Blocking and unconditioned response diminution in human classical autonomic conditioning

Four experiments examined blocking and UR diminution in human SCR conditioning. In Experiment 1, CS_X was conditioned in compound with previously conditioned CS_A, in one group, or in a compound with another novel stimulus, CS_N, in an additional group. UR diminution occurred, but there was no post-compound difference in CRs in the two groups and no difference in responding to CS_X and CS_A following equal training on each, i.e., no blocking. The correlation between blocking and UR diminution was not significant. In Experiment 2, two groups received a blocking procedure, but one was tested on CS_X and one on CS_A. UR diminution occurred, but there were no post-compound CR or UR differences. There was again no within-subjects blocking effect. The correlation between blocking and UR diminution was not significant, but this correlation was significant when data from Experiments 1 and 2 were combined. In Experiment 3, a differential conditioning procedure was used, followed by reinforcement of two compounds, one with CS_A+ and one with CS_A-. One subgroup was tested on CS_A+ and CS_A- with reinforcement; another was tested without reinforcement. UR diminution occurred, and there was significant blocking, but only after two nonreinforced tests. Blocking and UR diminution were significantly correlated. In Experiment 4, four groups received compound conditioning after initial training with CS_A. The compound contained CS_X and CS_A for three groups and two novel CSs for the fourth. Ten nonreinforced test trials were run. The three blocking groups received two CS_As plus eight CS_Xs, four CS_As plus six CS_Xs, or all CS_Xs. The fourth group received ten nonblocked CS_Xs. CR magnitude to blocked CS_X was significantly smaller than to nonblocked CS_X during the last six test trials, but not initially. Blocking and UR diminution were not correlated, in disagreement with the first three studies. The results indicated that repeated nonreinforced test trials are needed for blocking to be observed in this preparation. The proposition that blocking and UR diminution are both due to reduced processing of the US received only partial support.     

On the correlation of a naturally and an artificially dichotomized variable

A method is suggested for estimating the correlation of a naturally (X) and an artificially (Y) dichotomized variable. It is assumed that a normal random variable (L) underlies the artificially dichotomized variable. The proposed correlation coefficient recovers the product moment correlation coefficient between X and L from a fourfold table of X and Y. The suggested correlation coefficient ν is contrasted with the phi correlation and the biserial η. The biserial η was proposed by Karl Pearson and is conceptually related to the new correlation coefficient. However, in addition, Pearson's biserial η invokes the assumption that the marginal distribution of L is normal, which contradicts its basic assumptions and thus does not recover the true correlation of L and X. Finally, an approximation is provided to simplify the calculation of ν and its standard error.     

Maximum likelihood estimation of the joint covariance matrix for sections of tests given to distinct samples with application to test equating

Consider an old testX consisting ofs sections and two new testsY andZ similar toX consisting ofp andq sections respectively. All subjects are given testX plus two variable sections from either testY orZ. Different pairings of variable sections are given to each subsample of subjects. We present a method of estimating the covariance matrix of the combined test (X ₁, ...,X _s ,Y ₁, ...,Y _p ,Z ₁, ...,Z _q ) and describe an application of these estimation techniques to linear, observed-score, test equating.The author is indebted to Paul W. Holland and Donald B. Rubin for their encouragement and many helpful comments and suggestions that contributed significantly to the development of this paper.This research was supported by the Program Statistics Research Project of the ETS Research Statistics Group.     

Correlations between rats' spatial location and intracranial stimulation administration affects rate of acquisition and asymptotic level of time allocation preference in the open field

The present experiment explores the effects of the response (1-sec occupancy of a target area in an open field)-reinforcer (intracranial stimulation) contingency on time allocation in the open field in rats. The probability of reinforcement given response (X) and the probability of reinforcement given nonresponse (Y) were varied randomly across sessions within a subject. The 21 contingency treatments explored included all possible combinations of values (0, .1, .2, .3, .4, .5) of X and Y such that X ≥ Y. The results indicate that rate of acquisition and asymptotic level of time allocation preference to the target area are negatively related to the value of Y (for any given value of X). Variations in X (for any given value of Y) were less effective. Evaluation of proposed contingency metrics revealed that the Weber fraction (X − Y)/X most closely approximates performance, and that the value of the difference detection threshold derived from the Weber fraction is a constant.     

