Age-Induced Conservatism and the Right Hemisphere Aging Hypothesis

C. Brack and X. Zhang

I. Summary

Aging provides an excellent independent variable in the analysis of neurological phenomena, as neurochemical systems have a definite propensity to deteriorate with advancing age. Many psychopharmacological studies have documented the degeneration of the catecholamine systems, such as norepinephrine and dopamine, which have been proposed by Tucker and Williamson (1) to be distributed asymmetrically in the human brain, and engendering the left and right hemispheres to specialize in functionality.

Tucker and Williamson argued that the left hemisphere is organized around a dopamine activation system, making it superior for motor control and language. They further argued that the right hemisphere is organized around a noradrenergic activation system, which maintains alertness, integrates bilateral perceptual information, and analyses new stimuli. Brack and Zhang (2) have given evidence of hemispheric asymmetries and their influence on conservative and liberal mental attributes, which we now propose to be at least partially related to the asymmetric catecholamine theory of Tucker and Williamson.

Hemispheric asymmetry in aging has at least two different models---the right hemi-aging model, which proposes that the right hemisphere exhibits a greater age-related decline than the left, and the Hemispheric Asymmetry Reduction in Old Adults (HAROLD) model, which proposes that frontal cortex activity is less lateralized in older than in younger adults. These two models are not mutually exclusive. As early as 1958, Wechsler (3) reported visuospatial deficiencies in the elderly as related to younger controls. However, there was little or no decline in verbal and language comprehension tests between the elderly and young. This led Klisz (4) to the suggestion that aging leads to a greater loss in right versus left hemispheric functionality.

Our results are consistent with this theory, and may further suggest an improvement in literal language comprehension in the right hemisphere for people over 25. We have found a significantly greater reliance in the elderly on left ear dependence for single ear conversation (e.g. phone conversations). From Under 25 to Over 60, the shift to left ear preference for phone conversation more than doubles (from 26% to 56%). This shift is accentuated in right handers, presumably because it frees up the right hand for other tasks.

The auditory nerve of each ear is linked to both hemispheres, but the contralateral pathway has more nerve fibers than the ipsilateral pathway, indicating a greater presentation of auditory stimuli to the hemisphere opposite the stimulated ear. The shift from right to left ear is pronounced, and suggests that the right hemisphere progressively improves in its ability to process literal language over time. Since the right hemisphere has a demonstrated reduction in visuospatial performance in advanced age, the relative improvement in language performance may not be surprising.

We find concurrent evidence with our shape versus semantic word test, which requires that the subject indicate a preference of shape versus semantic translation for a word pair. The preference for shape drops from 27% for our Under 25 cohort to just 14% for our Over 60 cohort, providing further evidence of an age-related deterioration in spatial performance relative to language performance. Further, there is a noted decrease, from 44% in our Under 25 cohort to just 29% in our Over 60 cohort, for subjects reporting difficulty in maintaining attention while listening.

 

There are several possible models for this relative improvement in right hemisphere language comprehension. We suggest that a model of right hemispheric age-induced noradrenergic system degradation is the most plausible. Research linking dopamine with language syntax performance is considerable. Most notable for our purposes is Kischka et al (5) that found dopamine to improve the signal-to-noise ratio in semantic networks.

The "frontal-lobe aging hypothesis" proposes that the earliest and most severe age-related changes occur in the frontal lobes of the cortex. According to this theory, significant depletions in norepinephrine and dopamine decrease the cognitive functions of the prefrontal cortex. Combined with Klisz's hypothesis of enhanced right hemispheric aging, we propose that the impact of age-induced reduction in prefrontal activity reduces interference and cross talk with the right hemispheric cortical regions involved in language comprehension, such as the temporoparietal cortex. This improves the signal-to-noise ratio of these regions, improving language comprehension in the right hemisphere. This implicates that the hypothesized noradrenergic activation system of the right hemisphere is inhibiting ordinary semantic processing in that hemisphere.

This further implies either an age-induced elevation in left-hemispheric contributions to political and religious tendencies, which has been implicated in favoring more religious and conservative belief systems. Or, it may imply that the right hemisphere is functioning more like the left hemisphere due to the degradation in its proposed noradrenergic activation system. Indeed, we find a significant age-induced shift towards organized and unambiguous binary reality models in the liberal, which is highly correlated with political conservatism and traditional religious beliefs.

