Fluctuations in recall across successive test trials

The purpose of the experiment was to determine whether item fluctuation (intertrial forgetting and spontaneous recovery) depends upon the time allowed for recall and/or the demand characteristics of the experimental situation (manipulated via instructions to S). One hundred. and forty-four university undergraduates studied a 36-item list and then had two successive recall trials which were 9, 36, or 144 sec in duration. On the second recall trial, Ss were instructed to recall previously recalled items only (“old”), previously nonrecalled items only (“new”), or both previously recalled items and previously nonrecalled items (“both”). The results suggest two conclusions: (1) Although recall trial duration affects the overall amount of recall, it does not affect the amount of item fluctuation; and (2) an instruction to recall only “old” items or to recall only “new” items results in suppression of the nonrequested items without a corresponding facilitation for the requested items.     

Temporal parameters of the feature positive effect

Trial duration and intertrial interval duration were parametrically varied between groups of pigeons exposed to a discrimination involving the presence vs. the absence of a dot. Half the groups received the dot as the positive stimulus (feature positive groups) and half the groups received the dot as the negative stimulus (feature negative groups). Faster learning by the feature positive birds (feature positive effect) was found when the trial duration was short (5 sec) regardless of whether the intertrial interval was short (5 sec) or long (30 sec). No evidence for a feature positive effect was found when the trial duration was long (30 sec) regardless of the length of the intertrial interval (30 sec or 180 sec). The results suggest that short trial duration is a necessary condition for the occurrence of the feature positive effect, and neither intertrial interval nor trial duration/intertrial interval ratio are important for its occurrence. The suggestion that mechanisms underlying the feature positive effect and autoshaping might be similar was not supported by the present experiment since the trial duration/intertrial interval ration parameter appears to play an important role in autoshaping but not the feature positive effect.     

Function of intertrial interval in matching-to-sample

Twelve pigeons were trained on matching-to-sample using either a 0-, 5-, 15-, 25-, or 60-sec intertrial interval. Eight of these 12 pigeons were given one of the following intertrial interval changes: 0 to 60, 0 to 5, 5 to 0, 60 to 0, 15 to 25, 5 to 15, 60 to 5, 5 to 1, 1 to 5, 1 to 25, and 25 to 1 sec. Most intertrial interval changes were repeated at least once. The 0-sec intertrial interval subjects failed to match beyond chance levels, while other intertrial interval values resulted in matching acquisition. Changes from 0 sec to other intertrial interval values increased and changes to 0 sec decreased matching performance. Changes to intertrial interval values other than 0 sec resulted in little change in matching accuracy once stable performance had been attained.     

Common features of the “repetition” and “same-different” effects in reaction time experiments

Using comparable stimulus and response sets, and the same Ss, the “repetition” and “same-different” effects were studied in two experiments involving several reaction-time (RT) tasks. In Experiment 1, these effects were examined at a 2-sec interval between successive stimuli in the simple (SRT), the recognition (RRT), the choice (CRT), the same-different recognition(S-DRRT),and the same-different choice (S-DCRT) tasks. In Experiment 2, the effects were studied at a 1 O-sec interval in the CRT and S-DCRT tasks. The results suggest the following mainconclusions: (1)The positive repetition effect (i.e., shorter reaction times on “repeated” trials than on “nonrepeated” trials) is not only a feature of the CRT task but may also occur in the SRT and RRT tasks. (2) With increasing intertrial interval, the magnitude of the positive repetition effect diminishes and then reverses into a negative repetition effect. (3) The positive same-different effect (ie., shorter reaction times on “same” trials than on “different” trials) is affected by an increase in interstimulus interval ina manner that parallels the effect of intertrial interval on the positive repetition effect, suggesting that the processes underlying the two effects are mainly the same. (4) These changes in the magnitude and direction of the repetition and same-different effects are probably a function of discrimination difficulty.     

Your neighbors define your value: A study of spatial bias in number comparison

Several chronometric biases in numerical cognition have informed our understanding of a mental number line (MNL). Complementing this approach, we investigated spatial performance in a magnitude comparison task. Participants located the larger or smaller number of a pair on a horizontal line representing the interval from 0 to 10. Experiments 1 and 2 used only number pairs one unit apart and found that digits were localized farther to the right with “select larger” instructions than with “select smaller” instructions. However, when numerical distance was varied (Experiment 3), digits were localized away from numerically near neighbors. This repulsion effect reveals context-specific distortions in number representation not previously noticed with chronometric measures.     

