Wednesday, July 29, 2009

Spatial Attention and Negative Priming

Attention is what allows us to focus on the most salient aspects of our environment. Without attention or habituation, our systems would be overloaded from the constant bombardment of stimuli. With attention we are able to concentrate on the things that we want and are able to ignore others. In spatial attention, we are investigating how we are able to attend to or concentrate on relevant stimuli in our environment while ignoring distractors (sic). In an ERP based study of spatial attention and negative priming, subjects were asked to indicate a targets location while ignoring a distractor that was present in unequal proportions. Negative priming occurs when the processing of a stimulus previously ignored is inhindered in terms of error rate or reaction time.

In priming, it is assumed that previous experiences affect future experiences. Whether the stimulus has higher basal activation levels, is better encoded, has raised the overall activation level of a network or has been stored as a memory trace, all are possibilities used to explain the priming phenomenon. It is assumed that these techniques used to employ positive priming techniques are what hinder the system in a negative priming paradigm. Combining the aspect of attention, if a stimulus is to be actively processed and encoded, it takes your attention to complete, and inversely, attention to suppress the environmental noise or distractors. In negative priming it may be this active supression which explains the decline in behavioral responses.

Two leading theories hypothesize different mechanisms to explain the negative priming effect. Inhibition theory uses this supression of the response while retrieval theory supposes that it is old memory traces which interfer with the behavioral response. In order to parse apart these theories, it is necessary to look into the underlying neural behavior during a negative priming experience. Using ERP, one is able to take advantage of well known neural responses (including some that related to decision making) and good temporal resolution.

Friday, July 24, 2009

Wisdom in Words

I recently began to test subjects in a study of the association between words and wisdom. There is the general assumption that as we age, we become more wise. What is wisdom?
From dictionary.com...
1. the quality or state of being wise; knowledge of what is true or right coupled with just judgment as to action; sagacity, discernment, or insight.
2. scholarly knowledge or learning: the wisdom of the schools.
3. wise sayings or teachings; precepts.
4. a wise act or saying.
Thanks... let's try wise...
1. having the power of discerning and judging properly as to what is true or right; possessing discernment, judgment, or discretion.
2. characterized by or showing such power; judicious or prudent: a wise decision.
3. possessed of or characterized by scholarly knowledge or learning; learned; erudite: wise in the law.
4. having knowledge or information as to facts, circumstances, etc.: We are wiser for their explanations.
Apparently, wisdom is one of those huge, concepts which tries to defy definition, yet we all seem to inherently know what it means. Wisdom appears in many different domains, specifically, life planning, moral issues, and in reflection. A confound of the age and wisdom relationship, may be that younger people are unable to have the time in which they are able to see how their decisions are choices affect future outcomes. Perhaps I have made some momentously wise decision or choice, however am unable to see the effects of that choice yet. A description of the study from Dr. Jean Gordon follows...

"The current study explores the ambiguity of wisdom by focusing on how it is transmitted and perceived. Language is the medium by which wisdom-related knowledge is usually conveyed, and the sophistication of that language is proposed to significantly affect the spirit in which the knowledge is received. If one’s word choice and/or syntactic structure sound clever or profound, one is more likely to be perceived as wise. While wisdom is expected to increase with age, aspects of language use often decline with age. This may be why an age effect has been difficult to obtain in wisdom studies, and why society holds both negative and positive stereotypes of aging. If productive language use declines with age, despite the accrual of knowledge and life experience, then the ability to pass on acquired wisdom is also likely to decline.

To test this hypothesis, a pilot study is underway to establish the extent to which listeners’ perceptions are influenced by linguistic variables. Artificially manipulated language samples differing in grammatical complexity and word choice were created. The samples were written responses to two advice‐giving scenarios, such as what to say to a young girl who wants to run away from home. The study protocol was modified to have “listeners” read the transcripts of these responses, rather than listen to audio‐recorded versions. This was judged to be a more controlled test of the hypothesis, because it factors out vocal characteristics of the speaker which would likely influence perceptions of age and gender, and possibly other factors as well, such as educational level. (A follow‐up study could test these influences by comparing judgments of written and oral samples.) Young adult subjects were asked to read the responses and judge the speakers’ knowledge, judgment, sensitivity, perceptiveness, and ability to communicate ideas, as well as whether or not subjects agree with the advice provided in the responses. Subjects were also asked to estimate the speakers’ age and education levels. These ratings are designed to tap into dimensions of wisdom derived from the literature on explicit and implicit theories of wisdom (e.g. Sternberg, 1985). Gordon and her research team expect that language variables will affect these judgments, over and above the degree to which subjects agree with the response provided."

