Misperception of exponential growth

Exponential growth in numerical series and graphs is grossly underestimated in an intuitive extrapolation task. Subjects’ extrapolations are well described by a model with two parameters only: one for underestimation of the nonlinear growth, the other for linear compensation. The size of the effect is considerable; it is not unusual that two-thirds of the subjects produce estimates below 10% of the normative value. The effect increases with the exponent of the stimulus series, and with addition of a constant to the stimulus series. Neither special instructions about the nature of exponential growth nor daily experience with growth processes enhanced the extrapolations.

     

The effect of fluctuations of response criterion and sensitivity in a signal detection experiment

Summary Two basic conditions for the application of methods provided by signal detection theory are that the subject's response criterion and sensitivity remain stable during a series of presentations. It is experimentally shown that these conditions are significantly violated. This results in an average underestimation of d', amounting to 8 to 10 % on the average, but with large individual differences.     

The pond-and-duckweed problem; Three experiments on the misperception of exponential growth

The representation of duckweed multiplying itself in a pond is used as a research paradigm to study underestimation of exponential growth. The advantage of this paradigm is that the growth process is presented in a direct non-numerical way. The results show that the underestimation observed in earlier studies where growth was presented by means of tables or graphs, occurs in the pond-and-duckweed situation as well. By manipulating the way the process is presented it is possible to obtain some insight into the sampling strategies used by the subjects when they subjectively extrapolate the perceived processes. These experiments lead to the conclusion that subjects base their extrapolations on three or four samples only.     

Coordination Between Arm and Leg Movements During Locomotion

To evaluate the contrasting dynamical and biomechanical interpretations of the 2:1 frequency coordination between arm and leg movements that occurs at low walking velocities and the 1:1 frequency coordination that occurs at higher walking velocities, the authors conducted an experiment in which they quantified the effect of walking velocity on the stability of the frequency and phase coordination between the individual limb movements. Spectral analyses revealed the presence of 2:1 frequency coordination as a consistent feature of the data in only 3 out of 8 participants at walking velocities ranging from 1.0 to 2.0 km/h, in spite of the fact that the eigenfrequencies of the arms were rather similar across participants. The degree of interlimb coupling, as indexed by weighted coherence and variability of relative phase, was lower for the arm movements and for ipsilateral and diagonal combinations of arm and leg movements than for the leg movements. Furthermore, the coupling between all pairs of limb movements was found to increase with walking velocity, whereas no clear signs were observed that the switches from 2:1 to 1:1 frequency coordination and vice versa were preceded by loss of stability. Therefore, neither a purely biomechanical nor a purely dynamical model is optimally suited to explain these results. Instead, an integrative model involving elements of both approaches seems to be required.     

Within‐Pair Consistency in Child Witnesses: The Diagnostic Value of Telling the Same Story

Judges and jurors often rely on consistency for assessing veracity. The present study examined the diagnostic value of within‐pair consistency to predict truth‐telling in pairs of children aged 8 to 10 years. Twenty‐three pairs were questioned about one experienced event and one imagined event (which they had discussed before questioning). Within‐pair consistency was significantly higher for experienced events than for imagined events. The diagnostic value of within‐pair consistency to predict truth‐telling was, however, modest: approximately one out of three judgments based on this cue would have been mistaken. Analyses of children's discussions of the imagined events revealed that interview questions about topics that had been discussed before questioning did not effectively discriminate experienced and imagined events, providing support for theoretical assumptions underlying the unanticipated‐question approach. Practical recommendations for police interviewers are provided. Copyright © 2013 John Wiley & Sons, Ltd.     

Crashing Memories and the Problem of ‘Source Monitoring’

We demonstrate that it is relatively easy in a real life situation to make reasonably intelligent adults believe that they have witnessed something they actually have not seen themselves, but only heard reports about from others, and to make them report about particular details of the event. The event concerns the crashing of an El Al Boeing 747 on apartment buildings in Amsterdam. Over sixty per cent of the subjects said they had seen the crash on television, although no television film exists. Unexpectedly, women proved themselves significantly more vulnerable to this effect than men.     

The memory of concentration camp survivors

This study is concerned with the question whether extremely emotional experiences, such as being the victim of Nazi concentration camps, leave traces in memory that cannot be extinguished. Relevant data were obtained from testimony by 78 witnesses in a case against Marinus De Rijke, who was accused of Nazi crimes in Camp Erika in The Netherlands. The testimonies were collected in the periods 1943–1947 and 1984–1987. A comparison between these two periods reveals the amount of forgetting that occurred in 40 years. Results show that camp experiences were generally well-remembered, although specific but essential details were forgotten. Among these were forgetting being maltreated, forgetting names and appearance of the torturers, and forgetting being a witness to murder. Apparently intensity of experiences is not a sufficient safeguard against forgetting. This conclusion has consequences for the forensic use of testimony by witnesses who were victims of violent crimes.     

The fate of memory: comment on McCloskey and Zaragoza

McCloskey and Zaragoza (1985) argue that misleading postevent suggestions do not affect the availability of originally encoded information. Their hypothesis stems from empirical work using a modified paradigm in which no effect of postevent information is observed. Although their "no impairment" hypothesis is plausible, careful consideration of the predictions of their experimental test suggests that it may be insufficiently sensitive to reveal the impact of postevent information. A small effect of postevent information can be observed when their paradigm is repeated with a more sensitive recognition test. McCloskey and Zaragoza's no impairment hypothesis is also difficult to reconcile with numerous reports of "blend" memories that reflect a compromise between the original and postevent information.