Subjective pictorial information and visual search

The effects of a combination of variables previously studied in ordinary and dichotic immediate memory were examined in bisensory memory, wherein the visual and auditory modalities were employed. These variables. combined in a factorial design. were: (1) type of material; (2) rate of presentation of material; (3) order of recall for a modality. either first or second; (4) locus of instructions about order of report; and (5) overall differences in memory for each modality. The variables of instruction, order of report, and nature of materials yielded effects in the bisensory situation similar to those reported for the dichotic and ordinary immediate memory situations. On the other hand. interference effects due to the combination of materials in the two channels were practically nonexistent. Additionally, when the modalities were stimulated simultaneously each displayed curves predictable from data obtained when it was explored independently of the other modality.     

The pre/post cueing technique in the study of selective attention

Previous studies using pre/post cueing to study selective perception have typically confounded the disruptive effects of the post-cue with the possible facilitative effects of the pre-cue. The present experiments were designed to control for post-cue delay and interference effects by varying presentation rate but with post-cue delay constant. With both dichotic and bisensory presentation pre/post differences were found to decrease as rate increased. This is interpreted as indicating that the pre-cue did enhance performance of the selection task, that is, that selection occurred during not after intake of the split-span list on pre-cued trials. The results are discussed in terms of perceptual selection and response selection theories of attention.     

Attention to words in different modalities: Four-channel presentation with physical and semantic selection

Theoretical controversy surrounds the issue of whether central processing capacity is unitary and general or whether different types of processing capacity may be distinguished. Three bisensory experiments investigated the selection of words by physical and semantic attributes. It was found that recall was superior following bimodal (auditory and visual) rather than unimodal (auditory or visual) presentation. Furthermore, the difference between bimodal and unimodal recall was greater when the words were physically selected than when they were semantically selected. The results provide evidence that the availability of different types of processing capacity is dependent upon the mode of presentation of material and its required type of analysis.     

Component problems in dichotic listening

The experiments reported examined monitoring for semantically defined targets whilst concurrently shadowing (Experiment I) or listening silently (Experiment II). The word lists for monitoring were either visual or auditory. Monitoring and shadowing accuracy showed less interference when presentation was bimodal than when it was dichotic. However, monitoring latency and recognition memory for shadowed material did not show this effect. It is argued that these data reveal the existence of a number of different sources of potential difficulty in dichotic listening situations and the nature of these is discussed.     

Learning to utilize information presented over two sensory channels

In three separate experiments, Ss were provided with auditory, visual, or simultaneous auditory and visual information in a classification task. Difficulty of classification was manipulated by varying the stimulus exposure duration. Consistent bisensory facilitation effects were noted for later trials, with interference evident on earlier trials. Exposure duration influenced rate and not amount of learning, with bisensory performance being most affected by duration. A transfer paradigm was used in Experiment III, and little if any transfer was noted between unisensory and bisensory stimulus conditions. It was concluded that Ss were extracting the most salient bisensory stimulus components from the auditory and visual modes of information into a unidimensional information configuration.     

Phonological and semantic strategies in immediate serial recall

It has been suggested that certain theoretically important anomalous results in the area of verbal short-term memory could be attributable to differences in strategy. However there are relatively few studies that investigate strategy directly. We describe four experiments, each involving the immediate serial recall of word sequences under baseline control conditions, or preceded by instruction to use a phonological or semantic strategy. Two experiments varied phonological similarity at a presentation rate of one item every 1 or 2 seconds. Both the control and the phonologically instructed group showed clear effects of similarity at both presentation rates, whereas these were largely absent under semantic encoding conditions. Two further experiments manipulated word length at the same two rates. The phonologically instructed groups showed clear effects at both rates, the control group showed a clear effect at the rapid rate which diminished with the slower presentation, while the semantically instructed group showed a relatively weak effect at the rate of one item per second, and a significant reverse effect with slower presentation. The latter finding is interpreted in terms of fortuitous differences in inter-item rated associability between the two otherwise matched word pools, reinforcing our conclusion that the semantically instructed group were indeed encoding semantically. Implications for controlling strategy by instruction are discussed.     

