Three-year-olds’ memory for a person met only once at the age of 12 months: Very long-term memory revealed by a late-manifesting novelty preference

This study examined three-year-olds’ verbal and non-verbal memory for a person met only once after a 28 month interval. Children in the Test group (N = 50) had participated in an earlier experiment at our lab at the age of 12 months where they met one of two possible experimenters. At this past event half of the children were tested by one, the other half by the other experimenter. At the follow-up, run by a naïve experimenter, the children were shown two videos from the original experiment in a visual paired comparison task: One with the specific experimenter testing them at the original visit (the Target) and one of the other experimenter (the Foil), with whom they had no experience. When explicitly asked, the children’s responses did not differ from chance. However, eye-tracking data revealed a late-manifesting novelty preference for the “Foil” person indicating memory for the “Target” person met once before.     

Experimenter effects on responses to explicitly sexual stimuli

Experimenter effects on responses to explicitly sexual stimuli were investigated in 63 single undergraduate males and 89 single undergraduate females. A completely factorial design with sex of subject, sex of experimenter, and experimenter's style of interacting (informal vs formal) as the independent factors was employed. While the variables under investigation did not have an overriding effect on the outcome measures, at least one experimenter attribute was discovered to significantly influence a large percentage of the variables assessed: The data suggest that informal experimenters permit less socially desirable responses and more generalized arousal than formal experimenters. In addition to replicating earlier work on experimenter effects, the present study serves to delineate a possible set of cues by which experimenters may influence their subjects' arousal to explicitly sexual stimuli.     

Experimental pain thresholds influenced by sex of experimenter

Thresholds for pressure pain were tested in 64 adult human subjects (age: M=22.0 yr., SD=7.5). The subjects were young adults drawn from a student population. They were divided into two groups of men and two groups of women, with 16 participants in each group. A female experimenter tested one group of men and a male experimenter tested the other group. The women were tested in a similar way by an experimenter of the same sex for one group and the opposite sex for the other group. The two experimenters were dressed in a manner that emphasised their gender roles. The men tested by a female experimenter showed a higher average pain threshold than the men tested by a male experimenter, but there was no difference in the average pain thresholds of the two groups of women.     

Fourteen-month-olds know what others experience only in joint engagement

We investigated how 14‐month‐old infants know what others know. In two studies, an infant played with each of two objects in turn while an experimenter was present. Then the experimenter left the room, and the infant played with a third object with an assistant. The experimenter returned, faced all three objects, and said excitedly ‘Look! Can you give it to me?’ In Study 1, the experimenter experienced each of the first two toys in episodes of joint visual engagement (without manipulation) with the infant. In response to her excited request infants gave the experimenter the object she did not know, thus demonstrating that they knew which ones she knew. In Study 2, infants witnessed the experimenter jointly engage around each of the experienced toys with the assistant, from a third‐person perspective. In response to her request, infants did not give the experimenter the object she had not experienced. In combination with other studies, these results suggest that to know what others have experienced 14‐month‐old infants must do more than just perceive others perceiving something; they must engage with them actively in joint engagement.     

The role of goal-directed behavior in intention attribution in children

In this study, we addressed the question of the nature of the information needed by 13-month-old infants to understand another agent's intentions. In two experiments, an experimenter was either unable or unwilling to give a toy to an infant. Importantly, an implement (a gutter in which the toy could roll down toward the infant) was used to make the experimenter's behavior as similar as possible in the two conditions. When the experimenter remained still in both conditions, infants did not behave differently according to the experimenter's intentions, suggesting that they did not infer them. By contrast, in a second experiment, where the experimenter performed an action directed toward the gutter in both conditions, the infants looked away from the experimental setting more often and longer in the unwilling condition than in the unable condition. They also looked more toward the experimenter in the unable condition than in the unwilling condition. Therefore, we conclude that an agent's intentional attitude can already be inferred by a 13-month-old provided that this intention is concretely shown through a goal-directed action.     

