Relative numerosity discrimination by chimpanzees (Pan troglodytes): evidence for approximate numerical representations

Two adult chimpanzees were trained on a relative “numerosity” discrimination task. In each trial, two arrays containing different numbers of red dots were presented on a CRT monitor. The subjects were required to choose the array containing the larger number of dots. In Experiment 1, using numerosities between 1 and 8, 28 different pairs were presented repeatedly, and accuracy scores were analyzed to explore which cues the chimpanzee subjects utilized to perform the task. Multiple regression analyses revealed that the subjects’ performance was (1) not simply controlled by the “numerical” difference between arrays, but that it was (2) best described by Fechner’s Law–that is accuracy increased linearly with the logarithmic value of the numerical difference between arrays divided by the number in the larger of the two arrays. This relationship was maintained when using much larger numerosities (Experiment 3). In Experiment 2, the chimpanzees were tested on the effects of total area and density by manipulating dot size and presentation area. The results revealed that these factors clearly affected the subjects’ performance but that they could not alone explain the results, suggesting that the chimpanzees did use relative numerosity difference as a discriminative cue.     

Natural paths to invention: Reinventing the wheel

Four studies explored candidate pathways underlying the invention of the “wheeled cart.” In Study 1, heuristics were abstracted from subjects’ judgements of different precursor paths to the wheeled cart. In Studies 2 and 3, these heuristics were tested for generality across different precursor paths. In Study 4, subjects ranked the order of incorporating parts into the wheeled cart. While the studies cannot “prove” that the wheeled cart developed in one of the candidate ways, they show that interesting and important heuristics of invention can be uncovered from subject’s judgements. Examining candidate paths to important inventions is a method worthy of exploration. Together, the four studies indicate that important historical inventions might be examined experimentally. Doing so yields potentially important invention heuristics.     

Natural paths to invention: Reinventing the wheel

Four studies explored candidate pathways underlying the invention of the “wheeled cart.” In Study 1, heuristics were abstracted from subjects’ judgements of different precursor paths to the wheeled cart. In Studies 2 and 3, these heuristics were tested for generality across different precursor paths. In Study 4, subjects ranked the order of incorporating parts into the wheeled cart. While the studies cannot “prove” that the wheeled cart developed in one of the candidate ways, they show that interesting and important heuristics of invention can be uncovered from subject’s judgements. Examining candidate paths to important inventions is a method worthy of exploration. Together, the four studies indicate that important historical inventions might be examined experimentally. Doing so yields potentially important invention heuristics.     

How wearing eyeglasses affects facial recognition

Two studies examine the ability to recognize previously seen persons embedded among foils. Subjects in Study I tried to identify 20 persons among 20 foils (an easy task), whereas subjects in Study II tried to identify 50 persons among 50 foils (a difficult task). There were three independent variables: the stimulus person’s eyeglasses and sex, and the subject’s depth of processing. The first two independent variables were varied by photographs of males and females with or without glasses; depth of processing was manipulated by having subjects either judge traits (deep) or describe appearance (shallow) of the stimulus persons during the initial exposure phase. Responses were scored for “hits,” and “false alarms,” and these were transformed intod’ and β indices. Generally speaking, eyeglasses hindered facial recognition; deep processing facilitated the difficult recognition task more than the easy task; and there was a same-sex advantage in recognition. Analyses of subjects’ judgments suggest that glasses lessen attractiveness and discriminability. This project was partially supported by a grant from the Faculty Development Committee, Hanover College.     

Common marmosets (<Emphasis Type="Italic">Callithrix jacchus</Emphasis>) do not utilize social information in three simultaneous social foraging tasks

Social foraging is suggested to increase foraging efficiency, as individuals might benefit from public information acquired by monitoring the foraging activities of other group members. We conducted a series experiments with captive common marmosets (Callithrix jacchus) to investigate to what extent marmosets utilize social information about food location when foraging simultaneously with conspecifics. Subjects were confronted with dominant and subordinate demonstrators in three experiments which differed in the amount of information about food location available to the demonstrators. In all three experiments, the focal subjects’ performance in the social condition was not enhanced in comparison to a non-social control condition. Because we could rule out kleptoparasitism and aggressive displacements as explanations, we argue that the subjects’ tendency for scramble competition by avoiding others and dispersing over the foraging area seems to inhibit or mask the acquisition of social information about the location of rewarded patches.     

Coming out discourses of Asian American lesbians

The authors examined the accounts of a small group of Asian American lesbians regarding their experiences forming their sexual identities. Discourse analysis and the social constructionist approach were applied to the subjects’ accounts of their coming out. Focus group subjects’ discussions were transcribed in order to depict the practices they employed to render their experiences meaningful to themselves and others. There was an internal dialectical process between the subjects’ subjective and objective reality, during which they came to terms with their subjective identity, or came out to themselves. There was also an external dialectical process between the subjects and society, during which they negotiated with their objective world for their subjective identity, or came out to the public in general and to their families in particular. The research suggests that in these dialectical processes, Asian cultural values and beliefs served as the means through which the conflict between the subjects’ interiority and their social networks was reconciled. The desire to reabsorb the subjects served to motivate the family members to work collaboratively to overcome cultural barriers to acceptance. The authors are grateful for the help of Robert Dominguez and all the participants who made the study possible.     

