William A. Johnston

Cell Phone-Induced Failures of Visual Attention During Simulated Driving

This research examined the effects of hands-free cell phone conversations on simulated driving. The authors found that these conversations impaired drivers reactions to vehicles braking in front of them. The authors assessed whether this impairment could be attributed to a withdrawal of attention from the visual scene, yielding a form of inattention blindness. Cell phone conversations impaired explicit recognition memory for roadside billboards. Eye-tracking data indicated that this was due to reduced attention to foveal information. This interpretation was bolstered by data showing that cell phone conversations impaired implicit perceptual memory for items presented at fixation. The data suggest that the impairment of driving performance produced by cell phone conversations is mediated, at least in part, by reduced attention to visual inputs.

Driven to Distraction: Dual-Task Studies of Simulated Driving and Conversing on a Cellular Telephone

Dual-task studies assessed the effects of cellular-phone conversations on performance of a simulated driving task. Performance was not disrupted by listening to radio broadcasts or listening to a book on tape. Nor was it disrupted by a continuous shadowing task using a handheld phone, ruling out, in this case, dual-task interpretations associated with holding the phone, listening, or speaking. However, significant interference was observed in a word-generation variant of the shadowing task, and this deficit increased with the difficulty of driving. Moreover, unconstrained conversations using either a handheld or a hands-free cell phone resulted in a twofold increase in the failure to detect simulated traffic signals and slower reactions to those signals that were detected. We suggest that cellular-phone use disrupts performance by diverting attention to an engaging cognitive context other than the one immediately associated with driving.

Perceptual Fluency and Recognition Judgments

Items seen for the second time in an experiment (old items) can be perceived more readily (fluently) than items seen for the first time (new items) (e.g., Jacoby & Dallas, 1981). We hypothesized that perceptual fluency is used as a cue for discriminating old from new items. In the test phase of a recognition task, each item was gradually clarified until it was identified, at which time subjects made an old/new judgment. We expected that fluently perceived (quickly identified) items would tend to be judged old regardless of their actual old/new status. In Experiment 1, words were more likely to be judged old both if they were quickly identified and, independently of this, if they actually were old. The latter finding implicates a factor (e.g., directed memory search) other than perceptual fluency in recognition judgments. Experiment 2 succeeded in reducing the contribution of this additional factor by using nonwords rather than words. Recognition judgments for nonwords were much more dependent on speed of identificatio n than they were on actual old/new status. We propose that perceptual fluency is the basis of the feeling of familiarity and is one of two important factors that make variable contributions to recognition judgments.

Attention capture by novel stimuli

Abstract : In several experiments, observers were given glimpses of 4-word arrays. Accuracy of word location was tested after each array. Some words, called familiar, appeared many times across the series of arrays; others, called novel, appeared only once. The ratio of novel to familiar words in an array ranged from 0:4 to 4:0. When familiar and novel words were not intermixed (in 0:4 to 4:0 arrays), localization accuracy was higher for familiar words. However, when they were intermixed, especially in 1:3 arrays, accuracy tended to be higher for the novel words. This novel popout effect was the outcome of the suppressed localizability of the familiar words (relative to the 0:4 baseline) and the enhanced localizability of the novel words (relative to the 4:0 baseline). We attribute novel popout to the automatic orientation of attention away from more fluently unfolding regions of the perceptual field (familiar objects) and toward less fluently unfolding regions (novel objects).

The influence of expertise on X-ray image processing.

Observers with four different levels of radiological experience performed a recognition memory task on slides of faces and chest X-ray films. Half of the X-ray films revealed clinically significant abnormalities and half did not. Recognition memory for faces was uniformly high across all levels of radiological experience. Memory for abnormal X-ray films increased with radiological experience and, for the most experienced radiologists, was equivalent to memory for faces. Surprisingly, recognition memory for normal films actually decreased with radiological experience from above chance to a chance level. These results indicate that radiological expertise is associated with selective processing of clinically relevant abnormalities in X-ray images. Expert radiologists appear to process X-ray images the way that we all process faces, by quickly detecting and devoting processing resources to features that distinguish one stimulus from another. However, the selective processing of X-ray films appears to be restricted to clinically relevant abnormalities. As they develop the ability to detect these abnormalities, radiologists appear to lose the ability to detect variations in normal features.

