Bayesian t tests for accepting and rejecting the null hypothesis

Progress in science often comes from discovering invariances in relationships among variables; these invariances often correspond to null hypotheses. As is commonly known, it is not possible to state evidence for the null hypothesis in conventional significance testing. Here we highlight a Bayes factor alternative to the conventional t test that will allow researchers to express preference for either the null hypothesis or the alternative. The Bayes factor has a natural and straightforward interpretation, is based on reasonable assumptions, and has better properties than other methods of inference that have been advocated in the psychological literature. To facilitate use of the Bayes factor, we provide an easy-to-use, Web-based program that performs the necessary calculations.     

Bayesian tests of measurement invariance

Random item effects models provide a natural framework for the exploration of violations of measurement invariance without the need for anchor items. Within the random item effects modelling framework, Bayesian tests (Bayes factor, deviance information criterion) are proposed which enable multiple marginal invariance hypotheses to be tested simultaneously. The performance of the tests is evaluated with a simulation study which shows that the tests have high power and low Type I error rate. Data from the European Social Survey are used to test for measurement invariance of attitude towards immigrant items and to show that background information can be used to explain cross‐national variation in item functioning.     

Two tests of the stuck-in-time hypothesis

The authors report 2 experiments that test the stuck-in-time hypothesis, which argues that animals cannot time-date events and thus do not remember when events occurred and do not anticipate future events. In Experiment 1, rats in the experimental condition could earn a large reward by reentering the 1st arm that they visited on a radial maze. They did not learn to reenter this arm early and did no better than did a control group that was not given a large reward for reentering the first arm. In Experiment 2, rats in the experimental group could earn a large reward by delaying entry into a distinctive arm. These rats did not learn to delay entry into the distinctive arm, and they performed no better than did the control-group rats, which did not receive a large reward for delayed entry. These experiments provide further evidence in support of the stuck-in-time hypothesis.     

The semantic congruity effect: Some tests of the expectancy hypothesis

Subjects comparing items in memory along some dimension are usually quicker to specify the lesser (than the greater) of two low magnitude items and the greater (than the lesser) of two high magnitude ones. One account explains this congruity effect as due to subjects instructed to specify the higher as expecting high magnitude items to follow and the reverse being true for subjects specifying the lesser. Three experiments tested this expectancy hypothesis. In experiment 1, subjects were set to the actual size range of each pair before the pair was shown but the congruity effect still occurred. In experiments 2 and 3, subjects compared critical pairs from a narrow size range plus more from either the same or much broader ranges. Times to compare the critical pairs were the same regardless of the range of the other pairs that subjects were exposed to. These results are strong evidence against the expectancy hypothesis.     

The false consensus effect: A meta-analysis of 115 hypothesis tests

False consensus refers to an egocentric bias that occurs when people estimate consensus for their own behaviors. Specifically, the false consensus hypothesis holds that people who engage in a given behavior will estimate that behavior to be more common than it is estimated to be by people who engage in alternative behaviors. A meta-analysis was conducted upon 115 tests of this hypothesis. The combined effects of the tests of the false consensus hypothesis were highly statistically significant and of moderate magnitude. Further, the 115 tests of false consensus appear to be relatively heterogeneous in terms of significance levels and effect sizes. Correlational analyses and focused comparisons indicate that the false consensus effect does not appear to be influenced by the generality of the reference population, nor by the difference between alternative choices in actual consensus. However, the significance and magnitude of the false consensus effect was significantly predicted by the number of behavioral choices/estimates subjects had to make, and the sequence of measurement of choices and estimates. These patterns of results are interpreted as being inconsistent with the self-presentational, motivational explanation for the false consensus effect.     

