Trade-offs in detecting letters and comprehending text.

Critics of the letter detection task have questioned whether findings from that paradigm reflect normal reading processes. The present study addresses these questions using a new computerized version of the letter detection task in which reading rate along with letter detection and comprehension accuracy are examined. Previous letter detection findings were replicated with this new computerized task. Different conditions were compared in which detection and comprehension instructions were manipulated as well as the salience of the target letters. The requirement to comprehend had small effects on letter detection accuracy and reading rate, and letter detection only modestly reduced comprehension. Thus, the procedures developed in this study permit examination of the component processes contributing to performance in the letter detection task.     

Visual homing in the absence of feature-based landmark information

Despite that fact that landmarks play a prominent role in human navigation, experimental evidence on how landmarks are selected and defined by human navigators remains elusive. Indeed, the concept of a ‘landmark’ is itself not entirely clear. In everyday language, the term landmark refers to salient, distinguishable, and usually nameable objects, rendering the problem of landmark recognition a special case of the general object recognition problem. In contrast, in the insect and robot literature, this notion of landmarks is often replaced by the “local position information” [e.g., Trullier, O., Wiener, S., Berthoz, A., &; Meyer, J.-A. (1997). Biologically based artificial navigation systems: Review and prospects. Progress in Neurobiology, 51, 483–544], referring to the entire set of sensor readings obtained at one location. This set may then serve as a characteristic of the particular location. Honey bees have been shown to base place recognition and homing on a snapshot-like memory of the place’s visual environment, not on the distances to recognized objects [Cartwright, B., &; Collett, T. (1983). Landmark learning in bees. Experiments and models. Journal of Comparative Physiology A, 151, 521–543]. A number of theoretical models of snapshot-based homing [e.g., Franz, M., Schölkopf, B., Mallot, H. A., Bülthoff, H. H. (1998). Where did I take that snapshot? Scene-based homing by image matching. Biological Cybernetics, 79, 191–202; Vardy, A., &; Möller, R. (2005). Biologically plausible visual homing methods based on optical flow techniques. Connection Science, 17, 47–89] predict that the accuracy of snapshot-based homing should depend on image contrast. For rodent hippocampal place fields, models have been developed using additional image information such as three-dimensional depth and allocentric orientations (e.g., room axes) and are thus less sensitive to image contrast and noise [e.g. Barry, C., Lever, C., Hayman, R., Hartley, T., Burton, S., O’Keefe, J., et al. (2006). The boundary vector cell model of place cell firing and spatial memory. Reviews in the Neurosciences, 17, 71–79]. Here, we study human visual homing in a virtual environment void of objects and readily detected image features. The environment was a circular room with a homogenous colour gradient covering the wall and uniform floor and ceiling. Subjects were able to approach remembered places. Accuracy decreased with colour gradient modulation and room size, in qualitative agreement with the snapshot model but not with other models of place recognition. We conclude that human memory for places can make use of a snapshot algorithm.     

Global inhibition and midcourse corrections in speeded aiming

When some perceptual-motor relationships are reversed, participants might adopt a global inhibition strategy that replaces all normal movements with reversed movements. In two experiments, participants practiced moving a cursor from a start position to target locations. In a perceptual-motor reversal condition, in which horizontal but not vertical movements were reversed, participants were trained to move only to certain locations. Testing involved moving to all locations under the same reversal condition. Training on a subset of locations yielded partial transfer to untrained locations. These results support a global inhibition hypothesis modified to include both midcourse corrective movements and training specificity.     

A mental practice superiority effect: less retroactive interference and more transfer than physical practice

Two experiments explored the benefits to retention and transfer conferred by mental practice. During familiarization, participants typed 4-digit numbers and took an immediate typing test on both old and new numbers. Participants then typed old 4-digit numbers, either physically or mentally, with either a different response configuration or the opposite hand from that used during familiarization. On a delayed test, participants physically typed both old and new numbers with the same response configuration and hand used during familiarization. Mental practice led to less retroactive interference and more transfer than did physical practice, supporting the hypothesis that mental practice strengthens an abstract representation that does not involve specific effectors.     

