choice procedures.     

Electrophysiological responses to auditory novelty in temperamentally different 9‐month‐old infants

Behavioral reactivity to novel stimuli in the first half‐year of life has been identified as a key aspect of early temperament and a significant precursor of approach and withdrawal tendencies to novelty in later infancy and early childhood. The current study examines the neural signatures of reactivity to novel auditory stimuli in 9‐month‐old infants in relation to prior temperamental reactivity. On the basis of the assessment of behavioral reactivity scores at 4 months of age, infants were classified into groups of high negatively reactive and high positively reactive infants. Along with an unselected control group, these groups of temperamentally different infants were given a three‐stimulus auditory oddball task at 9 months of age which employed frequent standard and infrequent deviant tones as well as a set of complex novel sounds. In comparison to high positively reactive and control infants, high negatively reactive infants displayed increased amplitude of a positive slow wave in the ERP response to deviant tones compared to standard tones. In contrast, high positively reactive infants showed a larger novelty P3 to the complex novel sounds. Results are discussed in terms of optimal levels of novelty for temperamentally different infants.     

Predator videos and electric shock function as punishers for zebrafish (Danio rerio)

Zebrafish (Danio rerio) are a promising animal model for studying the effects of gene–environment interactions on behavior. Two experiments were conducted to assess punishment effects of presenting predator videos (Indian leaf fish; Nandus nandus) and electric shock on operant approach responses in zebrafish. In Experiment 1, the predator video and shock stimuli were presented upon a response maintained by a single variable‐interval schedule of food reinforcement in different groups of fish. In Experiment 2, the predator video and shock stimuli were presented upon one of two response alternatives maintain by concurrently available variable‐interval schedules of food reinforcement in different groups of fish. Responding decreased when the predator video and shock stimuli were presented relative to their absence in both experiments. Moreover, responding on an unpunished alternative did not reliably decrease in Experiment 2. These results indicate that the decrease in responding resulted from the punishment contingency rather than from elicited species‐specific defense responses or conditioned avoidance. Thus, the predator video and electric shock functioned as punishers of operant behavior for zebrafish. Identifying punishers for this species could lead to research on how gene–environment interactions influence individual differences in sensitivity to punishment.     

Effects of redundant auditory stimuli on reaction time

Auditory redundancy gains were assessed in two experiments in which a simple reaction time task was used. In each trial, an auditory stimulus was presented to the left ear, to the right ear, or simultaneously to both ears. The physical difference between auditory stimuli presented to the two ears was systematically increased across experiments. No redundancy gains were observed when the stimuli were identical pure tones or pure tones of different frequencies (Experiment 1). A clear redundancy gain and evidence of coactivation were obtained, however, when one stimulus was a pure tone and the other was white noise (Experiment 2). Experiment 3 employed a two-alternative forced choice localization task and provided evidence that dichotically presented pure tones of different frequencies are apparently integrated into a single percept, whereas a pure tone and white noise are not fused. The results extend previous findings of redundancy gains and coactivation with visual and bimodal stimuli to the auditory modality. Furthermore, at least within this modality, the results indicate that redundancy gains do not emerge when redundant stimuli are integrated into a single percept.     

Self-punitive behavior in humans: Effects of a self-fulfilling prophecy

Human subjects were exposed to contingencies which programmed aversive tones (100 db). Two types of contingencies were employed: self-confirming (i.e., self-fulfilling prophecies), in which the aversive tone was occasioned by the prediction it was about to occur; and self-disconfirming, in which the tone was probable when subjects predicted it would not occur. Experiments 1 and 2 used a modified classical conditioning paradigm, and demonstrated that a self-confirming contingency maintained reliable self-punitive responding, i.e., subjects consistently predicted and therefore obtained tones on every trial. Subjects in Experiment 3 were instructed to express predictions continuously throughout four sessions to ensure adequate sampling of the various predictions. Subjects exposed to a self-disconfirming contnngency reliably evidenced awareness of the contingency in effect (judged by answers on a postexperimental questionnaire), whereas subjects exposed to a self-confirming contingency failed to show effective avoidance behavior or contingency awareness. Experiment 4 investigated free-operant self-punitive behavior, utilizing a single prediction response button, which subjects depressed repeatedly. Subjects were exposed to either periodic or aperiodic punishment schedules over as many as four sessions. In general, more persistent self-punitive responding was found in the groups receiving periodic punishment. The results from the four experiments show that self-confirming contingencies can effectively prolong self-punitive responding in human subjects. The findings are consistent with a blocking interpretation of self-punitive behavior, which asserts that when an aversive event is already predicted by stimuli in the situation (including temporal cues), the association between a response and punishment is impaired, and self-punitive responding is likely to be maintained. An integration of human and animal self-punitive research is proposed.     