Contribution of perceptual fluency to recognition judgments

Following a shallow (count vowels) or deep (read) study task, old and new words were tested for both fluency of perception and recognition memory. Subjects first identified a test word as it came gradually into view and then judged it as old or new. Old words were identified faster than new words, indicating implicit, perceptual memory for old words. Independently of this effect, words judged old were identified faster than words judged new, especially after shallow study. Eight experiments examined the possible causal relationship between perceptual fluency and recognition judgements. Experiments 1 to 4 showed that fast identifications per se do not promote old judgments. Accelerating the identification of test items by semantically priming them or making them come more quickly into view did not affect recognition judgments. Experiment 5 showed that the usual association of fast identifications with old judgments is not an artifact of item selection because the association disappeared when the identifications and judgements were segregated into different phases of the test task. Experiments 6 and 7 showed tha the likelihood of old judgments increases directly with the pretested perceptibility of test words, but only after shallow study. Experiment 8 showed that the dependency of recognition judgments on perceptual fluency continues to hold when the requirement to identify the words before judging them is eliminated. We conclude that fluency of perception contributes to recognition judgments, but only when the fluency is produced naturally (e.g., through perceptual memory) and explicit memory is minimal.

Perceptual inhibition of expected inputs: The key that opens closed minds.

The mind appears to be biased simultaneously toward both expected and unexpected inputs. For example, familiar scenes are usually perceived more readily than novel scenes, indicating the former bias, but a single novel object sometimes pops out from a familiar field, indicating the latter bias. A diverse literature and a computational model converge on the following resolution to this paradox: The former bias is conceptually driven and actually suppresses data-driven processing of expected inputs; in turn, this suppression disinhibits data-driven processing of unexpected inputs, yielding the latter bias. Evidence for suppressed data-driven processing of expected inputs is drawn from studies of perceptual habituation, semantic satiation, memory inhibition, inhibition of return, repetition blindness, primed inhibition, the word-inferiority effect, registration without learning, and both expert- and schema-based inhibitory effects. Evidence for enhanced data-driven processing of unexpected inputs is drawn from studies of the orienting response, mismatch negativity, memory facilitation, both expert- and schema-based facilitatory effects, and perceptual popout. The model, calledmismatch theory, incorporates inhibitory and facilitatory perceptual dynamics and is found to simulate the opposing biases. Implications of mismatch theory for perceptual phenomenology, dynamic systems theory, mental health, and individual differences are also discussed.

Perceptual processing of nontargets in an attention task

The capability of nontargets to qualitatively influence the semantic processing of coincident targets was investigated in three experiments. Subjects were aurally presented a series of word pairs and attempted to detect homonymic instances of a predesignated category (e.g., animals). The nontarget with which a target (e.g., ANT) was paired was appropriate (e.g., CRAWLING), inappropriate (e.g., UNCLE), or neutral (e.g., STRAW). Experiments 1 and 2 established that detection of targets can be facilitated by appropriate nontargets and inhibited by inappropriate ones. Thus, nontargets can influence the way in which targets are semantically represented. Experiment 3 showed that this effect is eliminated when subjects are precued as to the ear of entry of targets. Thus, precuing appears to curtail the perceptual processing of nontargets. The data run counter to theories that claim that focused attention does not entail the perceptual suppression of nontargets.

Depth of Nontarget Processing in an Attention Task.

Two studies examined the effect of the sensory discriminability of targets from nontargets on depth of nontarget processing. Subjects shadowed target words that were binaurally presented with coincident nontarget words. Targets and nontargets were spoken in the same male voice under low sensory discriminability and in male and female voices, respectively under high sensory discriminability. Across the two studies, depth of nontarget processing was assessed in three ways: extent to which shadowing accuracy was disrupted by a semantic overlap between targets and nontargets, expenditure of capacity (reaction time to subsidiary light signals), and nontarget recall. All three possible measures of depth of nontarget processing decreased as sensory discriminability increased. The data support the assumption of multiple-loci theories of attention that nontargets can be perceptually inhibited; they contraindicate the assumption of late-selection theories that perceptual processing is automatic and irrepressible.

Long-term perceptual memory for briefly exposed words as a function of awareness and attention.

Two experiments investigated the possibility that perceptual memory for words is dependent on level of awareness of those words. In Experiment 1, subjects attempted to report briefly exposed words in a study phase and then identify words that faded into view in a test phase. Old words appeared in both the study and test phases, whereas new words appeared only in the test phase. Perceptual memory, indexed as the faster identification of old vs. new words, was observed only for words correctly reported in the study phase. In the study phase of Experiment 2, words were flanked by digits, and the distribution of attention between words and digits was varied. Perceptual memory increased from nil to high levels as more attention was allocated to the words. These findings suggest that long-term perceptual memory is dependent on level of awareness of words in the study phase.