Abstract
This study sought to investigate the fact that there is greater likelihood of one to falter in detecting the second target T2 after he has detected the first target T1. There had been concerns that participants in previous studies had problems in detecting the second target after 200 ms -500 ms from the first target. The researcher employed a 2 ×6 experimental design; it involved a randomized sample of 49 university students. Using web experiment software, Interactive Sensation Laboratory Exercise (ISLE), the researcher had students identifying letter S as the first target and letter T as the second target after 200 ms to 500 ms. Results indicated that participants had most difficulties in identifying the second target in the first probe. As students were involved in more trials, they became increasingly apt in identifying subesquent targets.
Attentional Blink
Attentional blink (AB) is a phenomenon experienced in a rapid serial visual presentation (RSVP). In a typical serial visual presentation, individuals’ temporal characteristics of attention are examined. Participants are required to identify one or two target items in a set of items, determined by the researcher (usually 10 items), within a second (Raymond, 2014). The target items can be letters, pictures or digits presented together with distracter items as a single set. Participants can be told to identify a letter or letters of certain color from a group of detractors. In a two step rapid serial visual presentation (RSVP), participants are presented with two stimuli to be separated from detractors. For instance, after choosing the first white letter, as the first target (T1), one is also required to identify a black letter, as the second target (T2) (Drew et al., 2014). Although the concept of attentional blink (AB) had been discussed in some published works of psychologists, they were Raymond, Shapiro and Arnell (1992) that first illustrated it using the current term. Studies have indicated that when a participant is presented with a sequence of visual stimuli, at the same spatial location for instance on screen, in a plan of rapid succession, he will fail to separate or detect the second target stimulus occurring between 180-450 milliseconds (Shapiro, Raymond & Arnell, 2009). Researchers have called this limitation in perceiving the second target as “repetition blindness” (Raymond, 2014).
Shapiro, Raymond and Arnell (2009) have indicated that AB should not be taken to mean the failure of attention. They conjecture that AB is usually a failure of an individual to retain memory concerning two targets until he or she is prompted with the target appearance at the end. An important aspect of the AB experiment is the inclusion of lags. Lag sparing enables the targets to be presented very closely, so that they appear in the intervals of 200 ms to 500ms (Kamienkowski, & Navajas, & Sigman, 2012). However, targets presented at greater lags can be impaired (Shapiro, Raymond & Arnell, 2009). According to the LC_NE Hypothesis, when an individual detects a meaningful stimulus, neurons in the brain’s locus coeruleus release norepinephrine. Norepinephrine is a neurotransmitter that enables one to detect the stimulus. However, the effect of norepinephrine lasts for only 100 milliseconds after the first salient target. It can therefore only benefit the second target if the second target is presented immediately, just after the first target (Dux & Colheart, 2008).
What Influences AB?
According to some researchers, attentional blinks can be moderated by effects of visual similarities between distracter and target stimuli. They have indicated that if the target stimuli posses some conceptual similarities, it will make the participants to easily involve in preconscious separation (Shapiro, Raymond & Arnell, 2009). For instance, Raymond (2003) concluded that despite attentional process limitations influencing the level of attention blink, features of the objects presented can also influence the attention. Nieuwenstein, Theeuwes and Potter (2009) are opposed to this view: they have conjectured that conceptual effects do not affect the AB. Their study indicated that whether distracters were present or not, the AB effects could still be felt. However, when the targets were put in a sequence, attention did not blink, indicating that distracters play crucial roles in causing AB.
The other important factor that influences AB outcomes is the work of emotions. Studies have indicated that when the second target (T2) is perceived with a lot of emotion as a relevant stimulus, it is likely to be separated more easily. The emotional relevance of T1 can also affect T2 due to elongated effects on AB. If emotional relevance of T1 is stronger than that of T2, the level of AB on T1 will be lengthened, whilst that on T2 will be reduced. Studies have also indicated that meditations can affect the Attention Blink. Individuals with intensive training in meditations can detect the two targets effectively. Meditations improve one’s focus so that he can involve in successful identification of the target. Adamo, Cain and Mitroff (2013) have indicated that self-induced Attention Blink can occur due to satisfaction search. Satisfaction obtained after detecting the fast target can decrease the motivation and concentration power needed for detecting the second target. The likelihood of decreased accuracy in the second target is more notable if the second target is to appear from 200 to 500 milliseconds.