II. Survey Data

A self-assessment Internet survey was conducted by Brack and Zhang on Neuropolitics.org. During the period of March 23-April 29, the survey collected 1,538 questionnaires, of which 148 cases were subsequently cleansed for probable duplicate or incomplete responses. This left 1,390 usable questionnaires, of which 615 indicated Conservative or Very Conservative beliefs, 569 indicated Liberal or Very Liberal beliefs, and 206 indicated Moderate belief systems.

 

1A. Left-Ear Preference for Conversation by Age and Political Cohorts.

The respondents were asked to rank their preference for left versus right ear in single ear conversations (e.g., phone conversations).

Figure 1: Left Ear Preference in Conversation by Age cohorts

This is based on 1,390 responses. Chi-square for this matrix is 56.6 (p < .0001). A noted and statistically significant shift in preference with age. Adding political affiliation (C=Conservative, L=Liberal) gives us Figure 2. We are leaving out an analysis of Moderates due to low sample size.

Figure 2: Left Ear in Conversation by Age and Political cohorts

Chi-square for this matrix is 131.8 (p < .0001). Left ear preference is remarkably consistent across political cohort, and statistically significant.

1B. Word-Pair Test Results by Age and Political Cohorts.

The respondents were given a categorization test for a word pair. The word pair in question was (KNIGHT, KNAVE). They were given two options, one, which forced a semantic translation (MASTER, SERVANT), and the other based on form (NIGHT, NAVE), with no semantic relationship.

Figure 3: Shape Preference for Word Pair by Age and Political cohorts

Chi-square for this matrix is 39.8 (p < .01). The Liberals exhibit a steep decline in shape versus semantic preference over time. The Conservatives indicate a more gradual decline from 25 through 60+.

1C. Conversational Attention Problems by Age and Political Cohorts.

The respondents were asked to categorize their ability to maintain attention during a non-specific conversation (see Figure 4).

Figure 4: Attention Problems During Conversation by Age and Political cohorts

Chi-square for this matrix is 27.2 (p < .01). The Liberals exhibit consistent problems until 60, where we then see a steep drop in the inability to maintain attention during a conversation. The Conservatives only indicate a slight drop in the 60+ cohort.

1D. Reality Model Preferences by Age and Political cohorts.

The respondents were asked to categorize their preference for simple versus complex models of reality (see Figure 5).

Figure 5: Preference for Simple vs. Complex Reality Models by Age and Political cohorts

Chi-square for this matrix is 165.1 (p < .0001). The Liberals exhibit an upward trend in preferences for simple versus complex reality models with age. There is no discernable trend for Conservatives.

1E. Binary Reality Model Preferences by Age and Political cohorts.

The respondents were asked to evaluate the truth of the statement "The world is embraced in a struggle between good and evil". (see Figure 6).

Figure 6: Binary Reality Model Preferences by Age and Political cohorts

Chi-square for this matrix is 539.9 (p < .0001). The Liberals exhibit an upward spike in binary reality model preference in the 60+ cohort. There is no discernable trend for Conservatives.

III. Discussion

The Liberal cohort indicated an age-dependent improvement in language comprehension performance to rival or exceed the performance of the Conservatives in the Over 60 age cohort. Concurrent with this language comprehension improvement is a shift towards more organized and unambiguous reality models for the Liberals. This corresponds to the general decline in right hemispheric cognitive functions, which interfere more with visuospatial performance than language comprehension. It also points to a more left hemisphere influenced thinking style, which is more prone towards stronger Conservative and Religious beliefs. It also implies that an aging voting population will tend more towards Conservative and Religious agendas, all other environmental factors being equal.

 

References:

1. Tucker and Williamson. Asymmetric Neural Control Systems in Human Self-Regulation. Psychological Review, 1984, 91, 185-215.

2. Brack and Zhang. Right and Left Hemispheric Biases in Political and Religious Tendencies: Part 1. Neuropolitics.org, March 2005.

3. Wechsler, D. 1958 The Measurement and Appraisal of Adult Inteligence. Baltimore MD, Williams and Wilkins.

4. Klisz, D. 1978. Neuropsychological evaluation in older persons. In The Clinical Psychology of Aging., M. Storandt, LC. Siegler, and M.F. Elias, eds. New York, NY: Plenum Press, 71-95.

5. Kischka U, Kammer T, Maier S, Weisbrod M, Thimm M, Spitzer M. Dopaminergic modulation of semantic network activation. Neuropsychologia, 1996 Nov: 34(11) 1107-13