The effects of increasing familiarity on infants' reactions to adult strangers

The influence of the presence and novelty of an adult stranger on the reactions of 12-mo-old infants was investigated. Subjects were placed near their mothers in a room containing a new toy and either the same, a different, or no adult stranger for 8 4-min trials. Results indicated that the Same-Adult Group spent more time near the adult, less time near and touching their mothers, and more time near and touching the toys than the Different-Adult Group. These trends emerged as the trials progressed, and evidenced the Same-Adult Group's growing familiarity with the adult. The No-Adult Group spent less time near or touching their mothers and more time near or touching the toys than the Different-Adult Group, but did not differ from the Same-Adult Group on these responses. The findings suggest that fearful or cautious reactions to adult strangers disappear rapidly as the adult becomes familiar and point to the value of studying the process whereby the infant becomes familiar with new people.     

The meaning of observed violence: Real vs. fictional violence and consequent effects on aggression and emotional arousal

Sixty male subjects were either attacked or treated neutrally by a confederate, after which each saw a videotape of two men fighting. Subjects were informed that fight was either real or fictitious or were given no explanation of it. Subjects who had previously been attacked and had observed the fight under a set to perceive it as real were subsequently more punitive in their treatment of the confederate than subjects in all other conditions. The combination of prior attack and observation of real violence also sustained blood pressure (BP) at near the level produced by the attack, whereas BP of attacked subjects in the other conditions declined during the time the fight was observed. Palmar sweat measures revealed that observation of real violence was more arousing than observation of fictitious fighting. The results are discussed in terms of the effects that the reality of observed violence has on emotional arousal.     

Discriminability and criterion differences between extraverts and introverts during vigilance

In a signal detection task introverts were better able than extraverts to distinguish between the signal and noise distribution (p < .001) and also set a higher criterion point for their responses (p < .01). The results show that superior vigilance in introverts reported by other investigators is due to two processes.     

Fixed and optional stopping models for two-choice discrimination times

Several current models for choice- or discrimination-time experiments represent the stimulus as a sequence of independent and identically distributed observations. This paper develops and compares models based on two different stopping rules that a subject might use to terminate his sampling process and convert his perceptual evidence into an observable response. The fixed and optional stopping rules yield different predicted forms for the speed/accuracy tradeoff function and for the relation between mean and variance of response times. These predictions are developed in the general case and then specialized for certain conditions of symmetry, so that the expressions are easier to apply and to compare between models. A later section considers how changes in stopping criteria (either between or within experimental trials) affect predictions about mean response times for correct responses and errors, and then uses these ideas to relate the optional stopping rule for the Random Walk models to those of the Accumulator models. A final section considers specialized models for stimulus detection and intensity discrimination that assume Poisson-distributed sensory input, and relates these models to the present fixed stopping model.     

Expectation theories of decision making for duplex gambles

Complete tests of subjectively expected utility (SEU), subjectively expected value (SEV), expected utility (EU) and expected value (EV) theories were made for duplex gambles without measuring subjective probability or subjective utility. All gambles were hypothetical and offered on booklets. The duplex gambles consisted of winning gambles, which offered a chance to win a certain amount of money or to break even; and losing gambles, which offered a chance to lose a certain amount of money or break even.The results indicated that SEU, SEV and EU theories could not account for the strategies of 33%, 53% and 86% of the Ss respectively in the losing form of gambles, while EV theory accounted for 78% of the behavior of Ss.In the winning form of gambles, SEU, SEV and EU theory held for 77%, 65%, and 54% of the Ss respectively, while EV theory held for only 40% of the Ss. Suggestions for further research were made.     

The role of inference in children's comprehension and memory for sentences

In a series of studies, young children often failed to construct and remember inferred relationships which they were capable of understanding. A cued recall procedure was employed to assess the relative effectiveness of implicit and explicit word prompts for sentence memory. The implicit cues were much less effective than the explicit cues for 6–7 yr old children while the cue types did not differ for 11–12 yr olds. Instructions to imitate the actions described by the sentences eliminated the memory difference for the young children. Developmental improvement in spontaneous inferential operations and intentional plans to remember are mechanisms which appear to yield an elaborated memory representation and greater access routes through indirect and implied relationships.