Essentialism in the absence of language? Evidence from rhesus monkeys (Macaca mulatta)

We explored whether rhesus monkeys (Macaca mulatta) share one important feature of human essentialist reasoning: the capacity to track category membership across radical featural transformations. Specifically, we examined whether monkeys – like children ( Keil, 1989 ) – expect a transformed object to have the internal properties of its original category. In two experiments, monkeys watched as an experimenter visually transformed a familiar fruit (e.g. apple) into a new kind of fruit (e.g. coconut) either by placing a fruit exterior over the original, or by removing an exterior shell and revealing the inside kind of fruit. The experimenter then pretended to place an inside piece of the transformed fruit into a box which the monkey was allowed to search. Results indicated that monkeys searched the box longer when they found a piece of fruit inconsistent with the inside kind, suggesting that the monkeys expected that the inside of the transformed fruit would taste like the innermost kind they saw. These results suggest that monkeys may share at least one aspect of psychological essentialism: They maintain category‐specific expectations about an object’s internal properties even when that object’s external properties change. These results therefore suggest that some essentialist expectations may emerge in the absence of language, and thus raise the possibility that such tendencies may emerge earlier in human development than has previously been considered.     

Physical Oracles: The Turing Machine and the Wheatstone Bridge

Earlier, we have studied computations possible by physical systems and by algorithms combined with physical systems. In particular, we have analysed the idea of using an experiment as an oracle to an abstract computational device, such as the Turing machine. The theory of composite machines of this kind can be used to understand (a) a Turing machine receiving extra computational power from a physical process, or (b) an experimenter modelled as a Turing machine performing a test of a known physical theory T. Our earlier work was based upon experiments in Newtonian mechanics. Here we extend the scope of the theory of experimental oracles beyond Newtonian mechanics to electrical theory. First, we specify an experiment that measures resistance using a Wheatstone bridge and start to classify the computational power of this experimental oracle using non-uniform complexity classes. Secondly, we show that modelling an experimenter and experimental procedure algorithmically imposes a limit on our ability to measure resistance by the Wheatstone bridge. The connection between the algorithm and physical test is mediated by a protocol controlling each query, especially the physical time taken by the experimenter. In our studies we find that physical experiments have an exponential time protocol; this we formulate as a general conjecture. Our theory proposes that measurability in Physics is subject to laws which are co-lateral effects of the limits of computability and computational complexity.     

The use of experimenter-given cues by South African fur seals (<Emphasis Type="Italic">Arctocephalus pusillus</Emphasis>)

Dogs can use a variety of experimenter-given cues such as pointing, head direction, and eye direction to locate food hidden under one of several containers. Some authors have proposed that this is a result of the domestication process. In this study we tested four captive fur seals in a two alternative object choice task in which subjects had to use one of the following experimenter-given cues to locate the food: (1) the experimenter pointed and gazed at one of the objects, (2) the experimenter pointed at only one of the objects, (3) the experimenter gazed at only one of the objects, (4) the experimenter glanced at only one of the objects, (5) the experimenter pointed and gazed at one of the objects but was sitting closer to one object than to the other, (6) the experimenter pointed only with the index finger at one of the objects, (7) the experimenter presented a replica of one of the objects. The fur seals were able to use cues which involved a fully exposed arm or a head direction, but failed to use glance only, the index finger pointing and the object replica cues. The results showed that a domestication process was not necessary to develop receptive skills to cues given by an experimenter. Instead, we hypothesize that close interactions with humans prior to testing enabled fur seals to use some gestural cues without formal training. We also analyzed the behavior of the seals depending on the level of difficulty of the task. Behavioral signs of hesitation increased with task difficulty. This suggests that the fur seals were sensitive to task difficulty.     

