Treisman and Gelade's (1980) feature-integration theory of attention proposes that the entire field of vision is available to be registered by the brain via parallel processing with respect to features (e.g. color, edges, orientation, location, movement, etc.), but the objects are not correctly unified (e.g. the color is not necessarily matched with the shape). The objects are correctly identified only when attention is focused on them which is a serial action. Serial processing combines all the separate features (conjunctions) of a particular object at a particular location together so that the object can be identified (Treisman & Gelade, 1980). If the unattended objects (objects that are not receiving attention) are not confounded with distracters or if the unattended object can be identified with top-down processing due to context or previous knowledge (i.e. the sun is yellow not blue) then a target can be found amidst the background using the faster parallel processing. Treisman and Gelade's (1980) research indicated that individual features can be searched for in parallel but if a conjunction of features must be located then a slower serial search is utilized; A serial search is indicated if the slope (time to find the target) increases in a linear fashion as the number of distracters increases and the negative condition (the target is not on the screen) slope is twice the value of the positive condition; Serial search is utilized even when the there is little similarity between the conjunctive target and the distracters; A parallel search is indicated if the slope of the positive condition is virtually flat as the number of distracters increases; and, Letters are broken into their individual features and then recombined. The remainder of this paper is a sample of the research methodology and results from their experiments. The researchers define the following vocabulary: Dimension is "the complete range of variation" such as color or orientation; Feature "refers to a particular value on a dimension" such as red or vertical (Treisman & Gelade, 1980). In their first experiment the participants scanned for either a feature (blue or S) or a conjunction (a Green T) during different trials. The distracters were variously colored letters. They varied the number of objects on the screen for each test. Table # 1 Data from Treisman and Gelade Experiment Number 1 Test condition Slope positive Slope negative Conjunction 28.7 67.1 Feature 3.1 25.1 They found that the number of objects on the screen had virtually no effect on the feature searches if the target was on the screen which indicates that the entire field of objects were processed in parallel. If the feature target (blue or S) was not on the screen then it took as long to scan as it took to find the conjunctive target (Green T) which indicates that each object was serially scanned looking for the non-existent target. In the conjunctive trials if the target was not on the screen it took twice as long to respond and the slope increased in a linear form as the number of distracters increased indicating a serial and self-terminating process of search. Further trials which allowed for practice did not improve the scan time and it was assumed that practice did not lead to automatic integration or allow for parallel conjunctive searches (Treisman & Gelade, 1980). *** Individual features can be searched for in parallel but if a conjunction of features must be located then a slower serial search is utilized. *** *** A serial search is indicated if the slope (time to find the target) increases in a linear fashion as the number of distracters increases and the negative condition (the target is not on the screen) slope is twice the value of the positive condition*** *** A parallel search is indicated if the slope of the positive condition is virtually flat as the number of distracters increases *** The second experiment independent variable was the similarity of the target and distracters, number of objects on the screen, and absence or presence of the target. Low similarity was o/n or red/green. High similarity was t/x or green/blue (where the green and blue inks were very similar). The experiment disproves the supposition that parallel search is used when the conjunction target is easy to find. The conjunction target in the low similarity (easy) test was found more quickly than in the high similarity (hard) test; but become slower (linear positive slope) as the number of objects on the screen increased and in the negative condition the slope was approximately double indicating that serial searching was utilized (Treisman & Gelade, 1980). *** Serial search is utilized even when the there is little similarity between the conjunctive target and the distracters *** The fourth experiment tested the recognition speed for a target distracted by letters that were similar to it and easily confused; or by letters that could be separated into features and then recombined to form an illusionary target (conjunction error). The conditions were presented with various frame sizes (number of distracters) and with presence or absence of the target (positive/negative). C: Conjunction Condition R/PQ T/IZ S: Similarity Condition R/PB T/IY c: Conjunction Condition Control R/Q T/Z s: Similarity Condition Control R/B T/Y h1: Heterogeneity Condition T/PQ h2: Heterogeneity Condition Control T/P h3: Heterogeneity Condition Control T/Q Table # 2 Data from Treisman and Gelade experiment number 4 Measured Factors Stub head Positive Slope Negative Slope Ratio of Slopes Conjunction T/IZ 12.2 34.7 .35 Conjunction R/PQ 27.2 52.1 .52 Average Conjunction 19.7 43.4 .45 Similarity