Experiment 2 – Attentional load
In this experiment subjects undertook a task of high perceptual load, and it was investigated whether or not a person’s name captured attention in this condition. Twenty subjects were used. An RSVP stream was shown in which a stream of green lexical stimuli was superimposed on a stream of red picture stimuli. The picture stream contained familiar objects and the lexical stream contained the subject’s name, 17 meaningful words, and 14 meaningless letter combinations. Practice trials were carried out before the experiment. The pairs of stimuli were shown every 500ms for 250ms and the subjects were asked to identify any repeats in the picture stream. A surprise recognition test was then carried out in which subjects were asked to identify, from a list containing the words which had appeared in the previous test as well as some new words, words which they remembered.
Results and conclusions
Exp. 1 - The results for the control subjects were as expected, i.e. all of the probes were detected almost all of the time. However for the experimental condition, it was seen that the tree was detected least frequently, the happy face was detected most frequently, and the upside down face was in between. It was found that the happy face does not suffer an attentional blink because no significant differences were found between different positions of this probe. On the other hand, the tree was clearly affected by an AB. The upside down happy face did not experience an AB, although this could be contributed to its similarity to the happy face, and the possibility that it may have been mistaken for the happy face on some occasions.
Exp.2 – It was seen from the results that there was no significant difference between recognition of new or old words; however a highly significant difference was observed between the recollection of these words and the subject’s name. The name was identified by 50% of the subjects, but the highest percentage for identification of any other word was only 20%, thus showing that the name did indeed capture attention even when the primary task was one of a high perceptual load.
Analysis of paper:
In order to analyse the merits of this paper, and its contribution to the knowledge of attention, it is necessary to discuss the various models of attention which had been proposed prior to this study. The first of the three most prominent models of attention was put forward by Broadbent in 1958 and is known as the Filter Model. This model says that a filter system carries information to the short-term memory, and if two sets of stimuli are present, only one is able to get through the filter, i.e. unattended stimuli do not get through. This model was proposed as a proponent of the early selection theory, which says that attention is subject to perceptual limitations. Treisman’s Attenuation Theory (1964), despite agreeing with Broadbent on the issue of early selection, differs in that it proposes that unattended information is attenuated and if significant enough, has the potential to capture attention, i.e. it is not ignored completely as suggested by Broadbent. The third classic model of attention was by Deutsch and Deutsch (1963), and proposed a model of late selection. It suggested that all information is analysed and selection or filtering occurs at the stage of the response.
The conflict between early and late selection models has been addressed by Lavie (1995) who proposed a model in which late selection occurs when the perceptual load is low, and early selection occurs when the perceptual load is high. The results of the study being analysed, which show that meaning captures attention, support this model to some extent. This is because they show that an increase in perceptual load results in only 50% of subjects reporting observation of their name in the unattended stream, as opposed to other studies involving inattentional blindness and attentional blink in which the vast majority of the subjects detect the presence of their name.
However the results also showed that even with a high perceptual load, the person’s name was able to capture attention relatively frequently, thus going against Lavie’s view, from which it was predicted that items in the unattended stream would not be perceived. This result also refuted the study by Rees et al.(1999), which supports Lavie’s model by concluding that when the task is of a high perceptual load, unattended and irrelevant would do not undergo processing. Therefore in the specific area of developing an accurate model of attention, this study was not definitive, since it did not provide solid evidence completely for or against any model, nor did it propose a new or adapted model of attention.
Despite this, the study did clarify the view that the happy face icon and the observer’s name capture attention due to their meaningfulness and not their familiarity. This agreed with a previous study (Mack and Rock, 1998) in which the subject’s name was altered by changing a vowel. This changed form of the name underwent inattentional blindness to a much greater extent than the original name which experiences no significant inattentional blindness at all.
In the previous study cited above, further evidence was found against the possibility that the ability to capture attention is on the basis of familiarity. In this study it was investigated whether the words THE and AND, would suffer inattentional blindness to a lesser extent than the words TIE and ANT. This would of course be expected to happen if familiarity was the defining factor in capturing attention, since THE and AND are much more common and familiar words than TIE and ANT. However there was no significant difference, thus indicating that familiarity is not the reason for capture of attention. This study substantiates the view that meaningfulness of the stimuli is the significant factor in capturing attention, because it was found that the happy face icon and the observer’s name were detected frequently in the unattended stream, and the familiarity of these stimuli is not likely to be the key factor in capture. With familiarity seemingly ruled out, it is highly likely on this evidence that meaning is indeed the vital factor in capturing attention.
Many subsequent studies have attempted to further explain inattentional blindness, the capturing of attention, and the various models of attention. Cartwright-Finch and Lavie (2006) investigated inattentional blindness and their findings were in favour of the perceptual load theory. They discovered that with a higher perceptual load, irrelevant stimuli were observed less frequently. However, one criticism of this study is that it did not use either of the stimuli which have been shown to capture attention consistently, i.e. the name, and the happy face. The study does dismiss the paper being analysed (Mack et al., 2002) by saying “as there were no direct manipulations of attention in these studies (referring to Mack et al., 2002) however, causal inferences about the role of attention in awareness cannot be drawn from these results” (Cartwright-Finch and Lavie, 2006).
With regards to the attentional blink paradigm, a study was conducted by Milders et al. in 2006 showing that the frequency of detection of fearful faces was greater than neutral faces, and happy faces. It also showed that conditioning of the neutral stimuli with the fearful face could adjust detection of the neutral stimuli.
A study by Downing et al. (2004) built on this study (Mack et al., 2002) by showing that images of the human body were also capable of capturing attention in an inattentional blindness task. An author of this study (Mack et al., 2002), Arien Mack published a review on inattentional blindness (Mack, 2003), in which he said that although attention, and in particular inattentional blindness has been well established and researched, many questions remain in this field. These uncertainties include whether or not all unattended stimuli are processed, the actual model of attention, whether two separate visual systems exist, and even the implications of inattentional blindness on life and death situations.
All of this evidence points to the vastness of this field, and the considerable amount of uncertain information regarding it. In the context of the field, the study by Mack et al. (2002) was worthwhile in that it has confirmed the ability of certain stimuli (the observer’s name and the happy face icon) to capture attention, and it has provided more evidence that the key factor in capturing attention is meaningfulness. It has also cast doubts on some aspects of the perceptual load theory (Lavie, 1995). However despite its usefulness, it can by no means be regarded as a ‘keystone’ study in the field as it was mostly attempting to verify information from previous research, and it provided few definitive answers to some of the important outstanding questions remaining in this field.
References
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