Testing the assumptions of exponential,additive reaction time models

Two assumptions commonly made by choice reaction time (RT) models are (1) that certain experimental tasks can be found that cause an extra processing stage to be inserted into the cognitive process and (2) that the duration of one or more processing stages is random with an exponential distribution. Few rigorous tests of either assumption exist. This paper reviews existing tests and presents several new results that can be used to test these assumptions. First, in the case in which the duration of an inserted stage is exponentially distributed, it is shown that the observable RT density functions must always intersect at the mode of the density requiring the extra processing stage. Second, when only the first assumption (Assumption 1) is made, it is shown that the cumulative RT distribution functions and, in many cases, the hazard functions must be ordered. Finally, when only Assumption 2 is assumed, it is shown that, under fairly weak conditions, the taft of the RT density function must be exponential. The first two results are applied to data from a memory scanning experiment, and the two assumptions are found to receive tentative support     

An experimental psychology laboratory system for the Apple II microcomputer

A system for on-line control of experiments is described that uses the Apple II microcomputer and requires no knowledge of programming. This system, APT, is used to construct test files, randomize stimulus order, and conduct experiments. Construction of an experiment is very easy through use of an interactive program. APT provides powerful options for controlling stimulus duration, feedback, and response type. Programs are available to conduct either a sequence of tests without any experimenter present or a single experiment. Over 200 subjects, ranging from 18 to 86 years of age, have completed a battery of cognitive and abilities tests using the system.     

Immediate carbon monoxide estimates and self-reported smoking

Because carbon monoxide (CO) is an easily understood danger of cigarette smoking, new breath CO analyzers may be useful in cessation programs. Self-reported cigarette consumption and breath CO correlated .70 using a 90-sec. CO-determination method. Smokers averaging 17 daily cigarettes had average breath CO of 24 parts per million (ppm), falling to 7.71 ppm for smokers claiming at least 24-hr. abstinence. Corresponding carboxyhemoglobin (COHb) estimates were 4.34% (slightly above World Health Organization 4% safety limit) and 1.39%. Smoking clinics can use CO-monitoring devices for feedback or surveillance, although feedback would provide the most benefits for participants.     

Manipulating the word frequency effect in free recall

A recall advantage for common words was not evidenced when subjects generated or rated the list words on the basis of commonness and on a semantic, phonological, or orthographic basis prior to recall. Recall of the same set of words following only structural judgments of the words resulted in the usual recall advantage for common words. Results were not consistent with interpretations based only on the associative strengths of the recalled items. A process based on categorization of the words to be recalled was suggested as an alternative explanation.     

The effects of alcohol and extreme provocation on the use of a highly noxious electric shock

Intoxicated and nonintoxicated subjects were given the opportunity to administer a potentially injurious level of shock to an opponent who behaved in either a provocative or an extremely provocative manner. The provocative opponent attempted to administer high-intensity shocks to the subject. The extremely provocative opponent attempted to administer high-intensity shocks and the potentially injurious level of shock. The intoxicated subjects in the extreme provocation condition evidenced the greatest increase in the use of the potentially injurious shock. It was concluded that aggression is a function of the interaction of alcohol consumption and level of provocation.     

Perceived objectivity and the effects of evaluative reinforcement upon compliance and self-evaluation in blacks

Two experiments were conducted to investigate the effects of positive and negative reinforcements upon black college students. In the first experiment subjects received either positive or negative reinforcement from a black or a white Evaluator. Behavioral change (compliance) was greater in response to negative reinforcement from a black Evaluator than in response to negative reinforcement from a white Evaluator, while there were no divergent effects of Evaluator's Race upon compliance with positive reinforcement. The same pattern obtained in subjects' self-evaluations. The second experiment offered a test of the hypothesis that the objectivity of black Evaluators was perceived as greater than that of white Evaluators, and that a manipulation aimed at equating the Evaluators on objectivity would attenuate the effects of Evaluator's Race upon compliance and self-evaluation in response to negative reinforcement. These hypotheses were generally supported by the results.     

Physical Distance and Helping: Some Unexpected Benefits of “Crowding In” on Others1

One hundred and sixty undergraduates (80 males, 80 females) participated in a field experiment designed to examine the influence of invasions of personal space and sex of requester upon subsequent helping. On the basis of previous research, it was predicted that helping would be markedly inhibited by invasions of personal space, and that the magnitude of these effects would be mediated by the sex of the individuals who perpetrated such intrusions. Surprisingly, however, results indicated that subsequent helping was actually facilitated by such invasions. A follow-up investigation replicated these results and suggested that they stemmed from a tendency on the part of subjects to perceive close physical approach by the requester as indicative of a high need for assistance.