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PubMed2006

Time-dependent phenomena in the potential response of ion-selective electrodes treated by the Nernst-Planck-Poisson model. 1. Intramembrane processes and selectivity.

The variability of selectivity coefficients, resulting from potential changes over time and the concentration ratio of primary to interfering ions, impedes many practical applications of ion-selective electrodes (ISEs). Existing theoretical interpretations of ISE selectivity are restricted by severe assumptions, such as steady state and electroneutrality, which hinder theorizing on this problem. For this reason, for the first time, the Nernst-Planck-Poisson equations are used to predict and visualize the selectivity variability over time and the concentration ratio. Special emphasis is placed on the non-Nernstian response in the measurements with liquid-ion-exchanger- and neutral-carrier-based ISEs. The conditions under which measured selectivity coefficients are true (unbiased) are demonstrated.

Journal Article↗
PubMed2000

Design and synthesis of a more highly selective ammonium ionophore than nonactin and its application as an ion-sensing component for an ion-selective electrode

A novel ammonium ionophore, which exhibits superior NH4+ selectivity compared with that of the natural antibiotic nonactin, was successfully designed and synthesized based on a 19-membered crown compound (TD19C6) having three decalino subunits in the macrocyclic system. This bulky decalino subunit is effective for (1) increasing the structural rigidity of the cyclic compound, (2) introducing the "block-wall effect", which prevents forming a complex with a large ion, and (3) increasing the lipophilicity of the ionophore molecule. In the ammonium ionophore design, the first factor contributes to increasing the NH4+ selectivity relative to smaller ions such as Li+, Na+, or even the closest size, K+, and the second factor increases the NH4+ selectivity over larger ions such as Rb+ and Cs+. The X-ray structural analysis proved that TD19C6 forms a size-fit complexwith NH4+ in its crown ring cavity. As an application of this ionophore, an ion sensor (ion-selective electrode) was prepared, which exhibited NH4+ to K+ and Na+ selectivity of 10 and 3,000 times, respectively. This electrode showed a better performance compared to the electrode based on nonactin, which is the only ammonium ionophore presently used in practical applications.

Journal Article↗
PubMed1995

Functionally selective M1 muscarinic agonists. 3. Side chains and azacycles contributing to functional muscarinic selectivity among pyrazinylazacycles.

In an attempt to improve upon the M1 agonist activity of the selective M1 agonist xanomeline and related compounds, the M1 muscarinic efficacies and potencies of 3- and 6-substituted pyrazinylazacycles were varied by changing both the 3- and 6-substituents as well as the azacycle. Significant improvements in efficacy and potency over the previously prepared [3-(hexyloxy)pyrazinyl]tetrahydropyridine 19 were obtained with the [3-(hexyloxy)pyrazinyl]-quinuclidine 5i. The M1 activity of 5i showed some enantioselectivity with (S)-5i being ca. 4-fold more potent than (R)-5i. Like 19 and xanomeline, 5i was a functionally selective M1 agonist that showed greater functional selectivity than widely studied pyrazinylquinuclidine 5n (L-689,660). The improved functional selectivity of 5i over 5n could be attributed to the additional binding interactions between the hexyloxy side chain of 5i and the M1 receptor that are not available to 5n. Although 5i may show M1 functional selectivity comparable to xanomeliine, 5i is a less efficacious and potent M1 agonist than xanomeline.

Animals↗
PubMed1994

kappa Opioid receptor selective affinity labels: electrophilic benzeneacetamides as kappa-selective opioid antagonists.

2-(3,4-Dichlorophenyl)-N-methyl-N-[1-(3- or 4-substituted phenyl)-2-(1-pyrrolidinyl)ethyl]-acetamides 3-6 were synthesized as kappa-selective affinity labels and evaluated for opioid activity. In smooth muscle preparations, the non-electrophilic parent compound (+)-S-2 and the affinity labels 3-6 behaved as kappa agonists in that they were potently antagonized by norbinaltorphimine (norBNI). In addition to the high binding affinity and selectivity of the 3-isothiocyanate 3 (DIPPA) to kappa opioid receptors, wash studies have suggested that this involves covalent binding. In the mouse tail-flick assay, the 3- and 4-substituted isomers (3 and 5, respectively) produced long-lasting antagonism of the antinociceptive effect of the kappa opioid agonist, (+/-)-trans-2-(3,4-dichlorophenyl)-N-methyl-N-[2-(1-pyrrolidinyl) cyclohexyl]acetamide ((+/-)-U50,488). In contrast, the non-electrophilic parent compound (+)-S-2 and the fumaramate derivative 4 were devoid of antagonist activity in the tail-flick assay. At substantially different doses, DIPPA (3) and the 4-isothiocyanate 5 also produced antinociception in the mouse abdominal stretch assay. In addition, DIPPA and the 3-fumaramate methyl ester 4 had improved in vivo kappa-selectivities compared to the unsubstituted parent compound (+)-S-2 and the para-substituted derivative 5. The improved kappa-selectivities of 3 and 4 and the different agonist and antagonist potencies of 3 and 5 may be explained respectively by the existence of multiple kappa agonist binding sites and distinct agonist and antagonist binding sites. In view of the antagonist selectivity and the apparent irreversible binding of DIPPA to kappa receptors, it may serve as a useful pharmacologic or biochemical tool to investigate kappa opioid receptors.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1988

