Control over response number by a targeted percentile schedule: reinforcement loss and the acute effects of d-amphetamine.

Two fixed-consecutive-number-like procedures were used to examine effects of acute d-amphetamine administration on control over response number. In both procedures, rats were required to press the left lever at least once and then press the right lever to complete a trial. The consecutive left-lever presses on each trial comprised a "run." Under the targeted percentile schedule, reinforcement was provided if the current run length was closer to the target length (16) than half of the most recent 24 runs. This differentially reinforced run length while holding reinforcement probability constant at .5. A second group acquired the differentiation under the targeted percentile schedule, but were then shifted to a procedure that yoked reinforcement probability by subject and run length to that obtained under the targeted percentile schedule. The two procedures generated practically identical control run lengths, response rates, reinforcement probabilities, and reinforcement rates. Administration of d-amphetamine disrupted percentile responding to a greater degree than yoked control responding. This disruption decreased reinforcement frequency less in the former than the latter procedure. The similar baseline responding under these two procedures suggests that this difference in sensitivity was due to behavioral adjustments to drug prompted by reduction of reinforcement density in the yoked control but not the percentile schedule. These adjustments attenuate the drug's effects under the former, but not the latter, procedure.     

The role of instructions in the transfer of ordinal functions through equivalence classes

In two experiments, adult subjects completed match-to-sample training and testing to establish four equivalence classes of four figures each. Then the subjects were taught one three-position sequence consisting of one stimulus from Class 1, one from Class 2, and one from Class 3. Inclusion of Class 4 stimuli in sequences was never reinforced, but two different stimuli from Class 4 appeared as distractors on each sequence trial. Tests assessed whether subjects would produce novel three-position sequences composed of members of Classes 1 through 3 that had not been used in sequence training. Three subjects in Experiment 1 received instructions about the match-to-sample and sequencing tasks, in addition to training contingencies. All 3 demonstrated equivalence class formation after match-to-sample training. After they were taught one sequence with one member of Classes 1 through 3, none of these subjects produced untrained sequences with other equivalence class members reliably. One additional sequence was trained directly; thereafter 1 subject showed some evidence of transfer of the trained ordinal functions across the remaining members of the equivalence classes, but the other 2 did not. Following a review of equivalence class training and testing and a review of the original sequence training, all 3 subjects produced most of the predicted, untrained sequences on tests. Experiment 2 replicated Experiment 1 with 2 adults but omitted all instructions except the minimal ones necessary to initiate responding. Unlike the subjects in Experiment 1, both of these subjects demonstrated virtually complete transfer of ordinal functions through the equivalence classes after direct training on just one sequence composed of one member of Classes 1 through 3.     

Writing with the right hemisphere

We studied writing abilities in a strongly right-handed man following a massive stroke that resulted in virtually complete destruction of the language-dominant left hemisphere. Writing was characterized by sensitivity to lexical-semantic variables (i.e., word frequency, imageability, and part of speech), semantic errors in writing to dictation and written naming, total inability to use the nonlexical phonological spelling route, and agrammatism in spontaneous writing. The reliance on a lexical-semantic strategy in spelling, semantic errors, and impaired phonology and syntax were all highly consistent with the general characteristics of right hemisphere language, as revealed by studies of split-brain patients and adults with dominant hemispherectomy. In addition, this pattern of writing closely resembled the syndrome of deep agraphia. These observations provide strong support for the hypothesis that deep agraphia reflects right hemisphere writing.     

Filtering by movement in visual search.

Search for a target defined by a conjunction of movement and form (e.g., an X moving up in a display of intermingled Os moving up and stationary Xs) is parallel. This result is also found if (a) the moving Os and target X move in unpredictable directions so that the moving stimuli do not form a clear perceptual group or (b) the nontarget Xs also move but in a known, different direction from the Os and target X. In contrast, search is slow and serial if the target may be unpredictably among either moving or stationary stimuli. These results suggest that a component of the visual system operates as a movement filter that can direct attention to stimuli with a common movement characteristic. The filtering cue can be moving (vs. stationary), or movement in 1 particular direction. The results do not support the view that attention can only be directed to groups defined by common fate.     

Understanding: Art and science

The arts and the sciences perform many of the same cognitive functions, both serving to advance understanding. This paper explores some of the ways exemplification operates in the two fields. Both scientific experiments and works of art highlight, underscore, display, or convey some of their own features. They thereby focus attention on them, and make them available for examination and projection. Thus, the Michelson-Morley experiment exemplifies the constancy of the speed of light. Jackson Pollock'sNumber One exemplifies the viscosity of paint. Despite their similarities, science and art might seem to differ in their attitude toward facts. Science is said to adhere to facts; art, to be indifferent to them. Such, I urge, is not the case. Science, like art, often scorns fact to advance understanding through fiction. Thought experiments, I contend, are scientific fictions; literary and pictorial fictions, aesthetic thought experiments.This paper was first published in 1991, in Peter A. French, Theodore Uehling Jr., and Howard Wettstein (eds.),Philosophy and the Arts, Midwest Studies in Philosophy, Vol. XVI, University of Notre Dame, Notre Dame, pp. 196–208.     

Self-concept and sociometric outcomes: a comparison of only children and sibling children from urban and rural areas in the People's Republic of China.