The generation effect: Further tests of the lexical activation hypothesis

Three experiments compared recognition memory for word versus nonword responses when they had been either read or generated using a rhyme rule and either a word or nonword stimulus. That is, either the wordshop or the nonwordthop was generated from either the wordchop or the nonwordphop. In Experiment 1, the lexicality of the stimulus and response terms was manipulated orthogonally between subjects; in Experiments 2 and 3, it was manipulated orthogonally within subjects. In Experiment 3, subjects also made a lexical (word-nonword) decision about each response term after it had been read or generated. In all three experiments, memory performance was better for generated than read responses. This generation effect occurred only if the response term was a word, regardless of whether the stimulus term was a word or a nonword. These results are discussed in terms of the roles that lexical memory and response unitization play in the generation effect.     

Effects of mood on memory: Experimental tests of a mood-state-dependent retrieval hypothesis and of a mood-congruity hypothesis

Summary In the present experiment a mood-state-dependent retrieval hypothesis and a mood-congruity hypothesis are tested. The first hypothesis states that recall is higher when mood at test matches mood at input than when it does not match. The second hypothesis states that people learn more about events that match their mood state. Both hypotheses are consistent with the network model of mood and memory proposed by Bower and his colleagues. Our study was conducted to test the cited hypotheses with normal subjects (instead of highly hypnotizable subjects as in the studies by Bower et al.) and with a comparatively mild mood-induction technique. Another aim was to test different predictions from the two hypotheses.We experimentally varied mood (happy vs. sad), both at learning and at recall by using the Velten technique. Additionally, the emotional content (pleasant vs. neutral vs. unpleasant) of the text to be learned was manipulated.The empirical evidence with some restrictions favored the mood-state-dependent hypothesis and disagreed with the mood-congruity hypothesis. Possible explanations for the failure to obtain a mood-congruity effect are offered, and the results are discussed with reference to a network model of mood and memory.     

The timing deficit hypothesis of dyslexia and its implications for Hebrew reading

Vast amounts of neuropsychological evidence have been collected in recent years in support of the hypothesis that developmental dyslexia is caused not only by phonological deficits, but also by timing deficits that affect all senses (e.g., Tallal, Miller, & Fitch, 1995; Stein & Walsh, 1997). In parallel, recent developments in the study of Hebrew reading place heavy emphasis on root awareness in the mental lexicon and early root extraction in the process of word identification (e.g., Frost, Forster, & Deutch, 1997). The present study creates a link between the timing hypothesis and the special demands of Hebrew reading. The performance of dyslexics and normally reading children is compared on tasks requiring visual extraction of trigrams that approximates extracting roots out of Hebrew words. Partial findings show that dyslexics take longer and make more errors while performing trigram extractions on all levels examined, and that sequentiality in the task affects dyslexics and skilled readers in different ways.     

Infants perceiving and acting on the eyes: tests of an evolutionary hypothesis

It has been hypothesized that an evolutionarily ancient mechanism underlies the ability of human infants to detect and act upon the direction of eye gaze of another human face. However, the evidence from behavioral studies with infants is also consistent with a more domain-general system responsive to the lateral motion of stimuli regardless of whether or not eyes are involved. To address this issue three experiments with 4-month-old infants are reported that utilize a standard face-cueing paradigm. In the first experiment an inverted face was used to investigate whether the motion of the pupils elicits the cueing effect regardless of the surrounding face context. In the second experiment pupil motion and eye gaze direction were opposed, allowing us to assess their relative importance. In a third experiment, a more complex gaze shift sequence allowed us to analyse the importance of beginning with a period of mutual gaze. Overall, the results were consistent with the importance of the perceived direction of motion of pupils. However, to be effective in cueing spatial locations this motion needs to be preceded by a period of direct mutual gaze (eye contact). We suggest that evolution results in information-processing biases that shape and constrain the outcome of individual development to eventually result in adult adaptive specializations.     