Experimenter naiveté and imaginal judgments

Finke and Kurtzman report that fields of resolution increase with increases in the diameter of both perceived and imagined circular patterns. Their study apparently was conducted by an experimenter who was aware of the hypotheses under test. In contrast to these results, we find no such increase for imagined circular patterns when the experimenter is not aware of the experimental predictions, even though our subjects received imagery training as extensive as that used by Finke and Kurtzman. Our results cannot readily be attributed to differences between the experiments, other than those associated with experimenter naiveté, for we replicated Finke and Kurtzman's observations that (a) the fields of resolution in perception increase with both the diameter and the relative brightness of the patterns and (b) the fields of resolution in imagery do not increase with the relative brightness of the patterns. Our results also challenge Finke and Kurtzman's contentions that imagery and perception are treated as functionally equivalent at area-processing levels of the visual system but not at contrast-processing levels.     

The effect of exposure to weapons on aggressive behavior from a cross-cultural perspective

An attempt was made to replicate the Berkowitz and Le Page (1967) study with a Swedish population, and to extend it. A pilot study was conducted to find out what other possible stimuli carry aggressive connotations and what stimuli might have aggression-inhibiting qualities. One hundred male high school students were either angered or not angered by an accomplice of the experimenter and then given an opportunity to counter-aggress. For one group of subjects there were weapons near the shock key and half of these subjects were told to handle them. For another group there were aggression-inhibiting stimuli present, e.g., a baby bottle. In other conditions there were no stimuli present. Parts of the TAT were administered to shed some light on the catharsis phenomenon. Subjects exposed to weapons gave the largest number of shocks to their partners, whereas the control group and the group exposed to aggression-inhibiting stimuli did not differ. The “weapons effect” was obtained with a Swedish population.     

Recognition and categorization of biologically significant objects by rhesus monkeys (Macaca mulatta): the domain of food.

To survive, organisms must be able to identify edible objects. However, we know relatively little about how humans and other species distinguish food items from non-food items. We tested the abilities of semi-free-ranging rhesus monkeys (Macaca mulatta) to learn rapidly that a novel object was edible, and to generalize their learning to other objects, in a spontaneous choice task. Adult monkeys watched as a human experimenter first pretended to eat one of two novel objects and then placed replicas of the objects at widely separated locations. Monkeys selectively approached the object that the experimenter had previously eaten, exhibiting a rapidly induced preference for the apparently edible object. In further experiments in which the same objects were used as tools or were manipulated at the face but not eaten, we fail to observe an approach bias, providing evidence that the monkeys' pattern of approach in the earlier experiments was specific to objects that were eaten. Subsequent experiments tested how monkeys generalized their preference for an edible object by first allowing them to watch a human experimenter eat one of two objects and then presenting them with new objects composed of the same substance but differing from the original, edible object in shape or color. Monkeys ignored changes in the shape of the object and generalized from one edible object to another on the basis of color in conjunction with other substance properties. Finally, we extended this work to infant rhesus monkeys and found that, like adults, they too used color to generalize to novel food objects. In contrast to adults, however, infants extended this pattern of generalization to objects that were acted on in other ways. These results suggest that infant monkeys form broader object categories than adults, and that food categories become sharpened as a function of maturational or experiential factors.     

Effects of personality and loss of anonymity on aggression: a reevaluation of deindividuation.

Zimbardo's deindividuation hypothesis was reexamined by individuating some subjects. Twelve four-person groups administered shock to a confederate in a 2 x 2 x 2 factorial design with two levels of social individuation (subjects' level of anonymity to group members), two levels of nonsocial individuation (subjects' opportunity to give identifying information to the experimenter on a word association test) and two levels of individual differences. It was found that subjects, who individuated themselves by giving information to the experimenter on the word association test showed more, not less, antisocial behavior. Furthermore, this increased antisocial behavior was exhibited only by externally oriented subjects: those with an external locus of control and a low mysticism score. Some of those more antisocial subjects were also more likely to report feeling like they stood out from the group. It was concluded that antisocial behavior in this paradigm may thus be a response to experimenter demand felt most strongly when subjects felt most identifiable.     