Impact of contingency manipulations on accessory stimulus effects

Accessory tone stimuli facilitate response performance despite being irrelevant for the current task. In order to investigate which processes are affected by accessory stimuli, we presented accessory tones in a simple response time (RT) task while varying the contingencies between accessory stimulation and either responses(Experiment 1) or stimulus conditions (Experiment 2). Accessory tones speeded up responding to a larger degree when they were conjointly presented within go compared with no-go trials. In contrast, contingency variation with stimulus conditions did not alter the impact of accessory stimuli. Additionally, accessory tones increased response force. Thus, we conclude that in simple RT tasks accessory tones influence response-related stages such as response selection and response execution rather than perceptual processes.     

The effect of prior acquisition of food aversion on the poisoned‐partner effect

It has been suggested that poisoned conspecifics function as aversive unconditioned stimuli for rats. The present study examined whether the prior acquisition of food aversion could enhance this effect. In phase 1, subjects were given pairings of cocoa‐flavored pellets and a toxin. In phase 2, they were given the cocoa‐flavored pellets and later presented with a poisoned or nonpoisoned conspecific. Subsequent testing involved a choice between the cocoa‐flavored pellets and regular pellets. Prior exposure to a poisoned conspecific prevented extinction of the conditioned aversion. In contrast, exposure to a nonpoisoned conspecific allowed extinction of the conditioned aversion. These findings suggest that a rat's reaction to a stressed conspecific is affected by their prior experience of aversive events.     

A comparison of preference‐assessment methods

In Study 1, we evaluated preference stability across 4 preference‐assessment methods for 6 individuals, 5 of whom had autism spectrum disorder and 1 of whom had traumatic brain injury. We also measured participants’ problem behavior as a corollary measure during all assessment methods. The highest mean correlation coefficients and Kendall rank coefficients of concordance across administrations were observed for the paired‐stimulus and multiple‐stimulus‐without‐replacement methods. Lower correspondence across administrations was observed for the free‐operant and response‐restriction methods. Although differentially higher levels of problem behavior did not occur with a single method, lower levels were consistently observed with the free‐operant method. During Study 2, we evaluated the implications of lower coefficients on reinforcer efficacy by comparing an initially identified and an immediately identified high‐preference stimulus in a reinforcer assessment. Initially identified and immediately identified high‐preference stimuli were equally effective reinforcers, suggesting that fluctuations in preference do not necessarily affect reinforcer efficacy in practice.     

The neural correlates of orienting to walking direction in 6‐month‐old infants: An ERP study

The ability to detect social signals represents a first step to enter our social world. Behavioral evidence has demonstrated that 6‐month‐old infants are able to orient their attention toward the position indicated by walking direction, showing faster orienting responses toward stimuli cued by the direction of motion than toward uncued stimuli. The present study investigated the neural mechanisms underpinning this attentional priming effect by using a spatial cueing paradigm and recording EEG (Geodesic System 128 channels) from 6‐month‐old infants. Infants were presented with a central point‐light walker followed by a single peripheral target. The target appeared randomly at a position either congruent or incongruent with the walking direction of the cue. We examined infants' target‐locked event‐related potential (ERP) responses and we used cortical source analysis to explore which brain regions gave rise to the ERP responses. The P1 component and saccade latencies toward the peripheral target were modulated by the congruency between the walking direction of the cue and the position of the target. Infants' saccade latencies were faster in response to targets appearing at congruent spatial locations. The P1 component was larger in response to congruent than to incongruent targets and a similar congruency effect was found with cortical source analysis in the parahippocampal gyrus and the anterior fusiform gyrus. Overall, these findings suggest that a type of biological motion like the one of a vertebrate walking on the legs can trigger covert orienting of attention in 6‐month‐old infants, enabling enhancement of neural activity related to visual processing of potentially relevant information as well as a facilitation of oculomotor responses to stimuli appearing at the attended location.     

