documentclass[10pt,letterpaper,oneside]{article}

usepackage[dvips,top=1.2in,bottom=0.65in,left=1.0in,right=1.0in,includefoot]{geometry}

usepackage{pst-node,pstricks-add,pst-func}
% set up float for putting figures where you want them
usepackage{float}


begin{document}

Using texttt{circle}:

begin{figure}[H]
centering
newpsstyle{Cempty}{fillstyle=solid,mnode=none}
newpsstyle{Cfill}{fillstyle=solid,fillcolor=blue!7,shadow=false}
rule[1.8cm]{0.0pt}{3.0cm}
psscalebox{0.935}{
$
psmatrix[colsep=1cm,rowsep=1cm,
    arrowscale=1.5,mnode=circle]
 [style=Cempty] ~ &  [name=N1,style=Cfill] phi_tp_t & [style=Cempty]  ~\
[name=N2,style=Cfill] phi_. p_t &  [style=Cempty] ~ & [name=N3,style=Cfill]  phi_t p_. \
 [style=Cempty] ~ &  [name=N4,style=Cfill] phi_.{p_.} &  [style=Cempty] ~
% node connections
psset{nodesep=5pt,arrows=->}
ncline[linecolor=red,linewidth=.05cm]{N1}{N2}
nbput*[nrot=0]{textbf{?}}
ncline[linestyle=dashed]{N1}{N3}
ncline[linestyle=dashed]{N1}{N4}
ncline[linestyle=dashed]{N2}{N4}
ncline[linecolor=red,linewidth=.05cm]{N3}{N4}
naput*[nrot=0]{textbf{?}}
endpsmatrix
$
}
end{figure}


Using texttt{Circle}, in order to control radius of the nodes:

begin{figure}[H]
centering
newpsstyle{Cempty}{fillstyle=solid,mnode=none}
newpsstyle{Cfill}{fillstyle=solid,fillcolor=blue!7,shadow=false}
rule[1.8cm]{0.0pt}{3.0cm}
psscalebox{0.935}{
$
psmatrix[colsep=1cm,rowsep=1cm,
    arrowscale=1.5,mnode=Circle,radius=0.55cm]
 [style=Cempty] ~ &  [name=N1,style=Cfill] phi_tp_t & [style=Cempty]  ~\
[name=N2,style=Cfill] phi_. p_t &  [style=Cempty] ~ & [name=N3,style=Cfill]  phi_t p_. \
 [style=Cempty] ~ &  [name=N4,style=Cfill] phi_.{p_.} &  [style=Cempty] ~
% node connections
psset{nodesep=5pt,arrows=->}
ncline[linecolor=red,linewidth=.05cm]{N1}{N2}
nbput*[nrot=0]{textbf{?}}
ncline[linestyle=dashed]{N1}{N3}
ncline[linestyle=dashed]{N1}{N4}
ncline[linestyle=dashed]{N2}{N4}
ncline[linecolor=red,linewidth=.05cm]{N3}{N4}
naput*[nrot=0]{textbf{?}}
endpsmatrix
$
}
end{figure}


end{document}

documentclass[10pt,letterpaper,oneside]{article}

usepackage[dvips,top=1.2in,bottom=0.65in,left=1.0in,right=1.0in,includefoot]{geometry}

usepackage{pstricks-add,pst-func,}
% set up float for putting figures where you want them usepackage{float}

begin{document}

Using texttt{circle}:

begin{figure}[H]
centering
newpsstyle{Cempty}{fillstyle=solid,mnode=none}
newpsstyle{Cfill}{fillstyle=solid,fillcolor=blue!7,shadow=false}
rule[1.8cm]{0.0pt}{3.0cm}
psscalebox{0.935}{
$
psmatrix[colsep=1cm,rowsep=1cm,
    arrowscale=1.5,mnode=circle, radius = 1cm]
 [style=Cempty] ~ & [name=N1,style=Cfill] phi_tp_t & [style=Cempty] ~\
[name=N2,style=Cfill] phi_. p_t & [style=Cempty] ~ & [name=N3,style=Cfill] phi_t p_. \
 [style=Cempty] ~ & [name=N4,style=Cfill] phi_.{p_.} & [style=Cempty] ~
% node connections
psset{nodesep=5pt,arrows=->}
ncline[linecolor=red,linewidth=.05cm]{N1}{N2}
nbput*[nrot=0]{textbf{?}}
ncline[linestyle=dashed]{N1}{N3}
ncline[linestyle=dashed]{N1}{N4}
ncline[linestyle=dashed]{N2}{N4}
ncline[linecolor=red,linewidth=.05cm]{N3}{N4}
naput*[nrot=0]{textbf{?}}
endpsmatrix
$
}
end{figure}


Using texttt{Circle}, in order to control radius of the nodes:

begin{figure}[H]
centering
newpsstyle{Cempty}{fillstyle=solid,mnode=none}
newpsstyle{Cfill}{fillstyle=solid,fillcolor=blue!7,shadow=false}
rule[1.8cm]{0.0pt}{3.0cm}
psscalebox{0.935}{
$
psmatrix[colsep=1cm,rowsep=1cm,
 arrowscale=1.5,mnode=Circle, radius=0.55cm]%,C
 [style=Cempty] ~ &[name=N1,style=Cfill]raisebox{depth}{$ phi_tp_t $} & [style=Cempty] ~\
[name=N2,style=Cfill] raisebox{depth}{$ phi_. p_t $} & [style=Cempty] ~ & [name=N3,style=Cfill] raisebox{depth}{$ phi_t p_. $} \
 [style=Cempty] ~ & [name=N4,style=Cfill] raisebox{depth}{$ phi_.{p_.} $} & [style=Cempty] ~
% node connections
psset{nodesep=5pt,arrows=->}
ncline[linecolor=red,linewidth=.05cm]{N1}{N2}
nbput*[nrot=0]{textbf{?}}
ncline[linestyle=dashed]{N1}{N3}
ncline[linestyle=dashed]{N1}{N4}
ncline[linestyle=dashed]{N2}{N4}
ncline[linecolor=red,linewidth=.05cm]{N3}{N4}
naput*[nrot=0]{textbf{?}}
endpsmatrix
$
}
end{figure}

end{document}