Biomedical subjects

Svein Magnussen

Publications and source records attributed to Svein Magnussen.

9 recordsLinked to original sources

PubMed2006

Credibility of the emotional witness: a study of ratings by court judges.

Previous studies have shown that the emotional behavior displayed during testimony may affect the perceived credibility of the witness. The present study compares credibility ratings by Norwegian court judges with those made by lay people. The participants viewed one of three video-recorded versions of a rape victim's statement, role played by a professional actress. The statement was given in a free-recall manner with one of three kinds of emotions displayed, termed congruent, neutral, and incongruent emotional expression. The results show that, in contrast to lay people, the credibility ratings of court judges and their votes for a guilty verdict were not influenced by the emotions displayed by the witness. Results are discussed in terms of professional expertise.

Adult↗

PubMed2006

What people believe about memory.

Two representative samples of adult Norwegians (n=2000) were asked a set of general and specific questions regarding their beliefs and opinions about human memory. The results indicate that on many questions, such as time of the earliest memories, inhibiting effects of collaboration, and memory for dramatic versus ordinary events, the views of the general public concurred with current research findings, and people in general had realistic views about their own memory performance. On other questions, such as the reliability of olfactory as compared with visual and auditory memory, the memory of small children in comparison with that of adults, the likelihood of repression of adult traumatic memories, and on more general questions such as the possibility of training memory and the capacity limitations of long-term memory, a large proportion of the participants expressed views that are less supported by scientific evidence. Implications of these findings are briefly discussed.

Adult↗

PubMed2006

Fast perceptual priming in the left and right hemispheres.

Visual field differences in fast perceptual priming of possible and impossible object decisions were investigated in a go/no-go task. Each participant (n = 74) was tested in two blocks of trials, each block containing 128 combinations of same-field and cross-field presentations of prime (blank) and target stimuli. The results indicate that fast perceptual priming of object decisions recruits processes that involve both cerebral hemispheres, independent of pre-existing representation. The priming effect was larger for possible than for impossible objects, but fast perceptual priming of object-decisions was demonstrated for both possible and impossible objects, in terms of both reaction times and accuracy. Left-hemisphere specific priming for impossible stimuli may be due to a left hemisphere encoding advantage for impossible parts, consistent with a structural description account.

Adult↗

PubMed2005

Hemispheric specialization and recognition memory for abstract and realistic pictures: a comparison of painters and laymen.

Recognition memory and hemispheric specialization were assessed for abstract colour/black and white pictures of sport situations in painters and visually naïve subjects using a forced choice yes/no tachistoscopic procedure. Reaction times showed a significant three-way interaction of picture type, expertise, and visual field, indicating that painters processed the abstract pictures in the right hemisphere and sport pictures leftwards relative to the novices. The novices showed an overall LVF/RH advantage, strongest for sport pictures. The opposing gradients in the painters indicate a preferential change of processing strategy by which descriptive systems appear to have developed for figurative, but not abstract pictures.

Adult↗

PubMed2004

Serial position effects in implicit memory for multiple-digit numbers.

Serial position effects in implicit and explicit memory were investigated in a short-term memory task. A study list composed of four, spatially distributed, two-digit numbers was presented, followed by an item recognition task (explicit test) and an implicit memory task in which participants were asked to verify a simple addition equation where the presented answer was either primed or not primed by one of the number pairs in the study list. Similar serial position effects were observed in explicit and implicit memory, with faster response times for correct decisions on the first than on the later list positions. The presence of a primacy effect but no recency effect is consistent with previous studies of explicit memory with visual presentation. The results suggest that similar principles of temporal information processing govern priming and episodic short-term memory.

Adolescent↗

PubMed2004

Unveiling the foveal blue scotoma through an afterimage.

The absence of short-wave-sensitive (S-) cones in the human foveola normally goes unnoticed, but the resulting foveal S-cone, or blue, scotoma can be visualized as the negative afterimage of a short-wavelength adapting field on a larger white background. The afterimage has an annular shape with a lighter inner region that corresponds to Maxwell's spot, and a small bright spot in the center corresponding to the foveal blue scotoma. We have shown that the visibility of the center spot in the afterimage approximately follows the spectral sensitivity curve of the S-cones. We further demonstrate that the central bright spot subtends a retinal area that is coincident with the tritanopic region of the foveola. The macular pigment distribution measured for the same observers also peaks in the central fovea, but has a relatively high density over a broader retinal region than the bright spot in the negative afterimage, and more closely corresponds to the lighter annular region of the afterimage. The results support the hypothesis of an active post-receptoral process for filling-in of chromatic scotomas.

Adaptation, Ocular↗

PubMed2003

Memory for a staged criminal event witnessed live and on video.

Memory for a staged robbery was tested in two groups of participants witnessing the event either live (n = 62) or on video (n = 64). Immediately after the event participants filled out a questionnaire probing memory with emphasis on the timing of the event and robber characteristics. The results showed that participants who watched a video recording of the event reported more details and with a higher accuracy than participants who were present on the scene, but the pattern of memory errors were similar in the two conditions. It is concluded that laboratory experiments may overestimate the memory of eyewitnesses but are otherwise able to simulate essential aspects of memory performance in naturalistic contexts.

Adult↗

PubMed2003

High-fidelity perceptual long-term memory revisited--and confirmed.

Experiments on short-term perceptual memory for elemental visual attributes, such as contrast, motion, orientation, and spatial frequency, have relied on a delayed discrimination technique in which the subject compares two stimuli presented at different points in time and memory is indexed by discrimination thresholds measured for the different time intervals between reference and test. In a variant of this procedure, used in experiments on long-term memory, the presentation of a single reference is followed by a memory test that combines two-alternative forced-choice decisions with the method of constant stimuli With this procedure, it is impossible to distinguish the effects of criterion-setting processes and memory on performance, but this confound can be eliminated by testing many subjects and having each subject make a single decision. The resulting "group thresholds" are stable across time intervals of 24 hr, confirming previous findings of high-fidelity storage in the long-term memory range.

Humans↗

PubMed2002

Hemispheric asymmetry in visual discrimination and memory: ERP evidence for the spatial frequency hypothesis.

Event related potentials (ERPs) were recorded during delayed discrimination of simple spatial frequency gratings in the high and low frequency bands. Analyses of the waveforms N170, P220, N310, P400, and slow wave (SW) indicated significant and regionally specific interaction of spatial frequency and hemisphere for N170 amplitude. This interaction was independent of memory conditions, and appeared to be in the opposite direction of what is predicted by the spatial frequency model of hemispheric asymmetry. Additional interactions between spatial frequency and hemisphere were observed for N310 in the encoding process (reference stimulus) and for SW in the retrieval process (test stimulus). The general hypothesis of an interaction of spatial frequency and hemisphere in visual cognition is supported, but the findings indicate caution in interpreting an increase in physiological measures as an indication of more efficient brain processing. Moreover, several stages of information processing may contribute to the asymmetry observed in behavioral studies, and hemispheric balance may change dynamically during the time course of processing.

Adult↗