T/IY 5.3 18.1 .29 Similarity R/PB 9.7 40.5 .24 Average Similarity 7.5 29.3 .26 Heterogeneity 4.9 20.5 .24 The control conditions where a target was to be located within a distracter field of identical letters (e.g. one T in a field of 14 I's) confirmed that letters that are similar in shape are found much more slowly than letters which simply share features (conjunction condition). The opposite result occurs in the test condition where the target is located either in a distracter field of letters which can create conjunction errors or a field of letters which are simply similar in shape. The time to locate the target in the Similarity Condition and the Heterogeneity Condition were basically the same. This disproves the possibility that the responsible variable was similarity of features and not conjunction of features. In the positive conjunction condition it took 2 to 3 times longer to find the target than in the condition where the target was hidden among letters which were similar to it. Letters should be so familiar that they are processed as templates but this slower time recognizing letters which share features indicates that the letters are broken into their component features and then a slow serial process must be used to identify each letter without putting it back together incorrectly with its neighbors features. In the negative condition the Conjunction condition was about twice as long as the positive condition indicating that the search was serial and self-terminating. In the Similarity condition it was about half this time indicating a different method of searching. *** Letters are broken into their individual features and then recombined. *** REFERENCES Treisman, A, and Gelade, G. (1980). A feature-integration theory of attention. Cognitive Psychology 12, no. 1: 97-136. MEDLINE, EBSCOhost (accessed July 19, 2009).
Thursday, July 30, 2009
Research Summary : A feature-integration theory of attention Treisman Gelade (1980)
Wider than the sky by Edelman
Well, I finished the book. That's the most I can say. I still don't understand where he believes consciousness arises. I'm going to take a break and then read the book again with a notebook and pencil in hand...and maybe a dictionary.
Monday, July 13, 2009
Summary of Lecture: The Brain & Mind by Mriganka Sur
Brain cells (neurons) are unique in that they are semi-permeable, can have around 100+ dendrites and have enough synapses on those dendrites to communicate with 10,000 + other neurons. The genes of the cells determine the type of cells that are formed and the pathways between the sensory organs and the sensory areas in the brain. The neurons of the auditory system are the same as the neurons of the visual center. The function of a particular area of the brain is due to networks forming and those networks form due to interactions with the environment. Dr. Sur rewired the eyes of a ferret to the auditory center of the brain before the areas of the brain became specialized. Testing of which groups of neurons in the auditory system were activated by the eyes viewing edges of various orientations indicated that the neurons of the auditory system formed networks that were normally found in the visual centers of the brain. Sur, M. (2003). MIT World Lecture Series: Fundamentals of the brain and mind: A short course in neuroscience. The brain and mind. Video retrieved on 13 July 2009 from http://mitworld.mit.edu/video/194
Monday, July 6, 2009
How the Mind Works by Pinker
I've read the first chapter and part of the second and my first impression is that I'm reading lots of words and getting very few ideas or facts. However, after walking away and now coming back I think perhaps he is preaching to the choir. I already believe in neural networks and the physicality of the mind. However, I'm only a short ways into the book and perhaps he will give me more meat soon. Here are my first thoughts which may not represent what he means at all. First, the mind is a group of organs developed through natural selection to solve problems our ancestors faced during the stone age – how to talk, how to walk, how to see, how to make predictions. Second, the radical part of his theory is that the rules we use to process new information are hard wired into the components of our brain. When I am presented with a stimulus then my brain runs a process of "if, then, else" using data I have accumulated over my life time. It is not obvious that my program is the same as your program because my inputs vary from yours in the same way that both of us can write a blog entry using Microsoft Word but the text created is unique based upon what we know and wish to present. Intelligence is simply the rational use of rules to pursue goals around obstacles in our path. It is not a supernatural otherness existing outside the physicality of our brains. The idea that people have an innate human nature and not one simply shaped by our culture leads some scientists and people to fear that Dr. Pinker counters these arguments but it is not necessary to explain that here as it is not necessary to understanding the theory. Here are some interesting videos This first video takes real audio and is a lecture Pinker gave at Rice University which summarizes several things from the first couple of chapters. Fast forward through the first 8 minutes of introduction speakers. http://www.youtube.com/watch?v=4A_r6_GGv3U&feature=related http://www.youtube.com/watch?v=vuwNfPca_Pw&feature=related http://robertsandberg.net/2009/06/23/steven-pinker-the-blank-slate-fallacy
Pinker Lecture at Rice University
http://realaudio.rice.edu/PresLect/Pinker/PinkerVid.ram
Here are some more videos.