Delayed effects of practiced versus unpracticed responses after observation of movie violence

University men participating in an ostensible study of “impression formation” first received either an insulting or neutral evaluation of themselves from their supposed partner and then watched either a prize fight or an exciting but nonaggressive scene. After this, they either had an opportunity to evaluate their partner right away or they had to wait an hour before evaluating him. On scoring the subjects' written statements about the partner (to be seen by him and the experimenter), it was found that (1) for those given the immediate opportunity to be aggressive, the violent movie increased the strength of the angered subjects' initial attack on their partner over that displayed by the similarly insulted men shown the nonaggressive film; (2) if the angry subjects had to wait an hour before evaluating their partner, there was no difference between the aggressive and nonaggressive movie groups; (3) the aggression-heightening effect of the violent scene did carry over the intervening hour, however, if the insulted men had been given the earlier opportunity to evaluate their partner. It is suggested that the performance of an aggressive response soon after seeing an aggressive film increases the persistence of the aggressive reactions over time.     

Personal problem-solving system for scoring TAT responses: preliminary validity and reliability data

Personal problem solving has emerged as an important construct in the cognitive-behavioral literature, yet there is a lack of clinically useful, performance-based measures practitioners can use to assess the personal problem-solving skills of their clients. Two studies evaluated the validity and reliability of a scoring system for measuring personal problem-solving processes via the Thematic Apperception Test (TAT; Morgan & Murray, 1935). In Experiment 1, undergraduate students (N = 87) completed two measures of personal problem solving, as well as three TAT cards, which were scored using the Personal Problem-Solving System (PPSS; Renan, 1990). In Experiment 2, an additional group of undergraduates (N = 56) responded to three TAT cards on two separate occasions and also completed a different measure of personal problem solving. Results from both studies supported the use of the PPSS for scoring TAT responses to assess personal problem-solving processes. Suggestions for future research are highlighted.     

Do infants have a sense of fairness?

Two experiments examined infants' expectations about how an experimenter should distribute resources and rewards to other individuals. In Experiment 1, 19-month-olds expected an experimenter to divide two items equally, as opposed to unequally, between two individuals. The infants held no particular expectation when the individuals were replaced with inanimate objects, or when the experimenter simply removed covers in front of the individuals to reveal the items (instead of distributing them). In Experiment 2, 21-month-olds expected an experimenter to give a reward to each of two individuals when both had worked to complete an assigned chore, but not when one of the individuals had done all the work while the other played. The infants held this expectation only when the experimenter could determine through visual inspection who had worked and who had not. Together, these results provide converging evidence that infants in the 2nd year of life already possess context-sensitive expectations relevant to fairness.     

Imitation and social responsiveness in autistic children

Fifteen autistic children, ages 4–6 years, participated in the present study. Imitation and object permanence skills were assessed. Language and social behaviors were observed during free play. Children were also exposed to three interactive procedures that differed in developmental sophistication. The experimenter either (1) simultaneously imitated the child's actions, (2) modeled a familiar action, or (3) modeled a novel action. It was found that the autistic children who had a low level of imitative ability (Piaget's Stages 2–3) were more socially responsive, showed more eye contact, and played with toys in a less perseverative manner when the experimenter imitated their behavior than when the experimenter modeled either a familiar or a novel action. When the experimenter modeled a familiar as opposed to a novel action, these children were more likely to spontaneously imitate the experimenter. The autistic children with more highly developed imitation skills, however, responded similarly to all conditions. They also were generally more socially and verbally responsive. These results suggest that developmental status is an important variable in designing intervention programs for severely impaired children.We would like to express our appreciation to the autistic children who participated in the study, and to their parents, and to the staff of the T.E.A.C.C.H. Division, University of North Carolina for their help and cooperation. We would also like to thank Karen Cotten, Pete Giordano, Vickie Hall, Lee Hendrix, Shari Jernigan, Kevin Lumley, Cindy Seagroves, Sheryl Solomon, Kathy Stetson, and Jeannie Teasley for their assistance in data collection and coding, and Mary Lynn Eckert and Anne Stanford for their secretarial assistance. Cathy Dent provided helpful suggestions on earlier drafts of the paper. Support was provided by UNC Research Council.     