In Zhao, Li, Ding and Chen (2012), it was noted that distracter detection made it easier for individuals to detect the target. If participants in their experiment identified or detected distracters quickly, they would easily identify the target. Therefore, it was important that individuals developed suppression mechanisms to avoid effects of AB. While investigating the effect of masking the first target, T1, Brisson and Bourassa (2011) also noted that when a distracter is removed, the significance of AB in the experiment can be reduced. In this regard, despite slowing down T1 processing, it also increases the period length of which the T2 has to wait to be consolidated.
For Janson et al. (2014), a mere presence of RSVP stream does not indicate the likelihood of AB. It is the content of the RSVP that determines the detection of T2. When a participant notices that RSVP stream has ever-changing stimuli, after detecting T1, he will be prompted to commit more resources to detect T2. The researchers propose that individuals have necessary and sufficient amount of attention to process distracting information.
Drew (2014) noted that the target set size influenced the level of AB. Earlier theories such as those of Shapiro (1994) indicated that since the brain deals with quick streams of information all the time, the brain has to distribute attentional resources to store, retrieve, comprehend and interpret the information properly. Although human brain can involve in complex tasks, it usually has restrictions. Attention blink is an example of manifestations of the restrictions (Chun & Potter, 2014). In an environment that is swarmed with streaming flows of information, restrictions in the brain make it hard for people to recognize some stimuli. Thus, when attentional processes are usually linked to identification of the first target, an individual is more likely to fail to recognize the second target (Asplund, et al., 2014).
Research Hypotheses
Hn: 1. Having just seen the first target does not affect the ability to detect the second target.
2. There are significant differences in interaction between targets and probes
Ho: 1. Seeing the first target does affect the ability to detect the next target.
2. There are no significant differences in interaction between targets and probes
METHOD
Participants
The study involved 54 students from a University Campus who took part in the experiment. The sample comprised approximately equal numbers of male and female participants. The students reported normal color vision and visual acuity, and neurological intactness. Five students were eliminated, making the study to remain with 49 students who formerly took part in the experiment. The experiment was a mandatory class requirement: the researcher did not obtain written consents from student or permission from the University research ethics committee before the experiment begun.
Apparatus and Stimuli
The experiment used Gateway computer systems. They had been programmed with the web-based Interactive Sensation Laboratory Exercise (ISLE) software. The RSVP presented in the centre of the screen had 2-6 digits, and alphabets H, K, M, N, P, R, S, T and U; all 14 items. The first target, T1, was letter S. The second target, T2, was letter T. All items were in Times New Roman format and font size 10.0. The background display value was 0.00. Both digits and alphabets were randomized after each probe so that no specific conceptual hint was evident to reduce the AB. Each probe involved running a complete stream so that all the letters and digits were seen by participants. Each item was shown on the screen for about 50 milliseconds, and it was separated from the next item by 30 milliseconds. This yielded a presentation rate of 10 items/ second.
Design
The study took a randomized approach. All the 54 participants were selected randomly from a large group of University student volunteers. It took the design of 2×6 repeated within-subject design; there were 6 trials (probes) on both T1 and T2 by every participant. Therefore, the first independent variable was repetition, and it had two levels: target 1 and target 2. The second independent variable was lag. In this case, the lag has six levels: probes 1-6.
Procedure
After preparation of all equipments for the experiment, each participant was to be involved in all 12 probes (six trials for T1 and six trials for T2). One was to report the identity of S (as T1) by pressing the key [S] on the keyboard. T2 was to be reported by pressing the key [T] on the keyboard. The next trial began within 200-500 ms after the first stream. The same procedure was repeated five times for the participant to identify T1 and T2 among detractors again.
RESULTS
Figure 1: RSVP Project (n=48)
In Figure 1, the 2×6 repeated measure design indicates that both T1 and T2 targets were functions of repetition and probes. As the number of probes increased, and participants were allowed to repeat trials, the extent of making errors in detecting T2 reduced. The mean percentage accuracy in detecting T2 tended to increase with the number of probes.
