The Virtual Personalities Model is a motive-based neural network model that provides both a psychological model and a computational implementation that explicates the dynamics and often large within-person variability in behavior that arises over time. At the same time the same model can produce—across many virtual personalities—between-subject variability in behavior that when factor analyzed yields familiar personality structure (e.g., the Big Five). First, we describe our personality model and its implementation as a neural network model. Second, we focus on detailing the neurobiological underpinnings of this model. Third, we examine the learning mechanisms, and their biological substrates, as ways that the model gets “wired up,” discussing Pavlovian and Instrumental conditioning, Pavlovian to Instrumental transfer, and habits. Finally, we describe the dynamics of how initial differences in propensities (e.g., dopamine functioning), wiring differences due to experience, and other factors could operate together to develop and change personality over time, and how this might be empirically examined. Thus, our goal is to contribute to the rising chorus of voices seeking a more precise neurobiologically based science of the complex dynamics underlying personality.

Two furrow irrigated field experiments were conducted for two years at the Research and Extension Center, Powell, WY to determine the influence of various mixed densities and durations of wild oat and wild mustard interference in sugarbeet. Sugarbeet root yields were reduced by competition from all examined densities of wild oat and wild mustard, alone and in combination. Root yield reduction was less than additive with mixed densities of wild oat and wild mustard. Root yields decreased as the duration of interference after sugarbeet emergence from a mixed density of wild oat and wild mustard increased. Sucrose content of sugarbeet was not altered by competition. Based on regression analysis, the minimum time that a mixed density of 0.8 wild mustard and 1 wild oat/m of row can interfere with sugarbeet before causing an economic root yield loss was approximately 1.6 weeks after sugarbeet emergence.

Field experiments were conducted at five locations in Colorado, Kansas, and Wyoming in 1994–1995 and 1995–1996 to compare the effects of MON 37500 rate and application timings on downy brome control and winter wheat tolerance. MON 37500 at 18 to 35 g ha−1 applied preemergence or fall postemergence reduced downy brome density 71 to 92% in 1995. Spring-applied MON 37500 suppressed downy brome growth but did not reduce plant density. No application reduced downy brome density in 1996. At each location, downy brome was controlled best by MON 37500 applied preemergence or fall postemergence at 35 g ha−1. MON 37500 did not affect wheat height at Archer or Torrington, WY, and Burlington or Stratton, CO, but wheat treated preemergence or fall postemergence was taller than untreated wheat at Hays, KS, in 1995. Spring-postemergence-treated wheat at Hays in 1995 was shorter than untreated, preemergence-, or fall-postemergence-treated wheat. Wheat head density did not differ among treated and untreated plots at Torrington, but herbicide treatment increased wheat yields. Wheat head density increased with all MON 37500 treatments at Hays in 1995, as did yield. However, preemergence and fall-postemergence applications resulted in the highest wheat yields. No herbicide treatment affected head density or yield at Hays in 1996.

Leafy spurge viable seed production and germination were reduced by 2,4-D applied during flower development and seed formation, in the field. Viable seed production was reduced when 2,4-D was applied at all growth stages after the start of flower bud development. The number of viable seed from untreated plants was 173, while, the number of viable seed from plants treated 0, 7, 14, 21, 28, or 35 d after the start of flower bud development was <1, 4, 7, 31, 53, and 62; respectively. Leafy spurge seed germination was higher in gibberellic acid than in water for seed collected from untreated plants and from plants treated with 2,4-D 7, 14, and 21 d after bud initiation. This research shows that 2,4-D must be applied prior to flower bud development to prevent seed production.

Twenty-nine wild oat (Avena fatua L. ♯3 AVEFA) and Avena sterilis L. ♯ AVEST accessions having various areas of origin and/or growth characteristics were grown to maturity in controlled environmental chambers. The four environments consisted of a 16-h photoperiod until 3 weeks after emergence, when the photoperiod was decreased (DP) 1 h per week for 8 weeks at a constant 14, 20, or 26 C (DP 14, DP 20, or DP 26); and an 8-h photoperiod until 3 weeks after emergence, when the photoperiod was increased (IP) 1 h per week for 8 weeks at a constant 20 C (IP 20). The relative growth rate of the accessions was similar in each environment. The length of the second leaf was up to 15 cm greater under 8- than 16-h day length at 20 C for some accessions, but was similar under both day lengths for other accessions. The width of the second leaf was greater under 14 than 20 C and was narrower with a 16-h than an 8-h photoperiod. Tiller initiation was slower in the DP 14 and IP 20 than in the DP 20 and DP 26 environments. Days to panicle emergence for individual accessions ranged from 10 to 57 days higher in the DP 14 than in the DP 20 environment. Seed produced on plants grown at 14 C had lower germination in water and 1500 ppm gibberellic acid than seed from plants grown at 20 C. Wild oat accessions varied in morphological characteristics, days to panicle emergence, and dormancy, and responded differently to changes in photoperiod and temperature. Wild oat morphological characteristics, days to panicle emergence, and dormancy did not consistently relate to species or area of origin.