The psychological refractory period of stopping

The author examined whether the act of control of stopping is subject to the psychological refractory period (PRP) and whether stopping causes a PRP for the processing of subsequent stimuli. The task was to execute or to stop a rapid finger tapping. PRP interference was predicted for double-stimulation trials, in which 2 signals to tap or stop were presented in rapid succession. The experiments showed that stopping ongoing action is subject to and produces PRP interference similar to starting. Responses to signals to continue an ongoing action do not produce PRP interference. The results suggest that selection or initiation of new responses, but not mere response choice, constituted the processing bottleneck that caused the PRP in the present task. Further results indicate that the inhibition of not-yet-executed actions, in contrast to action termination, does not suffer PRP interference and that response inhibitions and terminations should be distinguished. ((c) 2003 APA, all rights reserved)     

Mechanisms of eyewitness suggestibility: tests of the explanatory role hypothesis

In a recent paper, Chrobak and Zaragoza (Journal of Experimental Psychology: General, 142(3), 827–844, 2013) proposed the explanatory role hypothesis, which posits that the likelihood of developing false memories for post-event suggestions is a function of the explanatory function the suggestion serves. In support of this hypothesis, they provided evidence that participant-witnesses were especially likely to develop false memories for their forced fabrications when their fabrications helped to explain outcomes they had witnessed. In three experiments, we test the generality of the explanatory role hypothesis as a mechanism of eyewitness suggestibility by assessing whether this hypothesis can predict suggestibility errors in (a) situations where the post-event suggestions are provided by the experimenter (as opposed to fabricated by the participant), and (b) across a variety of memory measures and measures of recollective experience. In support of the explanatory role hypothesis, participants were more likely to subsequently freely report (E1) and recollect the suggestions as part of the witnessed event (E2, source test) when the post-event suggestion helped to provide a causal explanation for a witnessed outcome than when it did not serve this explanatory role. Participants were also less likely to recollect the suggestions as part of the witnessed event (on measures of subjective experience) when their explanatory strength had been reduced by the presence of an alternative explanation that could explain the same outcome (E3, source test + warning). Collectively, the results provide strong evidence that the search for explanatory coherence influences people’s tendency to misremember witnessing events that were only suggested to them.     

Functional anatomy of the null hypothesis and of tests of it

The author compared simulations of the "true" null hypothesis (zeta) test, in which sigma was known and fixed, with the t test, in which s, an estimate of sigma, was calculated from the sample because the t test was used to emulate the "true" test. The true null hypothesis test bears exclusively on calculating the probability that a sample distance (mean) is larger than a specified value. The results showed that the value of t was sensitive to sampling fluctuations in both distance and standard error. Large values of t reflect small standard errors when n is small. The value of t achieves sensitivity primarily to distance only when the sample sizes are large. One cannot make a definitive statement about the probability or "significance" of a distance solely on the basis of the value of t.     

The frontal hypothesis of cognitive aging: factor structure and age effects on four frontal tests among healthy individuals

With 101 healthy aging adult participants, the authors investigated whether executive functions are a unitary concept. The authors established the factor structure of the Wisconsin Card Sorting Test (WCST; E. A. Berg, 1948), the Stroop color and word test (C. J. Golden, 1978), verbal fluency using the Controlled Oral Word Association Test (COWAT; Benton, 1967), and the Digits Backwards subtest of the Wechsler Adult Intelligence Scale-Revised (WAIS-R; D. Wechsler, 1981). The authors also evaluated the extent to which age and other demographic variables predicted common underlying properties of these frontal tests. Results revealed an age-related decline in executive abilities differentially reflected by the selected tasks. These data suggest caution using the COWAT to evaluate executive abilities in older people. The authors interpret findings to support the unitary view of executive abilities and the executive decline proposed by the frontal hypothesis.     

The optional shift performance of reflective and impulsive girls

The optional shift performance of 52 reflective and 50 impulsive second-grade girls was assessed under two response-consequence conditions: (a) reward for correct responses only, and (b) reward for correct responses and a penalty for incorrect responses. Reflection—impulsivity was defined on the basis of performance on the Matching Familiar Figures test. The reflectives showed a significantly greater percentage of reversal shifts than the impulsives. The impulsives showed more reversal shifts under the penalty condition than the reward alone condition whereas the performance of the reflectives was the same in both consequence conditions. A test of statistical association indicated that reflection—impulsivity may be as strongly related to reversal shift performance as age and perceptual pretraining. The results are interpreted as indicating that individual differences in perceptual search strategies may have an important influence on the problem-solving behavior of children.