Children Use Temporal Cues to Learn Causal Directionality

The ability to learn the direction of causal relations is critical for understanding and acting in the world. We investigated how children learn causal directionality in situations in which the states of variables are temporally dependent (i.e., autocorrelated). In Experiment 1, children learned about causal direction by comparing the states of one variable before versus after an intervention on another variable. In Experiment 2, children reliably inferred causal directionality merely from observing how two variables change over time; they interpreted Y changing without a change in X as evidence that Y does not influence X. Both of these strategies make sense if one believes the variables to be temporally dependent. We discuss the implications of these results for interpreting previous findings. More broadly, given that many real‐world environments are characterized by temporal dependency, these results suggest strategies that children may use to learn the causal structure of their environments.     

Intuitive prediction: ecological validity versus representativeness

Insufficiently regressive intuitive predictions have been attributed to mistaken reliance on the representativeness heuristic. In contrast, we suggest that intuitive predictions stem from a conceptualization of ‘goodness of prediction’ that differs from the accepted statistical definition in terms of error minimization, namely, ecological validity—that is, representation of the substantive characteristics of the predicted variable Y and its distribution as well as of the relationship between Y and the predictor X—rather than minimization of prediction errors. Simultaneous satisfaction of the above representation requirements is achieved by multivalued prediction: The prediction of different Y′ values for the same X value, resulting in conditional distributions Y′|X for at least some X values. Empirical results supporting this hypothesis are presented and discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

Forward blocking in human learning sometimes reflects the failure to encode a cue–outcome relationship

In two “allergist” causal judgement experiments, participants were trained with a blocking design (A?+?|AB+). The procedure allowed different food cues to be paired with different fictitious allergic reactions. On test, participants were asked to rate the causal efficacy of the target cues and to recall the particular allergic reaction (outcome) that had followed each cue during training. Forward blocking was observed on the causal judgement measure and on the outcome recall measure in both Experiment 1 and Experiment 2. A backward blocking contingency was also trained in Experiment 2 (AB?+?|A+). Backward blocking was not observed either on the causal judgement or on the outcome recall measure. The evidence from the recall measure suggests that forward blocking in this task results from a failure to encode the B–outcome relationship during training. Associative and nonassociative mechanisms of forward blocking are discussed.     

Local measures of association: Estimating the derivative of the regression line

A local measure of association that allows both heteroscedasticity and a non‐linear association was developed during the 1990s. The basic goal is to measure the strength of the association between X and Y, given X, when Y=θ(X)+τ(X)ε for some unknown functions θ(X) and τ(X). Application of this method requires the estimation of the derivative of θ(X). The focus in this paper is on four alternatives to a very slight modification of the method used by Doksum et al. when estimating this derivative. The main result is that in simulations, a certain robust analogue of their method dominates in terms of mean squared error, even under normality. The bias of the method is found to be small but a little larger than the bias associated with the method used by Doksum et al. The method is based in part on bootstrap bagging followed by a lowess smooth.     

The contribution of vowel duration,F0 contour,and frication duration as cues to the/juz/-/jus/distinction

A model was quantified to describe the integration of vowel duration, fricative duration, and fundamental frequency (F₀) contour as cues to final position fricatives differing in voicing. The basic assumptions are that perceived vowel duration and perceived frication duration are cues to the identity of final position fricatives and that both F₀ contour and vowel duration influence perceived vowel duration. Binary choice and rating responses to synthetic stimuli varying independently along the three dimensions were collected. The results were consistent with the assumption that F₀ contour operates by modifying perceived vowel duration, which is a direct cue. Unfortunately, the nature of the modification appears to be very similar in form to that which results from the integration of two independent cues in syllable identification. Therefore, the results do not allow a rejection of the idea that the perception of F₀ contour may directly cue the identity of final position fricatives.     

The Relation of the Galvanic Skin Reflex Recovery Curve to Reactivity,Resistance Level,and Perspiration

The effect of stimulus compounding in classical conditioning was investigated by conditioning one group of rats to a compound CS consisting of a buzzer and light and then conditioning separate groups of rats to the individual elements of the compound CS. On hurdle-jump test trials, the group of Ss conditioned to the compound CS performed better than Ss conditioned to the elements of the compound. Strength of conditioning to each of the elements of the compound CS was about equal. There was some evidence of a summation effect resulting from conditioning to the compound CS. Strength of conditioning to the compound CS was somewhat greater than the sum of the response strengths conditioned to the elements of the compound CS.     