Dicamba, 2,4-D, picloram, and commercially available premixes of glyphosate plus 2,4-D or glyphosate plus dicamba were evaluated alone and in combination for field bindweed control in a winter wheat-fallow system in Colorado, Wyoming, Kansas, and Montana. Approximately one year after application, herbicide mixtures containing picloram at 0.14 or 0.28 kg ai ha-1 provided the best control. In five of seven locations, the control provided by picloram in herbicide mixtures was greater than the control provided by glyphosate plus 2,4-D, 2,4-D, or dicamba when these products were mixed with picloram. Glyphosate plus 2,4-D or glyphosate plus dicamba premixes, or 2,4-D added to dicamba were less effective for long-term control of field bindweed than mixtures containing 0.14 kg ai ha-1 or more of picloram. Under drought conditions in Kansas in 1988, picloram did not control field bindweed as well as in Colorado, Wyoming, or Montana where rainfall was normal.

The effectiveness of postemergence applications of triallate [S-(2,3,3-trichloroallyl)diisopropylthiocarbamate] for wild oat (Avena fatua L.) control in spring wheat (Triticum aestivum L. ‘Waldron’) was evaluated in the field and greenhouse. The stage of the wild oat plants at the time of treatment did not appear to influence wild oat control with postemergence applications of triallate in the field; however, in the greenhouse, wild oat plants became more resistant with increased maturation. Granular triallate was more effective than the emulsifiable concentrate for postemergence wild oat control. Fair season-long postemergence wild oat control was obtained with the granular formulation of triallate at rates of 2.24 kg/ha or greater. However, some wheat injury was observed in the field with the 2.80 and 3.36 kg/ha rates of granular triallate. Moisture and temperature influenced postemergence wild oat control with triallate.

The effects of various densities and durations of wild oat (Avena fatua L.) competition in soybean [Glycine max (L.) Merr. ‘Evans’] were determined in the field during a 2-yr period. Season-long competition by densities of 1, 3,9, and 30 wild oat plants/m of row reduced soybean seed yield an average of 6, 17, 32, and 51%, respectively. An infestation of 30 wild oat plants/m of row did not reduce soybean yield if the period of competition was limited to 4 weeks after crop emergence; however, yields were reduced 29, 50, 63, 58, and 63% when wild oat competed for 5, 6, 7, and 8 weeks, or season long, respectively. Wild oat competition reduced soybean pods per plant and seeds per plant more than seeds per pod or seed weight.

Two field experiments were conducted between 1990 and 1992 under sprinkler irrigation at the Research and Extension Center, Torrington, WY to determine the influence of mixed densities and durations of kochia and green foxtail interference in sugarbeet. Sugarbeet root yield and top weight generally decreased as densities of green foxtail and kochia increased whether alone or in combination. Reductions in sugarbeet root yield and above ground biomass from mixed densities of kochia and green foxtail were additive at the low and intermediate density but less than additive at the high density of either species. Sugarbeet root yield decreased as the duration of interference after sugarbeet emergence from a mixed density of kochia and green foxtail increased. Since sugarbeet plants were irrigated to avoid water stress and adequate nutrients were applied, it appears that kochia and green foxtail interfered with sugarbeet primarily for light, based on light and height measurements. Season-long as well as duration of interference did not show any significant effect on sucrose content. Based on regression analysis the lowest densities of kochia and green foxtail required to reduce root yield were approximately 0.3 and 0.06 plants/m of row, respectively. The minimum duration of time that 0.5 kochia and 3.0 green foxtail plants/m of row can interfere with sugarbeets before root yield is economically reduced was approximately 3.5 wk after sugarbeet emergence.