Phonological and semantic strategies in immediate serial recall

It has been suggested that certain theoretically important anomalous results in the area of verbal short-term memory could be attributable to differences in strategy. However there are relatively few studies that investigate strategy directly. We describe four experiments, each involving the immediate serial recall of word sequences under baseline control conditions, or preceded by instruction to use a phonological or semantic strategy. Two experiments varied phonological similarity at a presentation rate of one item every 1 or 2 seconds. Both the control and the phonologically instructed group showed clear effects of similarity at both presentation rates, whereas these were largely absent under semantic encoding conditions. Two further experiments manipulated word length at the same two rates. The phonologically instructed groups showed clear effects at both rates, the control group showed a clear effect at the rapid rate which diminished with the slower presentation, while the semantically instructed group showed a relatively weak effect at the rate of one item per second, and a significant reverse effect with slower presentation. The latter finding is interpreted in terms of fortuitous differences in inter-item rated associability between the two otherwise matched word pools, reinforcing our conclusion that the semantically instructed group were indeed encoding semantically. Implications for controlling strategy by instruction are discussed.     

Hemispheric specialization in learning disabled readers' recall as a function of age and level of processing

This study was designed to test the inadequacy of two theoretical accounts of learning disabled readers' memory deficiencies. Two age groups of learning disabled and nondisabled readers were compared on diotic and dichotic listening recall tasks for semantically organized, phonemically organized, and categorically unrelated word lists presented in either the left, right, or both ears. Dependent measures were free recall, serial recall, recall organization, and hierarchical organization. As expected, recall increases were a function of age, group, and level of word processing. However, the results clearly demonstrated that age and group recall differences were an interaction of both mode of presentation and level of processing. The recall differences between reading groups were attributed to word knowledge (superordinate categorization) rather than recall organization within cerebral hemispheres or differences in hemispheric capacity, per se.     

Perception of threat cues in post-traumatic stress disorder: Semantic processing without awareness?

Research suggests that anxiety-disordered patients semantically process, without awareness, threat cues occurring in unattended prose passages during dichotic listening (Mathews, 1984). In the present study, we attempted to demonstrate unaware semantic processing of threat cues in Vietnam combat veterans with post-traumatic stress disorder (PTSD). Control Ss included alcoholic and normal veterans, all without combat experience. To provide a rigorous test of the hypothesis, we employed a dichotic listening procedure that strictly controlled the S's attentional resources and prevented momentary attention shifts from producing results spuriously suggesting semantic processing without awareness. The processing measures included skin conductance responses and shadowing errors following presentation of threat words related to Vietnam, phonetically similar words, words threatening for other anxiety-disorder groups and neutral words. The results were inconsistent with the semantic processing without awareness hypothesis, suggesting that previous data adduced as evidence for the phenomenon may have stemmed from prose shadowing procedures that permitted momentary awareness of threat cues on the unattended channel.     

Temporal Grouping Effects in Immediate Recall: A Working Memory Analysis

The presence of temporal pauses during list presentation can markedly improve immediate memory for a sequence of verbal items. A series of experiments analysed this effect using Baddeley's (1986) model of working memory. Experiment 1 showed that the effect of temporal grouping on memory for visual sequences was removed by either articulatory suppression or reciting random digits. Experiment 2 indicated that effects of temporal grouping were insensitive to the word length of the items. Experiment 3 showed that articulatory suppression did not remove the temporal grouping effect for auditory lists. Experiment 4 showed that the temporal grouping effect was insensitive to the phonemic similarity of the items. The effects of concurrent articulation suggest that grouping influences the phonological loop component of working memory. However, the working memory model is insufficiently well specified to account for the insensitivity of grouping effects to word length and phonemic similarity. The main findings could be simulated by a connectionist model of the phonological loop, which invokes a context timing signal (Burgess & Hitch, 1992, in press), This assumed that pauses during list presentation affect the timing signal in a similar way to the pause before list presentation and made some novel predictions.     