Age-related positivity enhancement is not universal: older Chinese look away from positive stimuli

Socioemotional selectivity theory postulates that with age, people are motivated to derive emotional meaning from life, leading them to pay more attention to positive relative to negative/neutral stimuli. The authors argue that cultures that differ in what they consider to be emotionally meaningful may show this preference to different extents. Using eye-tracking techniques, the authors compared visual attention toward emotional (happy, fearful, sad, and angry) and neutral facial expressions among 46 younger and 57 older Hong Kong Chinese. In contrast to prior Western findings, older but not younger Chinese looked away from happy facial expressions, suggesting that they do not show attentional preferences toward positive stimuli.     

Cognitive complications moderate the speed‐accuracy tradeoff in data entry: a cognitive antidote to inhibition

Three experiments explored a speed‐accuracy tradeoff reflecting decreasing response times (RTs) and increasing errors across trials in a data entry task. In Experiment 1, cognitive and motoric stressors were independently added to data entry, with the combination of stressors yielding the greatest decline in accuracy across blocks. Experiment 2 compared mental multiplication and simple data entry and manipulated the provision of feedback. Accuracy improved with both mental multiplication and feedback. Experiment 3 varied only the concluding keystroke; this extra requirement led to overall improvements in accuracy. In each experiment, RTs improved across trials. These results suggest that cognitive complications can serve as antidotes to inhibitory effects and can overcome the decline in accuracy due to continuous work on data entry. Copyright © 2007 John Wiley & Sons, Ltd.     

EVALUATION AND TRAINING OF YES‐NO RESPONDING ACROSS VERBAL OPERANTS

Topographically similar verbal responses may be functionally independent forms of operant behavior. For example, saying yes or no may have different functions based on the environmental conditions in effect. The present study extends previous research on both the assessment and acquisition of yes and no responses across contexts in children with language deficits and further examined the functional independence of topographically similar responses. All participants in the present study acquired yes and no responses within verbal operants (e.g., mands). However, generalization of the responses across novel verbal operants (e.g., tacts to intraverbals) did not occur without additional training, thus supporting Skinner's (1957) assertion of functional independence of verbal operants.     

WITHIN‐SUBJECT REVERSIBILITY OF DISCRIMINATIVE FUNCTION IN THE COMPOSITE‐STIMULUS CONTROL OF BEHAVIOR

According to the composite-stimulus control model (Weiss, 1969, 1972b), an individual discriminative stimulus (S^D) is composed of that S^D''s on-state plus the off-states of all other relevant S^Ds. The present experiment investigated the reversibility of composite-stimulus control. Separate groups of rats were trained to lever-press for food whenever a tone or a light S^D was present. For one group, the nonreinforced S^Δ condition was tone-and-light absence ($\bar{T}$+$\bar{L}$). Tone-plus-light (T+L) was S^Δ in the other group. On a “stimulus compounding” test that recombined composite elements, maximum responding occurred to that composite consisting only of elements occasioning response increase. That was T+L for the group trained with $\bar{T}$+$\bar{L}$ as S^Δ and $\bar{T}$+$\bar{L}$ for the group trained with T+L as S^Δ. The S^Δ composite was next reversed over groups in Phase 2. In Phase 2 tests, maximum responding that was comparable in magnitude to that of Phase 1 was again controlled by the composite consisting only of elements most recently occasioning response increase—whether T+L or $\bar{T}$+$\bar{L}$. The inhibitory conditioning history of both composite-elements currently occasioning responding did not weaken the summative effect. These results confirm and extend Weiss''s composite-stimulus control model, and demonstrate that such control is fully reversible. We discuss how translating conditions of the stimulus-compounding paradigm to a composite continuum creates a functional and logical connection to intradimensional control measured through stimulus generalization, reducing the number of different behavioral phenomena requiring unique explanations.     

Pushing the limits of imagination: mental practice for learning sequences

In 2 experiments, the efficacy of motor imagery for learning to type number sequences was examined. Adults practiced typing 4-digit numbers. Then, during subsequent training, they either typed in the same or a different location, imagined typing, merely looked at each number, or performed an irrelevant task. Repetition priming (faster responses for old relative to new numbers) was observed on an immediate test and after a 3-month delay for participants who imagined typing. Improvement across the delay in typing old and new numbers was found for the imagined and actual typing conditions but not for the other conditions. The findings suggest that imagery can be used to acquire and retain representations of sequences and to improve general typing skill.