Concept identification: Effect of the intertrial interval on the efficacy and consistency of information processing

Two experiments following identical procedure except for the feedback duration (respectively, 2 sec and 1.5 sec) and the intertrial interval (respectively, 1 sec and 3 sec) are compared with respect to three sequential statistics whose theoretical interpretation is related to the degree of optimality of information processing. The results indicate that the values of the theoretical parameters representing the efficiency of information processing, the consistency of trial-by-trial decisions, and the efficacy of reinforcement are greater in the 3-sec interval condition. This is interpreted as a tentative explanation of the well-known effect of intertrial interval on the difficulty of the task with respect to the mean number of trials to criterion.     

Pavlovian conditioning of shock-elicited aggression: a discrimination procedure

Two auditory stimuli, separated by a fixed intertrial interval, were alternately presented to two rats in a closed environment. The positive conditioned stimulus (CS+) terminated with the offset of a 2-mA, 0.75-sec shock. The negative conditioned stimulus (CS-) terminated without shock. The incidence of the "stereotyped fighting posture" was recorded during the CS+, the CS-, the intertrial interval, and shock. The results showed an increase in the percentage of conditioned responses during the CS+, and a decrease during both the CS- and the intertrial interval, when the duration of the conditioned stimuli and the intertrial interval was 16 sec. Appropriate changes in the incidence of aggression during the two stimuli were obtained following the reversal of the stimulus functions. During the acquisition and reversal phases there was a between-session decrement and a within-session improvement in the incidence of aggression during the CS+, defined as warm-up. The presentation of free shocks before the conditioning sessions was effective in reducing the warm-up only when the interval between shocks was 64 sec. These data were interpreted as demonstrating classical conditioning of shock-elicited aggression, with little chance of non-associative factors contributing to the measurement of the conditioned response.     

Role of intertrial interval following an escape or avoidance response in bar-press avoidance

In three experiments, rats learned bar-press avoidance as a function of the intertrial interval following an escape or an avoidance. The general hypothesis is that the length of these intervals affects bar-press avoidance differentially, depending on whether an avoidance follows an escape (avoidance/escape) or an avoidance (avoidance/avoidance) on the previous trial. Specifically, it is proposed that short escape ITIs will facilitate avoidance/escape and avoidance/avoidance, while avoidance ITIs will have no effect on avoidance responding. The results tend to support this hypothesis. The shorter the intertrial interval following an escape, the higher the probability of both measures: avoidance/escape and avoidance/avoidance. No effect of avoidance interval was found on avoidance/avoidance. Unpredictedly, however, it was found that in comparison to a very short intertrial interval following an avoidance (0.5 sec), relatively long intervals (5 and 45 sec) facilitate avoidance/escape. These results were interpreted as mainly reflecting nonassociative factors such as shock-produced activity.     

The sex difference in rotary pursuit performance: aptitude or inhibition?

This study examined the hypothesis that male dominance in the acquisition and performance of rotary pursuit skill reflects a lower male proclivity for the generation and accumulation of reactive inhibition rather than some innately superior ability to profit from practice. On this hypothesis, the magnitude of male dominance should decline as the length of the intertrial interval increases. The experimental sample consisted of 120 Caucasian subjects (60 of each sex) who were given sixty 30-sec trials on rotary pursuit with intertrial intervals ranging from 0 to 40 sec. The principal finding was that the magnitude of the sex difference depended significantly upon the length of the intertrial interval, as hypothesized. When the interval was 10 sec or longer, performance levels of the sexes were essentially equal. The sex variance was reduced to insignificance even on the first trial when allowance was made for the inhibitory effect of practice. Thus, male dominance in rotary pursuit skill appears to be a procedural effect mediated by and inhibitory mechanism rather than a consequence of differential endowments of learning ability.     

The Sex Difference in Rotary Pursuit Performance

This study examined the hypothesis that male dominance in the acquisition and performance of rotary pursuit skill reflects a lower male proclivity for the generation and accumulation of reactive inhibition rather than some innately superior ability to profit from practice. On this hypothesis, the magnitude of male dominance should decline as the length of the intertrial interval increases. The experimental sample consisted of 120 Caucasian subjects (60 of each sex) who were given sixty 30-sec trials on rotary pursuit with intertrial intervals ranging from 0 to 40 sec. The principal finding was that the magnitude of the sex difference depended significantly upon the length of the intertrial interval, as hypothesized. When the interval was 10 sec or longer, performance levels of the sexes were essentially equal. The sex variance was reduced to insignificance even on the first trial when allowance was made for the inhibitory effect of practice. Thus, male dominance in rotary pursuit skill appears to be a procedural effect mediated by an inhibitory mechanism rather than a consequence of differential endowments of learning ability.     

