Ratings of kinetic depth in multidot displays

Subjects saw kinetic depth displays whose shape (sphere or cylinder) was defined by luminous dots distributed randomly on the surface or in the volume of the object. Subjects rated perceived 3-D depth, rigidity, and coherence. Despite individual differences, all 3 ratings increased with the number of dots. Dots in the volume yielded ratings equal to or greater than surface dots. Each rating varied with 3 of 4 factors (shape, distribution, numerosity, and perspective), but the ratings either between trials or between conditions were often uncorrelated. Object shape affected rigidity but not depth ratings. Veridically perceived polar displays had slightly lower rigidity but higher depth ratings than parallel projection displays. (Reversed polar displays were always grossly nonrigid.) The interaction of ratings and stimulus parameters requires theories and experiments in which different KDE ratings are not treated interchangeably.     

Contextual influences in aphasia: effects of predictive versus nonpredictive narratives

The influence of prior linguistic predictive and nonpredictive context on the comprehension of reversible passive sentences was investigated in 16 adults with aphasia. Eight subjects were classified as fluent and 8 as nonfluent. Subjects were presented with the sentences in isolation and preceded by nonpredictive and predictive contextual paragraphs. The overall results indicated that the subjects benefited significantly from the prior contextual narratives regardless of whether the paragraphs were predictive or nonpredictive. There were no significant differences between the two subject groups. The significant facilitation generated by the nonpredictive context suggests that redundancy of information may play a role in comprehension.     

Can dyslexia be treated? Treatment-specific and generalized treatment effects in dyslexic children's response to remediation

A total of 178 reading disabled children were randomly assigned to one of three treatment conditions providing training in word recognition and decoding skills (DS), oral and written language (OWLS), or classroom survival skills (CSS. an alternative treatment control). Pre- and post-treatment comparisons on an array of standardized and experimental measures indicated that the two experimental treatments (DS, OWLS) resulted in improvement on selected tests significantly greater than that resulting from a third treatment intervention which controlled for treatment time and individual attention (CSS). Effects specific to each experimental treatment were identified, as well as some generalized treatment advantages shared by both experimental groups at post-test. These results indicate that some of the deficits associated with developmental dyslexia are amenable to treatment. Greater generalization of treatment effects was observed following the DS than the OWLS treatment. While DS-instructed children exhibited better word recognition skills, however, their knowledge of grapheme-phoneme correspondence rules was not improved. Several OWLS-specific effects observed on experimental reading and language measures were not replicated on standardized tests which purport to measure the same skills. These results are discussed with respect to (i) possible mechanisms by which disabled readers may acquire word recognition skills, (ii) their failure to acquire and use grapheme-phoneme correspondence rules, and (iii) a possible reduced tendency in the present population to generalize newly acquired specific knowledge to related knowledge domains.     

The nature of prolonged word search

Two alternative hypotheses were considered concerning the process of prolonged search for an uncommon word in response to hearing its definition. One alternative is that a conscious retrieval effort brings the target progressively closer to threshold. The second is that the retrieval process is a random neural exploration outside of conscious control. A tachistoscopic probe was devised to compare word recognition thresholds after 10 sec versus 30 sec of presumed search time. Results failed to show a difference between the two delay conditions and were interpreted as inconsistent with the first alternative but consistent with the second.     

A componential model for mental addition

A componential model capable of representing simple and complex forms of mental addition was proposed and then tested by using chronometric techniques. A sample of 23 undergraduate students responded to 800 addition problems in a true-false reaction time paradigm. The 800 problems comprised 200 problems of each of four types: two single-digit addends, one single- and one double-digit addend, two double-digit addends, and three single-digit addends. The results revealed that the columnwise product of addends, a structural variable consistent with a memory network retrieval process, was the best predictor of mental addition for each of the four types of problem. Importantly, the componential model allowed estimation of effects of several other structural variables, e.g., carrying to the next column and speed of encoding of digits. High levels of explained variance verified the power of the model to represent the reaction time data, and the stability of estimates across types of problem implied consistent component use by subjects. Implications for research on mental addition are discussed.     

Age deficits in recall under optimal study conditions

Young and older adults studied lists of words under both standard and optimal study conditions for subsequent free recall. Under optimal conditions, the participants studied each word for as long as they wished, were allowed to take notes, and were encouraged to actively use whatever strategies they thought would maximize recall. Both age groups recalled more words under optimal study conditions than under standard conditions, but the improvement was greater for the young adults. This increase in the age-related recall deficit was not due to differences in study time. The results suggest that standard laboratory memory tasks do not overestimate the memory deficits of older adults because of a failure to provide either optimal learning conditions or sufficient study time.     

Expert evidence by psychologists: Sometimes problematic and often premature

This article provides a critical review of two major types of expert evidence: (a) clinical assessments, and (b) generalizations drawn from psychological research. Strong arguments both for and against both types of testimony have been offered by legal experts and psychologists. These arguments are evaluated and the conclusion is drawn that there are two fundamental problems for psychologists in the role of expert. First, the types of assessments clinicians are asked to make (e.g., concerning the accused's mental state at the time of committing the offense) may exceed the capacity of the discipline; such assessments are problematic. Second, the research foundation that psychologists employ in court does not always apply to the court situation in the way experts imply; the application of laboratory research findings to real world contexts is sometimes premature. The article concludes with an admonition that psychologists should adopt a more conservative response to requests to provide expert evidence.     

Perioral somatosensory determinants of nursing behavior in Norway rats (Rattus norvegicus)

Prior to assuming the upright crouching posture over their pups during nursing bouts, lactating rats typically engage in several oral behaviors, including nuzzling, licking and rearranging pups. By acutely depriving dams of various aspects of perioral stimulation from pups (with anesthesia of the mystacial pads or of the tongue, with mouth suturing, or with muzzling), we found the following: (1) Distal stimulation from pups maintains proximity-seeking behavior, but is insufficient to stimulate nursing behavior. (2) Lack of tongue feedback decreases pup licking and hastens the onset of crouching. (3) Snout, but not tongue, contact with pups is required for hovering over them. (4) The position of the dam while hovering over her litter enables the pups to gain access to her ventrum, thereby provoking her upright, crouching posture. (5) Older pups are capable of bypassing the dam's perioral attentions and stimulating crouching directly by burrowing under the dam's ventrum.