Tricyclic compounds as selective antimuscarinics. 2. Structure-activity relationships of M1-selective antimuscarinics related to pirenzepine.

In order to gain some insight into those structural features that control M1 selectivity, a selected set of pirenzepine analogues has been studied in which both the tricyclic ring system and the basic side chain have been varied. Binding studies were conducted in rat tissue homogenates from cerebral cortex (M1) and gastric fundus (M2). The ratio of IC50 values of the test compounds in the two different tissues was taken as a measure of M1 receptor selectivity. Several derivatives, especially those with flexible side chains, i.e. high degree of freedom of rotation around single bonds, proved to be nonselective. Among semirigid compounds only those containing 6-membered ring systems (11, 13, 14, and 15) showed significant M1 selectivity. Principles of structure-activity and structure-selectivity are discussed.

Animals↗
PubMed2001

The influence of temporal selection on spatial selection and distractor interference: an attentional blink study.

Both spatial and temporal selection require focused attention. The authors examine how temporal attention affects spatial selection. In a dual-task rapid serial visual presentation paradigm, temporal selection of a target (T1) impairs processing of a second target (T2) that follows T1 within 500 ms. This process is the attentional blink (AB). To test the effects of withdrawing temporal attention, the authors measured concurrent distractor interference on T2 when the distractors were presented during and outside of the AB. Perceptual interference was manipulated by the similarity in color between T2 and concurrent distractors, and response interference was manipulated by the flanker congruency task. Results showed that perceptual interference was larger during the AB. Response interference also increased during the AB, but only when perceptual interference was high. The authors conclude that temporal selection and spatial selection rely on a common attentional process.

Adult↗
PubMed1981

Effects of short-term and long-term treatment with cardio-selective and non-selective beta-receptor blockade on carbohydrate and lipid metabolism and on plasma catecholamines at rest and during exercise.

1. The effects on glucose and lipid metabolism and on plasma catecholamines at rest and during exercise, of 4 weeks treatment with non-selective beta-blockade (pindolol, 15 mg daily) and with cardio-selective blockade (metoprolol, 200 mg, and acebutolol, 500 mg, respectively) were compared in different groups of hypertensive men (mean age 37 years) by single blind cross-over technique. All patients continued the treatment with either metoprolol or acebutolol for another 12--14 months. 2. All antagonists reduced blood pressures and exercise heart rates in a virtually identical manner. Whereas lipolysis was similarly inhibited by both selective beta 1-antagonists and non-selective beta 1-beta 2-blockers, glycogenolysis in the muscle was inhibited only by non-selective beta-receptor blockade. 3. The inhibition of glycogen breakdown resulted in exercise hypoglycaemia and in increases of plasma adrenaline and ACTH, which probably reflect counter-regulatory mechanisms. No major metabolic changes occurred after 12--14 months compared with 4 weeks of treatment.

Acebutolol↗
PubMed1999

Haemodynamic influence and endothelin-1 plasma concentrations by selective or non-selective endothelin receptor antagonists in the pig in vivo.

