Mary C. Potter

A Two-Stage Model for Multiple Target Detection in Rapid Serial Visual Presentation

When 2 targets are presented among distractors in rapid serial visual presentation, correct identification of the 1st target results in a deficit for a 2nd target appearing within 200-500 ms. This attentional blink (AB; J.E. Raymond, K.L. Shapiro, & K.M. Arnell, 1992) was examined for categorically defined targets (letters among nonletters) in 7 experiments. AB was obtained for the 2nd letter target among digit distractors (Experiment 1) and also for a 3rd target (Experiment 2). Results of Experiments 3-5 confirmed that AB is triggered by local interference from immediate posttarget stimulation (Raymond et al., 1992) and showed that AB is modulated by the discriminability between the 1st target and the immediately following distractor. Experiments 5-7 further examined the effects of both local interference and global discriminability. A 2-stage model is proposed to account for the AB results.

Short-term conceptual memory for pictures.

Three converving procedures were used to determine whether pictures presented in a rapid sequence at rates comparable to eye fixations are understood and then quickly forgotten. In two experiments, sequences of 16 color photographs were presented at rates of 113, 167, or 333 msec per picture. In one group, subjects were given an immediate test of recognition memory for the pictures and in other groups they searched for a target picture. Even when the target had only been specified by a title (e.g., a boat) detection of a target was strikingly superior to recognition memory. Detection was slightly but significantly better for pictured than named targets. In a third experiment pictures were presented for 50, 70, 90 or 120 msec preceded and followed by a visual mask; at 120 msec recognition memory was as accurate as detection had been. The results, taken together with those in 1969 of Potter and Levy for slower rates of sequential presentation, suggest that on the average a scene is understood and so becomes immune to ordinary visual masking within about 100 msec but requires about 300 msec of further processing before the memory representation is resistant to conceptual masking from a following picture. Possible functions of a short-term conceptual memory, such as the control of eye fixations, are discussed.

Lexical and conceptual representation in beginning and proficient bilinguals

Two hypotheses about the association between the equivalent words in a bilinguals two languages are considered. The word association hypothesis proposes that a direct association is established between words in the two languages. During second-language acquisition, that association is used to understand and produce words in the second language by retrieving a word in the first language. The concept mediation hypothesis proposes that the only connection between the two languages is via an underlying, amodal conceptual system, one to which pictured objects also have access. The hypotheses make different predictions about the time to name pictures in the second language relative to the time to translate first-language words into the second language. Two experiments are reported, one with proficient Chinese—English bilinguals and the second with nonfluent English—French bilinguals (American high school students). Subjects read words aloud, named pictures, and translated words; one Chinese—English group categorized pictures and words. The results were consistent with the concept mediation hypothesis and contradicted predictions of the word association hypothesis. There was no evidence for a direct association between words in the two languages in either bilingual group.

Recognizing words, pictures, and concepts: A comparison of lexical, object, and reality decisions.

A series of five experiments addressed the question of whether pictures and the words that name them access a common conceptual representation. In the first three experiments the processing of words in the lexical decision task was compared with the processing of pictured objects in a formally analogous task which we called the object decision task . The results showed that the lexical and object decision tasks produce approximately similar response latencies and are similar in their sensitivity to a set of experimental manipulations (e.g., frequency effects, interference effects, semantic facilitation from related words or pictures). In two additional experiments the processing of words was compared with that of pictures in a mixed reality decision task in which a decision about whether a word or picture represents a real thing is to be made independent of the surface form. The results indicated that subjects were unable to make amodal decisions of this sort; the response latencies in reality decision were markedly longer than those in either a pure lexical or pure object decision and there was little conceptual transfer across repetitions of different surface forms. Overall, the results of the five experiments suggest that the major component in a lexical or object decision is a form-specific memory representation of the word or visual object.

