Different cognitive processes in two image-scanning paradigms

Mental image scanning is generally assumed to be a single process that allows people to shift attention across visualized objects. However, this implicit assumption is open to question. We report a set of three experiments based on the tasks originally designed by Kosslyn, Ball, and Reiser (1978) and Finke and Pinker (1982). Participants scanned the identical images of an array of dots in the two tasks. Nevertheless, the participants required more time to shift their focus over the imaged stimulus in the Kosslyn et al. (1978) paradigm. Moreover, correlational analyses revealed no consistent relationship between the slopes of the increases in scanning times with increasing distances in the two paradigms. We conclude that in the Kosslyn et al. (1978) paradigm, the participants draw primarily on transformational processes to scan, whereas in the Finke and Pinker (1982) paradigm, they draw primarily on attentional processes. Both processes, transforming the image and shifting an attention window, produce linear increases in time with increases in distance, but for different reasons.     

How to maximize reward rate on two variable-interval paradigms

Without assuming any constraints on behavior, we derive the policy that maximizes overall reward rate on two variable-interval paradigms. The first paradigm is concurrent variable time-variable time with changeover delay. It is shown that for nearly all parameter values, a switch to the schedule with the longer interval should be followed immediately by a switch back to the schedule with the shorter interval. The matching law does not hold at the optimum and does not uniquely specify the obtained reward rate. The second paradigm is discrete trial concurrent variable interval-variable interval. For given schedule parameters, the optimal policy involves a cycle of a fixed number of choices of the schedule with the shorter interval followed by one choice of the schedule with the longer interval. Molecular maximization sometimes results in optimal behavior.     

The assessment of subjective visual vertical: comparison of two psychophysical paradigms and age-related performance

Perception of the subjective visual vertical (SVV) is usually assessed by asking to subjects, in complete darkness, to adjust the position of a luminous rod that is variably tilted (i.e., by the method of adjustment [ADJ]). Conversely, the two-alternative forced choice (2AFC) method requires subjects to categorize, as tilted either clockwise (CW) or counterclockwise (CCW), stimuli that are presented on a computer screen and are variably tilted from vertical. In this study, we aimed to compare the results of these two methods and investigate age-related effects on the SVV. SVV was assessed in 102 healthy individuals, 50 women and 52 men, with a mean age of 45.7 (range 20–91), using both ADJ (ten trials, initial 1°, 2°, 4°, 8°, or 12° bar tilts both CW and CCW) and 2AFC (120 stimuli with a 1°–32° variable tilt). Also, 50 of the subjects performed the ADJ test twice, with different bar lengths. We estimated bias and threshold for the two methods, and found that neither measure differed across the methods. Age was a significant predictor of threshold (2AFC, R ² = .141; ADJ, R ² = .190; p < .001), implying lower sensitivity with increasing age. Moreover, the ADJ method showed a significant increase of bias when the initial tilt was farthest from vertical, whereas the rod length was irrelevant. SVV measures obtained with the ADJ and 2AFC methods were comparable, but the latter measures were more resistant to artifacts that might affect the measurement. The lower sensitivity found in older persons may have an influence on their ability to interact with the environment and may contribute to impairment of postural control.     

Control of the contents of working memory--a comparison of two paradigms and two age groups

Two experiments investigated whether young and old adults can temporarily remove information from a capacity-limited central component of working memory (WM) into another component, the activated part of long-term memory (LTM). Experiment 1 used a modified Sternberg recognition task (S. Sternberg, 1969); Experiment 2 used an arithmetic memory-updating task. In both paradigms, participants memorized 2 lists, one of which was cued as temporarily irrelevant. Removal of the irrelevant list from capacity-limited WM was indexed by the disappearance of list-length effects of that list on latencies for concurrent processing tasks. Young adults could outsource the irrelevant list within 2-3 s and retrieve it back into the central part of WM later. Old adults showed the same flexibility in the arithmetic updating task but seemed somewhat less able or inclined to temporarily move information into the activated part of LTM in the modified Sternberg task.     

Two paradigms of measuring serial-order memory: two different patterns of serial-position functions

There are two research paradigms in the area of serial-order memory. One typically uses serial recall (accuracy), and the other comparative judgment (reaction time) for measuring serial-order memory. Spontaneous subgrouping is commonly observed in the recall serial-position function in the form of multiple bowings. However, comparative judgment with a reaction time measure produces a single-bowing function. Researchers adopting these two approaches have opposing views on the form of the structure of serial-order memory with the former favoring a hierarchical, and the latter a unidimensional structure. The present study confirmed the above hypothesized relation between the two measuring procedures and the two different patterns of serial-position functions. It was suggested that a serial recall involves retrieving absolute position information, whereas a comparative judgment involves retrieving relative position information, and that subgrouping serves a facilitating function for the former, but may actually impede the latter process.     

Further evidence for two components in visual persistence.

The phenomenal durations of tachistoscopically presented letter arrays at five levels of redundancy were measured using a subtractive reaction-time technique. Phenomenal duration was inversely related to redundancy only when report of the letters was required. The duration of functional availability of stimulus information for stimuli at the five levels of redundancy was determined in a backward masking paradigm. The measurements of the duration of functional availability and phenomenal presence were convergent, indicating that one process is responsible for both the phenomenal and functional duration of a persisting representation of a visual stimulus. The results are interpreted as providing further evidence for two components in visual persistence: a physical component whose duration is unrelated to stimulus parameters and an informational component whose duration is inversely related to the efficiency of encoding stimulus information.     