Spatial perception and control

We investigated whether the perceived vanishing point of a moving stimulus becomes more accurate as one’s degree of control over the stimulus increases. Either alone or as a member of a pair, participants controlled the progression of a dot stimulus back and forth across a computer monitor. They did so via right and left buttonpresses that incremented the dot’s velocity rightward and leftward, respectively. The participants in the individual condition had control of both buttons. Those in the group condition had control of only one. As the participants slowed the dot to change its direction of travel, it unexpectedly disappeared. Localizations of the vanishing point became more accurate as the participants’ control over the dot increased. The data bridge a gap between accounts of localization error that rely solely on stimulus and cognitive factors, and accounts derived from research on action and spatial perception, which tend to rely on action-planning factors.     

Why does ADHD Confer Risk for Cigarette Smoking? A Review of Psychosocial Mechanisms

Research has documented that adolescents and young adults with attention-deficit/hyperactivity disorder (ADHD) are at increased risk for cigarette smoking, but less attention has examined why this risk exists. The current paper reviews the literature on different psychosocial mechanisms [self-medication hypothesis, social factors (social modeling, social impairments), cognitive factors (attitudes, coping skills), and psychological variables (ADHD symptom dimensions, comorbidity)] that might explain this increased smoking risk. Results of the review suggest that, while the self-medication hypothesis has some theoretical merit, it has not been adequately examined among adolescents and young adults with ADHD. Further, cognitive and social factors may be important mechanisms that help to explain the association between ADHD and cigarette smoking, but research in these areas is sparse. Finally, a larger body of literature suggests that different psychological aspects of ADHD (e.g., comorbidity, symptom dimensions) are related to smoking. Interpretation of findings of many of these studies was hindered due to significant methodological problems and the lack of a guiding theoretical orientation. Potential theories that might facilitate future work in this area are discussed. Future research should continue to explore these important psychosocial mechanisms as well as gene–environment interactions in examining the link between ADHD and cigarette smoking.     

DEVELOPMENT AND EVALUATION OF TREATMENT PARADIGMS FOR THE SUPPRESSION OF SMOKING BEHAVIOR1

A multiple-baseline component-analysis design was employed to assess the effectiveness of three treatment programs for suppressing the cigarette smoking behavior of 24 subjects. Satiation, cognitive control, and contingent shock procedures were evaluated. The results demonstrated a consistent relationship between contingent shock and suppression of smoking. It was further indicated that subjects should be exposed to the number of sessions necessary to achieve total suppression in order to gain maximally from treatment and to avoid relapse. Neither the satiation component nor the cognitive control component was correlated with clear, permanent decrements in smoking frequencies. To date, no other treatment program has demonstrated the dramatic effects of the contingent shock procedures used in the present study.     

Predictors of Parent-Reported Attention-Deficit/Hyperactivity Disorder in Children Aged 6–7 years: A National Longitudinal Study

This study examined the prenatal, postnatal and demographic predictors of parent-reported attention-deficit/hyperactivity disorder (ADHD) in an Australian population-based sample. Participants were families participating in the Longitudinal Study of Australian Children. There were approximately even numbers of males (51%) and females (49%) in the sample. Predictors of parent-reported ADHD status at Wave 2 (children aged 6–7 years) which were measured at Wave 1 (children aged 4–5 years) included cigarette smoking and alcohol use during pregnancy (prenatal factors); maternal postnatal depression, intensive care at birth, birth weight, and gestation (postnatal factors); and child gender, primary caregiver education, income, family composition, and maternal age at childbirth (socio-demographic factors). We found that male gender, cigarette smoking during pregnancy, and maternal postnatal depression were the only significant predictors (at the 5% level) of ADHD in the adjusted analysis (N = 3,474). Our results are consistent with previous findings that male gender and cigarette smoking during pregnancy are risk factors for ADHD. In addition, we found that postnatal depression was predictive of parent-reported ADHD.     

Contrafreeloading and the value of control over visual stimuli in Japanese macaques (<Emphasis Type="Italic">Macaca fuscata</Emphasis>)

Contrafreeloading, which means that animals work for food even though identical food is freely available, has been reported in animals’ feeding behavior. This phenomenon has been assumed to be explained by the information primacy model, in which the information about a food resource as well as the food itself is valuable for animals. This study confirmed a contrafreeloading-like phenomenon using movies as rewards rather than food in Japanese macaques (Macaca fuscata) and investigated the motivational system that exists behind contrafreeloading. In the experiment, movies that were presented dependently on subjects’ responses (earned movies) and movies that were presented automatically (free movies) were supplied simultaneously. The subjects continued to make responses to obtain the presentation of the earned movies although identical movies were available as free movies. These results provide the first evidence of contrafreeloading that occurs with movie rewards. The motivation maintaining the contrafreeloading behavior for movies may be control over the environment according to the competence theory.     