Sunday, July 5, 2009
Heritability, Shared and Non Shared Environment
Heritability, Shared and Non Shared Environment According to Turkheimer (2000) there are three nearly unanimously accepted "laws of behavior genetics". First Law: All human behavioral traits are heritable Second Law: The effect of being raised in the same family is smaller than the effect of genes. Third Law: A substantial portion of the variation in complex human behavioral traits is not accounted for by the effects of genes or families. The study of the way that people in a family are similar or different has three major parts. The first is how much of their personality depends on their genetics (h). The second is how much of their personality depends on their shared environment (E2). And the last is how much of their personality is different because of their non-shared environment (E1). Rowe and Plomin (1981) reviewed the family study research data from various researchers and described the following findings. Dizygotic (DZ) twins have a personality correlation of about .28 due to shared genetics and E2 (shared environmental factors) while non-twin siblings have a correlation of about .12. This means that about 75% of the variance in personality is due to E1 (non-shared environmental factors). Intelligence correlations show more effect of E2 but still leave 40% of the variance to non-shared factors. Table # 1 Correlation of Personality and Cognition (Rowe & Plomin, 1981) Sibling type Trait DZ Twin Non-twin sibling MZ Twin Adopted Siblings Personality .28 .12 .50 Cognition .62 .34 .86 .25 The weakness of the family study using DZ twins and non-twin siblings is that it does not separate out the genetic from the shared environmental factors. To separate these factors researchers turn to the adoption study to remove the shared environment factor or to the MZ twin study (monozygotic or identical) to remove the genetic factor. The correlation of personality between DZ twins is due to having about half (h/2) of their genes in common which is referred to as heritability (h) and having a shared environment (E2). The correlation of DZ twins (CDZ) = (h/2)+ E2. However there is no way pull out the heritability factor using just this formula. MZ twins have 100% of their genes in common so the correlation of MZ twins (CMZ) = h+ E2. Algebraically combining, removing the common environment, and solving for heritability results in a formula where heritability is roughly equal to twice the difference between the CMZ and CDZ (Plomin, DeFries, McClearn, & McGuffin, 2001) CMZ = h + E2 CDZ = (h/2) + E2 CMZ – CDZ = h – (h/2) + E2 – E2 CMZ – CDZ = (2h/2) – (h/2) CMZ – CDZ = h/2 h = 2(CMZ-CDZ) Once heritability is found then it can be used in the CDZ formula to find out what part of the CDZ is due to shared environment. The final element, non-shared environment (E1), represents the part that is different between the siblings will be the parts already known subtracted from 1. Shared genetics (h) 2(CMZ-CDZ) 2(.50-.28) .44 Shared environment (E2) CDZ - ( h /2 ) .28 - (.44 / 2) .06 Non-shared environment (E1) 1 – h – E2 1 - .44 - .06 .50 Table # 2 Factors Affecting Personality and Cognition between DZ Twins Calculated values Trait Shared genetics (h) Shared environment (E2) Non-shared environment (E1) Personality .44 .06 .50 Cognition .48 .38 .14 As adopted siblings share environment but no genetics the estimated E2 for DZ twins and the measured E2 for adopted siblings should be similar (DZ twins = .38 vs Adopted = .25). Rowe and Plomin (1981) suggest that the large effect of non-shared environment (E1) may imply that E1 events are random such as meeting a person outside the home that inspires a child to do something different, an illness not shared, birth order, peers not shared by siblings, pre-natal trauma, deidentification (child chooses to be different), or differing parental or sibling interactions. Turkheimer (2000) discussed the research of Plomin and Daniels (1987) research where they suggested that there are two kinds of nonshared environment. The first is objective where the event is actually not experienced by both siblings. The second is effective or subjective where the event is experienced by both siblings but interpreted differently. Turkheimer claims that this conjecture is false based on a review of 43 studies. I will leave his disagreement for discussion in a later post so that I can now discuss some of the research supporting that the non-shared environment can be analyzed if not completely then in parts. The research of Daniels, Dunn, Furstenberg, & Plomin (1985) discusses non-shared environmental effects of events that are actually happening in the family unit or with shared peers. This seems to be an example of effective or subjective non-shared environment (E1). They first reviewed other researcher's data that had indicated that non-twin siblings had about a .20 correlation in personality. Their nonshared environment included such factors as sex, age, and birth order which only accounted for 1% of variation and de-identification between first and second born children and between siblings of the same sex. The researchers proposed that the perceived and real differences in how people within the family and shared peers treated an individual affected the personality of the individual. Research with siblings age 11-17 years-of-age indicates that they perceived that the environmental influence of their differing relationships with family and peers was different than that of their siblings. Parents of the siblings reported minor differences in their relationship with each of their children. They found that perceived differences in Maternal Closeness, Siblings Friendliness, and Peer Friendliness account for 4% to 13% of the variance in sibling adjustment. They also found that there was only about a .15 correlation of emotional adjustment between siblings. The researchers (Daniels, Dunn, Furstenberg & Plomin, 1985) tested nine environmental areas:
- Parental Rule Expectations,
- Parental Chore Expectations,
- Maternal Closeness,
- Paternal Closeness,
- Child's Say in Decisions,
- Siblings Friendliness (parental perception & child perception)
- Peer Friendliness (parental perception & child perception).