In the present study the haemodynamical effects of endothelin (ET)-receptor antagonism was evaluated using selective and non-selective ET(A)- and ET(B)-receptor blockade in normoxic pigs in vivo. In addition, the influence of the ET-antagonists on circulating plasma ET-1 levels was determined. BMS-182874 (10 and 30 mg kg(-1) i.v.), a selective ET(A)-receptor antagonist decreased the pulmonary and systemic vascular resistances. bosentan (10 and 30 mg(-1) i.v.), a non-selective ET(A)- and ET(B)-receptor antagonist caused principally similar effects as ETA-antagonism alone. No effects were observed by selective ET(B)-blockade using BQ-788 (30 microg kg(-1) i.v.). Of the three antagonists used only bosentan increased the circulating plasma ET-1 levels. It may therefore be concluded that ET contributes to basal systemic and pulmonary vascular tone through ET(A)-receptor activation. ET(B)-receptors are likely to cause the elevated plasma levels of ET-1 observed after bosentan administration. Furthermore, circulating plasma levels of ET-1 do not reflect the physiological effects of ET-1.

Animals↗
PubMed1999

Novel retinoids with receptor selectivity and functional selectivity.

Retinoids mediate a number of physiological pathways through their effects on cellular growth and differentiation. Upon binding to retinoic acid receptors (RARs) and retinoid X receptors (RXRs), retinoids regulate cellular processes by directly modulating the expression of responsive genes. The wide-ranging effects of retinoid action are attributable to two main factors-the ubiquitous distribution of several subtypes and isoforms of RARs and RXRs, and the ability of these receptors to regulate numerous genes upon ligand activation. The broad range of effects mediated by retinoids means not only that they have many potential therapeutic applications but also that non-selective retinoids are associated with a high incidence of adverse effects. The design of retinoids that are receptor-selective and function-selective is a strategy that is proving successful in developing novel retinoids that offer not only good efficacy but also good tolerability. Tazarotene, a receptor-selective retinoid indicated for the topical treatment of psoriasis, is at the forefront of this new generation of retinoids. In the near future, other receptor-selective retinoids may prove useful for the treatment of other dermatological diseases, cancer, and diabetes.

Antineoplastic Agents↗
PubMed1999

The ligand-selective domains of corticotropin-releasing factor type 1 and type 2 receptor reside in different extracellular domains: generation of chimeric receptors with a novel ligand-selective profile.

The nonselective human corticotropin-releasing factor (hCRF) receptor 1 (hCRFR1) and the ligand-selective Xenopus CRFR1 (xCRFR1), xCRFR2, and hCRFR2alpha were compared. To understand the interactions of hCRF, ovine CRF (oCRF), rat urocortin (rUcn), and sauvagine, ligands with different affinities for type 1 and type 2 CRFRs, chimeric and mutant receptors of hCRFR1, xCRFR1, hCRFR2alpha, and xCRFR2 were constructed. In cyclic AMP stimulation and CRF-binding assays, it was established that different extracellular regions of CRFR1 and CRFR2 conferred their ligand selectivities. The ligand selectivity of xCRFR1 resided in five N-terminal amino acids, whereas the N-terminus of both CRFR2 proteins did not contribute to their ligand selectivities. Chimeric receptors in which the first extracellular domain of hCRFR1 replaced that of hCRFR2alpha or xCRFR2 showed a similar pharmacological profile to the two parental CRFR2 molecules. Chimeric receptors carrying the N-terminal domain of xCRFR1 linked to hCRFR2alpha or xCRFR2 displayed a novel pharmacological profile. hCRF, rUcn, and sauvagine were bound with high affinity, whereas oCRF was bound with low affinity. Furthermore, when three or five residues of xCRFR1 (Gln76, Gly81, Val83, His88, Leu89; or Gln76, Gly81, Val83) were introduced into receptor chimeras carrying the N-terminus of hCRFR1 linked to xCRFR2, the same novel pharmacology was observed. These data indicate a compensation mechanism of two differentially selecting regions located in different domains of both xCRFR1 and CRFR2.

Amphibian Proteins↗
PubMed2002

Differential effects of selective and non-selective NOS inhibition on renal arginine and protein metabolism during endotoxemia in rats.

BACKGROUND AND AIMS: The kidney is the main endogenous producer of circulating arginine. Renal arginine disposal is directed to protein synthesis, urea production and nitric oxide synthesis. The administration of nitric oxide synthase inhibitors during sepsis may be beneficial or detrimental depending on the specificity of the inhibitor. We aimed to measure the effects of two NOS inhibitors, with different specificity, on renal arginine and protein turnover in a rat model of sepsis. METHODS: Rats were subject to double hit endotoxemia and either L-NAME (non-specific), SMT (iNOS specific) or saline. Under anesthesia, vessels supplying and draining the kidney were catheterized. Systemic and intra-renal arginine and protein metabolism were measured using a primed continuous infusion of L-[2,3-(3)H]arginine and L-[2,6-(3)H]phenylalanine. RESULTS: Non-specific NOS reduced systemic protein and arginine turnover, whereas selective iNOS inhibition did not. In the kidney, blood flow was reduced by L-NAME, but not by SMT. In conjunction with this, non-selective NOS inhibition increased renal protein breakdown, whereas selective iNOS inhibition increased renal arginine production. CONCLUSIONS: This study shows that non-selective NOS inhibition using L-NAME is detrimental for systemic and renal protein metabolism. Selective NOS inhibition stimulates renal arginine synthesis, without changing circulating arginine levels.