Constraint, Alcoholism, and Electrodermal Response in Aversive Classical Conditioning and Mismatch Novelty Paradigms

This study investigated whether low levels of the personality trait of constraint and early-onset alcoholism would be associated with deficits in aversive conditioning and smaller responses to novelty in a stimulus mismatch protocol. Personality traits (constraint and socialization) and skin conductance responses (SCRs) during conditioning and novelty paradigms were assessed in alcoholics (n=41) and non-alcoholics (n = 32). The conditioning protocol involved measuring SCRs after conditioned stimuli (CS+: tones) paired with shock, CS- tones unpaired with shock, and CS+ probes unpaired with shock. The mismatch protocol involved measuring SCRs to auditory stimuli consisting of a series of 5 pure tones of the same pitch followed a shorter white noise stimulus (the novel stimulus). Contrary to the hypothesis, alcoholics did not differ from non-alcoholics in SCRs to CS+ probes or on the mismatch measure (SCR novel tone-SCR to 5th tone). Higher levels of constraint and self-reports of fear during conditioning were associated with smaller responses to both the CS+ probes and the CS- tones as well as the mismatch measure within non-alcoholics, but not within alcoholics. In alcoholics, low constraint was associated with greater habituation to CS+ probes, and poor differential conditioning on measures of change across trials in SCR to CS+ probes and CS- stimuli. The results suggest that different processes influence levels of constraint in non-alcoholics and alcoholics. The data indicate that low constraint in non-alcoholics is associated with allocating fewer processing resources to potentially significant stimuli, rather than being associated with a specific deficit in aversive conditioning per se.     

Assessing functions of stimuli associated with rich‐to‐lean transitions using a choice procedure

Under fixed‐ratio schedules, transitions from more to less favorable conditions of reinforcement (rich‐to‐lean transitions) usually generate extended pausing. One possible explanation for this effect is that stimuli associated with rich‐to‐lean transitions are aversive and, thus, extended pausing functions as escape. The purpose of this study was to characterize further the aversive function of different transitions, and the stimuli associated with them, by allowing pigeons to choose to complete select ratios in the presence of either a mixed‐schedule stimulus or a transition‐specific multiple‐schedule stimulus. The mixed schedule was preferred during transitions that signaled an upcoming lean reinforcer (rich‐to‐lean and lean‐to‐lean), whereas the multiple schedule was preferred during transitions that signaled an upcoming rich reinforcer (lean‐to‐rich and rich‐to‐rich). These findings support the notion that stimuli associated with rich‐to‐lean (and to some extent lean‐to‐lean) transitions can function aversively; whereas stimuli associated with other transitions (e.g., lean‐to‐rich and rich‐to‐rich) can function as conditioned reinforcers. When the opportunity to choose between schedule‐correlated stimuli was available, however, choice latency was controlled exclusively by the multiple‐schedule stimulus. That is, the opportunity to select the mixed schedule did not attenuate rich‐to‐lean pauses, suggesting that extended pausing may be more than simply escape.     