Translation and Cultural Comparison: Some Epistemological Reflections

In its traditional guise, cross-cultural psychology is a science of comparative measurement. Its chief method is the regulated observation or recording of behaviour in different cultural milieux and its quantitative conversion into a common metric. This method allows for the estimation of differences across cultures on the strength or magnitude of the behaviour. We can therefore speak of one cultural group doing more of Y, or being more Y, than some other group, where Y is a conceptually and operationally defined behaviour taken to apply equally well to both groups. The culture-independence of the definition supports examination of how the magnitude of the behaviour may be determined or conditioned by some cultural variable X. According to this picture, culture (the independent variable) differs from place to place and the features by which it differs produce more or less of the universally defined behaviour (the dependent variable) under study. The hypothetical contingency of ‘culture affecting behaviour’ that underlies this approach is thereby maintained. In this paper, I use the problem of translation to cast doubt on this picture of cross-cultural research and the inferential strength of its comparative method. In opposition, I argue that we never measure the same behaviour across cultures if behaviour is understood as socially significant action. Rather, the specification of analogous actions across cultures is a highly uncertain approximation involving the inevitable projection of one’s own conceptual scheme. I argue further that most social phenomena of interest to cross-cultural psychologists cannot be adequately defined in a manner that divorces them from the local linguistic conventions and normative frameworks through which they are realized as part of cultural life. For this reason, cross-cultural psychology cannot effectively model itself on the natural sciences. It is as much hermeneutics as psychometrics.     

The psychological side of Hempel’s paradox of confirmation

People often test hypotheses about two variables (X andY), each with two levels (e.g.,X1 andX2). When testing “IfX1, thenY1,” observing the conjunction ofX1 andY1 is overwhelmingly perceived as more supportive than observing the conjunction ofX2 andY2, although both observations support the hypothesis. Normatively, theX2&Y2 observation provides stronger support than theX1&Y1 observation if the former is rarer. Because participants in laboratory settings typically test hypotheses they are unfamiliar with, previous research has not examined whether participants are sensitive to the rarity of observations. The experiment reported here showed that participants were sensitive to rarity, even judging a rareX2&Y2 observation more supportive than a commonX1&Y1 observation under certain conditions. Furthermore, participants’ default strategy of judgingX1&Y1 observations more informative might be generally adaptive because hypotheses usually regard rare events.     

Significance tests to determine the direction of effects in linear regression models

Previous studies have discussed asymmetric interpretations of the Pearson correlation coefficient and have shown that higher moments can be used to decide on the direction of dependence in the bivariate linear regression setting. The current study extends this approach by illustrating that the third moment of regression residuals may also be used to derive conclusions concerning the direction of effects. Assuming non‐normally distributed variables, it is shown that the distribution of residuals of the correctly specified regression model (e.g., Y is regressed on X) is more symmetric than the distribution of residuals of the competing model (i.e., X is regressed on Y). Based on this result, 4 one‐sample tests are discussed which can be used to decide which variable is more likely to be the response and which one is more likely to be the explanatory variable. A fifth significance test is proposed based on the differences of skewness estimates, which leads to a more direct test of a hypothesis that is compatible with direction of dependence. A Monte Carlo simulation study was performed to examine the behaviour of the procedures under various degrees of associations, sample sizes, and distributional properties of the underlying population. An empirical example is given which illustrates the application of the tests in practice.     

The nontruncated marginal of a truncated bivariate normal distribution

Inference is considered for the marginal distribution ofX, when (X, Y) has a truncated bivariate normal distribution. TheY variable is truncated, but only theX values are observed. The relationship of this distribution to Azzalini's skew-normal distribution is obtained. Method of moments and maximum likelihood estimation are compared for the three-parameter Azzalini distribution. Samples that are uniformative about the skewness of this distribution may occur, even for largen. Profile likelihood methods are employed to describe the uncertainty involved in parameter estimation. A sample of 87 Otis test scores is shown to be well-described by this model.     

Blocking and nonsimultaneous compounds: Comparison of responding during compound conditioning and testing

Three blocking experiments were run using a conditional emotional response procedure with rats as subjects. In each experiment, following initial conditioning to a light stimulus, blocking rats were conditioned to a compound in which a short-duration (30-second) noise was superimposed on the terminal portion of the longer-duration light. In Experiment 1, the light was always three minutes in duration; in Experiment 2, the light was switched from a constant (three-minute) to a variable (0.5–5.0 minute) duration at the start of compound conditioning; in Experiment 3, the light was variable in duration throughout conditioning. Control rats received the same compound conditioning experiences as the blocking rats but did not receive prior conditioning to the light by itself. These temporal manipulations had strong and systematic influence on the rats’ pattern of responding during compound conditioning. Most notably, experience with a constantduration light resulted in both blocking and compound animals showing little conditional suppression to the early conditional stimulus portion of light by itself, followed by strong conditional suppression to the terminal 30 seconds of light plus noise. When testing was done with the noise in isolation subsequent to compound conditioning, however, an equally strong blocking effect was obtained across all the temporal manipulations. In all cases, the blocking animals showed much less conditional suppression to the noise than did the compound control animals. This lack of correspondence between the rats’ responding during compound conditioning and their response to the noise by itself is theoretically puzzling. The confounding effect of inhibition of delay may provide at least a partial explanation of this pattern of results.     