Animals↗
PubMed2002

Glycine residues in potassium channel-like selectivity filters determine potassium selectivity in four-loop-per-subunit HKT transporters from plants.

Plant HKT proteins comprise a family of cation transporters together with prokaryotic KtrB, TrkH, and KdpA transporter subunits and fungal Trk proteins. These transporters contain four loop domains in one polypeptide with a proposed distant homology to K(+) channel selectivity filters. Functional expression in yeast and Xenopus oocytes revealed that wheat HKT1 mediates Na(+)-coupled K(+) transport. Arabidopsis AtHKT1, however, transports only Na(+) in eukaryotic expression systems. To understand the molecular basis of this difference we constructed a series of AtHKT1/HKT1 chimeras and introduced point mutations to AtHKT1 and wheat HKT1 at positions predicted to be critical for K(+) selectivity. A single-point mutation, Ser-68 to glycine, was sufficient to restore K(+) permeability to AtHKT1. The reverse mutation in HKT1, Gly-91 to serine, abrogated K(+) permeability. This glycine in P-loop A of AtHKT1 and HKT1 can be modeled as the first glycine of the K(+) channel selectivity filter GYG motif. The importance of such filter glycines for K(+) selectivity was confirmed by interconversion of Ser-88 and Gly-88 in the rice paralogues OsHKT1 and OsHKT2. Surprisingly, all HKT homologues known from dicots have a serine at the filter position in P-loop A, suggesting that these proteins function mainly as Na(+) transporters in plants and that Na(+)/K(+) symport in HKT proteins is associated with a glycine in the filter residue. These data provide experimental evidence that the glycine residues in selectivity filters of HKT proteins are structurally related to those of K(+) channels.

Amino Acid Motifs↗
PubMed1978

Mathematical theory of group selection: Structure of group selection in founder populations determined from convexity of the extinction operator.

Genetic analysis for group selection is developed for the case of a biallelic locus (A, a) undergoing group selection of founder populations only. By contrast to R. Levins"E = E(x) models, extinction now depends on genetics at the propagule stage but acts uniformly on larger populations. Biological evidence supports this hypothesis, which also allows mathematical treatment at once simpler and biologically more general than the Fokker-Planck partial differential equation formalism adopted by Levins. It is presently possible to handle cytogenetics of both diploid and haplodiploid type. The model is set up as a quasideterministic recursion in the 5-simplex Sigma(5), collapsing both drift and mendelian selection effects into a single parameter u, which is a Fisher-Kimura-Ohta fixation probability. In the analysis, it is shown that the stability of the fixed points is determined by the convexity of the extinction operator acting on propagules, assumed to be of size 2.THUS, [FORMULA: see text] in which E(1) and E(3) are extinction probabilities for phenotypically uniform founder populations and E(2) is the corresponding probability for founder populations of mixed phenotype. Further parameter regions are defined where fixation of the group-selected gene is globally stable, and this is still possible even when extinction pressure acting on carrying capacity populations becomes weak relative to a fixed mendelian selection strength.

Journal Article↗
PubMed1995

Identification of strong modifications in cation selectivity in an Arabidopsis inward rectifying potassium channel by mutant selection in yeast.

