THE VISUAL SYSTEM'S MEASUREMENT OF INVARIANTS NEED NOT ITSELF BE INVARIANT

Abstract— When two shapes that differ in orientation or size have to be compared or objects have to be recognized from different viewpoints, the response time and error rate art systematically affected by the size of the geometric difference. In this report, we argue that these effects are not necessarily solid evidence for the use of mental transformations and against the use of invariants by the visual system. We report an experiment in which observers were asked to give affine-invariant coordinates of a point located in an affine frame defined by three other points. The angle subtended by the coordinate axes and the ratio of the lengths of their unit vectors systematically affected the measurement errors. This finding demonstrates that the visual system's measurement of invariants need not itself be invariant.     

Poisson signal-detection theory: Link between threshold models and the Gaussian assumption

The Gaussian model of signal detection cannot fit asymmetric data as long as the variances of the distributions are kept equal. It is therefore common practice to assume unequal variances in order to fit these data. But this assumption leads to the well-known crossover problem. The present paper provides new arguments for the abandonment of the Gaussian model with unequal variances. In its stead, this paper reevaluates multiple-parallel-threshold models. In particular, the Poisson model turns out to be very useful: it can handle data with any degree of asymmetry, giving a reasonable interpretation of the two parameters of the receiver-operating characteristic. The three-state-threshold model (Krantz, 1969) is given a new interpretation in light of the Poisson model. The slope of Poisson double-probability plots turns out to be much closer to unity than is predicted by the Gaussian approximation.     

Differential effects of person in the dog and in the human

People have marked effects on dog’s heart rate, with great individual variations for different persons. Apparently people to which the dog is attached have the greatest effect upon heart rate. Replications of the animal experiments using the psychotherapist and two other people revealed no effects upon the heart rate of a schizophrenic human. In the human the effects of people are probably best demonstrated in connection with verbal communication.     

Stress regulation and incision in borderline personality disorder-a pilot study modeling cutting behavior

Emotion dysregulation in Borderline Personality Disorder (BPD) is characterized by high baseline negative intensity, high reactivity, and slow return to baseline. Patients with BPD often engage in self-injurious behavior because it leads to immediate relief of stress levels. We aimed to assess stress regulation as well as the influence of tissue damage on subjective (aversive tension) and objective (heart rate) stress correlates in BPD. In 14 unmedicated patients with BPD and 18 healthy controls, a stress induction was followed by an incision into the forearm conducted by an investigator. For aversive tension, we found elevated baseline levels as well as slower return to baseline in BPD. In controls, incision resulted in a short-term increase of aversive tension, whereas tension and heart rate decreased in the BPD group. Our preliminary results support the hypothesis that tissue damage may play a role in disturbed stress regulation in BPD.     

Nonsymbolic numerical magnitude comparison: reliability and validity of different task variants and outcome measures, and their relationship to arithmetic achievement in adults

The numerical ratio effect (NRE) and the Weber fraction (w) are common metrics of the precision of the approximate numbers sense (ANS), a cognitive mechanism suggested to play a role in the development of numerical and arithmetic skills. The task most commonly used to measure the precision of the ANS is the numerical comparison task. Multiple variants of this task have been employed yet it is currently unclear how these affect metrics of ANS acuity, and how these relate to arithmetic achievement. The present study investigates the reliability, validity and relationship to standardized measures of arithmetic fluency of the NRE and w elicited by three variants of the nonsymbolic number comparison task. Results reveal that the strengths of the NRE and w differ between task variants. Moreover, the reliability and validity of the reaction time NRE and the w were generally significant across task variants, although reliability was stronger for w. None of the task variants revealed a correlation between ANS metrics and arithmetic fluency in adults. These results reveal important consistencies across nonsymbolic number comparison tasks, indicating a shared cognitive foundation. However, the relationship between ANS acuity and arithmetic performance remains unclear.     

Dogs (Canis lupus familiaris) are susceptible to the Kanizsa’s triangle illusion

Animal Cognition - The ability to complete partially missing contours is widespread across the animal kingdom, but whether this extends to dogs is still unknown. To address this gap in knowledge,...