Optimal Stimulus Parameters In Avoidance Conditioning Of Inbred Strains Of Mice

Highly inbred mice of fast and slow conditioning strains (N = 228) were trained in avoidance conditioning and 180 were continued to extinction. The principal goal was to determine optimal stimulus conditions for fast learning, small variances, and maximal strain differences. Conclusions are: a) the major effect of change in CS-US and intertrial intervals occurs, respectively, for intervals less than 3 sec. and 60 sec.; b) change in amperage (150-400 pa) or voltage (250-400 v.) caused no significant differences; c) strain differences in extinction occurred after nearly optimal conditioning, and d) strain differences were altered considerably as stimulus conditions became optimal. Optimal levels of parameters are: 3 sec. CS-US interval, 120-sec. intertrial interval, and 400 v. (220 K ohm impedance circuit).     

Acquisition and reversal of a discriminated autoshaped response in male and female rats: Effects of long or short and fixed or variable intertrial interval durations

Groups of male and female Wistar rats were exposed to autoshaping procedures in which the duration (50 vs 20 s) and the variablity (fixed vs variable) of the intertrial interval were manipulated. Pellet delivery occurred after one of the levers (CS+) had been presented for 10 s. Presentation of the other lever (CS−) was not associated with pellet delivery. CS+ contacts occurred more frequently and at higher rates when the intertrial interval was 50 s than when it was 20 s, while intertrial interval variability did not play an important role. Males contacted CS+ and CS− more frequently and at a higher rate than did females. Goal-directed activity (nose pokes in feeder tray) occurred more often when the intertrial interval was short than when it was long. Females showed higher goal-directed activity than did males, both during CS presentation and during the intertrial interval. When experimental contingencies were reversed, CS+ contacts decreased and CS− contacts increased for males and females, but the decrease in CS+ contacts occurred more slowly for males than for females. The results of these experiments add to a growing body of literature suggesting the existence of fundamental behavioral differences between the sexes. These differences are partly attributable to the influence of gonadal hormones during development and maturation and partly attributable to the behavioral requirements of the experimental procedures.     

Sex-role behavior and obedience to authority: A field study

Obedience by male and female subjects to male and female experimenters was investigated under various conditions of “perceived legitimacy.” The procedure involved an experimenter stopping a subject who was about to cross a street at a particular crosswalk, the subject was then instructed to cross at another designated location. The dependent variable was the level of obedience to these instructions. The four main factorial independent variables were the sex of the experimenter, the sex of the subject, and two conditions of “perceived legitimacy” (presence or absence of a “uniform,” presence or absence of an “explanation”). Significant results were obtained for the uniform and sex of subject main effects (more obedience with a uniform, more disobedience by females). Additional analyses indicated that “older” subjects disobeyed more often than “younger” ones, that “formally” dressed subjects disobeyed more often than “informally” dressed ones, and that ethnic minority group experimenters were disobeyed significantly more often than Caucasian experimenters. Significant interactions were also obtained, mainly due to the behavior of the younger men and the older women. Male and female experimenters were obeyed equally, in general. The results are discussed in relation to sex-role prejudice and discriminatory behavior.     

The effects of ITI fillers in autoshaping

The present experiments used pigeons in an autoshaping procedure to examine the effects of a nonreinforced, nontarget stimulus presented during the intertrial interval on responding to a target CS. Experiments 1 and 2 found that a filler stimulus presented during a substantial portion of the ITI retarded responding to the target CS relative to a group not exposed to the filler. This group difference in performance was subsequently abolished by continued training and omitting the filler in the former group (Experiment 1) or adding a filler for the latter group (Experiment 2). Experiment 3 found that when the “filler” occupied most of the interreinforcement interval, CS-US pairings embedded within the “filler” stimulus yielded superior autoshaping relative to a group that received CS-US pairings embedded in static apparatus cues in the absence of the filler. The results are discussed with reference to the ways that a nontarget stimulus during the ITI can influence contextual modulation of responding to a discrete CS and the necessity for comparator theories to incorporate a “local context” view of cycle time to explain the present findings.     