The Arabidopsis thaliana cDNA, KAT1, encodes a hyperpolarization-activated K+ channel. In the present study, we utilized a combination of random site-directed mutagenesis, genetic screening in a potassium uptake-deficient yeast strain, and electrophysiological analysis in Xenopus oocytes to identify strong modifications in cation selectivity of the inward rectifying K+ channel KAT1. Threonine at position 256 was replaced by 11 other amino acid residues. Six of these mutated KAT1 cDNAs complemented a K+ uptake-deficient yeast strain at low concentrations of potassium. Among these, two mutants (T256D and T256G) showed a sensitivity of yeast growth toward high ammonium concentrations and a dramatic increase in current amplitudes of rubidium and ammonium ions relative to K+ by 39-72-fold. These single site mutations gave rise to Rb+- and NH4(+)-selective channels with Rb+ and NH4+ currents that were approximately 10-13-fold greater in amplitude than K+ currents, whereas the NH4+ to K+ current amplitude ratio of wild type KAT1 was 0.28. This strong conversion in cation specificity without loss of general selectivity exceeds those reported for other mutations in the pore domain of voltage-dependent K+ channels. Yeast growth was greatly impaired by sodium in two other mutants at this site (T256E and T256Q), which were blocked by millimolar sodium (K1/2 = 1.1 mM for T256E), although the wild type channel was not blocked by 110 mM sodium. Interestingly, the ability of yeast to grow in the presence of toxic cations correlated to biophysical properties of KAT1 mutants, illustrating the potential for qualitative K+ channel mutant selection in yeast. These data suggest that the size of the side chain of the amino acid at position 256 in KAT1 is important for enabling cation permeation and that this site plays a crucial role in determining the cation selectivity of hyperpolarization-activated potassium channels.

Amino Acid Sequence↗
PubMed2000

Molecular determinants of tuberoinfundibular peptide of 39 residues (TIP39) selectivity for the parathyroid hormone-2 (PTH2) receptor. N-terminal truncation of TIP39 reverses PTH2 receptor/PTH1 receptor binding selectivity.

Tuberoinfundibular peptide of 39 residues (TIP39) and the parathyroid hormone-2 (PTH2) receptor form part of an extended family of related signaling molecules that includes the PTH1 receptor, which responds to PTH and PTH-related protein. TIP39 does not appreciably activate the PTH1 receptor, but in this study it is shown to bind the receptor with moderate affinity (59 nm). In this study, we investigated the molecular determinants of both ligand and receptor for the PTH2 receptor selectivity of TIP39 and quantitatively evaluated the role of molecular elements in the binding of TIP39 to the PTH2 and PTH1 receptors. A chimeric receptor composed of the N-terminal extracellular domain of the PTH1 receptor and the remainder (juxtamembrane domain) of the PTH2 receptor (P2-NP1) was fully activated by TIP39 (E(max) = 98% of the rPTH-(1-34), E(max), EC(50) = 2.0 nm). This receptor chimera bound TIP39 with an equivalent affinity to the wild-type PTH2 receptor (2. 3 and 2.0 nm, respectively). The reciprocal chimeric receptor (P1-NP2) was not activated by TIP39 and bound the ligand with an affinity equivalent to that of the PTH1 receptor. Thus, the juxtamembrane receptor domain specifies the signaling and binding selectivity of TIP39 for the PTH2 receptor over the PTH1 receptor. Removing six N-terminal residues of TIP39 eliminated activation of the PTH2 receptor and reduced binding affinity 70-fold. In contrast, this truncation increased affinity for the PTH1 receptor 10-fold, reversing the PTH2/PTH1 receptor binding selectivity and resulting in a high affinity interaction of TIP-(7-39) with the PTH1 receptor (6 nm). These findings can be explained by a strong interaction between the N-terminal region of TIP39 and the juxtamembrane domain of the PTH2 receptor, with the corresponding domain of the PTH1 receptor acting as a selectivity barrier against high affinity binding of TIP39. As a result, TIP-(7-39) is a highly potent, selective antagonist for the PTH1 receptor.

Amino Acid Sequence↗
PubMed1993

Diet selection in sheep: the ability of growing lambs to select a diet that meets their crude protein (nitrogen x 6.25) requirements.