In my short time of testing patients, I have had a lot of fun listening to and learning from the responses of the speakers in the task. It is interesting to see how the variety of life experiences, values and understanding combine to interpret the questions in a variety of ways. How will the different word variables play out in wisdom? At first I thought that more complex word variables would mean a higher rating of wisdom, however, then I started to think about it more. Some of the most wise people in history, have been the political and religious figures of our time. The ability of these people to communicate their ideas, ideals, and feelings was not through complicated speech and word structures, but through their ability to communicate effectively and colloqoially to the people. I think that ultimately it will be the message (semantics) rather than the style (syntax) which affects the rating of wisdom. It will be interesting to see how these play out.

Tuesday, July 14, 2009

Lexical decision in aging: Stimulus variables and response time components

A combination of a few lines of work. Not only does this combine three lines of research topics (word retrieval, aging and diffusion modeling) but it is also a melding of two researcher's experiences. I bring experience in word retrieval and diffusion modeling while Dr. Gordon brings her experience with word retrieval and aging. This collaboration is the result of these combinations. The lexical decision task investigates what is important in a word which makes it easier or harder to recognize. In aging research, it is known that reaction times slow down with age, but what specific variables have the largest impact on reaction times and accuracy. The diffusion model on the other hand parses apart the reaction time into separate cognitive processes which give a better description of what is occurring in this decision making process. The following is an abstract that is being submitted for a conference in aging and speech communication.

It is known that different types of variables affect word retrieval, including lexical (e.g. frequency, length), subject (e.g. age, education) and task factors (e.g. mode of retrieval, composition of the stimulus set). Moreover, recent studies have demonstrated, through diffusion modeling, that reaction time can be decomposed into several processes, those related to the decision (stimulus information accumulation, response bias) and non-decision processes (encoding, response execution), which may be differentially affected. We tested older (>50 yrs.) and younger adults in an auditory lexical decision task to investigate how aging affects these different aspects of word retrieval. For both word and non-word responses, older subjects were both slower (Word: 71ms, p=0.016; Non-word: 159ms, p=0.003) and less accurate (Word: 0.8%, p=0.038; Non-word: 4.4%, p=0.003) than younger subjects. Both older and younger subjects were affected by the length and phonological neighborhood density of the word and non-word targets, and by the frequency of the word targets. Measures of phonotactic probability tended to influence the non-word responses of younger subjects, but the word responses of older subjects. This stronger effect of sub-lexical factors on word recognition is likely due to declines in peripheral processes (hearing acuity, speed of processing). In the diffusion model, older subjects had a significantly lower rate of information accumulation for both word (p=0.005) and non-word (p=0.0003) responses. For non-word responses, older subjects also took longer for non-decision processes (p=0.007). These results help clarify the cognitive and non-cognitive factors that contribute to word recognition, and how these change with age.

Following analyses will investigate how subject variables such as hearing acuity affect the behavioral variables. This investigation will also be broadened to include aphasic patients. This is the second project that I have submitted to a conference. I should find out in early August whether I am able to attend the conferences and more importantly, whether I am awarded money to travel to the respective conferences. More to come...
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Sunday, July 12, 2009

Cognitive Framing

Last week, in morning meeting, there was a presentation about a study of the framing effect. This effect describes a cognitive bias, where presenting the same options in different formats can alter people's decisions. This effect appears to have a greater effect on people who are inconsistent with their choices and whether the question is framed in loses/gains. This is very prevalent in every day life. Think about being presented with the choice to choose this route or that one, this type of meat or that one, should I try to buy this stock or that one, it goes on and on. It seems as though this effect is one of the best tools in the arsenals of lawyers, advertising companies and politicians. By framing an argument, a brand or a policy in certain ways, perhaps you are able to persuade people to think one way or another.