Switching attention within and between categories: Evidence for intracategory inhibition

In a variation of the Posner and Snyder (1975b) paradigm, subjects made speeded “same” or “different” responses to pairs of digits or letters on the basis of name identity (Experiment 1) or physical identity (Experiment 2). Each target pair was preceded by an informative (letter or digit) or noninformative (plus-sign) warning signal. The letter or digit represented by an informative warning signal had a high probability of appearing in the subsequent target pair (expected condition). On trials in which the expected stimulus did not appear in the target pair, the target pair belonged with equal probability to either the same category (either letters or digits) as the expected stimulus or to the opposite category (unexpected-similar and unexpected-opposite conditions, respectively). The pattern of “benefits” and “costs” of attentional expectancy found by Posner and Snyder for “same” responses was replicated: Subjects were faster and more accurate in the expected condition than in the neutral (uninformative warning signal) condition, but slower and less accurate in the unexpected conditions. Present theoretical interest concerns “same” response times and accuracy for the two unexpected conditions. Under instructions emphasizing accuracy as well as speed (Experiments 1 and 2), performance was worse in the unexpected-similar condition than in the unexpected-opposite condition. Only when instructions deemphasized accuracy (Experiment 2) was performance better in the unexpected-similar condition than in the unexpected-opposite condition. The fact that subjects may have more difficulty switching attention within a category than between categories (at least when instructions emphasize accuracy as well as speed) contrasts sharply with current theoretical emphasis on intracategorical facilitation effects in the priming paradigm. The results are interpreted within the framework of a model of attention (Keele & Neill, 1978) in which the activation of associates to the focus of attention is actively and optionally suppressed so as to reduce present or potential interference with the focal information processing.     

The role of instrumental responding and contiguity of stimuli in the development of infant secondary reinforcement

Ten-month-old infants received contingent pairings of a tone (T+) and food reinforcer. Groups S^r and S^D received the food on an FI 23-sec schedule for target touching, the former group receiving T+ immediately after the response and 1.5 sec prior to food and the latter group receiving T+ at the end of the intertrial interval. Group SC received food reinforcers 1.5 sec after T+ with no response required. A second tone (Tⁿ) was heard by all groups once during each intertrial interval, at randomly determined points. All groups subsequently were given a spatial discrimination task, receiving T+ for one alternative and Tⁿ for the other. Group S^r gave significantly more responses for T+ than for Tⁿ, but neither of the other two groups produced a superiority for T+. Thus, both contiguity with a primary reinforcer and the presence of an operant during training appear to be necessary for a neutral signal to acquire the ability to enhance responding.     

Instructional Effects on Word Association Commonality in High and Low “Schizophrenic” College Students

In an attempt to assess the ability of normal Ss to give uncommon word associations and of “schizophrenic” Ss to give common ones, the effects of three types of instruction on the word association performance of 144 college students were measured. All Ss, including those with valid MMPI profiles suggestive of schizophrenia were able to increase their response commonality under instructions to give the word “most people” would give, and to decrease their commonality under instructions to give a word “no one else” would give, relative to the free association condition. Though Ss with high MMPI Schizophrenia scores produced more original associations under all conditions, there was an apparent floor effect on the production of popular responses under the “no one else” instructions.     

Effects of intertrial reinforcers on self-control choice.

In three experiments, pigeons chose between a small amount of food delivered after a short delay and a larger amount delivered after a longer delay. A discrete-trial adjusting-delay procedure was used to estimate indifference points--pairs of delay-amount combinations that were chosen about equally often. In Experiment 1, when additional reinforcers were available during intertrial intervals on a variable-interval schedule, preference for the smaller, more immediate reinforcer increased. Experiment 2 found that this shift in preference occurred partly because the variable-interval schedule started sooner after the smaller, more immediate reinforcer, but there was still a small shift in preference when the durations and temporal locations of the variable-interval schedules were identical for both alternatives. Experiment 3 found greater increases in preference for the smaller, more immediate reinforcer with a variable-interval 15-s schedule than with a variable-interval 90-s schedule. The results were generally consistent with a model that states that the impact of any event that follows a choice response declines according to a hyperbolic function with increasing time since the moment of choice.     

Discrimination training, partial reinforcement, and increases in intertrial interval all reduce response speed in a continuously reinforced key-pecking task

Pigeons were trained in a discrete-trial task in which a response to the center key obtained illumination of a side key and a single response to the side key terminated a trial with either reinforcement or nonreinforcement. Center-key speeds (i.e., reciprocals of latencies) declined with increases in intertrial interval, and it is argued that this effect is related to a decreased likelihood as intertrial interval increases that birds will be near the key at trial onset. Side-key speeds on trials with reinforcement decreased both with increases in intertrial interval and with shifts from continuous reinforcement to either a discrimination or a partial-reinforcement condition. The effects on side-key speeds are compared with effects observed in alley-running tasks using rats, and an interpretation in terms of frustration theory is offered for the results obtained in both types of task.