[To be continued next weekend]
Citations
Daniels, D., Dunn, J., Furstenberg, F., & Plomin, R. (1985). Environmental differences within the family and adjustment differences within pairs of adolescent siblings. Child Development, Vol 56(3), Jun 1985. pp. 764-774. Retrieved PsycINFO July 5, 2009. http://libproxy.uta.edu:2066/login.aspx?direct=true&db=psyh&AN=1985-25181-001&site=ehost-live
Plomin, R., DeFries, J.C., McClearn, G.E., & McGuffin, P. (2001). Behavioral Genetics. New York: Worth. P 350.
Rowe, D.C. & Plomin, R. (1981). The importance of nonshared (E-sub-1) environmental influences in behavioral development. Developmental Psychology, Vol 17(5), Sep 1981. pp. 517-531. Retrieved July 5, 2009 PsycARTICLES. http://libproxy.uta.edu:2066/login.aspx?direct=true&db=psyh&AN=1981-32469-001&site=ehost-live
Turkheimer, E. (2000). Three laws of behavioral genetics and what they mean. Current Directions in Psychological Science 9(5), (2000): 160-164. Retrieved July 2, 2009, http://www.psychologicalscience.org/newsresearch/publications/journals/currdir/cd9_5_5.pdf
Saturday, July 4, 2009
The Truth about Cinderella: A Darwinian View of Parental Love
In the book, The Truth about Cinderella: A Darwinian View of Parental Love by Daly, M., & Wilson M. (1999) the authors explain the steps leading up to their research on abuse in step-families and their methodology in doing the research. In many cultures there exists a variation of the Cinderella story in which a parent’s genetic children are favored over their step-children (p 1-4). The author’s research supported the real existence of this Cinderella effect and the authors contend that there are evolutionary reasons for this effect.
Evolutionary sexual selection adaptation (same sex/same species competition for limited resource of mating partner) comes into play when a new male partner kills the dependent children of his partner’s previous mate which allows him to more quickly produce his own children and have his genetics passed along (e.g. male lions pg. 9 and Jacanas p. 10). If a male did not do this then fewer of his children would be born compared to a male who practiced infanticide of step-children.
Infanticide of step-children is not evolutionarily adaptive if the risks outweigh the benefit which is the case in human society; but it does seem to exist in a more minor form where the scarce resource of parental attention is lavished more upon one’s genetic children than upon the genetic children of a rival. Attachment to a child would have made a male more likely to put up with the resource demands of a dependent child. Forming this bond indiscriminately with a rival’s child would have depleted the resources available for his genetic child. This would not have been advantageous to his genetic offspring and therefore his genetics would not have been passed along in a larger quantity than his rival’s (p 38-39).
The researchers analysis of existing child abuse records supports this contention since a greater percentage of all step-families in the population at large have recorded child abuse records. The number of step-families in the population at large is perhaps over estimated but if so then this indicates that the percentage of step-child abuse is even greater than the article represents.
In a Canadian municipality of 500 thousand the researchers found that 1 in 3000 pre-schoolers who lived with their genetic parents were reported for abuse but 1 in 75 pre-schoolers who lived with a step=parent were abused (p. 30). This abuse was far more likely to occur to pre-schoolers than teenagers (p. 30).
A possible flaw in the research is the existence of the Cinderella myth itself which might lead a neighbor to report possible abuse more readily if a step-parent was present. The researchers repeated their research using only fatal child abuse situations and found the same extreme rates of child abuse in step-families (p. 32).
Posts