A 3-yr study was conducted in eastern Wyoming from 1995 to 1997 to evaluate the effect of fertilizer placement on jointed goatgrass competitiveness with winter wheat. Fertilizer placement methods consisted of applying 45 kg/ha of nitrogen (50% as urea and 50% as ammonium nitrate) in a deep band 5 cm below and 2.5 cm to the side of the wheat row, broadcasting on the soil surface, or injecting fertilizer by spoke wheel 10 cm deep and 5 cm to the side of the wheat row. Neither fertilizer placement nor jointed goatgrass presence affected winter wheat stand. Wheat yield reductions from jointed goatgrass competition were 7 and 10% higher with the broadcast than deep-band or spoke-wheel injection methods, respectively. Wheat spikes/plant, seeds/spike, 200-seed weight, and plant height were not influenced by fertilizer placement; however, the presence of 35 jointed goatgrass plants/m2 reduced spikes/plant 21%, seeds/spike 12%, and 200-seed weight 6%. Jointed goatgrass populations were not influenced by fertilizer placement method; however, the number of spikes/plant was reduced 8 and 10%, joints/spike 3%, and biomass 15 and 21% by deep band or spoke wheel fertilizer placement.

Several labeled herbicide treatments reduced winter wheat height and grain yield when applied at different growth stages in 1984 and 1985. Yield reductions were related to reduced spike production. Wheat height and yield generally were greatest when herbicides were applied at Zadoks' Stage 29 and lowest at Stage 13. Herbicide treatments did not affect wheat kernels per spike, kernel weight, volume weight, or germination either year. However, most herbicide treatments either increased or decreased seed protein content, depending on the year.

Weed control and sugarbeet (Beta vulgaris L.) injury from applications of methyl m-hydroxycarbanilate m-methyl-carbanilate (phenmedipham) were influenced by additives, volume of additive, and species in both field and greenhouse experiments. Oils were more effective than the surfactant as additives to phenmedipham on green foxtail (Setaria virdis (L.) Beauv.), yellow foxtail (Setaria glauca (L.) Beauv.), redroot pigweed (Amaranthus retroflexus L.), or common lambsquarters (Chenopodium album L.). Herbicidal activity of phenmedipham on kochia (Kochia scoparia (L.) Schrad.) or wild mustard (Brassica kaber (D.C.) L.C. Wheeler var. pinnatifida (Stokes) L.C. Wheeler) was not enhanced by any additive. Linseed oil (2.34 L/ha) enhanced the herbicidal activity of phenmedipham on green foxtail, yellow foxtail, and redroot pigweed more than petroleum (2.34 L/ha) or sunflower (Helianthus annus L.) oil (2.34 or 9.35 L/ha). However, linseed oil reduced the herbicidal activity of phenmedipham on kochia.

Field experiments were conducted in 1983 and 1984 at two locations to determine the influence of various densities and durations of kochia interference in sunflower. Sunflower achene yield and dry weight were reduced by all densities of kochia, averaged over locations and years. Season-long competition by kochia densities of 0.3, 1, 3, and 6 plants/m of row decreased sunflower achene yield 7, 10, 20, and 27%, respectively. Sunflower achene yield and sunflower dry weight decreased as weeks of kochia competition increased. Only 2 weeks of kochia competition after sunflower emergence decreased sunflower achene yield 6%. Sunflower achene yield loss increased as the duration of kochia competition increased. Sunflower 200 achene weight, oil content, and plant height were not influenced by various densities or durations of kochia competition.

The response of ‘Era’ (tolerant) and ‘Coteau’ (susceptible) hard red spring wheat (Triticum aestivum L.) to CGA-82725 2-propynyl ester of {2-[4- [(3,5-dichloro-2-pyridinyl)oxy] phenoxy] propanoic acid} was determined in field and greenhouse evaluations. Era wheat was most susceptible to CGA-82725 applied at early jointing through the boot stage. Coteau wheat was most susceptible at die two-leaf stage and between early jointing through spike emergence. Coteau was injured more than Era wheat as the CGA-82725 rate was increased from 0.14 to 0.28 kg ai/ha. Wheat grain yield reductions were greatest when CGA-82725 was applied at the early jointing through boot stage for both cultivars and averaged 73% of the control. Absorption and translocation of 14C-CGA-82725 were similar and increased over time regardless of cultivar. Most of the absorbed 14C remained in the treated leaf in both cultivars.