HUMAN RESPONDING ON RANDOM‐INTERVAL SCHEDULES OF RESPONSE‐COST PUNISHMENT: THE ROLE OF REDUCED REINFORCEMENT DENSITY

An experiment with adult humans investigated the effects of response‐contingent money loss (response‐cost punishment) on monetary‐reinforced responding. A yoked‐control procedure was used to separate the effects on responding of the response‐cost contingency from the effects of reduced reinforcement density. Eight adults pressed buttons for money on a three‐component multiple reinforcement schedule. During baseline, responding in all components produced money gains according to a random‐interval 20‐s schedule. During punishment conditions, responding during the punishment component conjointly produced money losses according to a random‐interval schedule. The value of the response‐cost schedule was manipulated across conditions to systematically evaluate the effects on responding of response‐cost frequency. Participants were assigned to one of two yoked‐control conditions. For participants in the Yoked Punishment group, during punishment conditions money losses were delivered in the yoked component response independently at the same intervals that money losses were produced in the punishment component. For participants in the Yoked Reinforcement group, responding in the yoked component produced the same net earnings as produced in the punishment component. In 6 of 8 participants, contingent response cost selectively decreased response rates in the punishment component and the magnitude of the decrease was directly related to the punishment schedule value. Under punishment conditions, for participants in the Yoked Punishment group response rates in the yoked component also decreased, but the decrease was less than that observed in the punishment component, whereas for participants in the Yoked Reinforcement group response rates in the yoked component remained similar to rates in the no‐punishment component. These results provide further evidence that contingent response cost functions similarly to noxious punishers in that it appears to suppress responding apart from its effects on reinforcement density.     

Single-probe serial position recall: evidence of modularity for olfactory, visual, and auditory short-term memory

The present study examined and compared order memory for a list of sequentially presented odours, unfamiliar faces, and pure tones. Employing single-probe serial position recall and following a correction for a response bias, qualitatively different serial position functions were observed across stimuli. Participants demonstrated an ability to perform absolute order memory judgments for odours. Furthermore, odours produced an absence of serial position effects, unfamiliar faces produced both primacy and recency, and pure tones produced recency but not primacy. Such a finding is contrary to the proposal by Ward, Avons, and Melling (2005) that the serial position function is task, rather than modality, dependent. In contrast, the observed functions support a modular conceptualization of short-term memory (e.g., Andrade & Donaldson, 2007; Baddeley & Hitch, 1974), whereby separate modality-specific memorial systems operate. An alternative amodal interpretation is also discussed wherein serial position function disparities are accommodated via differences in the psychological distinctiveness of stimuli (Hay, Smyth, Hitch, & Horton, 2007).     

Constraint, alcoholism, and electrodermal response in aversive classical conditioning and mismatch novelty paradigms

This study investigated whether low levels of the personality trait of constraint and early-onset alcoholism would be associated with deficits in aversive conditioning and smaller responses to novelty in a stimulus mismatch protocol. Personality traits (constraint and socialization) and skin conductance responses (SCRs) during conditioning and novelty paradigms were assessed in alcoholics (n=41) and non-alcoholics (n=32). The conditioning protocol involved measuring SCRs after conditioned stimuli (CS+: tones) paired with shock, CS− tones unpaired with shock, and CS+ probes unpaired with shock. The mismatch protocol involved measuring SCRs to auditory stimuli consisting of a series of 5 pure tones of the same pitch followed a shorter white noise stimulus (the novel stimulus). Contrary to the hypothesis, alcoholics did not differ from non-alcoholics in SCRs to CS+ probes or on the mismatch measure (SCR novel tone—SCR to 5^th tone). Higher levels of constraint and self-reports of fear during conditioning were associated with smaller responses to both the CS+ probes and the CS− tones as well as the mismatch measure within non-alcoholics, but not within alcoholics. In alcoholics, low constraint was associated with greater habituation to CS+ probes, and poor differential conditioning on measures of change across trials in SCR to CS+ probes and CS− stimuli. The results suggest that different processes influence levels of constraint in non-alcoholics and alcoholics. The data indicate that low constraint in non-alcoholics is associated with allocating fewer processing resources to potentially significant stimuli, rather than being associated with a specific deficit in aversive conditioning per se.     

Emergence of response‐response relations

The present study examined whether bidirectional response‐response relations could be established without direct reinforcement. In AB training for 12 undergraduates, higher rates of touches to a white circle on the monitor screen (A1) produced two stimuli (B1 and B2) on half of the trials, whereas lower rates (A2) produced the same effect on the other half. Choosing one of the two stimuli was reinforced according to the preceding responding (A1B1 and A2B2). In BC training, touching a stimulus (B1 or B2) produced three white circles lined up horizontally on the screen, after which one of two different response sequences to the circles (left‐center‐right, C1 or C2, and right‐center‐left, C2 or C1) were reinforced, depending on the stimulus presented (B1C1 and B2C2). After AB and BC relations were established, 11 of 12 participants showed the emergence of untrained relations (BA, CB, AC, and CA) throughout five test sessions, and the remaining participant showed it in the first four test sessions. These response‐response relations were replicated with five other undergraduates and different trained relations.     

