Conflict in object affordance revealed by grip force

Viewing objects can result in automatic, partial activation of motor plans associated with them—“object affordance”. Here, we recorded grip force simultaneously from both hands in an object affordance task to investigate the effects of conflict between coactivated responses. Participants classified pictures of objects by squeezing force transducers with their left or right hand. Responses were faster on trials where the object afforded an action with the same hand that was required to make the response (congruent trials) compared to the opposite hand (incongruent trials). In addition, conflict between coactivated responses was reduced if it was experienced on the preceding trial, just like Gratton adaptation effects reported in “conflict” tasks (e.g., Eriksen flanker). This finding suggests that object affordance demonstrates conflict effects similar to those shown in other stimulus–response mapping tasks and thus could be integrated into the wider conceptual framework on overlearnt stimulus–response associations. Corrected erroneous responses occurred more frequently when there was conflict between the afforded response and the response required by the task, providing direct evidence that viewing an object activates motor plans appropriate for interacting with that object. Recording continuous grip force, as here, provides a sensitive way to measure coactivated responses in affordance tasks

Evidence for covert attention switching from eye-movements. Reply to commentaries on Liechty et al., 2003

We argue that our research objectives in Liechty, Pieters, and Wedel (2003) are to provide generalizable insights into covert visual attention to complex, multimodal stimuli in their natural context, through inverse inference from eye-movement data. We discuss the most important issues raised by Feng (2003) and Reichle and Nelson (2003), in particular the task definition, inclusion of ad features, object-based versus space-based attention and the evidence for the where and what streams.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45760/1/11336_2005_Article_BF02295611.pd

UBVRI Light curves of 44 Type Ia supernovae

We present UBVRI photometry of 44 Type la supernovae (SNe la) observed from 1997 to 2001 as part of a continuing monitoring campaign at the Fred Lawrence Whipple Observatory of the Harvard-Smithsonian Center for Astrophysics. The data set comprises 2190 observations and is the largest homogeneously observed and reduced sample of SNe la to date, nearly doubling the number of well-observed, nearby SNe la with published multicolor CCD light curves. The large sample of [U-band photometry is a unique addition, with important connections to SNe la observed at high redshift. The decline rate of SN la U-band light curves correlates well with the decline rate in other bands, as does the U - B color at maximum light. However, the U-band peak magnitudes show an increased dispersion relative to other bands even after accounting for extinction and decline rate, amounting to an additional ∼40% intrinsic scatter compared to the B band

Is evidence for late selection due to automatic or attentional processing of stimulus identities?

This study determined whether evidence for late selection is due to attention processing or to processing by an automatic system that is separate from attention (two systems framework; Eriksen, Webb, & Fournier, 1990). The task was a two-choice discrimination of a target that appeared in one of two sequentially cued locations in an eight-letter visual display. Attention was directed to the first cued location (cue 1), and whether identification processing occurred at a different location before the second cue (cue 2) directed attention there was determined. Cue validity varied across two experiments, and critical trials were those in which the target appeared at cue 2. For these trials, the target was preceded by a letter (either identical, neutral, or incompatible) that changed to the target at various time intervals following cue 2. Automatic identification was assumed if theincompatible letter interfered with response to the target when it appeared only before cue 2 onset and independent of cue validity. The incompatible letter appearing only before cue 2 onset interfered with the target when the target occurred equally often at cue 1 and cue 2, but not when the target occurred at cue 1 70% and at cue 2 30% of the time. This disconfirms the two systems framework and suggests that attention is required for spatial form processing and response competition

On the Dependence of P300 Latency on Stimulus Evaluation Processes

McCarthy and Donchin (1981) found that the latency of a late positive component of the event‐related potential (ERP) was influenced by the presence of noise in a stimulus matrix but not by the compatibility between the stimulus presented and the response required. They concluded that this component is a P300 and that its latency was influenced by stimulus evaluation but not by response selection processes. The present experiments were designed to confirm that the component identified by McCarthy and Donchin was indeed a P300 and to determine if its latency varies systematically with increases in stimulus evaluation time produced by graded changes in noise level. In Experiment 1, subjects performed a standard oddball task in which they were required to count the rarer of two stimuli (the words RIGHT or LEFT) which were, or were not, embedded in a noise matrix (characters from the alphabet). The positive component of the ERP, whose amplitude was larger for rare target stimuli, was labeled a P300, and the latency of this component was longer when the stimuli were embedded in noise. In Experiment 2, subjects performed a choice reaction time task. Following the procedures used by McCarthy and Donchin, stimulus words RIGHT and LEFT required right or left hand responses depending on the presence of a cue word SAME or OPPOSITE which preceded the stimulus. Stimulus words were presented in four different degrees of noise, the levels of which were manipulated by varying the set size of the alphabetic characters which could surround the stimulus words. Reaction time increased both with noise (by 325 ms) and as a function of stimulus‐response incompatibility (by 127 ms). In contrast, P300 latency increased substantially with noise (by 200 ms) but, to a much lesser extent (by 14 ms), with response incompatibility. These results indicate that the P300 is sensitive to the ease with which a target stimulus can be discriminated from noise. They confirm that P300 latency can be used as a measure of the timing of stimulus evaluation processes that is relatively independent of response selection and execution