Scene Consistency in Object and Background Perception

Does knowledge about which objects and settings tend to co-occur affect how people interpret an image? The effects of consistency on perception were investigated using manipulated photographs containing a foreground object that was either semantically consistent or inconsistent with its setting. In four experiments, participants reported the foreground object, the setting, or both after seeing each picture for 80 ms followed by a mask. In Experiment 1, objects were identified more accurately in a consistent than an inconsistent setting. In Experiment 2, backgrounds were identified more accurately when they contained a consistent rather than an inconsistent foreground object. In Experiment 3, objects were presented without backgrounds and backgrounds without objects; comparison with the other experiments indicated that objects were identified better in isolation than when presented with a background, but there was no difference in accuracy for backgrounds whether they appeared with a foreground object or not. Finally, in Experiment 4, consistency effects remained when both objects and backgrounds were reported. Semantic consistency information is available when a scene is glimpsed briefly and affects both object and background perception. Objects and their settings are processed interactively and not in isolation.

Two attentional deficits in serial target search: the visual attentional blink and an amodal task-switch deficit.

When monitoring a rapid serial visual presentation at 100 ms per item for 2 targets among distractors, viewers have difficulty reporting the 2nd target (T2) when it appears 200-500 ms after the onset of the 1st letter target (T1): an attentional blink (AB; M. M. Chun & M. C. Potter, 1995b; J. E. Raymond, K. L. Shapiro, & K. M. Arnell, 1992). Does the same deficit occur with auditory search? The authors compared search for auditory, visual, and cross-modal targets in 2 tasks: (a) identifying 2 target letters among digits (Experiments 1-3 and 5) or digits among letters (Experiment 6), and (b) identifying 1 digit among letters and deciding whether an X occurred among the subsequent letters (Experiment 4). In the experiments using the 1st task, the standard AB was found only when both targets were visual. In the 2nd task, with a change in selective set from T1 to T2, a task-switching deficit was obtained regardless of target modality.

Regeneration in the short-term recall of sentences ☆

Abstract Verbatim short-term memory for a sentence has been taken as evidence for a surface representation different from the conceptual representation characteristic of longer-term memory. In seven experiments we investigated an alternative hypothesis: that immediate recall involves regeneration of the sentence from a conceptual representation, using words that have been recently activated. A key claim is that the activated lexical items are unordered. To test this hypothesis, a synonym of a word in the sentence was presented in a secondary task before or after the sentence, prior to recall. As predicted, these lure words were intruded frequently (Experiments 1 and 2), but only when supported by the meaning of the whole sentence (Experiments 3 and 4). In Experiment 5 as high an intrusion rate was obtained for sentences read in RSVP at 100 ms per word as at the 200 ms rate of the other experiments. Experiment 6 showed that listeners make even more lure-based intrusions than readers. In Experiment 7 4-year-old children made intrusions similar to those of adults. The results support the hypothesis that a sentence is regenerated in immediate recall from a representation of its meaning, using recently activated words. Only when the right set of words is active will recall be “verbatim.”

Very short-term conceptual memory

Short-term memory for conceptual information is largely missing from current models of short-term memory. Several phenomena are discussed that give evidence for very brief conceptual representations of stimuli. Although these fleeting representations do not surface readily with many of the standard methods for studying and testing short-term memory, I argue that they are fundamental to cognitive processing and to the form that long-term memory takes.

Interference in visual recognition.

Pictures of common objects, coming slowly into focus, were viewed by adult observers. Recognition was delayed when subjects first viewed the pictures out of focus. The greater or more prolonged the initial blur, the slower the eventual recognition. Interference may be accounted for partly by the difficulty of rejecting incorrect hypotheses based on substandard cues.

The time course of competition for attention: attention is initially labile.

Competition for attention between 2 written words was investigated by presenting the words briefly in a single stream of distractors (Experiment 1) or in different streams (Experiment 2-6), using rapid serial visual presentation at 53 ms/item. Stimulus onset asynchrony (SOA) was varied from 0 to 213 ms. At all SOAs there was strong competition, but which word was more likely to be reported shifted markedly with SOA. At SOAs in the range of 13-53 ms the second word was more likely to be reported, but at 213 ms, the advantage switched to the first word, as in the attentional blink. A 2-stage competition model of attention is proposed in which attention to a detected target is labile in Stage 1. Stage 1 ends when one target is identified, initiating a serial Stage 2 process of consolidation of that target.