Explicitly modeling the effects of aging on response time

Research into the effects of aging on response time has focused on Brinley plots. Brinley plots are constructed by plotting mean response times for older subjects against those for young subjects for a set of experimental conditions. The typical result is a straight line with a slope greater than 1 and a negative intercept. This linear function has been interpreted as showing that aging leads to a general slowing of cognitive processes. In this article, we show that the slope of the Brinley plot is actually a measure of the relative standard deviations of older versus young subjects’ response times; it is not a measure of general slowing. We examine current models of the effects of aging on mean response time and show how they might be reinterpreted. We also show how a more comprehensive model, Ratcliff’s diffusion model (1978), can account for Brinley plot regularities and, at the same time, provide an account of accuracy rates, the shapes of response time distributions, and the relative speeds of error and correct response times, aspects of the data about which models designed to account for Brinley plots are mute. We conclude by endorsing a research approach that applies explicit models to response time data in aging in order to use the parameters of the model to interpret the effects of aging.     

Tracking the train of thought from the laboratory into everyday life: An experience-sampling study of mind wandering across controlled and ecological contexts

In an experience-sampling study that bridged laboratory, ecological, and individual-differences approaches to mind-wandering research, 72 subjects completed an executive-control task with periodic thought probes (reported by McVay & Kane, 2009) and then carried PDAs for a week that signaled them eight times daily to report immediately whether their thoughts were off task. Subjects who reported more mind wandering during the laboratory task endorsed more mind-wandering experiences during everyday life (and were more likely to report worries as off-task thought content). We also conceptually replicated laboratory findings that mind wandering predicts task performance: Subjects rated their daily-life performance to be impaired when they reported off-task thoughts, with greatest impairment when subjects’ mind wandering lacked metaconsciousness. The propensity to mind wander appears to be a stable cognitive characteristic and seems to predict performance difficulties in daily life, just as it does in the laboratory     

An instrumental cigarette smoke monitor designed for the direct measurement of smoke particulate matter generated in human smoking studies

An instrumental cigarette smoke monitor (CSM) system designed for human smoking studies has been developed and validated using a smoking machine as a human surrogate. The cigarette holder contains both smoke-mixing and flow-measurement orifices and a smoke-concentration sensor. Smoke flow through the holder and smoke concentration in the holder are determined simultaneously. The two signals are multiplied electronically and the product signal integrated. The integrated response is directly proportional to the amount of particulate matter collected immediately downstream of the holder, regardless of cigarette type or the particular way in which the cigarette is smoked. The CSM is sufficiently sensitive to quantitatively determine the amount of smoke TPM generated from cigarettes in the 1-mg Federal Trade Commission tar-delivery category.     

Components of analogical reasoning in a mildly head injured population

This study sought to investigate the effects of mild head injury on a particular type of cognitive ability, verbal analogical reasoning. The performance of 19 individuals with head injuries was compared to a group of 30 control subjects matched for age, education, and gender on 100 verbal analogies. Solution times and error rates were modeled. Unstandardized regression weights for individual subjects were correlated with subjects’ performance on a number of standardized ability tests. Results showed that compared to the control subjects, the head injured subjects: (a) were significantly slower to solve the analogies, and were particularly slow to perform certain processes: encoding/inference and comparison; (b) tended to show greater variability in performance; and (c) had data that had a poorer componential model fit. The data suggest that analogical reasoning is affected by a head injury, and that certain information processes may be responsible for performance deficits.     

Influence of item identification on the memory performance of mentally retarded and nonretarded adults

The role of item identification in the memory performance of mentally retarded and nonretarded adults was examined by varying the identification and memory parameters of a sequential same-different task. In Study 1, retarded subjects' identification ability was demonstrated to be less efficient than nonretarded subjects' ability. In Study 2, target duration and interstimulus interval were varied. Memory performance differed between groups, and the memory deficit for retarded subjects was demonstrated to be independent of their identification deficit. The target durations in Study 2 were relatively brief, and in Study 3, the target duration was increased to insure that all subjects could identify the target. Mentally retarded subjects were demonstrated to have a memory deficit. The results were discussed in terms of possible sources of the memory deficit.     

Vantage point in episodic memory

University undergraduates undertook a series of manual tasks (e.g., shaping objects out of clay) and later recalled the experiences they had while doing so from either afield or anobserver vantage point. In the former case, the subjects mentally reinstated the original task environment as if they were seeing it again through their own eyes; in the latter condition, the original task environment was envisioned from the perspective of a detached spectator. Analysis of the subjects’ recollections revealed marked differences in the contents of field and observer memories. For instance, whereas field memories afforded richer accounts of the affective reactions, physical sensations, and psychological states that the subjects experienced as they performed the tasks, observer memories included more information about how the subjects looked, what they did, or where things were. Discussion focuses on prospects for future research whose aim would be to investigate the forensic and clinical implications of the field/observer distinction.