ANOVA Results
In ANOVA results, the null hypothesis that means of target 1 and target 2 are not equal cannot be rejected. However, probes do not differ: results do not indicate any significant differences among them. With 95% confidence there are significant differences in means between target T1 and T2. The value of p= 3. 57E-17< α=0.05 indicates there are significant differences in the outcomes of T1 and T2. In probes, when p= 0.663509 > α=0.05, there are no significant differences among their outcomes. The value of p= 0.995968 > α=0.05 (in interactions), also indicates that there are no significant differences in interactions between probes and targets (see appendices, Table 1). The same results can be illustrated by the F-values. In targets, since the Fcrit1.806785 < Fcalc.10.30265, it can be noted that there exist significant differences among means and variances of target 1 and target 2 (see appendices, Figure 2 and Figure 3). In probes outcomes, Fcrit 2.621786 > Fcalc.0.527578, indicates that variances and means are significantly not different. Likewise in interaction, inferences Fcrit1.458602 > Fcalc.0.461679 indicate that variances and means are same (see appendices, Table 1). These can be evidenced in Figures 3 and 4. In the expanded of the graph, one can note that all lines are not roughly parallel. This indicates that interactions between probes and targets can be expected. The graphs of probes and targets are nearly bouncing around the same plots. The critical adjustment with the post hoc analyses indicates that there are no significant differences in interactions between T1 and probes. However, there are significant differences in interaction between T2 and probes (see appendices, Table 2).
DISCUSSIONS
Results indicate that there are significant differences in the outcomes of the first target T1 and outcomes of the second target T2. In figure 1, effects of first target T1 on the second target T2 are clearly shown during initial stages of the experiment. Better probe 1 performances in detecting the first target T1 will have an effect on detecting the second target T2 in probe 2. From probe 2 onwards, the standard deviation from mean percentage accuracy in T2 begins to reduce. It will continue that way to the point where both T1 and T2 will have the same results. The Shapiro, Raymond and Arnell (2009) study has indicated that when an individual is very emotional about the first target T1, he will have more concentration power on it, and thus there will be a tendency of him to focus on identifying the target. However, it is likely that an individual’s focus on the second target may be interrupted by the self satisfaction. This will be a clear recipe of AB during the identification of the second target T2. Thus, in Probe 1, while individuals showed higher results in the first target T1, there were higher likelihoods of them faltering in identifying the second target T2. From the first probe, an individual’s performances are more likely to improve. Janson et al. (2014) have noted that when an individual notices that the stream of the RSVP is ever-changing, he will be prompted to commit more resources in identifying the right object. The more an individual becomes focused on the stream of objects, the more he becomes more apt in identifying the second target. Studies have indicated that when an individual involves in trainings, such as those performed during meditation, his focus on particular targets increases. It is evident that variances among the first target T1 and the second target T2 decrease as participants are involved in more probes.
Although the studies have indicated differences in outcomes between targets, they have not done so on probes. This indicates that the numbers of trials are not significant in determining an individual’s concentration while identifying the target. It is rather harnessing of resources needed to identify the target. In this regard, if an individual still manifest attentional deficit, it will still be difficult for him to identify the target (Raymond, 2003). Moreover, according to Nieuwenstein, Theeuwes and Potter (2009), conceptual information was not consequential in this study: items in the sequences were randomized, and there was no chance that individuals would form and use conceptual frameworks from salient object features to identify the target. What individuals needed were necessary attentions to process distracting information so that they could identify the target. Subsequent identification of next target will be determined by the individual’s maintained level of attention. According to Brisson and Bourassa (2011), when a distracter is removed, the significance of AB in the experiment is more likely to be reduced for individuals that maintain necessary levels of foci to the end. Interaction between target outcome and the number of probe has not been significant in the study: there have been no significance differences in levels of interactions between the level of trials and targets. This indicates that the two variables do not interact to influence outcomes of target identification. They have emerged inconsequential in all respects from the first probe to the last probe. However, these results should be interpreted with caution: graphical realizations and post hoc analyses have indicated some interactions between probe and target. Indeed some researchers such as Nieuwenstein, Theeuwes and Potter (2009) have indicated that when items in the RSVP stream are put in certain sequence, the participant can easily identify the target due to inherent reduction of AB in the stream itself. Nonetheless, the researcher did not use objects that espouse special features such as real life objects. Such objects usually espouse conceptual categories that are salient for a person to identify the target.
CONCLUSION
In the study, as evidenced also in previous studies, an individual is more likely to fail to recognize the second target due to attentional deficit that is linked to identification of the first target. When the environment is swarmed with a lot of stimuli at the same time, an individual may find it hard to distribute attentional resources required for storing, retrieving, comprehending and interpreting information. This has also been the case of this experiment. During the first trial, an individual usually faces a fast stream of stimuli from which he has to identify the target. When he identifies the first target, it is unlikely that he will do so in the next 200ms -500ms to the second target. However, upon identifying the second target in the first trial, things would become easier due to attentional resources he puts in the experiment. Therefore, there are higher likelihoods that one will falter in the second trial but improve steadily thereafter. When an experiment is well randomized, external factors such as the number of trials and likely conceptual categories of objects in the set of stream will be inconsequential.
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Appendices
Table 4: Probes against targets
