Timing of facilitatory and inhibitory effects of visual attention

Three experiments were conducted to investigate influences on the precue-to-target delay at which response facilitation is first replaced by inhibition of return (IOR). In Experiment 1, different ranges of delays were used; the interpolated delay at which faster RTs for matching precue and target locations changed to slower RTs was inversely related to the length of the range of precue-to-target delays within a block of trials. These findings were replicated in Experiment 2, which additionally showed that task difficulty provided an insufficient explanation for the delay in the changeover time. These data allowed the conclusion that a shorter range of precue-to-target delays results in later onset of IOR than does a longer range of delays. The data from Experiment 3 suggested that a single character on the target screen confounds the interpretation of possible facilitation and/or inhibition due to the allocation of attention. These results were related to other reported findings and to theories of attention allocation.     

The Role of Irrelevant,Class-Consistent,and Class-Inconsistent Intraverbal Training on the Establishment of Equivalence Classes

The Psychological Record - The current study evaluated whether college students’ performance on visual–visual matching-to-sample (MTS) tasks were differentially affected by learning to...     

Time-course of sensitivity changes as attention shifts to an unpredictable location.

Shifting visual attention is often described as analogous to a spotlight moving through empty space between locations. In the present experiment, a peripheral precue summoned attention to an initial location, and 200 ms later a second peripheral cue appeared beside one of two possible second locations, each 14 degrees away from the initial location. The target was twice as likely to appear at the location that had been indicated by the immediately preceding cue as at the location that had been previously cued or that would be cued. Fine-grained temporal analyses indicated that, as attention was shifted, sensitivity to information at the second location gradually increased while sensitivity at the first location simultaneously decreased. Average sensitivity over the two locations during the shift remained significantly greater than average sensitivity immediately following the initial precue. In contrast, an attentional "spotlight" moving from the first to the second location would produce a decrease in average sensitivity to its initial level while the spotlight was between locations.     

Analog versus discrete shifts of attention across the visual field

Summary Two discrimination experiments were run to investigate analog versus discrete properties of a shift of visual spatial attention. Central cuing was used in Experiment 1, whereas peripheral cuing was used in Experiment 2. Presentation of a probe stimulus between fixation and the target (Distance 1), opposite fixation from the target (Distance 3), or away from an imaginary line running from the target through fixation (Distance 2) permitted a fine-grained analysis of attention at those loci across target-probe delays. D-prime analyses in both experiments suggest that attention is shifted in a discrete manner between locations. Sensitivity to probes was generally greater when the probe was aligned with the target and fixation, with Distance 3 equal to Distance 1, than when it was away (at Distance 2). Analysis of sensitivity to targets across cue-probe delays suggests that attention was directed to the probe upon its appearance.This research was supported by a grant from the National Science Foundation (BNS87-20421).     

Target letter inclusion in single and multiple word substrings and identification accuracy

In experiment 1, target letter discrimination in quadrigrams containing multiple subwords was found to be no more accurate than target letter discrimination in strings of four unrelated letters. Discrimination in quadrigrams, each including the target letter and a one-word trigram of which the target was not a part, was significantly poorer than discrimination in either of the other two types. In Experiment 2, a possible explanation of the latter result involving capacity limitations was eliminated by presenting the target above or below the other letters, which were presented in the same order as in corresponding strings in Experiment 1. The results are explained with respect to the interactive activation model of context effects in letter perception, with a modification proposed involving inhibitory connections between word nodes.     

Scanning,holistic encoding,and the word-superiority effect

The role of holistic encoding induced by scanning in the superior identifiability target letters in orthographic strings (words) enjoy over those in strings of unrelated letters was examined in two experiments. Both the set of potential targets and the critical position in the letter arrays were predesignated. One group in each experiment was induced to scan each array from left to right in a dot-counting task. A dot could precede the array to its left and/or appear with the array to its right. Only this group displayed the word superiority. For the second group in the first experiment, any dot(s) present always appeared with the array. The second group in the second experiment was shown no dots but, rather, performed the letter-identification task only. The absence of a word-superiority effect in other studies is related to holistic encoding stemruing from scanning requirements, and the implications for positional uncertainty explanations of the phenomenon are discussed.