Attention‐shift vs. response‐priming explanations for the spatial cueing effect in cross‐modal tasks

The task‐irrelevant spatial location of a cue stimulus affects the processing of a subsequent target. This “Posner effect” has been explained by an exogenous attention shift to the spatial location of the cue, improving perceptual processing of the target. We studied whether the left/right location of task‐irrelevant and uninformative tones produces cueing effects on the processing of visual targets. Tones were presented randomly from left or right. In the first condition, the subsequent visual target, requiring response either with the left or right hand, was presented peripherally to left or right. In the second condition, the target was a centrally presented left/right‐pointing arrow, indicating the response hand. In the third condition, the tone and the central arrow were presented simultaneously. Data were recorded on compatible (the tone location and the response hand were the same) and incompatible trials. Reaction times were longer on incompatible than on compatible trials. The results of the second and third conditions are difficult to explain with the attention‐shift model emphasizing improved perceptual processing in the cued location, as the central target did not require any location‐based processing. Consequently, as an alternative explanation they suggest response priming in the hand corresponding to the spatial location of the tone. Simultaneous lateralized readiness potential (LRP) recordings were consistent with the behavioral data, the tone cues eliciting on incompatible trials a fast preparation for the incorrect response and on compatible trials preparation for the correct response.     

Repeated magnitude estimations with a variable standard: Sequential effects and other properties

Twelve Ss made magnitude estimations of the loudness of each one of a sequence of pure tones according to the rule R(N) = R(N - 1) · [S(N)/S(N - 1)], where R(N) is the response on Trial N, R(N - 1) is the response on Trial N - 1, and S(N)/S(N - 1) is the judged ratio of the “loudness” of the pure tone presented on Trial N to that of the pure tone presented on Trial N - 1. It was found that these magnitude estimations were assimilated toward the immediately preceding stimuli as far as five trials back in the sequence of stimuli. In addition, ratio judgments were consistently asymmetric and the data displayed a form of “time order error.” In all cases, there are similar effects displayed in category judgment data. These and other data imply that at least some kinds of magnitude estimations may involve a judgment of the “difference” or “distance” between pairs of stimuli as a first step in the production of the response required by the judgment situation.     

Single-probe serial position recall: Evidence of modularity for olfactory,visual, and auditory short-term memory

The present study examined and compared order memory for a list of sequentially presented odours, unfamiliar faces, and pure tones. Employing single-probe serial position recall and following a correction for a response bias, qualitatively different serial position functions were observed across stimuli. Participants demonstrated an ability to perform absolute order memory judgments for odours. Furthermore, odours produced an absence of serial position effects, unfamiliar faces produced both primacy and recency, and pure tones produced recency but not primacy. Such a finding is contrary to the proposal by Ward, Avons, and Melling (2005) that the serial position function is task, rather than modality, dependent. In contrast, the observed functions support a modular conceptualization of short-term memory (e.g., Andrade & Donaldson, 2007; Baddeley & Hitch, 1974), whereby separate modality-specific memorial systems operate. An alternative amodal interpretation is also discussed wherein serial position function disparities are accommodated via differences in the psychological distinctiveness of stimuli (Hay, Smyth, Hitch, & Horton, 2007).     

Number discrimination in 10‐month‐old infants

Two experiments investigated developmental changes in large number discrimination with visual‐spatial arrays. Previous studies found that 6‐month‐old infants were able to discriminate arrays that differ by a ratio of 1:2 but not 2:3. We found that by 10 months, infants were able to reliably discriminate 8 from 12 elements (2:3) but not 8 from 10 elements (4:5). Thus, number discrimination improves in precision during the first year, and these findings converge with studies using auditory stimuli.