Development of clinical tests of vision: Initial data on two hyperacuity paradigms

Many basic psychophysical functions offer promise as clinical tests of vision. Here, we discuss problems that one encounters in the clinical setting, how one identifies a psychophysical test for potential clinical development, and an orderly approach to development of suitable test paradigms. Parameters are selected which are relatively insensitive to variables encountered in the field (clinic) in a normal population, but which are sensitive to changes in the response system being studied. Initial data on two hyperacuity tests are presented. These tests are adaptations of hyperacuity paradigms (Westheimer, 1979) to a clinical environment. This particular test set offers promise because it exhibits a unique threshold which is dependent upon neural data processing and is relatively independent of retinal image degradation.     

The persistence of false beliefs

Do false beliefs last? To explore this question, this study planted false beliefs or memories of a childhood experience with asparagus. We found that these false beliefs had consequences for subjects, when assessed directly after the suggestive manipulation. Moreover, subjects were brought back two weeks later to see if their false beliefs persisted. After two weeks, subjects' confidence in their new memories, and the consequences of those memories were diminished, but not extinguished. These false beliefs were found to be somewhat weaker than other subjects' true beliefs for the same events. Another novel finding was that the manipulation was sufficiently powerful to affect actual food choices.     

Application of two neural network paradigms to the study of voluntary employee turnover.

Two neural network paradigms--multilayer perceptron and learning vector quantization--were used to study voluntary employee turnover with a sample of 577 hospital employees. The objectives of the study were twofold. The 1st was to assess whether neural computing techniques offered greater predictive accuracy than did conventional turnover methodologies. The 2nd was to explore whether computer models of turnover based on neural network technologies offered new insights into turnover processes. When compared with logistic regression analysis, both neural network paradigms provided considerably more accurate predictions of turnover behavior, particularly with respect to the correct classification of leavers. In addition, these neural network paradigms captured nonlinear relationships that are relevant for theory development. Results are discussed in terms of their implications for future research.     

Tactile spatial acuity differs between fingers: a study comparing two testing paradigms

Tactile spatial acuity (TSA) is a reliable and reproducible measure of somatosensory system function that has been used to study abroad range of subject populations. Although TSA is most often assessed at the fingertip, published studies employing identical stimuli disagree on whether TSA differs between the fingers of neurologically normal subjects. Using a validated grating orientation discrimination task, we determined TSA bilaterally at the index and ring fingers of 16 healthy young adults. Motivated by earlier work, we utilized two stimulus presentation paradigms, the method of constant stimuli (MCS) and a staircase (SC) method. We found that TSA was significantly higher (the discrimination threshold was lower) at the index than at the ring finger, which was consistent with a prior study. Although mean thresholds at both fingers were higher when measured with the SC than with the MCS paradigm, this difference did not reach statistical significance (p = .14). These findings should facilitate both design and interpretation of future studies investigating TSA.     

Manipulations that disrupt generative processes decrease conformity to examples: evidence from two paradigms

Participants in six experiments viewed experimenter-provided examples of space creatures (Experiments 1-3) or nonwords (Experiments 4-5b) and then created their own novel space creatures or nonwords. Consistent with previous research, people borrowed many of the features found in the examples despite instructions to avoid using any aspects of the experimenter's examples. However, requiring people to include a designated shape in their space creatures or a designated letter in their nonwords attenuated this effect. Additionally, the type of shape or letter (conventional versus unconventional) also affected conformity. These results suggest that the strategies that people use to create novel products can affect the level of conformity and also highlight the importance of adopting unconventional, or at the very least, new strategies when creating new products.     

The persistence of object file representations

Coherent visual experience of dynamic scenes requires not only that the visual system segment scenes into component objects but that these object representations persist, so that an object can be identified as the same object from an earlier time. Object files (OFs) are visual representations thought to mediate such abilities: OFs lie between lower level sensory processing and higher level recognition, and they track salient objects over time and motion. OFs have traditionally been studied via object-specific preview benefits (OSPBs), in which discriminations of an object's features are speeded when an earlier preview of those features occurred on the same object, as opposed to on a different object, beyond general displaywide priming. Despite its popularity, many fundamental aspects of the OF framework remain unexplored. For example, although OFs are thought to be involved primarily in online visual processing, we do not know how long such representations persist; previous studies found OSPBs for up to 1500 msec but did not test for longer durations. We explored this issue using a modified object reviewing paradigm and found that robust OSPBs persist for more than five times longer than has previously been tested-for at least 8 sec, and possibly for much longer. Object files may be the "glue" that makes visual experience coherent not just in online moment-by-moment processing, but on the scale of seconds that characterizes our everyday perceptual experiences. These findings also bear on research in infant cognition, where OFs are thought to explain infants' abilities to track and enumerate small sets of objects over longer durations.     

The changing face of visual persistence

In three experiments, the effect of target luminance on estimates of visual persistence was determined on a popular successive-field task. Even though the experiments differed from each other only in terms of minor changes in stimulus conditions, very different effects were obtained across the three experiments. The different findings were attributed to the often overlooked roles of masking and target degradation on tasks of persistence. Implications for the numerous contradictory findings in the persistence literature are discussed, and the current popularity of the successive-field task is questioned.     

The impersistence of false memory persistence

When subjects study lists of thematically related words they sometimes falsely recognise non-presented words related to the theme. The gist extraction account of these findings provided by fuzzy trace theory suggests that false recognition should decline substantially more slowly than true recognition across a delay. In two experiments we demonstrated that corrected recognition of targets and critical lures can decrease by equivalent amounts across a 48-hour delay. However the results for uncorrected recognition were mixed. In Experiment 1 we found evidence that uncorrected recognition of targets declined more rapidly than uncorrected recognition of critical lures. In Experiment 2, we found evidence that uncorrected recognition of targets and critical lures declined at equivalent rates. Results are discussed in terms of their implications for fuzzy trace and source monitoring accounts of false memories.