To test the proposition that sheep are able to select a diet that meets their crude protein (N x 6.25; CP) requirements, feeds L, A, B, C and H with the same energy content (11 MJ metabolizable energy/kg feed) but different CP contents (78, 109, 141, 172 and 235 g CP/kg fresh feed respectively) were formulated. In addition, feed U, which was feed L plus 21.4 g urea/kg (CP content 132 g/kg), was also made. The feeds were offered ad lib. either singly (n 4 per treatment) or as a choice between feed H and another feed (pairs LH, AH, BH, CH and UH; n 9 per feed pair) to individually penned Suffolk x Scottish mule wether lambs, over the live-weight range 25-45 kg. On the single feeds the rates of live-weight gain were 273, 326, 412, 418, 396 and 407 g/day (SE of difference (SED) 34; P < 0.01) and protein (excluding wool) gain were 27, 32, 44, 45, 41 and 39 g/d (SED 4; P < 0.001) for feeds L, A, B, C, H and U respectively. When sheep were given a choice between a feed below (L or A) and a feed above their CP requirements (H; as judged by the single-feeding treatments) the CP concentration selected was not different between the two pairs: 131 (SE 4) v. 133 (SE 4) g CP/kg feed for pairs LH and AH respectively. On the choices BH and CH (a choice between two feeds above requirements) the feed lower in CP was constantly preferred (874 (SE 33) and 910 (SE 33) g feed B and C respectively per kg total feed intake; CP selected was 157 and 178 g CP/kg respectively). However, this was not the case with the UH choice on which sheep consumed only 599 (SE 61) g feed U/kg total feed intake, resulting in a selection of a higher CP in their diet (173 g CP/kg). The live-weight gains of the animals given a choice between two feeds were 416, 387, 415, 410 and 383 g/d (SED 37) and protein gains were 45, 40, 46, 50 and 43 (SE 7) for pairs LH, AH, BH, CH and UH respectively, which were comparable with the best performance achieved on a single feed. The results suggest that sheep were able to select a diet that meets their CP requirements and avoid, at least to a certain extent, excess of protein intake.(ABSTRACT TRUNCATED AT 400 WORDS)

Animal Feed↗
PubMed1995

Diet selection in sheep: the role of the rumen environment in the selection of a diet from two feeds that differ in their energy density.

The effect of the energy density (ED) of feeds offered as a choice on the diet selection of sheep, and the relationship between the rumen environment and the diet selected from feeds of different ED were investigated in two experiments. In the first experiment two feeds, L and H, and their mixture M (3:1 w/w) were formulated. All feeds had similar calculated metabolizable protein:metabolizable energy (ME) ratios, but differed in ED (7.4, 8.1 and 10.1 MJ ME/kg fresh feed for L, M and H respectively). The feeds were offered ad lib. either singly or in paired choices (L/M, L/H and M/H; n6 per treatment) to growing sheep. Although the rate of live-weight (Lwt) gain on feed H was higher than on feeds L or M, and the daily rate of feed intake lower, the sheep on feed choices did not consume only feed H. Instead they selected a mixture of both feeds offered, such that the total amount of H consumed per kg fresh feed was similar on choices L/H and M/H. The rate of Lwt gain of sheep on choices L/H and M/H was not different from that achieved on feed H alone. In the second experiment the choice L/H was offered to fistulated sheep (10 months of age, mean Lwt 57.5 kg) in an 8 x 8 Latin square, with 7 d periods. Treatments were infusions into the rumen (total volume 1 litre) over 4 h on days 1-4 of each period of acid (HCl; Acid 1, 400; Acid 2, 300 and Acid 3, 200 mmol/l), alkali (NaOH; Alk 1, 316; Alk 2, 212 and Alk 3, 109 mmol/l) and control (NaCl; Con 1, 315 and Con 2, 209 mmol/l). Infusate osmolalities (mOs/kg) were 795 (Acid 1), 585 (Acid 2, Alk 1 and Con 1), 390 (Acid 3, Alk 2 and Con 2) and 200 (Alk 3). Infusion treatment significantly affected the diet selection of the sheep (P < 0.05) according to the osmolality of infusate, but not according to rumen pH. During infusions intake of feed H tended to decline with increasing treatment osmolality, whereas intake of L remained constant. The effects on diet selection and feed intake were of a short duration with no carry-over effects.(ABSTRACT TRUNCATED AT 400 WORDS)

Animal Feed↗
PubMed2002

A quantitative model of optimal data selection in Wason's selection task.

The optimal data selection model proposed by Oaksford and Chater (1994) successfully formalized Wason's selection task (Wason, 1966). The model, however, involved some questionable assumptions and was also not sufficient as a model of the task because it could not provide quantitative predictions of the card selection frequencies. In this paper, the model was revised to provide quantitative fits to the data. The model can predict the selection frequencies of cards based on a selection tendency function (STF), or conversely, it enables the estimation of subjective probabilities from data. Past experimental data were first re-analysed based on the model. In Experiment 1, the superiority of the revised model was shown. However, when the relationship between antecedent and consequent was forced to deviate from the biconditional form, the model was not supported. In Experiment 2, it was shown that sufficient emphasis on probabilistic information can affect participants' performance. A detailed experimental method to sort participants by probabilistic strategies was introduced. Here, the model was supported by a subgroup of participants who used the probabilistic strategy. Finally, the results were discussed from the viewpoint of adaptive rationality.

Adult↗