The basic laws of conditioning differ for elemental cues and cues trained in compound

The cue-duration effect (i.e., longer cues result in less conditioned responding than shorter cues) was examined as a function of whether cues were trained alone or in compound. Compound (AX) or elemental (X) cues of either long or short duration were paired with the unconditioned stimulus. In testing with X alone, the cue-duration effect was observed with elementally trained cues, but not with compound cues. Instead, stronger responding resulted from training with long compound cues relative to short compound cues (i.e., a reversed cue-duration effect). Moreover, an overshadowing effect (i.e., decreased responding due to compound conditioning) was observed when conditioning was conducted with a short cue, but compound conditioning resulted in enhanced responding when it was conducted with a long cue (i.e., reversed overshadowing). These findings are consistent with other recent demonstrations that some laws of learning that apply to elementally trained cues do not similarly apply to cues trained in compound.     

Configural-like effects observed in the course of second-order conditioning in rats

After receiving first-order CER (conditioned emotional response) conditioning, four groups of rats were exposed to the first-order conditioned stimulus (CS₁) and a new stimulus (CS₂) according to one of three paradigms. For different groups, CS₂ preceded CS₁, was simultaneously compounded with it, or was explicitly unpaired with it. There was evidence of second-order conditioning (SOC) only when CS₂ preceded CS₁, with the effect diminishing when SOC training was continued for a long time. Though suppression to CS₁ extinguished in the course of SOC training, animals which had experienced CS₂ preceding CS₁ suppressed almost completely when later tested with CS₁ alone. This “protection-from-extinction” is formally similar to an analogous effect observed in the simultaneous compound group. Animals appear to “configure” elements of both simultaneous and successive compounds.     

What mediation analysis can (not) do

The present article is concerned with a common misunderstanding in the interpretation of statistical mediation analyses. These procedures can be sensibly used to examine the degree to which a third variable (Z) accounts for the influence of an independent (X) on a dependent variable (Y) conditional on the assumption that Z actually is a mediator. However, conversely, a significant mediation analysis result does not prove that Z is a mediator. This obvious but often neglected insight is substantiated in a simulation study. Using different causal models for generating Z (genuine mediator, spurious mediator, correlate of the dependent measure, manipulation check) it is shown that significant mediation tests do not allow researchers to identify unique mediators, or to distinguish between alternative causal models. This basic insight, although well understood by experts in statistics, is persistently ignored in the empirical literature and in the reviewing process of even the most selective journals.     

Stimulus and temporal cues in classical conditioning

In 2 experiments, separate groups of rats were given stimulus conditioning, temporal conditioning, untreated control and (in Experiment 2) learned irrelevance control procedures, followed by a compound with both stimulus and temporal cues. Stimulus conditioning consisted of a random 15-s duration conditioned stimulus (CS) followed by food; temporal conditioning consisted of food-food intervals of fixed 90 s (Experiment 1) or fixed 75 + random 15 s (Experiment 2). The stimulus group abruptly increased responding after CS onset, and the temporal group gradually increased responding over the food-food interval. When the food-food interval was fixed 90 s, the temporal cue exerted stronger control in the compound, whereas when the food-food interval was fixed 75 + random 15 s, the stimulus cue exerted stronger control. The strength of conditioning, temporal gradients of responding, and cue competition effects appear to reflect simultaneous timing of multiple intervals.     

Blocking of conditioned suppression: role of the first compound trial.

Four experiments, all employing the conditioned suppression of licking in thirsty rats, examined the extent to which reinforcement of one component, A, of a compound conditioned stimulus, AB, would "block" conditioning to the other element, B, on the first compound trial. Suppression to B was unaffected by prior reinforcement of A; that is, no evidence of blocking was obtained. If additional reinforced trials were given to the AB compound, further conditioning to B was blocked by prior reinforcement of A. Thus blocking appeared to take at least one trial to develop. These results suggest that blocking is not due to any competition between stimuli for association with reinforcement, but is a consequence of the animals' ignoring the added element once they have learned that it is redundant.