Here's an example...

A train is driving down a track, at a junction in the track there are two problems. On one track five people are tied down to the track and on the other track there is one person. You are there and next to a lever which you can throw to change or not change the course of the train (originally heading for the five people).

The two propositions are worded in the following ways...
1. You can throw the switch and save five people
2. You can throw the switch and kill one person

Although it is the same in both outcomes, people responded more positively to option 1.

The study that was proposed, would investigate framing in both normal and VMPC lesioned patients. The framing effects were broken into 6 different types of framing effects (e.g. Goal, Moral, Monetary). The researchers hypothesized that the VMPCs would differ from normals in there susceptibility to framing effects. With VMPCs, there is evidence of higher risk taking behavior and dysfunctional decision making behavior. It may be the case that the VMPCs may be more susceptible in certain framing situations and less in others.

They also proposed taking reaction times of the decisions. All though hard to measure, I think that it will be good to take into account both fast and slow reaction times. With fast reaction times, a situation is not being fully considered, while with a slow reaction time, the situation may be being thought out too much.

I can't remember the overall goal of the research, but I know that it is tied to moral reasoning. That's all for now

Wednesday, July 8, 2009

Blocked Cyclic Naming (Semantic Category Interference)

This effect reflects the finding that for naming, participants are slower when naming pictures out of a sequence of items from the same semantic category than from different categories. The naming of an object or a picture is a multi-step series of mental operations. If naming a dog, you must first recognize it and decide how you want to refer to that object. This part of the process is called conceptual preparation. You must then focus on the particular mental item ("lemma") in you mental lexicon, which is under competition of semantically related items. The operation of lexical selection is next, and you must access the selected item's form information ("phonological code"). You then syllabify the word by composing it syllables from the segments, this is the processs of "phonological encoding." For each of these syllables you access a stored motor instruction ("gestural score"). Finally you execute the gestures with overt speech as output. This is known as the core processing stages of the production of words (Levelt, Roelofs, and Meyer, 1999).

Cumulative interference for word retrieval by prior retrieval of other members of the same semantic category is similar to an inhibition being caused by these related members. An experiement by Howard et al. (2005) indicates that this inhibition effect can only occur if the spoken word production has three properties, competition, priming and semantic activation. Competition can be implemented through eithe lateral inhibition between candidates or a decision criterion. The priming of previously presented items would persist over time, even when other stimuli are inbetween the targets. The stregthening mapping can be from either semantics or lexical units. Shared activation refers to the activation through connected nodes in a semantically related network being activated. In the experiment, the investigators were able to examine the extent to which there are cumulative effects of semantic competitor priming.. The picture naming latency is slowed by an additional 30 ms for each preceding semantial

Maess, et al. (2002) attempted to distinguish the neuronal correlates of lexical access by using the phenomenon of blocked cyclic naming and MEG recording to note where in the brain, this effect took place. Results demonstrated that the left temporal region supports the processes underlying the semantic interference effect. A previous investigation had demonstrated that the time window of between 150-275 msec post picture onset was the core process of lemma selection. The time window of the current study for the activation of the left temporal region fits this same time frame.

So what does this all mean? In the present study that I am investigating, subjects were asked to name 400 pictures. They were also participants in an auditory lexical decision task in which they were to decide whether a word they heard was a real word or not. I coded these words into semantic categories. In the 400 word naming project there were 5 semantic categories, 3 large ones (animals, tools, and food)and 2 well defined but smaller ones (body parts and instruments). The reaction times of the participants were than regressed against the order of the items in the specific semantic categories. In the presence of other word variables the order of the categories only had an effect in the one group of participants. When the order of the semantic categories is looked at by itself, there is a huge effect of order, demonstrated by a 1.5 ms slowing for successive trials.

This is an interesting effect because you would think that the higher activation of the related targets would lead to a faster reaction time. However, this activation appears to be competitive and inhibitory. Perhaps it is the fact that when a word is being searched out, it has to enter the "search mechanism" with no previous activation. So if I name tiger which activates lion and then am asked to name lion, my mental lexicon has to actually go through a process of finding lion, seeing that it is activated, deactivating it and then go through the normal process.