The sound of enemies and friends in the neighborhood

Previous studies (e.g., Pecher, Zeelenberg, & Wagenmakers, 2005) found that semantic classification performance is better for target words with orthographic neighbors that are mostly from the same semantic class (e.g., living) compared to target words with orthographic neighbors that are mostly from the opposite semantic class (e.g., nonliving). In the present study we investigated the contribution of phonology to orthographic neighborhood effects by comparing effects of phonologically congruent orthographic neighbors (book-hook) to phonologically incongruent orthographic neighbors (sand-wand). The prior presentation of a semantically congruent word produced larger effects on subsequent animacy decisions when the previously presented word was a phonologically congruent neighbor than when it was a phonologically incongruent neighbor. In a second experiment, performance differences between target words with versus without semantically congruent orthographic neighbors were larger if the orthographic neighbors were also phonologically congruent. These results support models of visual word recognition that assume an important role for phonology in cascaded access to meaning.     

Phonemic and category encoding of unattended words in dichotic listening

The claim that unattended items in dichotic listening are categorized (Smith & Groen, 1974) was examined in three experiments using dichotic presentation and probe reaction time. Negative probe words from the unattended list were more difficult to reject when the dichotic lists shared a semantic category than when they differed in category, whether or not the attended list was precued, thereby replicating and extending Smith and Groen’s findings. The difficulty with intralist probes following dichotic lists of a homogeneous category was found to be a special case of the probe similarity effect, since extralist probes of the same category as the attended input were rejected more slowly (and with more errors) than different category probes. The effects of category homogeneity were evident on the attended, but not on the unattended, inputs (Experiment 2). The third experiment compared focused and divided attention with dichotic lists of unrelated items. Phonemically similar probes were more difficult to reject when related to items on the attended channel in the focused condition than either channel in divided attention, and easiest to reject when similar to an unattended item. Linear regression confirmed that the unattended input was processed only at a precategorical (acoustic) level.     

Switching attention between the ears to monitor tones Nigel Harvey

Alternating dichotic presentation of tones was compared with monaural presentation in two different perceptual tasks. When Ss were asked to detect higher frequency target tones in fists of six background tones, they missed less than 5%. However, when the presentation was fast (10/sec) and the tones alternated dichotically, Ss reported “hearing” only three or four tones. In two further experiments, Ss were asked to judge the number of tones or to report their spatial and temporal positions; these tasks were much less accurately performed, for the dichotic lists, than the target detection task. The differing effects of switching rate on these tasks are discussed in relation to the types of processing they require.     

Effects of modality preferences on learning and recall of bisensory stimuli

The performance of visual attenders and aural attenders, as defined by performance on a bisensory digit-span task, was compared on three bisensory tasks. First, in replication of an earlier study, performance was compared on a bisensory missing-unit paradigm, in which S was required to respond with missing units from two independent sets of stimuli, each set being presented on a separate channel. The results corroborated those of an earlier study in which an interaction between modality preferences and presentation modality was found. Further, differential recall patterns were found for each of the groups. While such comparable results were not found on the other two tasks, differential performance on a bisensory paired-associate task and a bisensory connected discourse task were found. The results are interpreted in accord with Murdock’s (1967) hypotheses concerning separate sensory storage mechanisms.     

Recognition-induced forgetting does not occur for temporally grouped objects unless they are semantically related

Recent evidence has shown that practice recognizing certain objects hurts memories of objects from the same category, a phenomenon called recognition-induced forgetting. In all previous studies of this effect, the objects have been related by semantic category (e.g., instances of vases). However, the relationship between objects in many real-world visual situations stresses temporal grouping rather than semantic relations (e.g., a weapon and getaway car at a crime scene), and temporal grouping is thought to cluster items in models of long-term memory. The goal of the present study was to determine whether temporally grouped objects suffer recognition-induced forgetting. To this end, we implemented a modified recognition-induced forgetting paradigm in which the objects were temporally clustered at study. Across four experiments, we found that recognition-induced forgetting occurred only when the temporally clustered objects were also semantically related. We conclude by discussing how these findings relate to real-world vision and inform models of memory.     

