Mats Dahl

Judging Words at Face Value: Interference in a Word Processing Task Reveals Automatic Processing of Affective Facial Expressions

Earlier research has indicated that some characteristics of facial expressions may be automatically processed. This study investigated automaticity as evidenced by involuntary interference in a wor ...

Asymmetries in the processing of emotionally valenced words

Earlier research has shown a valence dependent encoding asymmetry of emotional words (e.g., Pratto & John, 1991; White, 1996; Stenberg, Wiking & Dahl, 1998). To further study this asymmetry, two word detection experiments were performed based on the following hypothesis: when there is a more thoroughly processing of the valence, in this case a valence categorisation, there will be, in a subsequent task, prolonged latencies for negative words, compared to positive words. The result gave significantly prolonged response latencies for negative words compared to positive ones in the subsequent detection task when using an affective orienting task, something not found using a non-affective orienting task. The results support the Mobilization-Minimization hypothesis (Taylor, 1991), according to which negative events and stimuli occupy more cognitive resources, but with some limitation: the affective asymmetry, with prolonged latencies for negative words, occurs only when there is a deepened encoding of the affective component of the words.

The Realism in Older People's Confidence Judgments of Answers to General Knowledge Questions

The study investigated 2 aspects of the accuracy (i.e., realism) of confidence judgments of persons age 60-93 years (N = 1,384) regarding their answers to general knowledge questions. These aspects are the level of confidence (calibration) in relation to the proportion of correct answers and the ability to discriminate between correct and incorrect answers by means of confidence judgments. No age differences were found for either of the 2 aspects. Gender differences were found for proportion of correct answers and confidence but not for the realism in the confidence judgments.

The Role of Sparsely Distributed Representations in Familiarity Recognition of Verbal and Olfactory Materials

We present the generalized signal detection theory (GSDT), where familiarity is described by a sparse binomial distribution of binary node activity rather than by normal distribution of familiarity. Items are presented in a distributed representation, where each node receives either noise only, or signal and noise. An old response (i.e., a “yes” response) is made if at least one node receives signal plus noise that is larger than the activation threshold, and item variability is determined by the distribution of activated nodes as the threshold is varied. A distinct representation leads to better performance and a lower ratio of new to old item variability, than a more distributed and less distinct representations. Here we apply the GSDT to empirical data on verbal and olfactory memory and suggest that verbal memory relies on a distinct neural item representation, whereas olfactory memory has a fuzzy neural representation leading to poorer memory and inducing a larger ratio of new to old item variability.

Old and very old adults as witnesses: event memory and metamemory

Older people constitute an important category of eyewitnesses. Episodic memory performance in older persons is poorer than in younger adults, but little research has been made on older persons’ metacognitive judgments. Since more persons of advanced age will likely be called upon as witnesses in coming years, it is critical to characterize this population’s metacognitive abilities. We compared event memory metacognition in old adults (66-year-old, n = 74) to very old adults (87 or 90 years old, n = 55). Participants were tested on their memory of a film, using questions with two answer alternatives and the confidence in their answer. As expected, the very old group had a lower accuracy rate than the old group (d = 0.59). The very old group, however, monitored this impairment, since their over-/underconfidence and calibration did not differ from the old group but they displayed a poorer ability to separate correct from incorrect answers (discrimination ability). Possibly, the very old group was able to monitor the level of their over-/underconfidence because they applied general self-knowledge about their memory skills. In contrast, the discrimination of correct from incorrect answers may be more dependent on ability to attend to the features of each retrieved memory.

Analysis of eyewitness testimony in a police shooting with fatal outcome – manifestations of spatial and temporal distortions

Abstract Eyewitness statements are commonly used in the criminal justice system and viewed as having a high-probative value, especially when the witness has no motive to lie, other witness recollection corroborates the account, or the witness is highly confident. A fatal police shooting incident in Sweden had 13 witnesses (nine civilians and four police officers) and was also filmed with two mobile phones. All interviews were conducted before witnesses viewed the films, allowing for the analysis of discrepancies between their statements and the videos. In this incident, a police patrol was sent to find out a man who was reported to have attacked two persons with a knife. When found, the perpetrator refused to obey the officer’s commands, and the police eventually shot at him. The analysis showed clear differences between the witness testimonies and the film. Elements associated with perceived threat, for example, the assailant’s armament and movement direction and number of shots fired, were remembered fairly accurately. However, most witnesses poorly recollected when, that is, after which shot, the assailant fell to the ground. Moreover, memory of the actual order of events was altered and important aspects omitted that were crucial from a legal point of view.

Exploring how a traditional diluted yoghurt drink may mitigate heat strain during medium-intensity intermittent work : a multidisciplinary study of occupational heat strain

It is common practice in India to consume the dairy drink buttermilk as a way of mitigating occupational heat strain. This paper explores the thermoregulatory and hydration benefits of drinking buttermilk but also the impacts of work in a hot environment on the gut microbiota, renal and cognitive function. Twelve healthy participants were subjected to a 3-h period of medium load physical intermittent work in a climatic chamber (34°C, 60% RH). The subjects were given water, buttermilk (700 ml) or no rehydration at random. Mean body temperatures when no rehydration was given were significantly higher (p≤0.001). When subjects drank water or buttermilk they had a lower sweat rate than with no rehydration (p≤0.05) and the perception of feeling hot, uncomfortable, thirsty and physically exerted was significantly reduced (p≤0.05). A hormonal stress response at the end of the exposure was seen when not drinking (p≤0.05). No differences in cognitive abilities and gut microbiota were found. The exposure lowered the renal blood flow suggesting an acute impact of short term heat exposure. It was also found that buttermilk has a protective effect on this impact. Our results demonstrated that keeping hydrated by water/buttermilk consumption mitigates heat strain in well-nourished subjects.