Bobwhite quail (Colinus virginianus) hatchlings track the direction of human gaze

Gaze following allows individuals to detect the locus of attention of both conspecifics and other species. However, little is known about how this ability develops. We explored the emergence of bobwhite quail hatchlings’ ability to track human gaze by assessing their avoidance behavior in an open arena under five testing conditions: (1) a Direct Gaze condition, in which an experimenter looking down was positioned above one of two approach areas; (2) a Gaze Follow condition in which an experimenter, positioned equidistant between two approach areas, directed his/her gaze towards one of the areas; (3) a Masked Gaze Follow condition, in which the experimenter wore a mask during the Gaze Follow test; (4) a Deprived Face Experience condition, in which hatchlings were deprived of experience with human faces prior to the Gaze Follow test; and (5) a Control condition in which no experimenter was present during testing. Results revealed that hatchlings from the Direct Gaze condition preferred the non-gazed approach area at all ages tested. Hatchlings from the Gaze Follow condition preferred the non-gazed approach area at 48 and 72 h, but not at 24 h of age. In contrast, hatchlings from the Masked Gaze Follow, Deprived Face and Control conditions did not prefer either approach area at any age tested. These results indicate that experience with human faces plays a key role in the rapid emergence of gaze following behavior in bobwhite quail hatchlings.     

The influence of experimenter attitude on the performance of children of different cognitive ability levels

We investigated the influence of the experimenter's attitude on children's performance in a classification task. We chose 96 children (M age: 5 years, 9 months) on the basis of their performance in a spontaneous classification task. Forty-eight children made partial alignments on the basis of a link established from one object to the next (O-level group); 48 looked for objects having one common property (P-level group). The children had to perform a dichotomy task in two testing situations: one with a caring experimenter, and one with an indifferent experimenter. In the O-level group, the children's performance was superior when the experimenter was caring even though they did not seem to notice the difference between the two attitudes. P-level children clearly distinguished the experimenter attitudes, but their performance remained the same. To determine children's actual abilities accurately, researchers must take into account children's interactions with both objects and partners.     

Prior experience and patterning in a prisoner's dilemma game

Female college students first played a pseudo-prisoner's dilemma (PPD) game with the experimenter, who followed a fixed strategy. In the first experiment the experimenter's strategies for different groups of subjects were: (a) play tit-for-tat; (b) play randomly; (c) always cooperate; (d) always defect (‘cooperation’ and ‘defection’, defined as in an actual prisoner's dilemma game). Only the tit-for-tat group increased cooperation over trials; other groups decreased cooperation. After playing the PPD with the experimenter, subjects played an actual prisoner's dilemma (PD) game with each other. In the PD game, subjects began cooperating moderately but cooperation deteriorated regardless of what the experimenter's strategy had been in the earlier (PPD) game. In a second experiment, subjects again played a PPD game with the experimenter and then played a PD game with each other. Half played one trial at a time as in the first experiment while half played in patterns of four trials at a time. In the PD game, patterning of trials retarded the development of mutual defection regardless of previous experience. The cooperation-preserving effect of patterning of trials in this social task is compared with similar effects on individual tasks involving self-control and risk-aversion. © 1998 John Wiley & Sons, Ltd.     

The effects of reinforcement on the modification, maintenance, and generalization of social responses of mental patients

Social greeting responses of three withdrawn, chronic schizophrenics were experimentally modified. Initially, none of the subjects spoke to an experimenter. Prompts and cigarette reinforcement were employed to produce increases in the rates of greetings. Then, the prompts were faded so that the greetings came under the control of the presence of the experimenter. Reversal and subsequent reinforcement procedures were employed to demonstrate that the responses were controlled by their consequences. Next, the schedule of cigarette reinforcement was leaned out so that greetings continued to occur in the absence of cigarette reinforcement. However, low or zero rates of greetings occurred in the presence of a second experimenter. Five new experimenters employed the prompting, fading, reinforcement, and schedule-leaning procedures. Subsequently, all subjects emitted appropriately high rates of greetings in the presence of the second experimenter. Without further application of the experimental procedures, greetings were still occurring in the presence of both the first and second experimenters almost three months later.