Dichoptic and dichotic micropattern discrimination

Ss compared two rapidly successive, brief, discriminably different stimulus elements, called a micropattern, with a second micropattern composed of the same two stimulus elements presented in reverse temporal order. Discriminations could be made between two such micropatterns in the monaural (monocular) as well as in the dichotic (dichoptic) modes of presentation. Discrimination between micropatterns was based on the perceptual dominance of the temporally trailing stimulus element in both modalities and in both modes of presentation. While monaural (monocular) micropattern discrimination is significantly superior to dichotic (dichoptic) discrimination, the existence of dichotic (dichoptic) discrimination demonstrates that no essential peripheral process is required for micropattern discrimination.     

Shadowing in bisensory memory

Shadowing (vocalization-at-presentation) was applied to a bisensory situation where different messages were simultaneously presented to the visual and auditory modalities. Three groups of subjects were employed: Group I shadowed the visual modality; Group II shadowed the auditory modality; Group III was a control, shadowing neither modality. Shadowing in the present experiment facilitated recall of the shadowed modality, particularly the visual modality, which is usually inferior to auditory recall.

It also became apparent that visual recall in an ordinary bisensory situation was minimal if not near an incidental level and that a true bisensory situation with equal division of attention between the two modalities employed does not exist.     

Semantic Informativeness Mediates the Detection of Changes in Natural Scenes

Three experiments investigated whether the semantic informativeness of a scene region (object) influences its representation between successive views. In Experiment 1, a scene and a modified version of that scene were presented in alternation, separated by a brief retention interval. A changed object was either semantically consistent with the scene (non-informative) or inconsistent (informative). Change detection latency was shorter in the semantically inconsistent versus consistent condition. In Experiment 2, eye movements were eliminated by presenting a single cycle of the change sequence. Detection accuracy was higher for inconsistent versus consistent objects. This inconsistent object advantage was obtained when the potential strategy of selectively encoding inconsistent objects was no longer advantageous (Experiment 3). These results indicate that the semantic properties of an object influence whether the representation of that object is maintained between views of a scene, and this influence is not caused solely by the differential allocation of eye fixations to the changing region. The potential cognitive mechanisms supporting this effect are discussed.     

The effect of presentation rate on categorization

Homogeneous experimental (acoustically and semantically related) and control lists were presented to different groups of subjects at either 1 s or 6 s per word. The difference score between these two lists was used as a measure of categorization. Only words in the middle serial positions (representing retrieval from secondary memory) were scored. Clustering was also measured.

Slow presentation rate significantly increased categorization of the semantically similar words. This was not true of acoustically similar words. A possible explanation of this is that semantic categorization is time-consuming and acoustic categorization is not. Alternatively, the acoustic similarity effect may be a retrieval effect. The absence of acoustic clustering would seem to fit in with this latter interpretation.     

Eye-movement patterns in selective listening tasks of focused attention

Three experiments are described in which eye movements (Ems) were recorded in conjunction with either monaural or dichotic tasks of focused attention. Two main effects were observed in the Ems records: (1) Listening to auditory messages reduced the occurrence of spontaneous Ems. (2) Selective monitoring of one ear in the dichotic task was accompanied by a consistent pattern of directional Ems characterized by big saccades and long changes of eye fixation in the direction of the relevant ear. The pattern of Ems is affected by the following variables: the presentation rate of the auditory information, the frequency of demands to switch orientation between the ears, and the competition of the irrelevant channel in the dichotic task. It is suggested that the eye-movement mechanism is used in selective listening tasks as a general orientation indicator, when the adoption or maintenance of a certain selective set is difficult and demanding of effort. The Ems response is part of a general orientation pattern, although its usual function is in the field of visual perception.