Knowledge of natural kinds in semantic dementia and Alzheimer's disease

We examined the semantic impairment for natural kinds in patients with probable Alzheimer's disease (AD) and semantic dementia (SD) using an inductive reasoning paradigm. To learn about the relationships between natural kind exemplars and how these are distinguished from manufactured artifacts, subjects judged the strength of arguments such as "Humans have a chemical called sebum. Therefore, frogs have a chemical called sebum." These judgments depend on subjects' perception of the similarity between the familiar objects named in the premise and the conclusion. Controls rated arguments generalizing from a natural kind to an artifact as significantly weaker than arguments generalizing from one natural kind to another natural kind. SD patients demonstrated a graded profile of generalization without evidence of a categorical distinction between natural kinds and artifacts. AD patients' judgments also suggested more difficulty than controls at distinguishing between natural kinds and artifacts. Both SD patients and AD patients resembled controls in their judgments of arguments where both objects are from the natural kinds category. Semantic knowledge thus appears to be sufficiently preserved in both AD and SD to support within-category similarity judgments. We suggest that SD patients may be impaired in part at identifying the features critical to diagnosing membership in a semantic category, while AD patients' performance is consistent with their semantic categorization deficit.     

Guest Editorial: Who's Afraid of Life After Death?

The evidence for an afterlife is sufficiently strong and compelling that an unbiased person ought to conclude that materialism is a false theory. Yet the academy refuses to examine the evidence, and clings to materialism as if it were a priori true, instead of a posteriori false. I suggest several explanations for the monumental failure of curiosity on the part of academia. First, there is deep confusion between the concepts of evidence and proof. Second, materialism functions as a powerful paradigm that structures the shape of scientific explanations, but is not itself open to question. The third explanation is intellectual arrogance, as the possible existence of disembodied intelligence threatens the materialistic belief that the educated human brain is the highest form of intelligence in existence. Finally, there is a social taboo against belief in an afterlife, as our whole way of life is predicated on materialism and might collapse if near-death experiences, particularly the life review, were accepted as fact.     

Selective word-learning deficits in aphasia

The purpose of this study was to determine whether patients with focal brain damage can learn anything about a new word, and if so, whether selected aspects of the new word are acquired depending on the nature of the patient's language processing deficit. In the context of drawing pictures with a number of felt pens identical in all respects except color, agrammatic Broca's aphasics and fluent aphasics were exposed to the new word "bice," an adjective referring to the dark green portion of the color spectrum. Our findings revealed that brain-damaged patients can engage in lexical acquisition, but Broca's aphasics and fluent aphasics apparently learn about different aspects of the new word. Specifically, on successive exposures to "bice," both Broca's aphasics and fluent aphasics exhibit progressively more accurate hypotheses for identifying a bice-colored object. During subsequent assessments, agrammatic aphasics reveal on a metalinguistic judgment task their significant difficulty appreciating the grammatical form class of "bice"; on an object classification task, fluent aphasics are significantly impaired in their classification of bice-colored objects as "bice." Taken together, these unique word-learning profiles reinforce earlier observation on the selective nature of language processing deficits after focal left-hemisphere insult, and support the claim that separate language processing devices may be selectively compromised in different groups of aphasics. The relationship between syntactic and lexical semantic processing is discussed.     

Stimulus categorization by brain-damaged patients

Patients with localized insult to the right hemisphere, or to either the anterior or the posterior portion of the left hemisphere, as well as neurologically intact controls, evaluated stimuli on a seven-point rating scale for their degree of category membership. The stimuli were taken from one of two continua, one composed of fruit and vegetable items, and the other of items differing in hue and shape. Different subsets of stimuli provided different contexts for the judgments of category membership. The two left-hemisphere groups showed anomalies in categorizing the fruit and vegetable items but not the perceptual items, while the reverse was true for the right-hemisphere patients. Moreover, both left-hemisphere groups demonstrated context effects in their judgments of the representativeness of the fruit and vegetable items, but differed in the way in which they responded to changing contexts. Left posterior patients demonstrated weak category boundaries and even reclassified items. In contrast, patients with left anterior damage showed highly categorical responses and less differentiation of items within a category. All groups showed striking context effects in judgments of perceptual items in terms of changes in representativeness ratings and the location of a category boundary. Alternative interpretations of the results are offered.     

Diagnostic spatial frequencies and human efficiency for discriminating actions

Humans extract visual information from the world through spatial frequency (SF) channels that are sensitive to different scales of light-dark fluctuations across visual space. Using two methods, we measured human SF tuning for discriminating videos of human actions (walking, running, skipping and jumping). The first, more traditional, approach measured signal-to-noise ratio (s/n) thresholds for videos filtered by one of six Gaussian band-pass filters ranging from 4 to 128 cycles/image. The second approach used SF "bubbles", Willenbockel et al. (Journal of Experimental Psychology. Human Perception and Performance, 36(1), 122-135, 2010), which randomly filters the entire SF domain on each trial and uses reverse correlation to estimate SF tuning. Results from both methods were consistent and revealed a diagnostic SF band centered between 12-16 cycles/image (about 1-1.25 cycles/body width). Efficiency on this task was estimated by comparing s/n thresholds for humans to an ideal observer, and was estimated to be quite low (>.04%) for both experiments.     

Transgender youth and life-threatening behaviors

Sexual minority status is a key risk factor for suicide among lesbian, gay, and bisexual youth; however, it has not been studied among transgender youth. Fifty-five transgender youth reported on their life-threatening behaviors. Nearly half of the sample reported having seriously thought about taking their lives and one quarter reported suicide attempts. Factors significantly related to having made a suicide attempt included suicidal ideation related to transgender identity; experiences of past parental verbal and physical abuse; and lower body esteem, especially weight satisfaction and thoughts of how others evaluate the youths' bodies. Sexual minority status is a key risk factor for life-threatening behaviors among transgender youth.     

Social influences on creativity: the effects of contracted-for reward

Three studies were conducted to examine the effects of reward on children's and adult's creativity. The primary hypothesis was that explicitly contracting to do an activity in order to receive a reward will have negative effects on creativity, but receiving no reward or only a noncontracted-for reward will have no such negative effects. All three studies provided support for this hypothesis. Moreover, this support appears to be strong and generalizable across different subject populations, reward types, reward presentations, and creativity tasks. Possible mechanisms for the phenomenon are discussed.     

Cross-examination of the expert witness: Do hostile tactics affect impressions of a simulated jury?

Ninety-one introductory psychology students viewed a videotape of a simulated personal damage trial in which a psychologist expert witness testified about a plaintiff's psychological problems resulting from trauma. The defense attorney's cross-examination tactics, employed against the expert witness, were varied in the videotape. A 2 × 2 factorial design was used, with leading versus nonleading questions and a hostile versus nonhostile attorney. An interaction effect was obtained, in which a hostile attorney using leading questions and a nonhostile attorney using nonleading questions were perceived as least effective.