Field experiments were initiated in 1973 at Fargo and Williston, ND, to evaluate wild oats seed longevity in soil at six burial depths. The number of viable seed decreased rapidly during the first 7 mo from 99% to 21 and 15% at Fargo and Williston, respectively, when averaged over depths. The number of viable seed decreased gradually over the 7- to 168-mo period at Fargo; however, at Williston, viability remained relatively constant for 84 mo and decreased rapidly after 108 mo. At both locations, several wild oats seed were viable 168 mo after burial. More viable wild oats seed were recovered from deep than shallow depths regardless of sampling date. Seed viability at the 6- to 10-cm burial depth was lost more rapidly with nitrogen fertilizer than without nitrogen fertilizer. The percentage of dormant viable seed remained constant for 33 mo at Fargo and 60 mo at Williston regardless of burial depth, but decreased gradually thereafter. Dormant seed percentages at the various depths did not relate to differences in seed viability at these depths.

Research was conducted to evaluate the effects of primary tillage (moldboard plowing and chisel plowing), secondary tillage (row cultivation), and herbicides on weed species changes in the soil seed bank in three irrigated row cropping sequences over a 3-yr period. The cropping sequences consisted of continuous corn for 3 yr (CN), continuous pinto beans for 3 yr (PB), and sugarbeets for 2 yr followed by corn in the third year (SB). A comparison between moldboard and chisel plowing indicated that weed seed were more prevalent near the soil surface after chisel plowing. The density of certain annual weed seed over the 3-yr period increased more rapidly in the seed bank after chisel plowing compared to moldboard plowing. Species exhibiting the most pronounced increase included hairy nightshade and stinkgrass in the PB cropping sequence and redroot pigweed and common lambsquarters in the SB sequence. Conversely, kochia seed density in the SB sequence decreased more rapidly in chisel-plowed plots. Row cultivation generally reduced seed bank densities of most species compared to uncultivated plots. Herbicide use in each cropping sequence produced a shift in the weed seed bank in favor of species less susceptible to applied herbicides. In particular, seed of hairy nightshade became prevalent in the PB cropping sequence, and seed of kochia, redroot pigweed, and common lambsquarters became prevalent in the SB sequence.

A 4-yr field study was conducted near Grassrange, MT to determine the effects of single and repetitive picloram treatments for leafy spurge control in a native pasture. Single applications of picloram at 0.28, 0.56, 0.84, and 1.12 kg ae ha–1 averaged 0, 5, 22, and 61% leafy spurge shoot control 3 yr after treatment. Only the single applications of picloram at 1.68 and 2.24 kg ha–1 maintained leafy spurge control above 80%. A retreatment with 0.56 kg ha–1 picloram was required to maintain effective control for 3 yr when less than 1.68 kg ha–1 was applied. Leafy spurge canopy cover in the 1.68 and 2.24 kg ha–1 treatments averaged 14 and 6% 3 yr after treatment; however, all other single applications required retreatment.

Crop yield loss–weed density relationships critically influence calculation of economic thresholds and the resulting management recommendations made by a bioeconomic model. To examine site-to-site and year-to-year variation in winter Triticum aestivum L. (winter wheat)–Aegilops cylindrica Host. (jointed goatgrass) interference relationships, the rectangular hyperbolic yield loss function was fit to data sets from multiyear field experiments conducted at Colorado, Idaho, Kansas, Montana, Nebraska, Utah, Washington, and Wyoming. The model was fit to three measures of A. cylindrica density: fall seedling, spring seedling, and reproductive tiller densities. Two parameters: i, the slope of the yield loss curve as A. cylindrica density approaches zero, and a, the maximum percentage yield loss as A. cylindrica density becomes very large, were estimated for each data set using nonlinear regression. Fit of the model to the data was better using spring seedling densities than fall seedling densities, but it was similar for spring seedling and reproductive tiller densities based on the residual mean square (RMS) values. Yield loss functions were less variable among years within a site than among sites for all measures of weed density. For the one site where year-to-year variation was observed (Archer, WY), parameter a varied significantly among years, but parameter i did not. Yield loss functions differed significantly among sites for 7 of 10 comparisons. Site-to-site statistical differences were generally due to variation in estimates of parameter i. Site-to-site and year-to-year variation in winter T. aestivum–A. cylindrica yield loss parameter estimates indicated that management recommendations made by a bioeconomic model cannot be based on a single yield loss function with the same parameter values for the winter T. aestivum-producing region. The predictive ability of a bioeconomic model is likely to be improved when yield loss functions incorporating time of emergence and crop density are built into the model's structure.