We investigated differences in self-concept between 360 only children and 555 sibling children in the sixth grade of three urban schools and three rural schools in the People's Republic of China. Peer perceptions and teacher perceptions were also collected using sociometric measures. Self-concept was determined by the Self-Perception Profile for Children (Harter, 1985). Comparisons of sibling children and only children showed no differences on self-concept; however, urban residents had higher self-concept scores than children from rural areas, and boys scored higher than girls. No significant interaction effects between sibling status, gender, and residence were found.     

Increasing the salience of one's best selves can undermine inspiration by outstanding role models

The accessibility of people's highest hopes and achievements can affect their reactions to upward comparisons. Three studies showed that, under normal circumstances, individuals were inspired by an outstanding role model; their motivation and self-evaluations were enhanced. However, when their most positive self-views were temporarily or chronically activated, inspiration was undermined, and individuals' motivation and self-evaluations tended to decrease. Another study found that role models inspired participants to generate more spectacular hopes and achievements than they would have generated otherwise. It appears that increasing the accessibility of one's best selves undercuts inspiration because it constrains the positivity of the future selves one may imagine and prevents one from generating the more spectacular future selves that the role model normally inspires.     

Second-order reversed phi.

In a first-order reversed-phi motion stimulus (Anstis, 1970), the black-white contrast of successive frames is reversed, and the direction of apparent motion may, under some conditions, appear to be reversed. It is demonstrated here that, for many classes of stimuli, this reversal is a mathematical property of the stimuli themselves, and the real problem is in perceiving forward motion, which involves the second- or third-order motion systems or both. Three classes of novel second-order reversed-phi stimuli (contrast, spatial frequency, and flicker modulation) that are invisible to first-order motion analysis were constructed. In these stimuli, the salient stimulus features move in the forward (feature displacement) direction, but the second-order motion energy model predicts motion in the reversed direction. In peripheral vision, for all stimulus types and all temporal frequencies, all the observers saw only the reversed-phi direction of motion. In central vision, the observers also perceived reversed motion at temporal frequencies above about 4 Hz, but they perceived movement in the forward direction at lower temporal frequencies. Since all of these stimuli are invisible to first-order motion, these results indicate that the second-order reversed-phi stimuli activate two subsequent competing motion mechanisms, both of which involve an initial stage of texture grabbing (spatiotemporal filtering, followed by fullwave rectification). The second-order motion system then applies a Reichardt detector (or equivalently, motion energy analysis) directly to this signal and arrives at the reversed-phi direction. The third-order system marks the location of features that differ from the background (the figure) in a salience map and computes motion in the forward direction from the changes in the spatiotemporal location of these marks. The second-order system's report of reversed movement dominates in peripheral vision and in central vision at higher temporal frequencies, because it has better spatial and temporal resolution than the third-order system, which has a cutoff frequency of 3-4 Hz (Lu & Sperling, 1995b). In central vision, below 3-4 Hz, the third-order system's report of resolvable forward movement of something salient (the figure) dominates the second-order system's report of texture contrast movement.     

Shape constancy from novel views

Prior experiments on shape constancy from novel views are inconclusive: Some show that shapes of objects can be recognized reliably from novel views, whereas others show just the opposite. Our analysis of prior results suggests that shape constancy from novel views is reliable when the object has properties that constrain its shape: The object has volumetric primitives, it has surfaces, it is symmetrical, it is composed of geons, its contours are planar, and its images provide useful topological information about its three-dimensional structure. To test the role of some of these constraints, we performed a set of experiments. Solid shapes (polyhedra) were shown on a computer monitor by means of kinetic depth effect. Experiment 1 showed that shape constancy can be reliably achieved when a polyhedron is represented by its contours (most of the constraints are present), but not when it is represented by vertices or by a polygonal line connecting the vertices in a random order (all the constraints are absent). Experiments 2 and 3 tested the role of individual constraints. Results of these experiments show that shape constancy from novel views is reliable when the object has planar contours and when the shapes of the contours together with topological information about the relations among the contours constrain the possible interpretations of the shape. Symmetry of the object and the topological stability of its image also contribute to shape constancy.     

Role of the serotonin transporter gene in temperament and character

The biosocial model postulates that personality is comprised of two broad domains: temperament, which is largely due to inherited variations in specific monoamine neurotransmitter systems; and character, which arises from socioculturally learned differences in values, goals, and self-concepts and is the strongest predictor of personality disorders. The model also proposes that serotonin modulates the temperament trait of harm avoidance. We analyzed the association of temperament and character traits with the 5-HTTLPR, an inherited variation that modulates serotonin transporter gene expression, in 634 volunteer subjects. Contrary to theory, the 5-HTTLPR was most strongly associated with the character traits of cooperativeness and self-directedness. Associations with the temperament traits of reward dependence and harm avoidance were weaker and could be attributable largely to cross-correlations with the character traits and demographic variables. Psychometric analysis indicated that the serotonin transporter influences two broad areas of personality, negative affect and social disaffiliation, that are consistent across inventories but are more concisely described by the 5-factor model of personality than by the biosocial model. These results suggest that there is no fundamental mechanistic distinction between character and temperament in regard to the serotonin transporter gene, and that a single neurotransmitter can influence multiple personality traits.